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GEOCHEMICAL BALANCE OF THE DILLON RESERVOIR AND
INVESTIGATION OF THE EFFECTS OF ACID ROCK-DR.AINAGE IN
SUMMIT COLÎNTY, COLOR.ADO
DISSERTATION
Presented in Partial Fulfillment of the Requirements for the Degree of Doctor of
Philosophy in the Graduate School of The Ohio State University
By
LeeAnn Munk, B.Sc., VI.Sc.
The Ohio State University
2001
Dissertation Committee: Approved by
Dr. Gunter Faure. .Advisor i I J i ^ / Adviser Dr. Jerry M. Bigham Department of Geological Dr. Douglas E. Pride Sciences
Dr. Garrv .McKenzie UMI Number: 3011123
Copyright 2001 by Munk, LeeAnn
All rights reserved.
UMI
UMI Microform 3011123 Copyright 2001 by Bell & Howell Information and Learning Company. All rights reserved. This microform edition is protected against unauthorized copying under Title 17, United States Code.
Bell & Howell Information and Leaming Company 300 North Zeeb Road P.O. Box 1346 Ann Arbor. Ml 48106-1346 Copyright hy LeeAnn Munk 2001 ABSTRACT
This study examines the effects of acid-mine drainage (AM D ) and acid-rock drainage ( ARD) in streams flowing into the Dillon Reservoir. Summit County.
Colorado. The Dillon reservoir was formed in 1963 and has been accumulating metal-rich sediment since that time. The streams entering the reservoir transport trace metals that are dissolved in the water and sorbed to hydroxide particles.
Weathering of ore samples in the laboratory indicate that the pH and chemical composition of the solutions evolve and become similar to samples of .AMD collected in the field. The results demonstrate that the mineral composition of the ore controls the chemical composition of the experimental mine effluent.
The distribution of trace metals between water and precipitates is controlled
by sorption depending on the pH. which ranges from 2.8 to near 8.0 in the drainage.
The dissolved metal concentrations in the water include Zn (up to 3050 ppb). Cu (up
to 454 ppb). Pb (up to 30 ppb). and Mo (up to 437 ppb). The highest concentrations
of Zn. Cu. and Pb occur in Peru Creek near the Pennsylvania Mine, whereas Tenmile
Creek has the highest concentration of Mo. The hydroxides of Fe and A1 that form at
the confluence of the Snake River with Deer Creek are enriched in trace metals whose
concentrations in the sediment of the Dillon Reservoir include Zn (up to 3217 ppm).
Cu (up to 195 ppm). Pb (up to 401 ppm), and Mo (up to 83 ppm).
ii The total value of recoverable metals from a I cm thick layer of sediment in the Dillon Reservoir is estimated at $1,414,550. which can offset the cost of dredging the reservoir in the future.
The water in the Dillon Reservoir has higher concentrations of major elements and lower concentrations of trace metals than predicted based on the chemical composition of tributaries weighted by their respective monthly average discharges.
The addition of Na and Ca is likely caused by road salt used by the towns surrounding the reservoir. The deficit of the trace metal concentrations can be e.xplained by soqnion in response to increases of pH as well as by uptake by aquatic organisms.
The importance of pH in controlling trace-metal concentrations of the Dillon
Reservoir is confirmed by the fact that these concentrations are strongly correlated to the pH of the water leaving the reservoir.
Ill To Jens
IV ACKNOWLEDGMENTS
1 am grateful to my advisor. Gunter Faure, not only for his continuous suppon in my research and for teaching me how to be a geochemist, but also for his friendship. I thank Jerry Bigham for all the lab work that improved the quality of this research and for his guidance. I am thankful to my husband. Jens, for all his encouragement, help with math whenever I needed it. all the laughs, camping excursions, and for his assistance in the field. 1 thank my parents. Tom and Bonnie and my sister. Lisa, for being proud of me.
To my great sampling team. Doug Pride and Charles S. Robinson, thank you tor getting in the cold water when 1 needed you to and for all the good times. I also thank Garry McKenzie for his support in my teaching and research. I thank Giehyeon
Lee. Nadine Piatak. and Linda Centeno for being great office mates.
I would also like to thank the Graduate School and the Department of
Geological Sciences and The Ohio State University for funds that helped support my research.
In addition. I am thankful to Tom Vogel for all of his support and for helping me to move on to reach my goals. I thank my undergraduate advisers. Tim Flood and
Nelson Ham for pointing me in the right direction in the first place. VITA
February 19, 1973 ...... Bom - Milwaukee. Wisconsin
1995 ...... B.S. Geology. St. Norbert College. Wisconsin
1997 ...... M.S. Geology. Michigan State University
199S-200Ü...... Instructor. The Ohio State University - .Vlarion
August 2001 ...... Assistant Professor of Geology. University of Alaska - Anchorage
Research Publications
Refereed .lournals
1. Munk. L.A.. Faure. G.. Pride. D.E.. and Bigham. J.M.. 2001. Sorption of Trace Metals to an .Aluminum Precipitate in a Stream Receiving Acid Rock- D rain age: Snake River. Summit County. Colorado. .Applied Geochemistry (in press ).
2. \'ogel. T..A.. Cambray. F.W.. Feher. L.A.. Constenius. K.N.. 1997. Petrochemistry and emplacement history of the Wasatch Igneous Belt. Utah. Geolog} and ore deposits of the Oquirrh and Wasatch Mountains. Utah. Society of Economic Geologists. Guidebook Series, v. 29. pp. 47-63.
Published abstracts
3. Munk. L..A.. Faure. G.. Pride. D.E.. Bigham. J.M.. 2000. Sorption and transport of trace metals; Snake River and Deer Creek confluence. Summit County. Colorado. National Geological Society of America Annual Meeting .Abstracts with Programs.
VI 4. Faure, G., Pride, D.E., Lee, G. Munk, L ,A „ Piatak, N.M., Centeno, L „ 2000. Geochemical processes affecting cations and anions in metal-rich acid streams of Colorado and Tennessee, USA. 3 U‘ International Geological Congress.
5. M unk, L..A. and, Faure, G „ 1999. E.xperimental weathering of a sulfide- beanng ore: an acid-mine drainage water component for Peru creek. Summit County, Colorado. North-Central Geological Society of .-kmerica .-\nnual Meeting .-\bstracts with Programs.
6. Feher, L..A., and Ryder, G., 1998. Chemical variation within and among samples of the .Apollo 17 aphanitic impact melt rocks: generation, relationships, and crustal sources. Lunar and Planetary Science Conference, Houston, Te.xas.
7. Feher, L..A., Constenius, Kurt N., and Vogel, Thomas A., 1996. Relationships between the Wasatch Intrusive Belt and the Keetley Volcanics, North Central Utah. Geological Society of .America Annual Meeting .Abstracts with Programs, Denver, Colorado.
S. Feher, L.A., and Flood, T.P., 1995. Vesicles and Breccia due to Injection of mafic magma into partially lithified sediments of the Early Proterozoic Ironuood Iron-Formation, Western Gogebic Range, NW Wisconsin. Institute on Lake Superior Geology .Annual Meeting .Abstracts with Programs.
9. Feher. L..A.. and Flood, T.P., 1995. The petrology of some Proterozoic argillites and associated igneous rocks from the Western Gogebic District, NW Wisconsin. Wisconsin Academy of Sciences, Arts, and Letters .Annual Meeting .Abstracts with Programs.
10. Feher. L..A., and Burg. C. .VI.. 1994. .An analysis of recent sediment types around .Achutupo Island, Panama, Central .America, Wisconsin .Academy of Sciences. .Arts, and Letters .Annual Meeting .Abstracts and Proceedings.
M.S. Thesis
11. Feher. L..A., 1997. Petrogenesis of the Keetley Volcanics in Summit and Wasatch Counties. North-Central Utah. M.S. Thesis, Michigan State Universitv.
Fields of Study
Major Field: Geological Sciences
.Minor Field: Geochemistry
Vll TABLE OF CONTENTS
Paae
Abstract ...... ii
Dedication ...... iv
Acknowledgments ...... v
\ ’ita ...... vi
Table of Contents ...... vii
List of Figures ...... \i
List of Tables ...... xx
Chapters:
1. Introduction ...... 1
2. Methods ...... 5
2.1 Sample Collection ...... 5 2.2 Sample Preparation ...... 6 2.3 Chemical Analyses ...... 7 2.4 Blank Preparation and Analyses ...... 7
3. Regional Geology and Hydrology ...... 10
3.1 Regional Geology and Ore Deposits ...... 10 3.1.1 Snake River Basin ...... 10 3.1.2 Blue River Basin...... 19 3.1.3 Tenmile Creek Basin ...... 22 3.1.4 Origin of the Ore Deposits in the Dillon Watershed ...... 24 3.2 Hvdroloav ...... 25
VI11 4. Environmental Geochemistry of the Snake River Basin ...... 30
4.1 Introduction ...... 30 4.2 Methods ...... 31 4.3 Results and Discussion ...... 32 4.4 Conclusions ...... 40
5. Formation of Aluminum Hydro.xysulfate and Removal of Trace Elements at the Snake River Deer Creek Confluence ...... 42
5.1 Introduction ...... 42 5.2 Methods ...... 44 5.2.1 Water and Precipitate Samples ...... 44 5.3 Results and Discussion ...... 48 5.3.1 Precipitate Vlineralogy and Metal Sorption at the Snake River/Deer Creek Confluence ...... 48 5.3.2 Sulfate and Organic Carbon at the Snake River/Deer Creek Confluence ...... 53 5.3.3 Neutralization E.\ peri ment ...... 54 5.3.4 Sorption and Transport Processes at the Snake River/Deer Creek Confluence ...... 58 5.4 Conclusions ...... 59 b. E.vpenmental Weathering of Sulfide-Bearing Ores form the Peru Creek Basin ...... 61
6.1 Introduction ...... 61 6.2 Methods ...... 63 6.3 Results and Discussion ...... 64 6.3.1 Weathering of Ore from the Shoe Basin M ine ...... 64 6.3.2 Weathering of Pennsylvania Mine Ore ...... 72 6.4 Comparison of SBM and PM Weathering Experiments ...... 78 6.5 Water Chemistry of Peru Creek near the Pennsylvania M ine ...... 80 6.6 Conclusions ...... 86
7. Distribution of Elements in the Sediment of the Dillon Reservoir ...... 87
7.1 Introduction ...... 87 7.2 Methods ...... 89 7.3 Results and Discussion ...... 90 7.3.1 Mineral Composition...... 90
IX 7.3.2 Distribution of Elements in the Sediment from the Dillon Reservoir ...... 92 7.3.3 Distribution of Fe and A1 ...... 101 7.3.4 Acid-Soluble Fraction of Sediment ...... 104 7.3.5 Distribution of Trace Metals ...... 109 7.3.6 Distribution of Molybdenum ...... 114 7.4 .Amount of Sediment and Value of Metals in the Dillon Reserv'oir ...... 115 7.5 Conclusions ...... 119
S. Chemical Composition of Water in the Dillon Watershed.
5.1 Introduction ...... 121 5.2 Methods ...... 121 5.3 Results and Discussion ...... 122 8.3.1 pH of Water in the Dillon Watershed ...... 122 8.3.2 Major Elements ...... 125 8.3.3 Trace Elements ...... 134 8.3.3.1 Molybdenum ...... 136 8 .3.3.2 Zinc. Copper. Nickel, and Cadmium ...... 138 8.4 Conclusions ...... 147
9. Conclusions ...... 149
APPENDICES
APPENDIX A ...... 154
APPENDIX B ...... 157
APPENDIX C ...... 162
APPENDIX D ...... 168
APPENDIX E...... 172
APPENDIX F...... 174
APPENDIX G ...... 178
APPENDIX H ...... 183
List of References ...... 190 LIST OF FIGURES
Fieurc Pa»e
3.1 Generalized geologic map of the Snake Ri\ er. Blue River, and Tenmile Creek basins. (Modified after De.vheimer. 1982) ...... 14
3.2 E.vposure of the Cretaceous Pierre Shale near the Snake River mouth (top). The Pennsylvania Mine (bottom) along Peru Creek, including a holding pond (pH=3.0) intended for water treatment, and old mine structures in the background ...... 15
3.3 .Mine drainage (pH= 6.S) at the Tiger Mine (left) located in the Swan River basin, and effluent (pH=7.0) from the Wellington Mine (right) draining through dredge tailings in French Gulch...... 21
3.4 Photograph of the Climax Molybdenum Mine and part of the Robinson Climax tailings ponds. The telephone pole is approximately 30 feet high for scale ...... 23
3.5 Snake River. Blue River, and Tenmile Creek basins, show ing their major tributaries and the Dillon Reservoir. (modified after Dexheimer. 1982) ...... 26
3.6 Hydrographs of the Snake River. Blue River. Tenmile Creek, and the outflow from the Dillon Reservoir into the Blue River for the period o f September 1998 through October 2000 ...... 27
4.1 Map of the Snake River Basin. Stream sample locations are labeled, except for SR -8 and SR-9. which were collected further downstream near the mouth of the SnakeRiver ...... 31
XI 4.2 \ ’aiiation of pH along the Snake River. Note that acidic water of the Snake River is neutralized by water from Deer Creek (DC-2) whereas the Sts. John Creek (SJC-1) and Peru Creek (PC-2) do not change the pH of the Snake River appreciably ......
4.3 Two-component mi.xing model for water in the Snake River (SR-2) with water of Deer Creek (DC-2). The concentrations of Na. Vlg and S of the mixed water (SR-3 ) fit the mixing model, whereas Ca is enriched by 16.Sfr ...... 34
4.4 X’ariations in the Ca concentration of the Snake River water and its tributaries Deer Creek (DC-2). Sts. John Creek (SJC-1 ). and Peru Creek (PC-2). The Ca concentration continually increases from SR-l to SR-5 ...... 35
4.5 Tw o-component mixing of the Snake River water and Deer Creek water. Concentrations of Fe. .-\1. and Mn in the water collected above the contluence of Snake River (SR-2) and Deer Creek (DC-2) and below the contluence (SR-3) in the Snake River ...... 36
4.6 Concentrations of Zn. Cu. and Co in the water at the contluence of Snake River (SR-2) and Deer Creek (DC-2) and below the contluence in the Snake River (SR-3) ...... 37
4.7 Photographs of the Snake River/Deer Creek contluence looking upstream. A. The contluence during high discharge in June 1999. B. The contluence during low tlow in September 1998 with orange, tan and black coatings on the streambed ...... 39
4.S Concentrations of Mg and S in mine water. groundwater, and meteoric water in the Snake River Basin. The mine w ater is enriched in S and Mg as expected ...... 40
5.1 Map of the Snake River/Deer Creek contluence. The sample sites 1-7 are where both water and flocculent precipitate were collected. The star indicates where a large sample of Snake River water was collected for the neutralization experiment ...... 45
XII 5.2 Changes in pH as a function of distance downstream at the Snake River/Deer Creek contluence. Concentrations of Zn. Cu, Pb, Ni, and SO^ (ppm) in the precipitates formed at the Snake River/Deer Creek contluence as a function of distance downstream ...... 52
5.3 Concentrations of Al, Fe, and OC (organic carbon) in the precipitates as a function of distance downstream ...... 54
5.4 .Amount of sorbent (mg/L) formed as a function of pH. Sorption edges for Pb, Cu, Zn, and Ni, and percent removal of SO 4 from neutralization of Snake River water. Filled circles arc data points from this experiment and the dashed curves are interpolated from solid line sorption curves reported by Dzombak and Morel (1990). The concentration of .Al in the water of the Snake River was 1.5 x ID”* mol/L whereas, Fe ranged from 1.00 x 10"* to 1.00 x 10'^ mol/L in the experiments reported by Dzombak and Morel ( 1990). The concentrations of the trace metals in the Snake River and those that were used in the experiments in Dzombak and Morel ( 1990) were Pb = 3.4 x 10 (this study) and Pb = 5.00 x 10 ' mol/L (Dzombak and Morel. 1990); Cu = 1.5 X 10" and 5.00 x 10 ' mol/L; Zn = 1.6 x lO " and 7.58 x 10 ' mol/L; and Ni = 3.4 x 10 and 5.00 x 10 ' mol/L; SO 4 = 7.70 x 10"* and was 1.00 x lO" mol/L respectively ...... 56
5.5 .Al'* activity and SO 4 activity for the step-wise neutralization of Snake River water as a function of pH ...... 57
5.6 Predicted sorption of Cu obtained from sorption data points for Cu in the Snake River and changes in pH measured as a function of distance downstream. Numbers next to data points indicate the pH values used to interpolate percent sorbed from the experimental sorption data ...... 59
6.1 Location map show ing Peru Creek, the Shoe Basin Mine, and the Pennsylvania M ine ...... 62
6.2 pH profile of solutions over time for the SBM weathering experiment. Fe and Al concentrations in solution over time. Dashed lines are used to connect data points because it is not known whether the concentrations increase or decrease linearly between data points ...... 65
XllI 6.3 Log saturation index vs. time in terms of the length of the weathering experiment. If log saturation index lies above the equilibrium line the solutions are supersaturated with respect to the solid phase and if log saturation index lies below the equilibrium line the solutions are understaturated with respect to the solid phase. If log saturation index lies on or close to the equilibrium line the solution is in a state of chemical equilibrium with respect to the solid phase ...... 66
6.4 Congruent solubility of Fe( 0 H)3(am) and .Al(OH):,(am) as a function of pH. Thermodynamic data used to derive spéciation of Fe and .Al in equilibrium with Fe(OH).' and Al(OH)n respectively, from Faure ( 1998). am = amorphous ...... 67
6.5 Concentrations of Na, K. Ca. and Mg over time for weathering of ore from the Shoe Basin Mine ...... 69
6.6 pH profile and concentrations of Cu, Zn. Pb. and Ni in solution over time ...... 71
6.7 pH profile over time for weathering of PM ore and Fe and .Al concentrations in solution over time ...... 74
6.8 Na. K. Ca, Mg. and 50^ concentrations in solution for the weathering of the PM ore ...... 75
6.9 Schematic representation of the effect of sulfate ions on sorption of cations at low pH. Closest to the surface of the hydroxide mostly hydrogen ions are sorbed due to the low pH of the surrounding solution, causing most of the surface sites to have a positive charge. Negatively charged sulfate ions are then attracted towards the surface. The sulfate ions then cause the majority of surface sites to have a negative charge and cations are sorbed to those negative sites. Ions are shown with true valence even though they loose some of their charge due to the formation of bonds ...... 76
6.10 pH profile over time of the weathering experiment of the PM ore and concentrations of Cu. Zn. Cd. and Pb in solution ...... 77
XIV 6.11 Log saturation index for PbS 04 in solutions over time for the PM weathering experiment, the dashed line indicates log saturation index equal to zero where equilibrium exists between Pb"^ and SO..' ions and PbS 04,si. The solutions lie on or near the equilibrium line indicating that PbS 04 could precipitate from the solutions. The log saturation index for CdSÜ 4 demonstrates that the solutions are undersaturated with respect to the formation of CdS 04; therefore CdS 04 did not precipitate from these solutions ...... 7S
6. 12 Temar\' diagram illustrating the composition of experimentally derived mine waters and natural mine waters for SBM ore in terms of three components (Fe. .-\1. and Mn). The square represents a hypothetical starting composition of mine drainage water at low pH (high Fe concentration) and the dashed arrow illustrates the direction along which the composition of the water should evolve as pH is increased and Fe and .Al precipitate enriching the solution in Mn. Dashed arrow illustrates the path along which the experimentally derived water from the PM should evolve if the pH of the solution increased ...... SO
6. 10 pH profile of Peru Creek water and PM water. The starting point (0 meters) is located just upstream from the Pennsylvania Mine on Peru Creek. The mine water is labeled as PM. Fe. Al. and SO4 concentrations in PM water are higher than those in Peru Creek ...... 82
6.14 Photograph of the location where mine effluent drains into Peru Creek just down slope from the Pennsylvania Mine. Notice the gradation in color o f the precipitate from orange to tan in the direction away from the riverbank. The orange precipitates are mostly schwertmannite and the tan precipitates have high .Al concentrations ...... S3
6.15 X-ray diffraction pattern o f orange precipitate collected at site shown in Figure 6.14. This pattern is indicative of the mineral schwertmannite (Fes 0 s(0 H)6S04)...... 84
6.16 Concentrations of Zn. Cu. Ni. and Cd in the PM water and Peru Creek. Notice that the mine water (PM) has elevated concentrations of these trace metals, but the water in Peru Creek has low concentrations of these trace metals ...... 85
XV 7.1 XRD pattern for synthetic 2-line ferryhydrite and for sediment sample D R -13 which is representative of all six samples analyzed from the Dillon Reservoir ...... 91
7.2 Map of the measured water depths of the Dillon Reser\ oir. The sample sites (black circles) are identified in red...... 93
7.3 Concentrations of Fe and Al in the sediments in the Dillon Reservoir. Cl is the contour interval in ppm ...... 94
7.4 Concentrations of Mn in the sediments of the Dillon Reservoir. Sediment collected in the main body of the reservoir close to the dam has the highest concentration of M n ...... 95
7.5 Concentrations of Pb and Cu in the sediments in the Dillon Reservoir. Site 10 in the Snake River arm has elevated concentrations of Pb and Cu as does the main body of the reservoir. .•\dditionally. the sediment at sites 16 and 17 has elevated concentrations of Pb and Cu ...... 96
7.6 Concentrations of Zn and Ni in the sediments of the Dillon Reservoir. Sediment at site 10 in the Snake River arm and in the main body of the reservoir have elevated concentrations of Zn and Ni. .Additionally, sediment at sites 16 and 17 are enriched in Zn ...... 97
7.7 Concentrations of Cd and Co in the sediments from the Dillon Reservoir. Sediment at site 10 in the Snake River arm and in the main body of the reserv oir have elevated concentrations of Cd and Co as do sites 4, 12. 13. and 14 ...... 98
7.8 Concentrations of Ag in the sediments from the Dillon Reservoir. Sample sites labeled in blue and contour values in black. Sediment from site 10 in the Snake River arm and from sites 12. 13. and 14 have elevated concentrations of A g ...... 99
7.9 Concentrations of Mo in the sediments from the Dillon Reservoir. Sediment at site 17 in the Tenmile Creek arm of the Dillon Reservoir and sediment at sites 13 and 14 in the main body of the reservoir have elevated concentrations M o ...... 99
7.10 Profiles of water depth, and concentrations of Fe and .Al in the acid soluble fractions of sediment along the Snake River arm. Sample sites for concentrations of Fe and Al are identified bv number ...... 101
XVI 7.11 Profiles of water depth, and concentrations of Fe and A l in the acid soluble fractions of sediment along the Blue River arm. Sample sites for concentrations o f Fe and •Al are identified by number ...... 102
".12 Profiles of water depth, and concentrations of Fe and .Al in the acid soluble fractions of sediment along the Blue River arm. Sample sites for concentrations of Fe and Al are identified by number ...... 103
7.13 .A three-component mixing diagram used to determine the concentrations of the acid-soluble fraction of the sediment samples from the Dillon Reservoir ...... 104
".14 The percent of acid soluble sediment vs. Fe and .Al concentration in the sediment from the Snake River arm. the Blue River arm. and Tenmile Creek arm ...... 105
7.15 Three-component mixing for average sediment in the Dillon Reservoir. Because the average sediment concentration of .Al is above the mixing triangle, the sediment is enriched in Al or depleted in Fe. or both relative to the sediment in the arms ...... lOS
". 16 Concentrations of Pb. Cu. Zn. and Ni and water depths along a transect of the Snake River arm of the Dillon Reservoir ...... 110
7.17 Concentrations of Pb. Cu. Zn. and Ni and water depths along a transect o f the Blue River arm ...... I l l
7.18 Concentrations of Pb. Cu. Zn. and Ni and w ater depths along a transect of the Tenmile Creek arm ...... 112
7.14 Total metal concentrations as a function of Fe plus .Al and the concentration of acid soluble sediment for all sediment samples from the Dillon Reservoir ...... 113
7.20 Water depth and distribution of Mo in the acid-soluble sediment from the Tenmile Creek arm ...... 114
S. 1 pH measurements taken near the mouths o f the Snake River. Blue River, and Tenmile Creek. Two measurements were taken in September 1998 and 1999 and in October 1999 and 2000 ...... 123
xvn s.2 pH as a function of discharge near the mouths of the Snake River, Blue River, and Tenmile Creek ...... 124
8.3 Na concentrations as a function of average monthly discharge for all water samples collected from the mouths of the Snake River, Blue River, and Tenmile Creek for this study. The period of time represented is September 1998 through October 2000 ...... 125
8.4 Effect of evaporation and dilution on the composition of water in the Dillon Reservoir (DR) relative to the predicted composition (P) ...... 132
8.5 Three-component mi.xing of the predicted concentrations of Na. Mg (a). Ca. and Mg (b) in the water of the Snake River (SR). Blue River (BR). Tenmile Creek (TMC). The weighted average concentrations derived by mixing of the stream water are represented by point P. whereas DR is the average chemical composition of the out How water, which represents the water in the Dillon Reservoir ......
8.6 Zn concentrations as a function of average monthly discharge for water samples collected from the mouths of the Snake River. Blue River, and Tenmile Creek. The period of time represented is September 1998 through October 2000 ...... 135
8.7 Three component mixing of the predicted concentrations of Mo in water in Dillon Reservoir and the actual concentration in the water flowing out of the reservoir in the Blue River below the dam ...... 136
8.8 Three component mixing of average weighted river water to determine the concentrations of Zn, U. and Se in the water in Dillon Reservoir. The actual concentrations in the water were measured in water flowing out of the reservoir below the dam. .Abbreviations are the same as in Figure 8.4 ...... 139
8.9 Three component mixing of the predicted concentrations of Zn. Cu. Cd. and Ni in the water in Dillon Reservoir and the actual concentrations in the water flowing out of the reservoir in the Blue River below the dam. Abbreviations are the same as in Figure 8.4 ...... 140
8.10 Zinc and Mo concentrations as a function of pH in the water of the Dillon Reservoir ...... 142
XVIII s. 11 Sorption curves derived from neutralization of Snake River water. The area outlined in the box is shown at larger scale in Figure 8 .12 in order to determine the percent sorbed at near neutral pH ...... 143
S. 12 Portion of the sorption curve for Cu outlined in Figure S. 11 used to determine the percent of Cu sorbed at near neutral pH values 143
S. 13 pH interval as a function of the ACu/AZn ratio ...... 146
XIX LIST OF TABLES
Tahic Page
2.1 Vlinimum and maximum concentrations of trace elements of the acid-soluble fraction of sediment from the Dillon Reservoir and from the Fe and AI hydroxide precipitates from the Snake River/Deer Creek confluence. .Average blank concentrations and minimum and maximum percent corrections are also listed. With the exception of the minimum concentration of Cr. all the blank corrections are less than I T . therefore, no blank corrections were necessary for any of the sediment or precipitate samples analyzed in this study ...... 9
3.1 Geologic column for the Snake River, Blue River, and Tenmile Creek basins. Compiled from Lovering and Goddard ( 1950) ...... 11
3.2 Whole rock chemical analyses by XRF for bedrock in the Snake River basin ...... 16
3.3 Chemical composition of three grab samples of Pierre Shale (Cretaceous) collected near the mouth of the Snake River. Samples IA and IB are duplicate analyses. Elements below the detection limit are (As. W. Sn. Sb. Cd. Ag. Bi) ...... 17
7.1 .Minimum and maximum concentrations of elements in the acid-soluble fraction of the sediment of the Dillon Reserx oir. expressed relative to the dry weight of the bulk sediment. Concentrations reported in ppm ...... 100 7.2 Fraction of acid-insoluble and acid-soluble sediment ...... 105 7.3 Density determinations of sediment in the Dillon Reservoir ...... 116 7.4 .Amount of metals in Dillon Reservoir sediment and values of the recoverable metals in a 1 cm thick laver of drv sediment ...... 1 IS
XX s. 1 Weighting factors and weighted concentrations of Na in the Snake River. Dates and concentrations in bold are measured concentrations, all other concentrations are interpolated from Figure 8.1 ...... 127
5.2 Weighting factors and predicted concentrations of Na in the Dillon Reservoir compared to the observed Na concentration in the Dillon Reservoir ...... 128
5.3 .Minimum and maximum concentrations of major and trace elements in terms of the Snake River (SR). Blue River (BR). and Tenmile Creek (TMC) ...... 129 b.4 Concentrations of major and trace elements used to predict the average chemical composition of water in the Dillon Reservoir and comparison of the predicted concentrations with those of the Dillon Reservoir measured at the outtlow into the Blue River ...... 130
8.3 Log CR for Mo in the acid soluble sediment, water in the Dillon Reservoir, and pore water. The errors are 2 standard deviations of the mean ...... 137
S.6 Percent Cu and Zn sorbed for each pH interval and the resulting change in Cu and Zn concentrations from the predicted (P) concentrations in the water of the Dillon Reservoir ...... 145
XXI CHAPTER 1
INTRODUCTION
The chemical composition of water and sediment in streams, lakes, reservoirs, groundwater, and the oceans is affected by trace metals derived from anthropogenic and natural sources. The global scope of this environmental problem is the motivation for this investigation of contaminated water and sediment caused by acid- mine drainage (.AMD) and acid-rock drainage (ARD) in the Dillon watershed.
Summit County. Colorado.
The Dillon Reservoir was formed in 1963 when a dam was constructed across the Blue River just below its confluence with Tenmile Creek and the Snake River.
The drainage basin of the Dillon Reservoir is underlain by rocks of Prccambrian.
Paleozoic. Mesozoic, and Cenozoic age. In addition. Quaternary glacial drift deposits occur throughout the basin. The study area lies within the Colorado Mineral Belt, w Inch has been mined for .Au. .Ag. and various sulfide minerals since the 1860s
I Lo\ cring and Goddard. 1950). .Although most mining was discontinued in the
1930s. some of the streams are still contaminated by .AMD as well as by ARD.
When sulfide minerals such as pyrite are o.xidized at or near the surface of the earth, ground and surface waters typically become acidic and are enriched in SOj. Fe.
.Ai. and trace elements (Wentz. 1974). Some of the mobilized trace elements
I associated with acid drainage pose a potential threat to the health of plants, animals, and humans (Adriano, 1986; McBride, 1994). As acidic Fe- and Al-rich streams are neutralized, amorphous to semi-crystalline o.xyhydro.xides and hydro.xysulfates of Fe or .\\ can form (Stumm and Morgan, 1996). These precipitates have surface sites that sorb cations and anions depending on their charge, which is primarily controlled by the pH of the surrounding solution. The suspended particles and precipitates arc transported downstream during periods of high flow and are deposited in lakes and reser\oirs.
The objectives of this dissertation include 1) studying the removal of trace elements from watei by sorption to hydro.xides of Fe and A1 in high sulfate waters as a function of an increase in pH, 2) e.\ peri mental investigation of chemical weathering of sultlde-bearing ores to understand the chemical evolution of .AMD and ARD, 3) determining the distribution of major and trace elements in the acid-soluble fraction of sediment in the Dillon Reservoir, and 4) studying seasonal fluctuations in the chemical composition of water in the Dillon Reservoir basin as a function of discharge and pH. New approaches and methods for investigating the distribution of trace elements in the environment have been developed in this dissertation.
The objective of the study at the Snake River and Deer Creek confluence
(Chapter 5 1 was to test the hypothesis that the partitioning of trace metals in the
Snake River at and just below its confluence with Deer Creek is controlled predominantly by an increase of pH and the resulting precipitation of an Al- hydroxysulfate. This study is linked to the overall objective of investigating the weathering of mineralized rocks in the drainage basin of the Snake River and to studying the geochemical processes that control the concentrations of trace elements in the Dillon Reservoir, which is one of the principal sources of drinking water for the city of Denver.
Chapter 6 presents the results and interpretation of e.xperimental weathering studies of ore in the Peru Creek drainage. The objective of these e.xperiments was to weather crushed ore specimens m the laboratory and to compare the chemical composition of the resulting solutions to natural acid mine- water in the Peru Creek drainage. This study is necessary because it is difficult to sample pristine mine-water in the field because it mixes continuously with meteoric and ground water.
The accumulation of sediment in the Dillon Reservoir is a concern because the acid-soluble fraction contains elevated concentrations of trace metals. Chapter 7 illustrates the distribution of major and trace elements in the acid-soluble fraction of sediment in the Dillon Reservoir and documents the physical and chemical charactenstics of the sediment. It is important to know the chemical and
mineralogical composition of the sediment because the Dillon Reservoir will esentually require dredging and the sediment w ill have to be recovered and
remediated before it is disposed of.
It is also important to know the chemical composition of the water in the
Dillon Reservoir and the factors that control it because the water is a major source of
drinking water for the citizens of Denver. It is also used for recreational purposes and
as a habitat for wildlife. Therefore, the objective of Chapter 8 is to determine the relationship between the composition of the water entering the Dillon Reservoir and the observed composition of the water flowing out of the reservoir in the Blue River at the outflow of the dam. CHAPTER 2
SUMMARY OF METHODS
Water, sediment, and rock samples were collected and analyzed to characterize and explain the geochemistry of the Dillon watershed. This chapter hne!l\ sLimmanzes the methods used to collect the samples and to prepare them for analysis. The analytical methods are discussed in detail in the following chapters. In addition, the locations of sampling sites are provided in the appropriate chapters.
2.1. Sample collection
A ll stream samples were collected between September 199S and October
2(H)(). The pore water samples were collected with the sediment from the bottom of the Dillon Reservoir in July 2000. The water samples were stored in new
polyethylene bottles that were rinsed twice with stream water on site. In addition, the
pH of each w ater sample was measured in the Held using a Model pHep3 (Hanna
Instrument) pH meter.
Precipitates of Fe and .AI hydroxides were collected from the streambeds of
the Snake River and Peru Creek with plastic Tygon™ tubing attached to a
polyethylene syringe and were stored in polyethylene bottles along with stream water
collected at each site. Sediment samples collected from the bottom of the Dillon Reservoir were collected using a box sampler that was lowered from the side of a boat at known locations, triggered with a metal messenger, and brought back to the boat. Enough sediment to fill 500 mL bottles was taken from each site and stored in polyethylene bottles along with pore water and lake water that was unavoidably included as the sampler was pulled up through the water column.
2.2 Sample Preparation
.All water samples were filtered in the laboratory using 0.45 pm pore filters to recover the suspended sediment and the filtered water was acidified with concentrated reagent-grade nitric acid. Laboratory results show that the 0.45 filters remove 9S.4 percent by weight of suspended sediment from the water samples used in this study.
The precipitates collected from the streambed of the Snake River and Peru
Creek and the sediment samples were collected from the bottom of the Dillon
Reservoir were freeze-dried before any chemical analyses were pertbrmed. The precipitates and the sediment were analyzed by X-ray diffraction to identify the mineral phases. .A known weight of each precipitate was reacted with 2N HCl. and the resulting solutions were diluted to either 100 mL or 250 mL with deionized water in calibrated volumetric flasks.
Samples of Swandyke Gneiss and the Idaho Springs Formation were collected from talus piles in the Snake River Basin. A sample of the Montezuma stock was collected from a rock pile outside the ventilation shaft to the Roberts Tunnel along the road to Montezuma. .All the ore specimens used in this study were collected from tailings piles at each mine.
6 2.3 Chemical Analyses
Major element concentrations of the water, precipitate, and sediment samples were determined by ICP-OES and trace element concentrations were measured by
ICP-MS at X R A L laboratories in Toronto. The detection limits for all elements are listed in the .Appendix, Triplicate analyses of water samples collected by Centeno
(2001 ) indicate that the reproducibility for elements with concentrations less than 10 ppb range I’rom IT- to 40T-. However, the reproducibility is better than 5T- when the concentrations exceed 10 ppb.
.All X-ray diffraction patterns were obtained using top-fill powder mounts and
CuKa radiation on a vertical, wide-range goniometer (Philips PVV 1316/90) equipped
'A nil a theta-compensating slit, a 0.2 mm receiving slit and a diffracted-beam monochrometcr. Specimens were scanned from 10 to 70" 20 with a 4 second step time and a 0.05" 20 step interval. Peak positions were determined by using the Jade
3.0 software of Materials Data Inc.
The bedrock samples that were collected from the Snake River basin were crushed and sieved through 0.125 mm brass screens. Approximately one gram of the
rock powder was mixed with lithium tetraborate, melted in platinum crucibles, and
formed into glass disks for analysis of major and trace elements by X-ray
tluorescence at Michigan State University.
2.4 Blank Preparation and Analyses
.A blank was prepared by filtering 1 L of deionized water through a 0.45 pm
filter and acidifying it with 1 to 2 drops of concentrated HNO 3. The results in the
.Appendix indicate that the only elements above the lim it of detection were: Mn (0,2 7 ppb). Sr (0.2 ppb). Cu (0.3 ppb), Pb (0.02 ppb). Zn (2.0 ppb). Ni (O.l ppb). and Cd
(0.02 ppb). Because the concentrations were near the detection lim it of the instrument, no blank corrections were needed for the concentrations of these elements in the water samples.
Two additional blanks were prepared by Centeno (2001) using 70 mL of 2N
HCl diluted to a volume of 100 mL with deionized water to compare with the solutions prepared by leaching 0.5 g of sediment with 2N HCl. The concentrations of trace elements in the sediment and precipitate samples used in this study and the range of eiTor for the minimum to maximum concentrations of each element are listed in Table 2.1. The blank corrections amount to only 0.0002 to 1.074 T of the measured concentrations. Therefore, no blank corrections were required for analyses o f the acid-soluble fractions. Minimum Maximum g j ^ concentration concentration Average Minimum Maximum .. . ' in sediment in sediment Blank concentration concentration , and and Concentration % corrected % corrected ^ precipitate precipitate (ppb) error error (ppb)______(ppb)
Cr 0.1 7800 168,700 83.8 1.074 0.050
Co 0.1 400 22,400 BD 0 0
Ni 0.1 11,200 196.700 1.1 0.010 0.001
Cu 0.1 31.000 402,600 9.3 0.030 0.002
Zn 0.1 542,700 11,414,600 23.6 0.004 0.0002
Mo 1 2000 83,000 1 0.050 0.001
Cd 0.01 690 14,900 0.15 0.022 0.001
Pb 0.01 64,000 401,200 5.83 0.009 0.001
BD = below detection
Table 2.1. .Minimum and maximum concentrations o f trace elements o f the acid-soluble fraction o f sediment from the D illon Reservoir and from the Fe and A1 hydroxide precipitates from the Snake River/Deer Creek confluence. Average blank concentrations and minimum and maximum percent corrections are also listed. With the e.xception o f the minimum concentration of Cr. all the blank corrections are less than ift. therefore, no blank corrections were necessary for any o f the sediment or precipitate samples analyzed in this study. CHAPTER 3
REGIONAL GEOLOGY AND HYDROLOGY
3.1 Regional Geology and Ore Deposits
This chapter summarizes the regional geology of the Snake River. Blue
River, and Tenmile Creek basins. The ages and names of rock formations are listed in Table 3.1 in the form of a geologic column compiled from Lovering and Goddard
11950). In addition, the tvpes of ore deposits and mining historv in each basin w ill be discussed.
3.1.1 Snake River Basin
The Snake River basin is underlain by Precambrian metamorphic rocks, which are overlain by Cretaceous sedimentary rocks and intruded by Tertiary quartz
monzonite plutons (Figure 3.1). In addition. Quaternary glacial drift occurs
throughout the basin. The most prominent bedrock unit of the Snake River basin is
the Prccambrian Idaho Springs Formation, which consists of quartz-biotite-sillimanite
schist and gneiss and was formed by metamorphism of Middle Proterozoic
sedimentary rocks. These two rock units have been reclassified by the UGSG ( 1981).
but the onginal names w ill be used throughout this paper.
10 Age Snake River Basin Blue River Basin Tenm ile Creek Basin
Quaternary glacial and Quaternary glacial and Quaternary glacial and Quaternary fluvial deposits fluvial deposits fluvial deposits
Tertiary Rhyolite Porphyry Rhyolite Porphyry Chalk Mt. Rhyolite
Montezuma Quartz Lincoln Porphyry Lincoln Porphyry Monzonite
Quartz Monzonite Quartz Monzonite Quartz Monzonite
Diorite Porphyry Granodiorite Porphyry Quail Porphyry
Augite Diorite Latite Porphyry Elk Mt. Porphyry
Rhodacite Porphyry
Upper Pierre Shale Pierre Shale Cretaceous Niobrara Formation Niobrara Formation
Benton Shale Benton Shale
Cretaceous Dakota Sandstone Dakota Sandstone
Triasslc Wyoming Formation Wyoming Formation
Upper Jurasic Morrison Formation
Permian and Maroon Formation Maroon Formation Pennsylvanian Volcanics
Pennsylvanian Minturn Formation
Mississippian Leadville Dolomite
Devonian Chaffee Formation
Ordivician Harding Quartzite
Table 3.1. Geologic column for the Snake River, Blue River, and Tenmile Creek basins. Compiled from Lovering and Goddard ( 1950).
11 Table 3.1 continued
Cambrian Peerless Formation Sawatch Formation
Precambrian Pegmatites Pegmatites Pegmatites
Silver Plume Granite Silver Plume Granite
Pikes Peak Granite Pink Granite Pink Migmatite
Quartz Diorite Quartz Diorite Gneiss
Granite Gneiss Gneissic Granite
Quartz Monzonite Pegmatites
Swandyke Gneiss Gneiss Banded Gneiss
Idaho Springs Idaho Springs Formation Granulite Formation
12 The Precambrian Swandyke Gneiss is mainly a hornblende schist and gneiss with thin interlayered beds of quartz-biotite schist. The protolith of the Swandyke izneiss is thought to be diorite and andésite that formed sills and/or lava flows in the upper part of the Idaho Springs Formation.
The Tertiary Montezuma stock is the largest intrusion of quartz monzonite in the basin (Figure 3.1 ) with an exposed surface area of approximately 16 square miles.
The intrusion of the Montezuma stock resulted in pyrite-rich mineralization of the suiTounding Precambrian rocks. .Additional smaller porphyritic intrusive stocks of
Laramide age and younger occur throughout the drainage and range in composition from gabbro to quartz monzonite (Lovering and Goddard. 1950).
Intrusive bodies of Precambrian age including the Boulder Creek granite.
Pikes Peak granite, and the Silver Plume granite also occur among the older
Precambrian metamorphic rocks throughout the Snake River drainage. A granitic gneiss sequence of the Boulder Creek granite is the host of the ore at the
Pennsylvania Mine in the Peru Creek drainage (Lovering and Goddard. 1950).
The Cretaceous Pierre Shale is exposed about three miles west of Montezuma as well as along the Snake River near the Dillon Reservoir (Figure 3.2) and is approximately 1.2 km thick. It consists of greenish-gray to black shales with some beds of bentonite, calcareous sandstone, and shaly limestone in the lower part grading to a more arenite composition in the upper part (Lovering and Goddard. 1950).
13 Dillon Reservoir
IINontezuma
k7 A
Quatemarv
Tertian
Palco/oic and Mcso/oic
m Prccambnan
Fault Anticline axis ■ Climax' 5 Km Svncline axis
Figure 3.1. Generalized geologic map o f the Snake River, Blue River, and Tenmile Creek basins. (Modified after Dexheimer, 1982).
14 Figure 3.2. Exposure of the Cretaceous Pierre Shale near the Snake River mouth (top). The Pennsylvania Mine (bottom) along Peru Creek, including a holding pond (pH=3.0) intended for water treatment, and old mine structures in the background.
15 Formation Idaho Springs Swandyke Gneiss Montezuma Stock biotite-sillimanite Rock Type hornblende gneiss quartz monzonite schist Age Precambrian Precambrian Tertiary
SiOo 67.87 74.98 63.96
AI2O 3 15.69 12.53 15.6
FeO 5.38 3.15 4.63
MgO 1.47 1.36 1.71
CaO 1.34 1.99 3.62
Na^O 3.07 3.57 3.46
K2O 2.55 1.41 3.69
TiO . 0.69 0.3 0.76
P2O 5 0.08 0.04 0.31
MnO 0.08 0.09 0.09
Total 98.22 99.42 97.83
C r' 52 BD(65) 973
N i' 23 BD(25) 101
C u' 12 4 26
Z n' 101 109 40
Rb' 133 54 168
Sr' 208 213 678
Y* 40 20 32
Zr" 261 270 249
N b' 23 11 28
La' 46 32 74
B a' 332 418 716
Concentrations reported as % unless otherwise noted 'Concentration in ppm BD = below detection limit, detection limit in parentheses
Table 3.2. Whole rock chemical analyses by XRF for bedrock in the
Snake River basin.
16 Cretaceous Cretaceous Cretaceous Cretaceous Element Detection limit Pierre Shale Pierre Shale Pierre Shale Pierre Shale
1A IB 2 3
S 1O 2 0.01 59.8 59.9 64.3 60.9
AI2O 3 0.01 13.4 13.4 15.5 12
FeO 0.01 5.69 5.69 4.99 5.13
MgO 0.01 2.67 2.67 1.8 2.61
CaO 0.01 4.09 4.09 2.31 5.4
N a: 0 0.01 0.7 0.7 0.72 0.74
K2O 0.01 2.85 2.83 3.09 2.47
TiOn 0.01 0.58 0.579 0.648 0.531
P2O 5 0.01 0.25 0.25 0.23 0.21
MnO 0.001 0.03 0.03 0.03 0.05
Cr;03 0.01 0.02 0.02 0.02 0.02
LOI 0.01 7.7 7.65 6.5 8.55
Total 97.8 97.8 100.1 98.6
Be' 0.5 2 2 2.3 1.7
Sc* 0.5 10.3 10.8 9.6 9.1
V 2 229 236 193 238
Co' 1 8 9 10 9
Zn' 0.5 132 136 131 291
S e' 3 BD BD BD 13
Sr' 0.5 118 122 84.6 139
Y' 0.5 16.7 17.8 15.4 16.6
Zr' 0.5 54.8 59.4 64.8 56.9
M o' 1 BDBD 2 2
Ba' 1 568 566 591 480
La' 0.5 30.1 28.6 36.6 26.7
Pb' 2 15 13 16 18 'concentrations in ppm BD = below detection limit
Table 3.3 Chemical composition o f three grab samples o f Pierre Shale (Cretaceous) collected near the mouth o f the Snake River. Samples lA and IB are duplicate analyses. Elements below the detection lim it are (.As, W, Sn. Sb. Cd. .■Xg. Bi). 17 The whole-rock chemical analyses of the rocks in the Snake River basin are listed in Table 3.2 and Table 3.3. The concentration of SiO: of the Swandyke Gneiss in Table 3 .1 is high considering that the protolith is assumed to be andésite and diorite; however, the specimen analyzed contained layers of quartz-biotite schist, u hich account for the high silica concentration. The Idaho Springs Formation has a higher concentration of ANO- than the Swandyke gneiss and the Montezuma stock, consistent with the presence of sillimanite (.AFSiOs).
Piatak (2000) compared the composition of weathered and unweathered samples of the Pierre Shale and found that Tl. Pb, Cu, Cr, and As are enriched in the w eathered sample and that the concentrations of Se, U, Sc, Hf, Cd, Mo, \V, Sb, Bi,
Ta. Th. and Hg are less in the weathered shale than in the unweathered shale.
Therefore, these elements are removed from the shale during weathering and are released into the Snake River. In particular. Piatak (2000) found that the Sc and U concentrations in the Snake River water were elevated near where the shale samples were collected. In addition. Piatak (2000) found that the unweathered Pierre Shale along the Snake River near the Dillon Reservoir has up to three times higher than average concentrations of Ta, Se, AS, Cd, W, V, Sb, Mo, and Sc compared to samples of average marine shales found elsewhere and that the concentrations of Mn,
Ba. La. and Tl are lower than in other shales.
The Idaho Springs Formation and the Swandyke gneiss are part of a northwestward-trending syncline that is about 5 mile wide. During the Laramide orogeny these rocks were fractured by faulting and by the intrusion of the quartz
monzonite stocks.
IS The Snake River Basin contains the Montezuma and Argentine Mining
Districts. The mineralization in these districts resulted from hydrothermal activity associated with the intrusion of the Tertiary stocks. The mines in the Montezuma
Mining District include the Sts. John Mine at the headwaters of Sts. John Creek and
the Burke-Martin mine near the village of Montezuma. The mines in the Argentine
Mining District include the Pennsylvania Mine (Figure 3.2) and the Horseshoe Basin
Mine along Peru Creek. The ore deposits in the Snake River basin are mesothermal
\eins containing silver, galena, sphalerite, sulfarsenides, gold, and sulfantimonides of
siUor. copper, and some bismuth (Lovering and Goddard. 1950).
The first silver lode discovered in Colorado was found in 1864 on Glacier
Mountain about one mile south of Montezuma. This discovery led to e.\tensive
prospecting in the Montezuma and .Argentine mining districts. During the period
from 1886 to 1928 64.572 ounces of silver. 807.019 pounds of lead. 65.232 pounds
of copper. 462.629 pounds of zinc, and 160.89 ounces of gold were shipped out of the
Montezuma district (Lovering and Goddard. 1950).
The Pennsylvania Mine was one of the most productive mines in the
Montezuma quadrangle with a recorded output of 31.142 tons of ore from which at
least 761.020 ounces of silver. 2.858 ounces of gold, and 6.590.206 pounds of lead
were extracted (Lovering and Goddard. 1950).
3.1.2 Blue River Basin
Most of the rocks exposed in the Blue River basin are Paleozoic and Mesozoic
sedimentary rocks underlain by Precambrian quartz-biotite schists and gneisses
( Figure 3.1 ) exposed in the southern and western parts of the basin. The Paleozoic
19 Lind Mesozoic sedimentary rocks include red. gray, and black shales, conglomerates, sandstones, quartzites. limy shales, and limestones. Intrusive monzonite porphvries of Tertiary age are common throughout the basin, and range from hornblende monzonites to quartz monzonites. The intrusive activity resulted in hydrothermal activity, which caused the alteration of the country rock and the mineralization in the area. The basin also contains glacial deposits of Quaternary age.
The rocks in the Blue River basin form the western limb of a regional syncline. about two miles west of the fold a.\is. The structures in the region are very complex, but fractured and down-faulted sections with normal and reverse faults are common. The most productive mines in the Blue River basin worked mineralized veins that trend between N 40'’ E and N 80'’ E.
The Breckenridge Mining district in the Blue River basin is famous for placer- gold mining, the high-grade gold veins of Famcomb Hill, and for a significant output of lead-silvcr-zinc ore. The types of ore deposits in the Breckenridge district include contact metamorphic. stockwork. intrusion breccias, veins, and placer deposits. The
minerals abundant enough to be o f commercial importance included native gold,
silver minerals, sphalerite, and galena. Many of the deposits were affected by
supergene enrichment.
Gold placers in the Breckenridge District were first mined in 1859 followed
by the mining of gold veins in 1880 and of the lead-silver-zinc ores starting in 1869.
The Wellington Mine was the most productive mine in the area which began mining
sil\er-lead ore in 1910. In addition, between 1859 and 1879. $7,000,000 in gold was
produced from the placer deposits o f the Blue River and its tributaries. Later, in
20 w
Figure 3.3. Mine druinuge (pM=6.8) al ihe l'iger Mine (leIt) located in the Swan River basin, and effluent (pi 1=7.0) from the Wellington Mine (right) draining through dredge tailings in French Gulch. LS9S gold dredges were introduced and recovered an additional $7,000,000 in gold through 1937.
Figure 3.3 shows mine drainage from an adit at the Tiger Mine along the
Swan River and from the Wellington Mine flowing through dredge tailings in French
Gulch.
3.1.3 Tenmile Creek Basin
The two major bedrock types in the Tenmile Creek basin are the Precambrian
Silver Plume Granite and Idaho Springs Formation (schist). The Precambrian rocks are overlain by Paleozoic and Mesozoic sedimentary rocks including sandstones, siltstones. mudstones, dolomite, quartzites. and conglomerate. Tertiary quanz monzonites intrude the Precambrian rocks and have caused significant hydrothermal alteration, especially near the Clima.\ porphyry stock where veins containing molybdenite, pyrite, and quartz were formed. In addition, glacial deposits of
Quaternary age e.xist throughout the basin (Lamey. 1966).
The Precambrian rocks in the Tenmile Creek basin are part of a regional doubly plunging anticline characterized by complex folding. Folding also deforms the overlying sedimentary rocks, but the structures are less complex than those of the underlying Precambrian basement (Lovering and Goddard. 1950).
The Climax Molydenum Mine and one of the tailings ponds are shown in
Figure 3.4. The t'lrst ore was produced from this mine in 1915. but production
increased significantly between I9I7-1918 and 1942-1948 during World War I and
World War II. respectively (Lamey. 1966). Presently the mine is not at full-scale
operation. Figure 3.4. Photograph of the Climax Molybdenum Mine and part of the Robinson Climax tailings ponds. The telephone pole is approximately 30 feet high for scale.
23 The major ore mineral mined at the Climax Mine was molybdenite in stockwork vein deposits associated with hydrothermal alteration caused by the intrusion of the Climax porphyry stock. Low quantities of galena, sphalerite, rhodochrositc. and lluoritc also occur in veins near the contact of the stock and the
Prccambrian rocks (Lovering and Goddard. 1950). Small prospect tunnels and holes that date back to the 1860s occur throughout the area, but none as significant as the
Climax .Mine ( Voynick. 1996).
The Climax .Vline produced 453.451.153 pounds of Mo from 1913 to 1953.
In addition. 1.973.086 pounds of WO 3, 121.420 pounds of tin. and 65.000 pounds of p\rite were extracted (Lamey. 1966). Three large tailings ponds (Figure
3.4) remain near the Climax Mine and water that drains from these ponds is diverted through a \\ater treatment plant and then discharged into Tenmile Creek.
3.1.4 Origin of Ore Deposits in the Dillon Watershed
The ore deposits in the Snake River. Blue River, and Tenmile Creek basins arc the result of magmatic intrusions, which caused fracturing and hydrothermal activity in the country rock. The metals that form the ore deposits originated either from subducted metal-rich sediments that are now represented by intrusive bodies or
from the surrounding Prccambrian basement rocks. Marine sediments and sultlde-
rich deposits produced by submarine volcanism at ancient seafloor spreading ridges
were subducted under the North .American craton as the North .American plate
overrode the Pacific plate. The metals were subsequently incorporated into the
magmas that t'ormed the Tertiary plutons and were ultimately deposited by
hydrothermal fluids in fractures to form vein deposits. Alternatively, metals may-
24 have been leached from the Precambrian basement rocks, in particular the Idaho
Springs Formation and the Swandyke Gneiss (Table 3.1). whose protoliths formed by sedimentation and volcanic activity in an ocean basin. Therefore, as hydrothermal tluids passed through the Precambrian country rock, additional metals were added to the tluids from which the vein deposits as well as disseminations of ore and gangue mineral were deposited.
3.2 Hydrology
The drainage basins for the Snake River. Blue River, and Tenmile Creek in
Summit County and their tributaries are shown in Figure 3.5. The hydrographs of these rivers for the period of September 1998 through October 2000 in Figure 3.6 and of the Blue River Dam Outtlow indicate that high and low flow conditions tor each stream occur seasonally with high How in early summer and low tlow lasting from late autumn through early spring. The identification numbers of the gauging stations from u hich the average monthly discharge values were obtained are: 09047500
(Snake River). 09046600 (Blue River In tlow). 09050100 (Tenmile Creek), and
09()5()70() (Blue River dam outtlow) (USGS. 2001).
The drainage basin of the Snake River covers an area of 57.7 square miles.
The major tributaries to the Snake River include Peru Creek. Deer Creek, and Sts.
John Creek. The highest daily discharge that occurred during the period from
September 1998 to October 2000 was 499 tV/s (July 1999) and the lowest daily discharge of 9 ft '/s occurred in February of 1999.
2o Reëervo:
North Tenmile
r4 ^v!2L2ïia. ‘ Bre cke nrldge j
\Kokomo
•o Climax Tailinas
Climax
5 km
Figure 3.5. Snake River. Blue River, and Tenmile Creek basins, showing their major tributaries and the Dillon Reservoir. ( modified after De.xheimer. 19821
26 2000
Snake River ^ 1500
S 1000
500
2000 Blue River inflow
Cl 1500
1000
500
2000 Tenmile Creek
UÎ 1500 t3 O) 1000
500
0
2000 Blue River Dam Outflow cn 1500 Ü o C) Ç5 1000 u
~ 500
3/1/99 9/1/99 3/1/009/1/98 9/1/00 time (montfis) Figure 3.6. Hydrographs o f the Snake River. Blue River. Tenmile Creek, and the outflow from the Dillon Reservoir into the Blue River for the period of September 1998 through October 2000.
17 The Blue River drains an area of 121 square miles and has two major tributaries, the Swan River and the French River. The highest daily discharge during the period from September 1998 to October 2000 of the Blue River was 593 ft '/s and the lowest discharge was 17 ft Vs during March 1999.
Tenmile Creek has a drainage area of 93.3 square miles and has higher average monthly discharge than the Snake River and Blue River. The highest daily discharge that occurred in the time period from September 1998 to October 2000 was
T'O ft Vs in June 2000 and the lowest discharge was 17 ft'Vs in February 1999.
The average monthly discharge in the three streams w ill be used in Chapter 8 to calculate weighting factors that w ill be used to estimate the concentrations of major and trace elements in the water entering the Dillon Reservoir. The average chemical composition of the water in each of the major streams discharging into the Dillon
Reservoir reflects the geology and types of ore deposits of each basin. The chemical composition of the acid-soluble sediment in the reservoir w ill be discussed in Chapter
The citizens living in the communities in the Snake River basin are concerned about the water quality and possible increase in concentrations of trace metals in the
Snake River. The reason for their concern is a proposed ski area in the Arapahoe
National Forest in the basin of the North Fork. .According to the proposal, water would be withdrawn from the North Fork to make snow for the ski area thereby temporarily reducing the discharge into the Snake River. The data in Chapters 4 and
28 5 describe the geochemistry o f the Snake River basin and provide information that may be useful to those concerned about the impact of the proposed ski area on the water quality of the Snake River.
29 CHAPTER 4
ENVIRONMENTAL GEOCHEMISTRY OF THE SNAKE RIVER BASIN
4.1 Introduction
The Snake River originates near the continental divide in southern Summit
County where it Hows over Precambrian gneisses and recent ferricrete deposits. .As the u ater in the Snake River Hows downstream, it mixes with water from its trihutanes including Deer Creek. Sts. John Creek, and Peru Creek. Sts. John Creek carries drainage from the abandoned Sts. John Mine. In addition, the Burke Martin
.Mine is located on the Snake River upstream of the village of Montezuma. Peru
Creek drains several abandoned mines including the Shoe Basin Mine and the
Pennsylvania Mine.
Water samples were collected along the Snake River to determine changes in
Its chemical composition that may be attributable to the discharge of acid mine
eftluent. The results o f this work revealed that major changes occur in the chemical
composition of the Snake River before it discharges into the Dillon Reservoir.
30 4.2 Methods
Water samples were collected from the Snake River Basin from the Snake
River and its tributaries (Deer Creek. Sts. John Creek, and Peru Creek) during low flow conditions in late September and early October of 1995 (Figure 4 .1 ). In
Snake River Basin Montezuma Mining District Colorado
Dillon SR-7 Reservoir SR-5 Montezuma / Saints John Creek Deer Creek ncR -2\sR -i
DCR-1
Miles T ® Kilometers ^
Figure 4.1. Map of the Snake River Basin. Stream sample locations are labeled, e.xcept for SR -8 and SR-9, which were collected further downstream near the mouth of the Snake River.
31 addition, samples of groundwater, mine drainage, and fresh snow were collected from various parts of the drainage basin. A ll samples were stored in 500 mL polyethylene bottles. The pH of all water samples was measured in the field.
The samples were filtered through 0.45 p.m filters under vacuum and acidified with reagent-grade nitric acid. The filtered and acidified samples were analyzed by
ICP-OES for major and trace element concentrations, which are reported in .Appendi.x
E.
4,3 Results and Discussion
The pH of the Snake River in Figure 4.2 increases from about 3.1 at its head to about 6.0 after it mi.xes with Deer Creek. Subsequently, the pH continues to increase slightly as the water flows toward the Dillon Reservoir. The pH of the Snake
River is not significantly affected by mixing with Sts. John Creek or Peru Creek because the pH of both streams is similar to that of the Snake River. The water in
Peru Creek has a pH of 4.5 Just downstream of the Pennsylvania Mine, but by the time the water flows into the Snake River, the pH increases to 5.3 (PC-2. Figure 4.1).
Because of the significant increase in pH of the Snake River water at the confluence w ith Deer Creek, further investigation of this site was undertaken to
determine w hether the pH is controlling the chemical composition of the stream
water.
32 10 SJC-1 8 DC-2
7 6 I X ■' o O Q. ; 3 PC-2 4
2
10^ 15 ^ 20 25 distance downstream (km)
Figure 4.2. Variation of pH along the Snake River. Note that acidic water of the Snake River is neutralized by water from Deer Creek (DC-2) whereas the Sts. John Creek (SJC-1 ) and Peru Creek (PC-2) do not change the pH of the Snake River appreciably.
The concentrations of conservative ions in streams are controlled by mi.xing with tnbutarics and groundwater and by dilution with meteoric water. Changes in pH of the Snake River at its confluence with Deer Creek and other tributaries are not likely to affect the concentrations of alkali metals, alkaline earth metals, or sulfate because the hydro.xides of these elements are generally soluble, except for .Mg(OH):
(Faure 1998). In addition, the sulfate ion may form complexes with cations if the concentrations are high enough. Theobald et al. ( 1963) originally described the presence of Fe, ,A1, and Mn-rich coatings on the stream bed below the confluence of the Snake River and Deer Creek and reported that these precipitates contained Co, Ni,
Cu, Zn, Pb and ,Ag in concentrations ranging between 10 and 700 ppm. The presence
33 of these coatings indicates that Fe, A i, Mn and the trace metals are non-conser\'ative
in the Snake River.
In order to determine whether Na. Ca. Mg, and S are conservative in the water of the Snake River at the confluence with Deer Creek, samples SR-2. DC-2, and SR-3
in Figure 4.3 were used to plot mixing diagrams.
2.5 E Q. SR-3 R-2 a. CO z DC-2
SR-2 !
Mg ppm
Figure 4.3. Two-component mixing model for water in the Snake River (SR-2) with water of Deer Creek (DC-2). The concentrations of Na. Mg and S of the mixed water (SR-3) fit the mixing model, whereas Ca is enriched bv 16.8%
34 The results indicate that Na. Mg, and S are conservative because SR-3 fits the two-component mixing lines defined by SR-2 (Snake River) and DC-2 (Deer Creek).
However. Ca does not behave conservatively because its concentration increases by
16.S ^. as indicated by the fact that SR-3 lies above the mixing line. The Ca concentration of the Snake River in Figure 4.4 continues to increase as a function of
30 O SJC-1 25 5 ^ S 20 â 15 ‘ ' CO DC-2 o ^ 10 0*0 4 PC-2 7 8
5
0 5 10 15 20 25 distance downstream (km)
Figure 4.4 Variations in the Ca concentration of the Snake River water and its tributaries Deer Creek (DC-2). Sts. John Creek iSJC-l). and Peru Creek (PC-2). The Ca concentration continuallv increases from SR-I to SR-5.
distance downstream from SR-l to SR-5 presumably due to leaching o f Ca from bedrock and soil by the acidic water in the upper Snake River basin.
Other major elements were also tested for conservative or non-conscrvative beha\ ior in the Snake River. Two component-mixing diagrams for Fe. .4.1. and Mn in
Figure 4.5 reveal that concentrations of these elements in the water downstream of the contluence (SR-3) plot below the mixing line between SR-2 and DC-2. .Vccordingly,
35 400
SR-2! & 200 0) DC-: ^ 100 SR-3
5000 -, 4000 Q. 3000 SR-2 ^ 2000 DC-2 1000 SR-3
1000 800 SR-2 ■§- 600 I 400 SR-3 200 DC-2 0 0 1 2 3 4 5 6 Mg ppb
Figure 4.5. Two-component mi.xing of the Snake River water and Deer Creek water. A-C. Concentrations of Fe, Al. and Mn in the water collected above the confluence of Snake River (SR-2) and Deer Creek (DC-2) and below the confluence (SR-3) in the Snake River.
the Fc concentration in the Snake River is decreased by 37.8%. the Al concentration is decreased by 75.5%. and the Mn concentration is decreased by 16%. indicating that these elements are being removed from solution by the formation of hydroxide precipitates that coat the bottom of the stream at the confluence.
The concentrations of Zn. Cu. and Co in the Snake River (Figure 4.6) also decrease. The Zn concentration decreases by 19.4%, Cu concentration decreases by
36 600 500 X3 400 SR-2 Q. o- 300 N 200 SR-3 100 DC-2 0 30 SR-2 rj CL
DC-2 4 SR-3
20
15 SR-2 Q. DC-2 o 10 SR-3 O 5
0 0 1 2 3 4 5 6 Mg ppb
Figure 4.6. Concentrations of Zn. Cu. and Co in the water at the confluence of Snake River (SR-2) and Deer Creek (DC-2) and below the confluence in the Snake River (SR-3).
72.2'r. and Co concentration decreases by 28.6%. indicating that these elements are also not conservative.
Photographs of the confluence of the Snake River and Deer Creek taken in
June 1999 and September 1998 in Figure 4.7.A-B indicate that the streambed is coated with orange, tan. and black coatings in September (Figure 4.7B): but in June, during snow melt, the discharge of both streams increases sufficiently to prevent the
37 precipitates from accumulating on the streambed (Figure 4.7A). Because of the evidence that the trace elements are non-conservative, further investigations were
undertaken to study the process by which the trace metals are sorbed by the
precipitates and how the precipitates are ultimately transported into the Dillon
Reservoir.
•Additional information that evolved from this preliminary study was the effect
of mine water and natural rock drainage on the chemical composition of groundwater
in the vicinity of .Montezuma. Because the concentrations of major conservative
elements are the result of mi.xing of meteoric water, groundwater, and mine water, the
concentrations of Mg and S in Figure 4.S demonstrate that mine water has the highest
concentrations of both Mg and S. whereas meteoric water contains very low
concentrations of these elements and groundwater is intermediate in composition.
The approximately linear relation between the concentrations of M g and S indicates
that the local groundwater is a mi.xture of mine effluent and meteoric water and that
e\ cn the mine water has a wide range of chemical compositions because it is variably
diluted by groundwater and meteoric water. The contamination of the groundwater is
a concern for people in the region who drink the water because the mine water that
mixes with groundwater has elevated concentrations of S and many metals derived
from mineralized bedrock.
The results of this preliminary study prompted a further investigation of
weathering of mineralized rocks in the Snake River Basin in order to determine the
chemical composition of water produced by weathering ore specimens in the
38 SlUlkc Rl\ Ul'
B
■ a s - '
Figure 4.7. Photographs of the Snake River/Deer Creek contluence looking upstream. A. The confluence during high discharge in June 1999. B. The contluence during low flow in September 1998 with orange, tan and black coatings on the streambed.
39 140
120
100 mine/rock water E 80 Q. Q. 60
40 ^ ground water 20 meteoric water 0 10 15 20 25 Mg ppm
Figure 4.8. Concentrations o f Mg and S in mine water, groundwater, and meteoric water in the Snake River Basin. The mine water is enriched in S and Mg as e.xpected.
laboratory and to compare the synthetic solutions with samples of mine effluent collected at the Shoe Basin Mine and the Pennsylvania Mine.
4.4 Conclusions
In summarv’. the preliminary results presented in this chapter offer insight into contamination of the surface and groundwater in the Snake River Basin by .A.VID as well as by .ARD which is produced by natural weathering of mineralized rocks.
Because of significant decreases in the concentrations of Fe. Al. Mn. Zn. Cu. and Co in the Snake River water at the confluence with Deer Creek, further investigation of
40 this site was undeiiaken to determine what controls the major and trace element concentrations of the precipitates. The results from that study are presented in
Chapter 5. In addition, a laboratory' study was performed on the weathering of sulfide ores in the Peru Creek watershed to explain the effect of mine drainage on the composition of Peru Creek water. The results of that study are presented in Chapter
6.
The results of these investigations are relevant to an understanding of the chemical and mineralogical composition of the sediment accumulating in the Dillon
Reservoir. The hydroxides of Fe and Al which form when acidic water is neutralized, arc Hushed into the Dillon Reservoir during snowmelt and been accumulating for the past 36 years. Therefore, the sediment may contain high concentrations of trace
metals, which w ill create an environmental hazard when the metal-rich sediment must be disposed of after it is dredged from the reservoir. The contamination of surface and groundwater by drainage from mines and natural weathering of mineralized rocks poses a potential risk to plants, animals, and humans. This work is intended to demonstrate innovative ways to study the distribution and fate of potentially toxic
trace elements in the environment.
41 CHAPTER 5
SORI*TION OF TRACE METALS TO AN ALLMINUM PRECIPITATE IN A STREAM RECEIVING ACID ROCK-DRAINAGE: SNAKE RIVER, SLTVIMIT COLmV, COLOR/\DO*
5.1 Introduction
When sulfide minerals such as pyrite are oxidized at or near the surface of the earth, ground and surface waters typically become acidic and are enriched in SO 4. Fe,
Al. and trace elements (Wentz, 1974). Some of the mobilized trace elements associated with acid drainage pose a potential threat to the health of plants, animals, and humans (.Adriano. 1986; McBride. 1994). .As acidic Fe- and Al-rich streams are
neutralized, amorphous to semi-crystalline oxyhydroxides and hydroxysulfates of Fe or .Al can form (Stumm and Morgan. 1996). These precipitates have surface sites that
sorb cations and anions depending on their charge, which is primarily controlled by
the pH of the surrounding solution. The suspended particles and precipitates on the
bottom of stream channels are transported downstream during periods of high How
and may be deposited in lakes and reservoirs.
" Chapter 5 has been accepted for publication in Applied Geochemistr,\
42 The Snake River in the Dillon watershed. Summit County, Colorado, provides an opportunity to study the distribution o f trace elements between water and precipitates that are composed predominantly of an Al-hydroxysulfate. This uatershed lies within the Colorado Mineral Belt, which has been mined for Au, Ag, and various sulfide minerals since the 1860s (Lovering and Goddard, 1950).
Although mining was discontinued in the 1930s, some of the streams are still contaminated by acid mine-drainage (AM D) as well as by acid rock-drainage (.ARD).
The drainage basins of the Snake River and Deer Creek are underlain by granitic gneisses (Idaho Springs Formation and Swandyke Hornblende Gneiss, respectively) of Precambrian age that were intruded by Tertiary quartz monzonite plutons
( Lovering. 1935). The bedrock contains disseminated pyrite as well as quartz veins w ith pyrite and other metallic sulfides (Loveiing and Goddard. 1950). Whole-rock chemical analyses indicate that the Idaho Springs Formation is A l- and Si-rich, whereas the Swandyke Hornblende Gneiss has relatively high concentrations of Ca.
Mg. and Fe.
Theobald et al. ( 1963) reported the presence of brown, tan. and black precipitates on the streambed at the confluence of the Snake River and Deer Creek and determined that some of these precipitates contained Fe. Al, Mn, and the trace
metals Pb. Cu. and Zn. McKnight and Bencala (1988. 1989) subsequently showed that Fe concentrations in the Snake River vary hourly due to photoreduction of Fe'^ to
Fe'*. In addition. McKnight et al. (1992a) correlated the concentrations of Fe and
organic carbon in the precipitates with decreasing metal concentrations and suggested
43 that this relationship implies that some metal cations are sorbed onto humic substances in the precipitates.
Numerous laboratory investigations of trace element sorption to Fe- hydroxides have provided a basis for understanding the partitioning of trace elements between solution and sorbent (Ballistrieri and Murray, 1982; Dzombak and Morel.
199Ü; Stumm. 1992). In addition, field studies addressing various aspects of the transport and fate of metals in waters receiving .AMD by Rampe and Runnells (1989).
Broshoars et at. ( 1996). Scheme) et at. (2000). and others have provided information about the interaction of multiple variables such as pH. sorbent composition, dow nstrcam transport, etc. that control the distribution of trace metals in natural aquatic environments.
The objective of this study was to test the hypothesis that the partitioning of trace metals in the Snake River at and just below its contluence with Deer Creek is controlled predominantly by an increase of pH and the resulting precipitation of an
.Al-hydroxysulfate. This study is linked to the overall objective to investigate the
weathering of mineralized rocks in the drainage basin of the Snake River and to study
the geochemical processes that control the concentrations of trace elements in the
Dillon Reservoir, which is one of the principal sources of drinking water for the city
of Denver.
5.2. .Methods
5.2.1 Water and Precipitate Samples
Water and samples of tan to white tlocculant precipitates were collected from
the streambed over a 60 m interval at the confluence of the Snake River and Deer
44 o sample site To Dillon ★ water sample site Reservoir for neutralization experiment
culverts
Mixing zone
Deer Creek
10 meters
50 feet
105'52'30'W 39'30'32.5‘N . .
Figure 5.1. Map of the Snake River/Deer Creek confluence. The sample sites 1-7 are where both water and flocculent precipitate were collected. The star indicates where a large sample of Snake River water was collected for the neutralization e.xperiment.
45 Creek (Figure 5.1 ). Precipitates were collected using a 60-mL polypropylene syringe with attached plastic ™Tygon tubing. The precipitates and associated water were transferred to high-density polyethylene bottles that were rinsed with stream water at each collection site. In addition, the pH was measured twice at every sampling location. The water and precipitate samples were refrigerated immediately upon returning to the laboratory, and within 2 days the samples were centrifuged and the supernatant water was decanted, filtered through 0.45 pm filters, and acidified by adding 1-2 drops of concentrated reagent-grade HNO;,. Our laboratory results show ed that 0.45 pm filters removed 98.4 percent by weight o f suspended solids from the water samples used in this study. Other workers such as Schemel et al. (2000) and McKnight et al.( 1992b) have also used 0.45 pm filters to separate suspended
panicles from natural waters. .A. blank was prepared with the deionized water that
w as used for all laboratory procedures in this study. The water used as a blank was exposed to the same type of sample bottle, filtered using the same filtering apparatus,
and acidified w ith HNO 3 in the same way as the water samples. The concentrations
of trace metals detected in this blank are reported in the Appendix. The only
elements that were above detection limits were: Mn (0.2 ppb). Sr (0.2 ppb), Cu (0.3
ppb). Pb (0.02 ppb). Zn (2.0 ppb). Ni (0.1 ppb). and Cd (0.02 ppb). Therefore, no
blank corrections were necessary for any of the elements included in this study.
The precipitates were dialyzed in order to remove any soluble salts by using
Spectra/Por dialysis tubing with a wet tube diameter of 48 mm and a molecular
w eight cut off of 12.000-14.000 Daltons. The deionized water surrounding the
dialysis tubing was changed every 48 hours for one week (Winland et al.. 1991 ). The 46 precipitates were subsequently freeze-dried and X-ray diffraction patterns were obtained using top-fill powder mounts and CuKa radiation on a vertical, wide-range goniometer (Philips PW 1316/90) equipped with a theta-compensating slit, a 0.2 mm receiving slit and a diffracted-beam monochrometer. Specimens were scanned from
10 to 70' 20 with a 4 second step time and a O.Oa'^ 28 step interval. Peak positions were determined by using the Jade 3.0 software by Materials Data Inc.
.•\pproximateIy 50 mg of the precipitates were dissolved in 75 mL of reagent-grade
2M HCI, centrifuged, decanted, and diluted to 100 mL with additional 2.VI HCl in volumetric 11 asks. The precipitates were found to be between 96.2% to 99.9% acid soluble with quartz as the primary mineral residue. The precipitates were analyzed tor total organic carbon by Huffman Laboratories, Golden, Colorado, using standard methods.
The concentrations of trace elements in the water and in the dissolved precipitates were determined by XR.AL Laboratories in Toronto.Canada by ICP-MS.
w hereas concentrations of major elements were measured by ICP-OES. Detection
limits for both methods are presented in Tables 1 and 2.
The sulfate concentrations of the water and precipitates were determined by
precipitation of BaSCL after adding 5.0 mL of saturated BaCL solution to known
volumes of sample solution. After a period of 5 days, the BaSCL solids were
recovered with 0.45 pm filters, air-dried, and weighed.
2.2 Neutralization E.xperiment
In order to determine the fraction of trace metals sorbed as a function of pH, a
sample of Snake River water was progressively neutralized. Water collected from
47 just above the confluence with Deer Creek was filtered through a 0.45 p,m filter, and
150 mL aliquots were placed into seven separate 200 mL Pyrex beakers. The initial
pH of this water was 3.1 when measured in the laboratory. One sample served as a
reference for the remaining six subsamples, which were neutralized by adding a
saturated solution of NaOH dropwise to obtain final pH values of 4.2. 4.8. 5.7. 6.0.
6.4. and 6.7. The solutions were stirred once a day for one week and the pH of each
beaker was measured daily until it stabilized. The increase in pH caused white
precipitates to form, which were similar in appearance to those collected in the field.
Afier recovering the precipitates by filtering through 0.45 |.im filters, the filtered
solutions were acidified with reagent-grade HNO 3 and were analyzed for major
elements by ICP-OES and for trace elements by ICP-MS. Sulfate concentrations
were determined by BaSCL precipitation as described above. The fraction sorbed of
each element w as calculated from the observed decrease in the concentrations of the
filtered solutions as compared to the control solution in the first beaker. A ll ion
activities were calculated using the PHREEQC Interactive computer spéciation model
( Parkhurst. 1995).
5.3. Results and Discussion
5.3.1 Precipitate Mineralogy and Metal Sorption at the Snake River/Deer
Creek Confluence
The pH of the Snake River increases from 3.0 above the confluence to 6.3 just
below the confluence with Deer Creek and then stabilizes at 5.2-5.3 further
downstream where the water is more completely mixed (Figure 5.2). .A flocculent tan
to w hite precipitate occurs on the streambed in the mixing zone and further
48 downstream. Chemical analyses indicate that the precipitates collected from the
Snake River streambed are composed predominantly of Al-hydro.xysulfate with significant quantities of associated Fe and organic carbon (Appendix D). X-ray diffraction analyses of the tan to white precipitates yield broad diffraction bands centered at about 4.4. 2.2. and 1.5 Â that are indicative of a material with very shon- lange structural order. No further retlnements of the precipitate mineralogy were attempted. The most abundant trace metals in the precipitates include; Zn. Cu. Pb.
Ni. Cr. and W (Appendix D). Concentrations of Zn, Cu. Pb, and Ni in the streambed precipitates are shown in Figure 5.2 increase with rising pH and then decrease again farther dow nstream as the pH decreases.
In order to describe the distribution of cations between water and precipitates forming at the confluence, the concentration ratio iCR) is introduced, which is defined as:
"'TK-
Where (.V), is the concentration of an element in the precipitate and (X)/ is the concentration of the element in the associated water. This parameter is not necessarily identical to K j because it is not certain that equilibrium existed between the flowing water and the precipitates that accumulated on the streambed. In addition, an unknown fraction of the precipitate collected at each site may have been transported from locations upstream. The concentration ratio (CR) should therefore be thought of as an enrichment factor, because the concentrations of metals in the accumulated precipitates are up to three orders of magnitude higher than those
49 15000.0 2 10000.0 ^ 5000.0
450.0 Cu 2 300.0 ^ 150.0 0.0 400.0 Pb
Q . 200.0 Q.
0.0 300.0 2 200.0 100.0 0.0
150000 2 100000 ^ 50000 0 0 20 40 60 distance downstream (m)
Figure 5.2. Changes in pH as a function of distance downstream at the Snake River/Deer Creek confluence. Concentrations of Zn. Cu. Pb. Ni. and SO 4 (ppm) in the precipitates formed at the Snake River/Deer Creek confluence as a function of distance downstream.
50 measured in the water. Nevertheless, the numerical values of log CR for the metals included in this study increase with rising pH as expected for log K j with log CR Pb
> log CR Cu > log CR Zn > log CR Ni. At pH 5.3 in the stream, log CR Pb is 5.3. log CR Cu is 4.S. log CR Zn is 2.4. and log CR Ni is 1.9. This sorption sequence is in agreement with laboratory experiments reported by Dzombak and Morel ( 1990) for the K,j of these trace metals sorbed on fresh precipitates of hydrous ferric oxide.
Trace elements are concentrated in the precipitates that form along the Snake
River channel, whereas the water in the mixing zone at the confluence is depleted in these elements. The mixing zone is defined by samples 1. 2. and 3 in Figure 5.1. The data in .-\ppendix D indicate that 75 percent or more of the dissolved Zn. Cu. Pb. Ni. and Co are removed from the water over a distance of only 12 m. .As a result, the quality of the water that flows through this geochemical mixing zone is significantly improved. The concentrations of trace-metals in water samples 4 through 7 are slightly increased (.Appendix D). probably due to the decrease in pH downstream. In addition, the interaction of acid water with two galvanized metal culverts under the road in Figure 1 may contribute some Zn and Fe to the Snake River water.
.According to single-element batch experimental data, cations should sorb least at low pH due to the net positive charge of oxyhydroxide surfaces (Dzombak and
Morel. 1990 and Langmuir. 1997). However, the precipitates formed at the confluence of the Snake River and Deer Creek have high concentrations of Cu (180 ppm) and Pb (220 ppm) even though the water is distinctly acidic (pH = 3.6). Zinc and Ni are also sorbed at pH = 3.6. but their concentration ratios {CR) are lower than
51 those of Pb and Cu. The most likely explanation for this phenomenon is that sorption of cations at low pH is facilitated by the presence of sulfate anions that form bridging complexes between positively charged sites on the sorbent and the sorbate cation.
Webster et al. ( 1998) showed that sulfate ions enhance the sorption of Pb, Cu. and Zn onto natural mine-drainage precipitates and synthetic specimens of schwertmannite and ferrihydnte.
The presence of humic substances may also enhance the sorption of some trace metals (McKnight, 1992b): however. Smith et al. (1999) reported that the presence of natural organic matter (NOM) in acid sulfate waters containing high concentrations of Fe and A1 did not enhance the sorption of cations. Similarly.
Webster et al. ( 1998) reported that the presence of humic acids had a negligible effect on the sorption of Cu to ferric hydroxides. In addition. A li and Dzombak (1996a.
1996b) demonstrated that at low pH sulfate ions compete extremely well with simple organic acids for sorption sites on goethite. and that the presence of sulfate ions enhances the sorption of Cu‘ ^ by forming ternary complexes. Most recently. Zuyi et al. ( 2000) reported that, in the pH range 4 to 8 . variable concentrations of fulvic acid do not increase the sorption of Zn to surfaces of .A 1;0:,. but that fulvic acid does compete for sorption sites with univalent inorganic anions such as I ". Therefore, humic substances appear only to enhance cation sorption at low pH in solutions that lack high concentrations of divalent anions such as SOj.
In accordance with sorption theorv. the concentrations of trace metals in the precipitate downstream of the confluence should remain high because sorption of cations is favored at elevated pH values of 5 to 6. The reason for the comparatively
52 lower observed concentrations of trace metals in the precipitate downstream of the confluence is that significant amounts o f metals were removed from the water upstream in the mixing zone. Therefore, trace-metal concentrations of the precipitates are not only pH dependent, but are also a function of the distance downstream from the point of contamination due to the rapid depletion of trace metals by precipitation/sorption reactions.
5.3.2 Sulfate and Organic Carbon at the Snake River/Deer Creek Confluence
Many metallic and nonmetallic elements form oxyanions in well-oxygenated surface waters. These ions are preferentially sorbed at low pH. but desorb as the pH rises. .Aecordingly, the SO 4 concentration of the precipitates decreases from site I
I pH = 3.6) to site 3 (pH = 6.3) and then increases again downstream as the pH decreases to 5.2-5.3 (Figure 3.2). Organic carbon concentrations also decrease as a
function of distance downstream (Figure 3.3) and appear to be correlated with Fe. but
not with .Al. as reported by McKnight et al. (1992b).
In the Snake River. SO 4 is removed at pH = 3.6 due to the formation of an .Al-
hydroxysulfate precipitate and because of sorption of SO4 to the surfaces of the
.Al(OH)'. The concentration of SO4 in the precipitates at pH 6.3 is lower than at pH
3.6. either because microcrystalline gibbsite (A 1(0 H)3) formed or because of
desorption of some of the SO4. or due to a combination of both processes. Farther
downstream the concentration of SO4 in the precipitate increases again because the
pH decreases from 6.3 to 5.2. which is optimum for the precipitation of hydroxy Al
sulfate.
53 300000 - - AI 250000 • • Fe 200000 Q. 150000
100000 50000
0 10 20 30 40 50 60 distance downstream (m)
Figure 5.3. Concentrations of Al, Fe. and OC (organic carbon) in the precipitates as a function of distance downstream.
5.3.3 .Neutralization Experiment
In order to understand how trace elements are distributed between water and the precipitates that form in the Snake River at its confluence with Deer Creek, a sample of Snake River water, collected above the confluence, was progressively neutralized in the laboratory. .As the pH increased to 4.8 and above, the amount of white precipitate increased (Figure 5.4). The activity of .W* in these solutions begins to decrease near pH 4.8 in Figure 5.5. which also corresponds with the lowest SO: activity in Figure 5.4. These results indicate that at and above pH = 4.8 the solutions were in equilibrium with .Al-hydro.xysulfate and/or solid A1(0H)3, which is in agreement with results reported by Nordstrom and Ball ( 1986) for Al-rich acid- contaminated waters. The concentrations of trace metals in the filtered water prior to
neutralization were; Pb = 71 ppb. Cu = 96 ppb. Zn = 499 ppb. and Ni = 20 ppb. The
fraction of Pb. Cu. Zn. and Ni sorbed increased with increasing pH (Figure 5). At pH 54 = 4.s. Pb and Cu were 75 percent sorbed, whereas Zn was only 11 percent sorbed and
Ni w as 1S percent sorbed. Lead was completely sorbed at pH = 5.7 and Cu at pH =
6.4. whereas Zn and Ni were not completely sorbed even at the highest pH (6.7)
reached in this experiment. Sulfate removal from solution began at pH = 4.2 with the
formation of the sorbent and maximum removal was reached at pH = 4.8, which
coiTcsponds to the first hydrolysis constant for .Al. Removal of SO 4 from solution
decreased w ith increasing pH. The activities of trace-metal ions indicate that the
solutions remained undersaturated with respect to all possible trace-metal salts over
the entire pH range. Therefore, trace metals were removed from the water by
sorption on the surfaces of solid .AKOH); and/or .Al-hydroxysulfate that formed rather
than by precipitation of insoluble salts. The concentrations of Fe were below the
detection limit in all of the solutions utilized for this experiment. The sorption of Pb,
Cu. Zn, and Ni in Figure 5.4 increases with increasing pH in the same sequence as
previously reported from laboratory experiments with simple solutions (Dzombak and
Morel. 1990 ). Therefore, the results of our neutralization experiment indicate that
sorption of ions from Snake River water was influenced by the composition and the
amount of sorbent that formed, and by the pH which controlled the solubility of the
sorbent and the polarity o f charged sites on its surface. Sorption of the trace metals
and removal of SO 4 did not begin until pH 4.2 in this experiment because of the
initial absence of sorbent in the filtered water.
0 0 Figure 5.4. Amount of sorbent (mg/L) formed as a function of pH. Sorption edges for Pb. Cu. Zn. and Mi. and percent removal of SO^ from neutralization of Snake River water. Filled circles are data points from this e.xperiment and the dashed curves are interpolated from solid line sorption curves reported by Dzombak and Morel ( 1990). The concentration of Alin the water of the Snake River was 1.5 .\ lO”* mol/L whereas. Fe ranged from 1.00 \ lO"^ to 1.00 10'^ mol/L in the experiments reported by Dzombak and Morel (1990). The concentrations of the trace metals in the Snake River and those that were used in the experiments in Dzombak and Morel ( 1990) were Pb = 3.4 x 10" (this study) and Pb = 5.(X) x 10" mol/L I Dzombak and Morel. 1990); Cu = 1.5 x lO^and 5.00 x 10" mol/L; Zn = 1.6 X 10 " and 7.58 x 10" mol/L; and Ni = 3.4 x 10" and 5.00 x 10" mol/L; SOj = 7.70 x 10 and was 1.00 x 10 " mol/L respectively.
56 ■2 •4 Al " in water ■6 8
12
•3.1
-3.2
3 -3.3 o SOj in water O) -3.4 o -3.5 3 4 5 6 7
pH
Figure 5.5 .Al * activity and SO 4 activity for the step-wise neutralization o f Snake River water as a function o f pH.
The sorption curves tor the cations in Figure 5.4 are compared to data reported by Dzombak and Morel ( 1990) for sorption on synthetic ferric hydroxide (dashed cur\cs). .A corresponding data set for sorption of trace metals to Al-hydroxysulfate or to microcrystalline A1(0H)3 has not been reported. Therefore, the data from
Dzombak and Morel ( 1990) were used for comparison even though in the neutralization experiment the sorbent was mostly an .Al-hydroxysulfate and/or
.All OH);, and the water contained a mixed suite of dissolved species. The sorption edges for Pb. Cu. Zn. and Ni derived by laboratory neutralization of Snake River water generally occur at lower pH than the sorption curves reported by Dzombak and 57 Morel {1990). The variation is attributable to one or more of the following factors: differences in the sorbate:sorbent ratio of the aqueous phase and in the composition of the sorbent, as well as the presence of SO 4 and dissolved organic material in the
Snake River water. Sulfate removal appears to be lower in the Snake River experiment compared to experimental results reported by Dzombak and Morel
( 1990). probably because the concentration of SOj in the Snake River is an order of magnitude higher and complete removal/sorption of all the SO 4 does not occur.
5.3.4 Sorption and Transport Processes at the Snake River/Deer Creek
Confluence
The pattern of trace metal concentration in the A 1-oxyhydroxide precipitates
in the channel of the Snake River is reproduced for Cu in Figure 5.6 by a simple calculation based on the results of the neutralization experiment described above.
The calculation assumes that water in the Snake River at pH = 3.0 contains 100
ng/mL of Cu as it Hows into the mixing zone where the pH rises to 6.3 due to dilution
w ith w ater from Deer Creek. According to the results of the neutralization
experiment. 90 percent of the Cu sorbs at pH = 6.0. Therefore. 90 ng of Cu are
sorbed from each mL of water in the stream, leaving only 10 ng/mL in the water.
Farther dow nstream at pH = 5.5. 85 percent of the Cu is sorbed causing 8.5 ng of Cu
to be removed by the precipitate and leaving 1.5 ng/mL in solution. Still farther
dow nstream at pH = 5.0. 80 percent of the remaining Cu is sorbed transferring 1.2 ng
of Cu to the precipitate for each mL of water such that its concentration is reduced to
0.3 ng/mL. Similar calculations were performed for the other trace elements, which
58 produced curves having similar shapes as that in Figure 5.6. Therefore, this empirical calculation adequately explains why the concentrations of trace metals in the
100 - .UJ
80 •a 0) 60 o 03 3 40 O c 0 ?0 P 0 Q. 0 10 20 30 40 50 60 distance downstream (m)
Figure 5.6. Predicted sorption of Cu obtained from sorption data points for Cu in the Snake River and changes in pH measured as a function of distance downstream. Numbers next to data points indicate the pH values used to interpolate percent sorbed from the experimental sorption data.
precipitate decrease downstream even though the pH of the water remains between
5.2 and 5.3. This calculation also demonstrates why the concentrations of trace metals in the Snake River decrease in the mixing zone at the confluence with Deer
Creek, thereby improving the water quality of the Snake River.
5.4. Conclusions
The Snake River is contaminated by acid rock-drainage. which results from the oxidation of pyrite and other sulfide minerals within the underlying bedrock of the drainage basin. .As the Snake River mixes with Deer Creek, chemically active. Al- hydroxysulfate precipitates form and sorb trace metals as the pH of the water increases. 59 Experimental neutralization of Snake River water shows that Pb. Cu. Zn, and
Ni are sorbed with increasing pH. whereas sulfate is initially removed from the water at low pH and is subsequently released as the pH increases. In addition, the neutralization experiment confirmed that there is a preferred sorption sequence such that Pb is removed at the lowest pH followed by Cu. Zn. and Ni. Sorption of trace metals at low pH is enhanced by the presence of anions such as SOa. which form ternary bridging complexes with the sorbent. The results of the neutralization experiment demonstrate that the sorption of trace elements can be effectively in\estigated by neutralizing natural water samples in the laboratory.
.A sorption/transport calculation that combines the results of the sorption experiment with observed changes in pH of the water reproduces the patterns of trace metal distribution at the Snake River/Deer Creek confluence. In addition, the ealeulation accounts for the progressive depletion of trace metals in the water and for the resulting improvement in water quality.
Therefore, the changes in pH of the environment control not only the formation and the composition of the sorbent, but also the partitioning of trace elements between water and the precipitates. The progressive downstream depletion of trace metals in the Snake River limits the amount of trace metals available for sorption farther downstream and results in an improvement in the water quality by natural processes.
60 CHAPTER 6
EXPERIMENTAL WEATHERING OF SULFIDE-BEARING ORES FROM THE PERU CREEK BASIN
6.1 Introduction
Pristine mine drainage water is difficult to sample in the field due to immediate mixing w ith meteoric and groundwater. Therefore, samples of ore from the Peru Creek drainage were weathered experimentally in order to determine the chemical composition of the acid mine drainage in the Peru Creek watershed. The objective of these experiments was to produce solutions in the laboratory by weathering crushed ore specimens and to compare the chemical composition of the resulting solutions to natural acid mine drainage w ater in the Peru Creek drainage. This study was undertaken because
I t is important to know the composition of all components of water in the Dillon
w atershed in order to achieve a geochemical mass balance of water in the drainage basin.
There are two abandoned mines along the upper part of the Peru Creek drainage:
the Shoe Basin Mine (SBM) near Argentine Pass and the Pennsylvania Mine (PM) which
61 Drainage Basin of the Snake River, Summit Count} , Colorado
Horse Shoe Basin Mine
/ Pennsylvania Mine Sts. John Creek
10 VOLES
10 KILOMETERS
Figure 6.1. Location map showing Peru Creek, the Shoe Basin Mine, and the Pennsylvania Mine.
62 is located fanher downstream (Figure 6. 1). Even though these mines are no longer in operation, metal-rich contaminated water is draining from both mines. The water coming out of the Shoe Basin Mine has a pH near 5.0. whereas that of the water at the
Pennsylvania Mine is about 2.8. The ore collected at the Shoe Basin Mine is composed predominantly of pyrite, hematite, and siderite in contrast to the ore at the Pennsylvania
Mine, \\hich is composed mostly of pyrite, galena, and quartz.
6.2 Methods
Representative ore samples from the Shoe Basin Mine (SBM) and the
Pennsylvania Mine (PM) were ground in a ™Spe.\Mi.xer M ill and the fractions equal to or less than 125 tim were used in both e.xperiments. Two-gram aliquots of the powdered ore from the SB.M were placed into five 250 mL beakers with 150 mL distilled water in equilibrium with CO: from the atmosphere. The mixtures of powdered ore and water were stirred using magnetic stirrers at room temperature for up to 22 days. A ir was continually bubbled into each solution to prevent H:S from forming and the pH of each solution w as measured at regular intervals throughout the duration of the experiment.
The first beaker was stopped after one day and the solid particles were allowed to settle prior to filtering the solutions through a 0.45 pm filters. The remaining beakers were stopped at 2. 4. 10. and 22 days. The filtered solutions were acidified with a small amount of nitric acid and analyzed by ICP-MS for trace metal concentrations and by ICP-
OES for major element concentrations by XR AL Laboratories in Toronto. Detection
limits for all elements are listed in the Appendix. The same procedure was followed for
the PM ore sample except that nine separate samples were prepared. The beakers were
progressively stopped at 1.2. 5. 10. 15. 25. 35. 45. 60 days to recover solutions for
63 chemical analyses. The concentrations of all ions were used to calculate the activities of all ionic species and their saturation indices by means of PHREEQC interactive
(Parkhurst. 1995). The results were used to determine whether any compounds could precipitate during the e.xperiment including hydroxides of Fe and Al.
6.3 Results and Discussion
6.3.1 Weathering of Ore from the Shoe Basin Mine
The pH of the solutions increased from 5.7 to 6.7 after approximately one day. and then decreased to 5.1 at the end of the experiment (Figure 6.2A). The initial pH of
5.7 was the result of allowing the deionized water to equilibrate with CO: in the atmosphere prior to starting the experiment. The pH increased to 6.6 during the first day of the experiment due to hydrolysis of the crushed mineral fragments and release of carbonate ions into solution. Subsequently, the pH decreased to 5.1 due to the oxidation of sulfide minerals such as pyrite, which causes the formation of Fe(OH); and the
subsequent release of IE ions as follows:
FeS: + H :0 + 7/20: Fe‘ ^ + 2H^ + 2SO4-
Fe-* + 1/40: + FT Fe"* + 1/ 2H :0
Fe"* + 3H :0 Fe(OH):, + 3H*
FeS: + 15/4 O: + 7/2 H :0 FefOH): + 2 S O / + 4 H*.
However, the solutions did not become strongly acidic due to the presence of carbonate
species in solution that buffered the pH. For example, when a carbonate mineral
dissolves in water: CO?''. HCO 3 . and H:CO; ions exist in solution and OH' ions are
64 released increasing the buffering capacity of the system. The following reactions illustrate what happens when a carbonate mineral dissolves in water, where X represents a divalent cation;
XCO3 + H;0 X-" + CO3- + HnO
CO3- + H ;0 ^ HCO? + OH
HCOi + H2O ^ H;C03 + OH .
pH
15000 Fe .aQ. 10000 Q. 5000
0
200 Al 150 â 100 50 ♦ ♦ 0 10 15 20 25
time (days)
Figure 6.2. pH profile of solutions over time for the SBM weathering experiment. Fe and .Al concentrations in solution over time. Dashed lines are used to connect data points because it is not known whether the concentrations increase or decrease linearly between data points.
65 10 8 6 supersaturated •ao 4 2 0 •equilibrium -2 -4 undersaturated -ô -8 -10 10 20 30 40 50 60 time (days)
Figure 6.3. Log saturation index vs. time in terms of the length of the weathering experiment. If log saturation index lies above the equilibrium line the solutions are supersaturated with respect to the solid phase and if log saturation index lies below the equilibrium line the solutions are understaturated w ith respect to the solid phase. If log saturation index lies on or close to the equilibrium line the solution is in a state of chemical equilibrium with respect to the solid phase.
The Fc concentration of the solutions ranged from < 50 ppb (detection lim it) to
13.000 ppb in the course of the experiment (Figure 6.2). After 24 hours, the Fe concentration of the water was still below the detection lim it of 50 ppb. However, it increased subsequently and reached 13.000 ppb after 10 days, but decreased to < 50 ppb at the end of 22 days. The solutions were at or near saturation with respect to ferric hydro.xide from day 2 to the end of the experiment. This was determined by the saturation indices calculated by PREEQC interactive. The log saturation index is equal to log l.-\P (ion activity product) minus the log Ksp for any given compound. In the case that log LAP is equal to log Ksp. the log saturation index is equal to zero the solution is
66 considered to be saturated, and a state of equilibrium exists between the ions in solution and the solid. If the log saturation index is negative, the solution is undersaturated with respect to the solid phase and if it is positive, the solution is supersaturated with respect to the solid phase (Figure 6.3)
From the beginning of the experiment to day 10, the concentration of Fe in solution continually increased because Fe was being released from the rock. .Alter day
10. the concentration of Fe in solution began to decrease, presumably because the rate at which Fe precipitated from the solution was faster than the rate it was released from the rock.
10
Fe(OH)aa^i -r AI(0H)3
10 0 1 2 34 5 67 8 9 10 11 12 pH
Figure 6.4. Congruent solubility of Fe(OH)j(am) and .AKOHlitam) as a function of pH. Thermodynamic data used to derive spéciation of Fe and .Al in equilibrium with Fe(OH)-. and Alt OH); respectively, from Faure ( 1998). am = amorphous
67 The Al concentrations of the solutions also varied and ranged from < 50 ppb
(detection lim it) to 180 ppb over the time of the experiment (Figure 6.2). Similar to Fe. the .Al concentration after day 1 was < 50 ppb and remained below the detection lim it for
2 days. Subsequently, the .Al concentration increased and reached ISO ppb on day 10 but then decreased to 120 ppb at day 22. The saturation index calculated by PHREEQC interactive indicates that the solution was saturated with respect to A l(O H )i from day 4 to
22. Initially. .Al was released from the rock faster than AKOH); could form. However, after day 10. the rate of Al precipitation exceeded the rate at which .Al was weathered
I'rom the rock and therefore, the concentration of Al in solution began to decline.
However, because .Al is more soluble than Fe at pH 5.1 (Figure 6.4). some .Al remained in solution at the end of experiment.
68 15000
■S 10000
0
8000
6000 K Q. Q. 4000 2000 0
15000 n Q. 10000 Q. oi 5000
0 20000 Ca 15000 Q. Q. ra 10000 o 5000 0 10 15 20 25 time (days)
Figure 6.5. Concentrations of Na. K. Ca. and Mg over time for weathering of ore from the Shoe Basin Mine.
The .\'a and K concentrations in Figure 5 increase continuously throughout the experiment. Sodium (Figure 6.5) increased rapidly from 1.000 ppb in the beginning of the experiment, to 9.000 ppb by day 4 and then continued to increase more gradually to
12.000 ppb by the end of the experiment. The concentration of K (Figure 6.5) remained
69 relatively constant (500-1.000 ppb) for the first four days and by day 10 increased to
1.500 ppb and reached 6.500 ppb by the end of the experiment. The reason why Xa was initially released faster than K is that most of the Na was probably contained within plagioclase feldspar which weathers at a faster rate than potassium feldspar. Neither Na nor K concentrations stabilized by the end of the experiment because these elements were continuing to be leached from the ore sample and their concentrations were not significantly reduced by precipitation or sorption reactions.
The concentrations of Mg and Ca have similar patterns as Na up to day 10 of the experiment (Figure 6.5C&D). The Mg concentration ranged from 3.000 ppb to 12.000 ppb and stabilized by the end of the experiment (Figure 6.5C). The Ca concentration increased from 10.750 ppb at day 1 to 18.830 ppb by day 10 and then decreased slightly to 16.340 ppb on day 22 (Figure 6.5D). The removal of Ca from solution is most likely due to sorption to Fe and .Al hydroxides rather than the formation of Ca salts.
Magnesium does not appear to be affected by sorption because hydrated radius is larger
than that of Ca ions in solution (Piatak. 2000).
The Cu and Pb concentrations are highest near day 4 and then continued to
decrease throughout the experiment. The concentration of Zn was highest on day 10.
whereas the Ni concentrations continued to increase throughout the experiment (Figure
6.6B). The activities of these trace metals were too low for any salts to precipitate during
the experiment. Therefore, the removal of metals from solution occurred due to sorption
onto freshly precipitated Fe and .Al hydroxides that formed during the experiment. The
concentrations of Pb and Cu decreased significantly from day 4 to day 22. Zn decreased
only slightly, and the Ni concentrations increased throughout the
70 pH
S ' 2000 Q. I Cu -g 1500 g m 1000 . Zn ..-A-
S 500 O Ni U 1 . 10 15 20 25 Time (days)
Figure 6.6. .A. pH profile over time. B. Concentrations of Cu, Zn. Pb. and Ni in solution over time.
e.xperiment. .According to single-element batch experiments reported in Dzombak and
Morel ( 1090). the order of preferential sorption among trace metals is such that Pb
IS sorbed most efficiently at low pH followed by Cu. Zn. and Ni. The results of this weathering experiment follow that pattern. Lead decreased from 587 ppb to 83 ppb from day 4 to day 10 and Cu decreased from 1590 to I.OOO ppb during that same period. The
Zn concentrations peaked on day 10 at L I 10 ppb and decreased only slightly to 954 ppb by the end of the experiment. Nickel did not seem to be affected by sorption in this experiment because its concentration continually increased throughout the experiment.
71 The results of this weathering experiment provided information about how the concentrations of major and trace elements change over time when a sulfide ore is weathered in a laboratory setting. Major element concentrations of Na. K, Ca. and Mg increased with time and only the Ca concentrations decreased by sorption onto the surfaces of Fe and .Al hydroxides. The concentrations of the trace elements including Cu.
Zn. and Pb increased initially and then decreased due to sorption. Nickel increased throughout the experiment and therefore does not seem to be affected by sorption in the pH range of the solutions that formed in this experiment.
6.3.2 Weathering of Pennsylvania Mine Ore
Because only five beakers were used in the weathering of the SBM ore. there wore many gaps in time that allowed only a limited interpretation of the changes in concentration of major and trace elements during the experiment. Therefore, an additional weathering experiment was performed on an ore sample from the Pennsylvania
Mine. This experiment was allowed to run for 60 days and sampled more frequently to provide a more comprehensive data set.
.As in the weathering experiment of the SBM ore. the initial pH of the solutions in the PM experiment was 5.7 because the de-ionized water was allowed to equilibrate with
CO; from the atmosphere prior to beginning the experiment. .After the experiment started, the pH continued to decrease until it reached 2.9 at the end of the 60-day period
I Figure 6.7). The pH of the final solution was lower than that in the weathering experiment of the SBM ore because; 1) the experiment with the PM ore was allowed to run for 38 davs longer than that for the SBM ore. 2) the ore from the Pennsvlvania Mine
72 lacked carbonate to buffer the pH of the solution and, 3) the PM ore was composed mostly of pyrite and quartz.
The Fe concentrations of the water increased from 235 ppb to 4.900 ppb except for day 35 when it dropped to 1500 ppb (Figure 6.7). The saturation indices for Fe hydroxide indicate that the solutions remained undersaturated with respect to the formation of Fe(0H)3 throughout the experiment. After day 10 of the experiment. Fe concentrations continued to increase until the end of the experiment. This trend is attributable to the continued dissolution of Fe from the rock and/or the lack of precipitation of Fe-hydroxides due to the decrease in pH.
The .41 concentration of the solutions increased slowly to day 35 and then increased to 2,730 ppb on day 45 and subsequently dropped to 2,190 ppb on day 60
( Figure 6.7 ). .According to the saturation index, the solutions remained at or near saturation w ith respect to Al(0H)3(am) and other .Al compounds such as alunite
KAl-,(SOa):(OH)(, and gibbsite A1(0H)3 through day 5 of the experiment. Because of the decrease in pH of the solutions over time. .Al was released into solution and the formation of .Al compounds was not favored.
73 6
5 pH
3
2 6000
^Q. 4000 Q.
2000 Fe
3000 2500 2000 â 1500 AI < 1000 500 0 10 20 30 40 50 60 time (days)
Figure 6.7. pH profile over time for weattiering of PM ore. Fe and AI concentrations in solution over time.
The Na. K. Ca. Mg. and SOj concentrations in solution are illustrated in Figure
6.S. The concentrations of these elements increased until day 35 and then decreased, with the exception of sulfate, which increased throughout the experiment. Even though
Na. K. Ca. and Mg are typically considered to be conservative, their removal from
solution may be attributed to sorption on Fe and A1 hydroxides due to SO4 bridging which enhances the sorption of cations at low pH. or due to the formation of compounds not
considered by PHREEQC interactive because the concentrations of silicic acid and other
anions were not measured.
74 20000 15000
CO=- 10000 ♦ ^ 5000 0
15000 a 10000 Q. Q. ^ 5000
0 2500 2000 I ; 1500 « 1000 500 0 I 1000 800 n CL Q. 600 O) 400 200 0 140 120 Ê 100 Q. Q. 80 d 60 CO 40 20 0 20 40 60 time (days)
Figure 6.8 . Na. K. Ca. Mg. and SO 4 concentrations in solution for the weathering of the PM ore.
75 OH- H* Al P b f" OH- H* OH- C u -' SO; P k f ' Al OH- H' 5 0 / C u '* OH- H' Al OH_ H' s o ; Z rr'
Figure 6.9. Schematic representation of the effect of sulfate ions on sorption of cations at low pH. Closest to the surface of the hydro.xide mostly hydrogen ions are sorbed due to the low pH of the surrounding solution, causing most of the surface sites to have a positive charge. Negatively charged sulfate ions are then attracted towards the surface. The sulfate ions then cause the majority of surface sites to have a negative charge and cations are sorbed to those negative sites. Ions are shown with true valence even though they loose some of their charce due to the formation of bonds.
The Cu, Zn. and Cd concentrations in Figure 6.10 increased over time as pH decreased presumably because of the absence of a sorbent such as FetOHh or .-\l(OH)i.
The concentration of Cu remained below 100 ppb until day 25 and then increased to 2460
ppb at the end of the e.xperiment. The concentration of Zn was 18.470 ppb after day 1
and increased to 41.600 ppb by the end of the experiment. The Cd concentration in
solution was 89 ppb at day 1 and increased to 208 ppb by the end of the experiment. The
concentration of Pb initially increased to 10.800 ppb but then decreased after day 5 to the
end of the experiment to a concentration of 906 ppb. .After day 2 of the experiment, the
solutions were at or near saturation with respect to PbSOa. which may account for the
decrease in Pb concentrations even though the pH decreased as well.
76 6 5
i . 4 3 2
3000
Q. 2000 Q. *' 1000
60000
■g. 40000 Q. 20000
300
■ § . 200 CL O 100 * * 0 15000
-g. 10000 Q. i. 5000 ♦ ♦
10 20 30 40 50 60 time (days)
Figure 6.10. pH profile over time of the weathering e.xperiment of the P.VI ore and concentrations of Cu, Zn. Cd. and Pb in solution.
Saturation indices for PbSOa and CdSOj are shown in Figure 6.11. The solutions w ere at or near saturation with respect to PbSO^ throughout the experiment, which explains w hy the Pb concentration in solution decreased continually (Figure 6.10).
77 20 40 60 time (days)
Figure 6.11. Log saturation index for PbSOi in solutions over time for the PM weathering experiment, the dashed line indicates log saturation index equal to zero where equilibrium exists between Pb‘ * and SOL' ions and PbSO.i.,1. The solutions lie on or near the equilibrium line indicating that PbS04 could precipitate from the solutions. The log saturation index for CdSOa demonstrates that the solutions are undersaturated with respect to the formation of CdSOj, therefore CdSOj did not precipitate from these solutions.
The CdSO^ saturation index in Figure 6.11 indicates that the solutions were undcrsiaturated by up to 10 orders of magnitude with respect to the formation of CdSO^.
The results of this experiment give additional information about laboratory weathering of
sulfide-bearing ores. Because the pH of the solutions in this experiment were much
lower than that in the SBM experiment the results are quite different.
6.4 Comparison of the SBM and PM Weathering Experiments
One notable difference between the SBM and PM weathering experiments is that
the pH of the final SBM solution was 5.1. whereas the final solution of PM reached a pH
of 2.9. Even though both ores contained a significant amount of sulfides, the SBM ore 78 also contained carbonate minerals, which had a buffering effect on that solution.
However, the final pH values obtained in the e.xperiments are similar to those measured in the field 2.S for PM and 5.0 for SBM.
.-\nother difference between the two experiments is that in the SBM experiment
Fe and .A.1 hydroxides did not redissolve as time passed because the pH did not decrease suftlciently. In the PM experiment, no Fe hydroxides precipitated and Fe and A\ concentrations increased with time because the pH of the solutions in the PM experiment decreased to 2.9. For the same reason, the trace metal concentrations (Cu. Pb. Zn) in the
SBM experiment initially increased and then decreased presumably due to sorption,
\\ hereas the Ni concentrations increased throughout the experiment. In the PM experiment the Cu. Zn. and Cd concentrations continued to increase throughout the experiment, whereas the Pb concentration decreased. The increase in concentrations of
Cu. Zn. and Cd is due to the decreased pH and the lack of formation of a sorbent. The decrease of the concentration of Pb was caused by the formation of PbSOa.
The composition of the final experimental solutions and of the natural mine drainage waters are represented in Figure 6.I2A-B in terms of a three-component mixture of Fe. .A.1. and Mn. These components were chosen because the precipitation of Fe. .Al. and/or Mn hydroxides is controlled by the pH o f the water and the presence of these precipitates causes sorption of trace metals in solution. The diagram demonstrates that the experimental waters derived from the weathering of the SBM and the PM ores are
\ery different in composition in terms of the three end-members. The SBM water that
was collected in the field is enriched in Mn presumably because Fe and/or Al precipitated
from solution before it was discharged at the surface. If the PM water were to be
79 Fe Fe
• saM # r W C EXP water S8M 0_Exp_water PM □ •
->
Mn
Figure (i. 12. Ternar\’ diagram illustrating the composition of e.xperimentally derived mine waters and natural mine waters for SBM ore in terms of three components (Fe. Al. and Mn). The square represents a hypothetical starting composition of mine drainage water at low pH ( high Fe concentration) and the dashed arrow illustrates the direction along which the composition of the water should evolve as pH is increased and Fe and Al precipitate enriching the solution in Mn. Dashed arrow illustrates the path along which the experimentally derived water from the PM should evolve if the pH of the solution increased.
neutralized progressively. Fe would precipitate first enriching the remaining water in .AI and Mn. followed by .AI precipitation which would cause the water to become enriched in
Mn as the SBM water already is. This chemical evolution of the water would follow a path similar to those indicated by the dashed curves in Figure 6.12.
6.5 W ater chemistry of Peru Creek near the Pennsylvania Mine
The water draining from the Pennsylvania Mine has a low pH (2.8) and elevated concentrations of major and trace elements. The Fe and Al concentrations in the water draining from the PM are three orders of magnitude higher than those of the water in Peru
Creek upstream of the mine (Figure 6.13). Due to an increase in pH of the mine water
80 when it mixes with Peru Creek, significant amounts of Fe and A l hydroxides precipitate on the streambed (Figure 6.14), leaving the water in Peru Creek with relatively low concentrations of Fe and Al. The SO4 concentration of the PM water is high, but when it mixes with Peru Creek the sulfate is removed from solution due to the formation of Fe and .A.1 hydroxysulfate compounds.
•X-ray diffraction patterns of the red-orange precipitate collected from the Peru
Creek w here it mixes with the mine water indicate that this material is predominantly schwertmannite (Figure 6.15), which is a incompletely crystallized mineral with a tunnel structure and has the chemical formula FegOslOHleSOj (Bigham et al.. 1996).
Trace element concentrations in Peru Creek show a similar pattern to that of Fe.
.Al and SO 4 (Figure 6.16). The PM water has elevated concentrations of Cu. Zn. Xi. and
Cd. When the PM water mixes with Peru Creek, the pH of the mine water is increased
from 2.S to 4.5 within a 50-meter interx al causing the sorption of metal cations onto the
surfaces of Fe-. .Al- and SO^-rich precipitates including schwertmannite.
81 7 6 5 4 3 PM 2
15000 PM Q. 10000 CL O U_ 5000
30000 PM a 20000 Q. Q. < 10000
0
800
E 600
? 400 200
0 1000 2000 3000 4000 5000 distance downstream (meters)
Figure 6.13. pH profile of Peru Creek water and PM water. The starting point (0 meters) is located just upstream from the Pennsylvania Mine on Peru Creek. The mine water is labeled as PM. Fe, .-M. and SOjconcentrations in PM water are higher than those in Peru Creek.
82 Figure 6.14. Photograph of the location where mine effluent drains into Peru Creek just down slope from the Pennsylvania Mine. Notice the gradation in color of the precipitate from orange to tan in the direction aw ay from the riverbank. The orange precipitates are mostly schwertmannite and the tan precipitates have high Al concentrations.
83 y
Figure 0.15. X-ray diffraction pattern of orange precipitate collected at site shown in Figure 6.14. This pattern is indicative of the mineral schwertmannite (FesOs(OH)oSO.i).
84 50000 40000
Q . 30000 Q. c 20000 10000 0 +
8000 ♦ P M ^ 6000 ^ 4000
^ 2000
250 200 â 150 Q. 7 100
200 ♦ RM 150 a. a 100 ■a O 50
0 0 1000 2000 3000 4000 5000 distance downstream (meters)
Figure 6.16. Concentrations of Zn. Cu, Ni. and Cd in the P.VI water and Peru Creek. Notice that the mine water (PM) has elevated concentrations of these trace metals, but the water in Peru Creek has low concentrations of these trace metals.
85 6.6 Conclusions
These laboratory weathering experiments provide information about the
production and compositional evolution of acid mine water that cannot be determined
from natural samples alone. The mineral composition of the ore may initially control the
composition of water that w ill form from weathering of the rock. The major variable that
affects the concentrations of elements in solution over time is the pH which is intluenced
b>: 1 ) the release of H ' ions during the formation of Fe and .Al hydroxides by hydrolysis;
and 2) the presence of carbonate minerals that have a buffering effect on the pH of the
solutions. The pH of the solutions affects I ) the spéciation of trace metals in solution. 2)
the t'ormation of a sorbent such as Fe or .Al hydroxides, 3) the polarity of surface sites on
these sorbents and 4) the sorption coefficient of trace elements such as Cu. Pb. Zn. Cd.
and Xi. As a result of these reactions, the concentrations of Fe. Al. Mn. and trace metals
decrease w hen the pH of acid mine-water is increased.
The water draining from the Pennsylvania Mine has a low pH and elevated
concentrations of major and trace elements. .As this water mixes with water in Peru
Creek, the pH rises causing the formation of Fe-. .A1-. and SO4- rich precipitates including
schweiimannite. Trace metals are then sorbed to these precipitates. Therefore, the water
in Peru Creek is not significantly contaminated by the PM water. .As the water in Peru
Creek fiows dow nstream it is diluted causing trace metal concentrations to decrease
continuallv.
86 CHAPTER?
DISTRIBUTION OF ELEMENTS IN THE SEDIMENT OF THE DILLON RESERVOIR
7.1 Introduction
The Dillon Reservoir was formed in 1963 when a dam was constructed across the
Blue River just below its confluence with Tenmile Creek and the Snake River (Figure
7.2 ). Because the Dillon Reservoir provides drinking water to the city of Denver and is also used for recreational purposes, it is of value to those who live near it. The Dillon
Reservoir is a temporary storage basin for water that drains from the surrounding 335 square miles of the Dillon watershed, which has been mined in the past for Au. .Ag, and various sulfide minerals. The water is contaminated due to the mining activity and because of the natural weathering of mineralized rocks in the watershed, which releases metals into the environment. In addition, sediment from the watershed accumulates in layers on the bottom of the reservoir. This sediment is potentially toxic because of trace metals sorbed to hydroxides of Fe and .AI that have been accumulating for the past 38 years. .As shown in Chapter 5. Fe and .Al hydroxides form in the Snake River as the water is neutralized by mixing with the water of its tributaries. These hydroxide precipitates are eventually carried downstream, especially during periods of high discharge, and are deposited as part of the sediment load in the reservoir.
87 The three watersheds, which contribute water to the Dillon Reservoir, include the Snake River. Blue River, and Tenmile Creek. Mining has occurred in all of these drainage basins in the past, but the Snake River basin has been affected the least by mining activities. However, due to the weathering of mineralized rocks in the Snake
River basin, the water is naturally contaminated. None of the mines located in the drainage to the Dillon Reservoir are currently in operation, but contaminated water continues to drain from tailings piles and from abandoned mines and adits on the hillsides.
The Snake River basin has a drainage area of 57.7 square miles and was the site of mining primanly for Ag in the late 1800s and early 1900s. Peru Creek, which is a major tnbutary to the Snake River, has two abandoned mines located in its upper drainage; the Pennsylvania Mine and the Shoe Basin .Mine both of which discharge contaminated water into Peru Creek. In addition, the Sts. John Mine is located near the headwaters of Sts. John Creek which is a small tributary to the Snake River, and the
Burke-Martin mine is located along the Snake River near the village of Montezuma.
•Although, these two mines do not significantly affect the water quality of the Snake
Ri\ cr. mineralized rocks at the headwaters of the Snake River contribute significant
amounts of Fe and Al as well as trace metals to the dissolved and suspended load of the
stream even though no mines are located there.
The Blue River drains an area of 121 square miles and has two main tributaries:
the French Gulch and the Swan River. The Brec ken ridge Mining District is located
within the Blue River basin and contains a large number of abandoned mines, including
88 the Wellington Mine which was mined for Zn, Pb, Ag, and Au, and the Tiger Mine which was primarily a ,Au, .Ag, and Pb producing mine.
Tenmile Creek has a drainage area of 93.3 square miles. It contains the Clima.\
Molybdenum Mine which operated continuously from 1917 to 1980 and intermittently from 1980 to 1992 (Voynick, 1996). In addition to the Clima.x Mine, several prospect holes and mining tunnels in this basin date back to the 1860s. .Also, three tailings ponds, including the Robinson Tailings Pond, the Tenmile Tailings Pond, and the Maytlower
Tailings Pond were built between 1936 and 1957.
In order to calculate a geochemical mass balance of the Dillon watershed, it was necessary to determine the distribution and concentrations of trace metals in the sediment of the reservoir. It is important to document the physical and chemical characteristics of the sediment because the Dillon Reservoir will eventually require dredging and the sediment w ill have to be recovered and remediated before it is disposed of.
7,2 Methods
Eighteen sediment and water samples were collected from the Dillon Reservoir in
July of 200Ü. The sediment samples were collected with a box sampler at locations
determined by a Magellan GPS 2000® Satellite Navigator. .At some sites, the GPS unit
gave inaccurate readings, probably due to blocking of satellites caused by the
surrounding mountainous terrain. Therefore, these sites were located by triangulation.
The sediment collected at each site was placed in 500 mL polypropylene bottles that were
previously rinsed with water from the reservoir. The water depth was measured at each
sampling site using a FR-300 hand-held sonar device with a range of 4-499 feet and an
89 accuracy of 6 inches. The sediment collected in the box sampler was water-rich but coherent and layering was detectable.
The sediment samples were freeze-dried in the laboratory, homogenized with a mortar and pestle, and approximately 1-gram aliquots of each were leached with 50 mL of 2.\ HCl for 24 hours. The resulting solutions were decanted and filtered through 0.45
Lim filters and the remaining sediment in each beaker was rinsed with deionized water to remove all of the acid solution. The solutions were diluted with deionized water in calibrated 250 mL volumetric flasks and analyzed for major and trace elements by ICP-
OES at XR.4L Laboratories in Toronto. Canada. The concentrations of major and trace elements leached from the sediment are reported in ppm of the dry weight of bulk sediment.
In addition, six of the sediment samples were analyzed by X-ray diffraction by methods descnbed in Chapter 2.
Contour maps of the concentrations of major and trace elements in the sediment were produced using the software program ®Surfer 7.0. In order to emphasize the data points in the contouring, some values of 0 concentration were added around the shoreline to pre\ ent the contours from going outside the boundary of the reservoir.
7.3 Results and Discussion
7.3.1 Mineral Composition
X-ray diffraction patterns for six sediment samples show that the major crystalline
mineral phases include goethite. muscovite, plagioclase. kaolinite. and quartz. In
addition, it is plausible that ferrihydrite is also present in the sediment samples (Figure
7.11, although it is difficult to distinguish its XRD pattern because of the abundance of
90 DR-13 Sediment
1500-1
ÎQOO- o
SCO-!
SCO
Synthetic 2-tine "emhydrite
300
d
Figure 7.1. XRD pattern for synthetic 2-line ferryhydrite and for sediment sample DR-13 which is representative of all six samples analyzed from the Dillon Reservoir.
91 crystalline material. The XRD pattern for synthetic 2-line ferrihydrite in Figure 7.1 shows a rise in the baseline between 2-theta values of 20 to 30 degrees that is also apparent in the XRD pattern for the reservoir sediment.
7.3.2 Distribution of Elements in the Sediment from the Dillon Reservoir
The measured water depths in Figure 7.2 range from 40 to 200 feet. The deepest water occurs near the middle of the reservoir and along the old river channels in the
Snake River. Blue River, and Tenmile Creek arms. The distributions of Fe, .A.1, and Mn are contoured in Figures 7.3, 7.4, and 7.5. The distribution of Pb, Cu, Zn, Ni, Cd, Co,
Ag, and Mo are contoured in Figures 7.6 through 7.9. The minimum and maximum concentrations of all elements in the acid-soluble fraction of the sediment are listed in
Table 7.1. Even though the acid-soluble fraction was used for chemical analyses, the concentrations are reported as ppm of the bulk sediment.
The distribution of elements in the sediment of the Dillon Reservoir form consistent patterns. The concentrations of the elements increase with increasing water depth and distance from the mouths of the Snake River, the Blue River, and the Tenmile
Creek. .As a result, Mn and all trace metals have elevated concentrations in the sediment of the main body of the reservoir represented by samples from sites 5, 12, 13, 14, and 15.
92 Water Depth
Blue RIverOam
m
Tenmile Creek
/Y|7^ W o W Roberts -Y: Tunnel
To Denver
Cl = 20 feet
Blue River Snake River
Figure 7.2. Map o f the measured water depths o f the Dillon Reservoir. The sample sites (black circles) are identified in red.
93 TMC .\rm û
CI = 4000 ppm
1» SR .\rm
BR .Arm
CI = 2000
Figure 7.3. Concentrations of Fe and Al in the sediments in the Dillon Reserv oir. Cl is the contour interval in ppm.
94 Cl = 1500 ppm
Figure 7.4. Concentrations of Mn in the sediments of the Dillon Reservoir. Sediment collected in the main body of the reservoir close to the dam has the hiahest concentration of Mn.
95 CI = 40 ppm
CI = 20 ppm
Figure 7.5. Concentrations of Pb and Cu in the sediments in the Dillon Reservoir. Site 10 in the Snake River arm has elevated concentrations of Pb and Cu as does the main body of the reservoir. Additionally, the sediment at sites 16 and 17 has elevated concentrations of Pb and Cu.
96 CI - 400 ppm
CI = 5 ppm V
Figure 7.6. Concentrations of Zn and Ni in the sediments of the Dillon Reservoir. Sediment at site 10 in the Snake River arm and in the main body of the reservoir have elevated concentrations of Zn and Ni. Additionally, sediment at sites 16 and 17 are enriched in Zn.
97 Cl = 2 ppm
Cl = 2 ppm
Figure 7.7. Concentrations of Cd and Co in the sediments from the Dillon Reservoir. Sediment at site 10 in the Snake River arm and in the main body of the reservoir have elevated concentrations of Cd and Co as do sites 4. 12, 13. and 14.
98 Cl = 0.5 ppm
Figure 7.8. Concentrations ofAg in the sediments from the Dillon Reservoir. Sample sites labeled in blue and contour values in black. Sediment from site 10 in the Snake River arm and from sites 12. 13. and 14 have elevated concentrations of .As.
Cl = 10 ppm
Figure 7.9. Concentrations of Mo in the sediments from the Dillon Reservoir. Sediment at site 17 in the Tenmile Creek arm of the Dillon Reservoir and sediment at sites 13 and 14 in the main body of the reservoir have elevated concentrations Mo.
99 Element Minimum Maximum
Fe 8948 31810
AI 3697 13952
Mn 353 14171
Pb 64 299
Cu 31 195
Zn 912 3217
Ni 7 51
Cd 5 13
Co 4 22
Ag 1 7
Mo 4 83
Table 7.1. Minimum and ma.ximum concentrations of elements in the acid-soluble fraction of the sediment of the Dillon Reservoir, e.xpressed relative to the dr\' weight of the bulk sediment.
Concentrations reported in ppm.
100 7.3.3 Distribution of Fe and Al
In order to illustrate the patterns of Fe and Al distribution beyond the patterns seen in the contour maps, longitudinal profiles for the arms of the Dillon Reser\'oir formed by the Snake River, Blue River, and Tenmile Creek were constructed in Figures
7.10. 7.1 Land 7.12.
0 -10 V Snake River Arm Main Body -20 10 Q o ■a -30 5 -40 m 5 -50 ...... i -60
3 5 0 0 0 ♦ 3 0 0 0 0 • . • 2 5 0 0 0
o 20000 * . * ...... ♦ LL ' 1 5 0 0 0 10000
15000 * 1 13000
E Q. 11000 Q. 9000 . 1 7000 1 5000 0 1000 2000 3000 4000 5000
distance from mouth of Snake River (m)
Figure 7.10. Profiles of water depth, and concentrations of Fe and .Al in the acid soluble fractions of sediment along the Snake River arm. Sample sites for concentrations of Fe and Al are identified bv number.
101 ^ Blue River Arm £ -10 Main Body £ -20 2 (U 3 T3 -30 O -40 « 5 -50 -60
40000 ! ^ 30000 _ * ! â 20000 OJ ______i * ; 10000 ♦ ' 1 0
14000.0 12000.0 10000.0 E 8000.0 â 6000.0 4000.0 2000.0 0.0 1000 2000 3000 4000 5000 6000 distance from mouth of Blue River (m)
Figure 7.11. Profiles of water depth, and concentrations of Fe and Al in the acid soluble fractions of sediment along the Blue River arm. Sample sites for concentrations of Fe and Al are identified bv number.
The transects along each of the arms indicate the change in Fe and Al concentrations and the average concentration of the acid-soluble fraction of sediment in the main body of the reservoir collected at sites 5. 12. 13, 14, and 15. The major difference between the patterns of Fe and Al concentrations in the arms is that the highest concentration in each arm occurs at different distances from the mouths of the respective nvers.
102 Tenmile Creek Arm Main Body ! 18 ♦ . £ -20 ■••37 1 Q. •O(U *'-]6 1 a5 -40
1 ! -60
32000.0 28000.0 £ 24000.0 â 20000.0 “ 16000.0 12000.0 8000.0 12000.0
10000.0
a. 8000.0
6000.0
4000.0 1000 2000 3000 4000 5000 6000
distance from Tenmile Creek mouth (m)
Figure 7.12. Profiles of water depth, and concentrations of Fe and Al in the acid soluble fractions of sediment along the Blue River aim. Sample sites for concentrations of Fe and .Al are identified bv number.
The concentrations of Fe and Al in the sediment of the Snake River arm are higher than those in the Blue River and Tenmile Creek arms even though historically there was significantly less mining in the Snake River basin than in the Blue River and
Tenmile Creek basins. Evidently, the natural weathering of mineralized rocks in the
Snake River basin contributes a significant amount of Fe and A l hydroxide to the 103 sediment of the reservoir (e.g. the confluence of the Snake River and Deer Creek and the
Pennsylvania Mine on Peru Creek discussed in Chapters 4 and 5).
7.3.4 .Àcid Soluble Fraction of Sediment
35 A
30
25
20 < c 15
10
0
0 B 04 8 12 16 20 24 28 32 36 40 44 48 52
% Fe in Fe(0H)3
Figure 7.13. A three-component mi.xing diagram used to determine the concentrations of the acid-soluble fraction of the sediment samples from the Dillon Reservoir.
The fraction of acid-soluble sediment was determined by graphical means. Figure
7.13 illustrates how the fraction of acid-soluble sediment in sample DR-4 was derived by
an application of mixing theory. The two end members .A and B in Figure 7.13 are pure
.AllOH); and pure Fe(OH);. Therefore, any mixture of Fe and Al hydroxides forms a
104 Acid Acid Sample insoluble Soluble Fraction Fraction DR-1 97.1 2.9
DR-2 94.5 5.5
DR-3 95.2 4.8
DR-4 89.8 10.2
DR-5 94.1 5.9
DR-7 94.2 5.8
DR-8 93.1 6.9
DR-9b 94.1 5.9
DR-10 89.9 10.2
DR-11 93.2 6.8
D R-12 90.7 9.3
DR-13 94.2 5.8
DR-14 94.2 5.8
DR-15 95.2 4.8
DR-16 88.6 11.4
D R-17 93.1 6.9
DR-18 95.3 4.7
Table 7.2 Fraction of acid-insoluble and acid-soluble sediment.
105 point on line AB. The black diamond in Figure 7.13 indicates that sample DR-4 is a mixture of the three components; Fe(0H)3, AlfOH)?. and sediment composed of silicate minerals and organic matter that do not contain Fe and A\ that is leachable with 2N HCl.
The amount of acid-soluble sediment was calculated by dividing the length of line segment "a" by the length of line segment "b". The results indicate that the concentration of the acid-soluble fraction of DR-4 in Figure 7.13 is 10.2T and the concentration of acid-msoluble fraction is S9.Sf7. The results for the all samples are listed in Table 7.2.
If the acid-soluble sediment is composed mostly of hydroxides of Fe and .41 as predicted, then the concentration of acid-soluble sediment should be correlated with the
Fe and .41 concentrations. Figure 7.14 confirms the expected positive correlations of Fe and .41 concentrations in the acid-soluble fraction of sediment with its concentration in the three arms of the Dillon Reser\oir.
If the concentrations of Fe and .41 in the acid-soluble sediment in the main body of the reservoir are the result of mixing of the inputs from the Snake River, the Blue
Ri\er. and Tenmile Creek, then the average concentrations of Fe and .41 in the sediment m the mam body of the reservoir should define a point within a three-component mixing triangle w hose end members are the average concentrations of Fe and .41 of the acid-
soluble sediment in the Snake River. Blue River, and Tenmile Creek, respectively.
Figure 7.15 reveals that the sediment in the central basin of the reservoir is enriched in .41
rclatis c to Fe because the point representing these sediment samples lies outside of the
mixing tnanzle.
106 15
o Snake River Arm n ^ £ 10 # I "o y roÜ (A 03
15 o Blue River Arm II 10 0 15 o Tenmile Creek Arm 3 ÇC 10 o 0 (/3 E 5 -5 U 0 0 W sS 10000 20000 30000 40000 50000 Fe + Al ppm Figure 7.14. The percent of acid soluble sediment vs. Fe and Al concentration in the sediment from the Snake River arm, the Blue River arm, and Tenmile Creek arm. 107 10500.0 10000.0 SR 9500.0 DR 9000.0 E Q. 8500.0 Q. 8000.0 TMC 7500.0 7000.0 BR 6500.0 6000.0 16000 18000 20000 22000 24000 Fe ppm Figure 7.15. Three-component mixing for average sediment in the Dillon Reservoir. Because the average sediment concentration of Al is above the mixing triangle, the sediment is enriched in Al or depleted in Fe. or both relative to the sediment in the arms. The apparent enrichment of the reservoir sediment in Al is most likely caused by differential transport and deposition of the .Al-bearing fraction of the hydroxide component of the sediment relative to FefOH)^. The hydroxide of .Al may be transported farther into the reservoir than Fe hydroxide because the molecular weight of AlfOH)] is 27.0^f lower than that of Fe(OH):, Therefore, the sediment accumulating in the main body of the reservoir is enriched in Al and depleted in Fe relative to the sediment in the arms of the rivers. In order to test this hypothesis, the density of sediment in each of the arms and in the main body of the reservoir was measured (calculations shown in section 7.4 below). 108 The average density of sediment from the Snake River arm. the Blue River arm, and the Tenmile Creek arm is 2.0197 g/cm'’ whereas that of the central basin of the reservoir is 1.8910 g/cm’’. The data indicate that the average density of sediment in the main body of the reser\ oir is about 69c less than the average density of sediment in the three arms. The density difference is consistent with the Al enrichment of sediment in the central basin of the reservoir. The low values of density of the sediment in the Dillon Reser\ oir are attributable to the presence of organic matter and the occurrence of phytoliths identified by microscopic e.xamination of one sediment sample by Dr. P.N. Webb. 7.3.5 D istribution of Trace .Metals The variations of the concentrations of Pb. Cu. Zn and Ni in the sediment of the Snake River arm in Figure 7.16 are similar to those for Fe and .Al in Figure 7.10 with the c.xception that the Zn and Ni concentrations in the main body of the reservoir are higher than those in the Snake River arm. The concentrations of Pb. Cu. Zn. and Ni in the sediment of the Blue River arm increase with increasing distance from the mouth and with water depth (Figure 7.17). In the Tenmile Creek arm. the concentration of Pb in the sediment peaks at site 17 (Figure 7.18). The concentrations of Cu. Zn. and Ni increase with distance from the mouth of the creek and with increasing depth of the water in the reservoir. 109 11 4 Snake River Arm I Main Body { s. -20 10 9 i 0) ! *D * * I -40 . 8 7! j * « ^ -60 600.0 400.0 * 4» . Q. • ■ g 200.0 1 0.0 300.0 I 5 200.0 Q. i Q. u 100.0 0.0 3000.0 E 2500.0 è 2000.0 N 1500.0 1000.0 1000 2000 3000 4000 5000 distance from mouth of Snake River (m) Figure 7.16. Concentrations of Pb. Cu, Zn, and Ni and water depths along a transect of the Snake River arm of the Dillon Reservoir. 110 0 - Mam Body E -20 .c Q. -40 ■ a Blue River Arm -60 ^ 300 E 200 a.Q. o . 100 0 150.0 E 100.0 CL O 50.0 4000.0 3000.0 E â 2000.0 C 1000.0 0.0 40 30 20 10 0 0 1000 2000 30004000 5000 6000 distance from mouth of Blue River (m) Figure 7.17. Concentrations of Pb. Cu. Zn. and Ni and water depths along a transect of the Blue River arm. I l l Tenmile Greek Am 1 Main Body ^ s -20 CÜQ. •D 5 -40 ------i 1 -60 350 1 300 I 250 I 200 150 100 100 ! E 80 Q. Q. 1 i O 60 1 40 3 5 0 0 E 2 5 0 0 ♦ ----- .K N 1 5 0 0 ! 5 0 0 40 E S 20 " 10 0 1000 2000 3000 4000 5000 6000 distance from mouth of Tenmile Creek (m) Figure 7.18. Concentrations of Pb. Cu, Zn. and Ni and water depths along a transect of the Tenmile Creek aim. 112 4000 z c 3500 N 3000 d 2500 E __ ♦ CL Q . 2000 Q. 1500 c5 E 1000 S 500 Ô 1 - 0 10000 20000 30000 40000 50000 Fe + Al ppm 4000 c N 3500 ♦ 3 3000 O ♦ E 2500 Q- Q. % ^ 2000 I z 1500 ~ 1000 % 500 0 2 4 6 8 10 12 % acid soluble sediment Figure 7.19. Total métal concentrations as a function of Fe plus .Al and the concentration of acid soluble sediment for all sediment samples from the Dillon Reservoir. The concentrations of the trace metals in the sediment are correlated with the concentrations of Fe and .Al in the sediment as e.xpected if the hydroxides of Fe and .Al are the pnmar>’ sorbent of the trace metals. In addition, because all the elements reported in this study originated from the acid-soluble fraction of the bulk sediment, the concentrations of Pb. Cu. Zn. and Ni should show a positive correlation with the abundance of the acid-soluble component of the sediment. The postulated positive 113 correlations between the sum of the concentrations of Pb, Cu, Zn, and Ni with the concentrations of Fe and Al and with the concentration of acid soluble sediment are confirmed in Figure 7.19. 7.3.6 Distribution of Molybdenum The concentrations of Mo of the sediment in the Tenmile Creek arm are high, consistent with the fact that Tenmile Creek drains the tailings ponds of the Clima.x .Molybdenum Mine. Even though the water flowing out of the tailings ponds is presently 0 Tenmile Creek Arm Main Body i E -10 18*. g -20 Q. " ■ ■ T , ,e <2 -30 T 3 « I 5 -40 t Ï -50 1 -60 100.0 80.0 I 60.0 a ^ 40.0 20.0 0.0 1000 2000 3000 4000 5000 6000 distance from mouth of Tenmile Creek (ft) Figure 7.20. Water depth and distribution of Mo in the acid-soluble sediment from the Tenmile Creek arm. 114 being treated for the recovery of dissolved metals, some Mo is apparently entering into the Dillon Reservoir. The Mo may e.x.ist either as the .MoO:""^ ion or as the M oOj*' ion in the water of the reservoir. Since the Mo is sorbed to hydro.xides of Fe and Al in the sediment, it is likely that the Mo exists as the MoO;""^ ion because under the near neutral conditions in the reservoir, only positively charged ions are sorbed. The data in this chapter indicate that the sediment that has accumulated in the Dillon Reservoir has elevated concentrations of many metals, which may have commercial value. 7,4 Amount of Sediment and Value of Metals in the Dillon Reservoir In order to calculate the value of the metals in the reservoir the weight of the sediment in the Dillon Reservoir was estimated from its volume and density. The densities of five sediment samples were initially measured by weighing known volumes of sediment packed tightly into polyethylene beakers. The results in Table 7.3 are identified as the values of D|. Because these densities were anomalously low, a second method of measurement was performed in which the sediment was compressed under 16 tons per square inch in a ™Spex 30 ton press. The second set of densities (D : in Table 7.3) is on the order of 2 to 3.5 times higher than the D| measurements. The difference is attributed to the removal of air from pore spaces due to the compression under 16 tons per square inch. Table 7.3 also lists average densities for the arms, the main body of the reser\oir. and for the reservoir as a whole. 115 Sample Di (g/cm^) Dz (g/cm^) DR-17 Tenmile 0.9307 2.0226 Creek DR-10 Snake River 0.9006 2.0199 DR-2 Blue River 0.7914 2.0165 Average for 0.8742 2.0197 sediment from arms DR-13 Main Body 0.5200 1.8717 DR-12 Main Body 0.6468 1.9102 Average for Main 0.5834 1.8910 Body Average for Dillon 0.7579 1.9682 Reservoir Table 7.3. Density determinations of sediment in the Dillon Reservoir. The value of the recoverable metals in a layer of dry sediment 1.0 cm in thickness was calculated for a measured area of 14.5 km ' for the Dillon Reservoir, by taking the a\ orage density of the dry sediment to be 1.9682 g/cm’’ and based on the price of metals m 2000 (L'SGS, 2001). The weight of a 1 cm thick layer of sediment is equal to 1 cm .\ 1.45 X lO" cm ' X 1.9682 g/cm^ = 2.8538 x lO " g. The concentrations of metals are listed in Table 7.4 Because iron ore is sold in units of metric tons of Fe^O] the average concentration of Fe in the sediment was recalculated to the amount of Fe ;03 as follows: 116 Moles Fe = > jy 4 .1 micrograms . 1 gram ^ ^ 1 ^ = 3.46 x10'-* moles Fe/g 1 g 10° mierograms 33.b4/ g Moles Fe^O. — = 1.73x10“ -* molesFe^Og Weight Fe.OU = 1.73x10 xl59.9a = 2.76x 10'"g/a . 2 3 The vs eight of FezO; in a 1 cm thick layer of dry sediment is calculated using the weight of a 1 cm thick layer of sediment and the weight of Fe;0:, (2) as follows; Mass FotO, = 2.8538 x 10^ ^ g x 2.76x 10~" = 7.88 x 10^ g = 7.88 x 10^ metric tons . (where 1 metric ton is equal to lO'’ grams.) The \ alue of Fe:0-, in a 1 cm thick layer was calculated using the total weight of FezOi and the price of iron ore per metric ton: Value Fe^O . = 7.88x 10^ x $26.00 = $204.880 The \ alues of the other recoverable metals in Table 7.4 were calculated by converting their concentrations to grams and then by converting from grams to either pounds or troy ounces and multiplying by their listed price. 117 Average Average Value of Value of metal in 1 concentration of amount of metal metal as a cm thick layer of Metal elem ent in in 1 cm thick commoditiy Dillon Reservoir sediment (ppm) layer (g) for 200CT Sediment Fe as 19324.1 5.5E+09 S26.00/mt* S204.880 Pb 202.6 5.8E+07 S0.44/lb. S56.077 Cu 94.7 2.7E+07 S0.89/lb. 353.002 Zn 2084.2 5.9E+08 S0.56/lb. $734.295 Ni 25.3 7.2E+06 S3.907/lb. 362.348 Mo 24.4 7.0E+06 S5.90/kg 341,056 Ag 3.0 8.6E+05 S5.25/troy oz. 3144.669 Cd 10.4 3.0E+06 SO. 10/lb. 3653 Co 12.1 3.4E+06 815.50/lb. 3117.571 Total metal value SI .414.550 "ml = metric ton 'from Mineral Commodity Summaries 2001. USGS. US Government Printing Office, Wasfiington. D.C. Tabic 7.4. .Amount of metals in Dillon Reservoir sediment and values of the recoverable metals in a 1 cm thick laver of drv sediment. The estimated value of metals in a 1 cm thick layer of sediment can be e.xtrapolated to determine the value of metals in the total thickness of sediment in the reservoir. In view of the increase in the world’s population and the corresponding demand for natural resources, it would be wasteful and unsafe to place the dredged sediment from the Dillon Reservoir in landfills without recovering the useable metals. 118 The metals from sediment in the Dillon Reservoir could be recovered by acid-leaching and then shipped to a chemical plant to be extracted from solution. The value of the recos erable metals can be used to off-set the cost of dredging and remediating the sediment. 7.5 Conclusions The results of this study indicate that the sediment accumulating in the Dillon Reservoir does contain elevated concentrations of Fe. .A.1, and Mn and vanous trace elements such as Pb, Cu. Zn. N'i, Cd, Co, .A,g and Mo. The concentrations of metals increase with the water depth and with increasing distance from the mouths of the streams. In addition, most of the elements have anomalously high concentrations at certain locations in each of the arms of the Dillon Reservoir, caused by the separation of the lou density, fine-grained colloidal particles from the high density, coarse-grained detrital sediment. .A. three-component mixing triangle for Fe and Al concentrations in the acid- soluhle sediment shows that the sediment accumulating in the main body of the reservoir is enriched in .Al (or depleted in Fe) due to mechanical separation of less dense .Al(OH)i from higher density Fe(OH):,. The density of the sediment in the main body of the reservoir is approximately 6% less than that of the sediment in the arms, which is consistent w ith the ,A1 enrichment of the sediment in the central basin of the reservoir and supports the hypothesis that the hydro.xides of Fe and A l are separated from each other because of differences in their densitv. 119 The abundance of acid-soluble sediment is positively correlated with the concentrations of Fe and A l and with the total amount of trace metals in the sediment, which confirms that the trace metals are sorbed to hydroxides of Fe and Al. The Tenmile Creek arm has anomalous concentrations of Mo as does the main body of the reservoir. This observation indicates that the Mo is present as M oO :'* because only cations are sorbed under near-neutral conditions. Therefore, even though w ater from the tailings of the Climax Molybdenum Mine is being treated to remove metals, some Mo is getting into the sediment of the Dillon Reservoir. The sediment in the Dillon Reservoir contains high concentrations of metais whose commercial value can be used to off-set expenses when the reservoir must be dredeod in the future. 120 CHAPTER 8 CHEMICAL COMPOSITION OF WATER IN THE DILLON WATERSHED 8.1 Introduction The chemical composition of water in the Dillon Reservoir and the factors that control it need to be understood because the water is a major source of drinking water for the citizens of Denver, and is also used for recreational purposes and as a habitat for wildlife. The Dillon Reservoir receives water from the Snake River, the Blue River, and from Tenmile Creek. Water leaves the reservoir through the Blue River Dam. and by the Roberts Tunnel, which transports it to the Denver area for use. The objective of this chapter is to compare the chemical composition of the water entering the Dillon Reservoir and the observed composition of the water flowing out of the reservoir into the Blue River. 8.2 .Methods Between September 1998 and October 2000 si.\ samples were collected from the mouths of the Snake River and Tenmile Creek, whereas five samples were collected from the mouth of the Blue River and from the outflow (June 1999 to October 2000). The major-element concentrations of the water samples were determined by ICP-OES and 121 trace element concentrations were determined by ICP-MS, both by X R A L Laboratories in Toronto. Discharge values were obtained from the USGS National Streamflow Information Program (http://waterdata.usgs.gov/nwis-w/US/) at gauging stations that are located near the mouths of all three streams. The Snake River gauging station (09047500) is located about 4 km upstream of the mouth and downstream of the confluence with Peru Creek. The other gauging stations on the Blue River inflow (09046600) and on the outflow (09050700) as well as on Tenmile Creek (09050100) are all located near the mouths of these streams. The concentrations of elements during months for which no samples were taken were estimated by interpolation along curves defined by the known concentrations and the average monthly discharges obtained from the USGS. This technique is not appropriate for the Blue River outflow because the chemical composition of the water is not related to the discharge, which is controlled by the dam. Therefore, an average concentration of the elements in the five samples taken at the outflow was used. 8.3 Results and Discussion 8.3.1 pH of Water in the Dillon Watershed The pH measurements of the Snake River. Blue River. Tenmile Creek, and the Blue Riser outflow below the dam in Figure 8.1 vary significantly with the season and generally range from about 6.5 to 8.5. Low values occur during snowmelt from May to July but significant fluctuations occur at different times during the water year. 122 9 8.5 Snake River 8 1999* i . 7.5 7 6.5 1998* 6 9.0 1999* 8.5 8.0 ♦ 2000 ^ 7.5 7.0 6.5 Blue River Inflow i 6.0 9.0 8.5 Tenmile Creek 8.0 ^ 7.5 2000* 7.0 6.5 1999^ 6.0 9.0 8.5 1999* 8.0 1999 i . 7.5 2000* 7.0 6.5 1998 * Blue River Outflow ! 6.0 // month Figure 8.1. pH measurements taken near the mouths of the Snake River. Blue River, and Tenmile Creek. Two measurements were taken in September 1998 and 1999 and in October 1999 and 2000. 123 9.0 8.5 Snake River 8.0 i . 7.5 7.0 6.5 6.0 9.0 8.5 Blue River Inflow; 8.0 7.5 7.0 6.5 6.0 9.0 8.5 Tenmile Creek 8.0 i . 7.5 V 7.0 6.5 6.0 200 400 600 800 discharge cfs Figure 8.2. pH as a function of discharge near the mouths of the Snake River, Blue River, and Tenmile Creek. The variation of pH in relation to discharge in Figure 8.2 indicates that the pH of the water in the rivers decreases with increasing discharge and that the pH reaches its maximum values at low tlow. 124 8.3.2 M ajor Elements The major elements with significant concentrations reported in this study include Na. K. Mg. and Ca. The concentrations of these elements vary systematically with discharge in each of the streams that empty into the reservoir. The Na concentrations 4000 Snake River: 3000 ri cn^ 2000 Z 1000 4000 Blue River 3000 2000 (U^ z 1000 10000 Tenmile Creek: 8000 Q. 6000 c . I 4000 U 2000 0 100 200 300 400 500 600 700 800 discharge cfs Figure 8.3. Na concentrations as a function of average monthly discharge for all water samples collected from the mouths of the Snake River. Blue River, and Tenmile Creek for this study. The period of time represented is September 1998 through October 2000. 125 in Figure S.3 decrease with increasing discharge in each of the three rivers. The same relation also holds for K, Mg, and Ca (not shown). The concentrations at low flow are variable because, under these conditions, even a small input of the elements can affect the concentration significantly. The decrease of the concentrations at high discharge is due to dilution with water released by snowmelt. The concentrations of Fe and .-\1 in the Dillon Reservoir water are below the detection lim it (50ppb); however, in some of the Snake River samples A\ ranged from 52 to 249 ppb. and in some of the Tenmile Creek samples from 60 to 239 ppb. Iron is below the lim it of detection in all the streams. The presence of AI and lack o f Fe in the water samples is consistent with the fact that .AI hydroxide is more soluble at near neutral pH than Fe h>dioxide. In addition, the results are consistent with those presented in Chapter 5. where it was shown that Fe precipitates in the Snake River in the form of sulfate-rich hydroxides as the acidic water is neutralized, whereas, some of the .Al remains in solution. The concentrations of conserxative elements were weighted according to the average monthly discharge of each stream. The weighting factors were calculated by summing the average monthly discharge for each stream over the period from September I99S to October 2000 (26 months) and then dividing each average monthly discharge by the sum of these averages. The weighting factors were then multiplied by the concentrations of elements for each month as exemplified for Na in the Snake River in Table S. 1. 126 Average Weighted Na monthly Weighting Na concentration Date concentration discharge Factors (ppb) (ppb) (cfs) Sep-98 31 0.017 2750 46 Oct-98 30 0.016 2013 33 Nov-98 20 0.011 2904 32 Dec-98 14 0.008 3432 26 Jan-99 12 0.006 3683 24 Feb-99 9 0.005 3894 19 Mar-99 10 0.006 3828 21 Apr-99 15 0.008 3366 27 May-99 78 0.042 1643 69 Jun-99 431 0.233 1770 413 Jul-99 201 0.109 1393 151 Aug-99 120 0.065 1485 96 Sep-99 48 0.026 3020 78 Oct-99 32 0.017 3380 59 Nov-99 22 0.012 2891 34 Dec-99 15 0.008 2508 20 Jan-00 12 0.007 3689 24 Feb-00 11 0.006 3762 22 Mar-00 11 0.006 3755 23 Apr-00 24 0.013 2574 33 May-00 184 0.100 1419 142 Jun-00 211 0.114 1386 158 Jul-00 202 0.109 2280 249 Aug-00 42 0.023 1901 43 Sep-00 37 0.020 1967 39 Oct-00 26 0.014 3590 51 Sum 1848 1.001 1934 Table 8.1 Weighting factors and weighted concentrations ofNa in the Snake River. Dates and concentrations in bold are measured concentrations, all other concentrations are interpolated from Figure 8.1. 127 Sum of Predicted Na weighted Na Total monthly concentrations Weighting Stream concentrations discharge for Dillon Factors from Table 8.1 (cfs) Reservoir (ppb) (ppb) Snake River 1934 1848 0.26 506 Blue River 2677 2449 0.35 928 Tenmile Creek 5094 2768 0.39 1996 Sum 7065 1.00 3430 Table S.2 Weighting factors and predicted concentrations of Na in the Dillon Reservoir compared to the observed Na concentration in the Dillon Reservoir. The average chemical composition of the water in the Dillon Reservoir was estimated by multiplying the average weighted concentrations o f each element from each stream by a second set of weighting factors. These weighting factors were obtained by summing the total discharge of the Snake River. Blue River, and Tenmile Creek for the 26-month period and dividing the total discharge of each stream by the sum of the discharges of all the streams for the period of this study. A ll data and weighting factors are listed in Table 8.2. The resulting average weighted concentrations of all elements were used in Table S.3 to identify the streams having ma.\imum and minimum concentrations. The data indicate that Tenmile Creek has the ma.\imum concentrations of Na. K. Ca. Mg. U. and Mo, whereas the Snake River has the maximum concentrations of Zn. Cu. and Cd. and the Blue River has the maximum concentration of Se. The differences in chemical 128 Minimum Maximum Element '^^ighted Weighted Concentration Concentration (ppb) (ppb) Na SRTMC K SR TMC Ca SRTMC Mg SR TMC Zn TMCSR Cu BR SR Ni BR TMC Cd BR SR USR/BR TMC Se TMC BR Mo SR/BR TMC Table 8.3. Minimum and ma.ximum concentrations of major and trace elements in terms of the Snake River (SR). Blue RivenBR). and Tenmile Creek (TMC). 129 percent gain or loss of increase or element Snake Blue Tenmile Blue River Predicted element in the decrease from ppb River River Creek Outflow Mixture Dillon Reservior predicted concentration Na 1914 2677 5094 4306 3430 876 25.6 K 729 1018 5680 2556 2770 -214 -7.7 Ca 9856 19072 51891 36960 29554 7406 25.1 Mg 2320 4003 5374 4218 4107 111 2.7 Zn 203 67 23 27 85 -58 -68.6 Cu 3,2 0.5 0.7 0.9 1.3 -0.4 -30.7 Ni 2.2 0.7 2.8 1.5 1.9 -0.4 -21.1 Cd 0.8 0.4 0.7 0.3 0.6 -0.3 -50.0 U 0.1 0.1 2.0 0.4 0.9 -0.5 -53.1 Se 1.2 1.4 1.0 1.2 1.2 0.1 8.3 Mo BD BD 191 61 75 -14 -18.6 BD = below dectecion limit Table S.4. Concentrations of major and trace elements used to predict the average chemical composition of water in the Dillon Reservoir and comparison of the predicted concentrations with those of the Dillon Reservoir measured at the outflow into the Blue River. composition are a reflection of the differences in geology in each basin. The presence of the Clima.x Molybdenum Mine in the Tenmile Creek basin accounts for the high concentration of Mo in Tenmile Creek. In addition, because of the large volume of finely crushed rock in the tailings ponds of the Climax Mine, chemical weathering is occurring at an accelerated rate, which accounts for the higher concentrations of the major elements and some minor elements (e.g. Mo. U. and Ni), compared to water in the Snake River and 130 Blue River. The elevated concentrations of Zn and Cu in the Snake River are the result o ' ac'd mi ne-drain age from the Shoe Basin Mine and Pennsylvania Mine into Peru Creek (sec Chapter 5). In addition, De.xheimer ( 1982) reported high concentrations of Zn (2 - 1192 ppb) and Cu ( 105 - 225 ppb) in the Snake River and also showed that the concentration of Zn in the water of the Blue River decreased with increasing pH. The Blue River appears to have the lowest concentrations of all elements with the e.xception of Se, but the difference between the maximum and minimum Se concentrations is only 0.4 ppb. Because of mining in the Blue River basin, these results are une.xpected; however most of the An was recovered by placer mining which does not contribute significantly to the contamination of the water. Three component-mixing triangles were constructed from the average weighted .Na, K. Mg, and Ca concentrations in each stream (Table 8.4). The points labeled P in Figure 8.4 are the predicted concentrations (P) of major elements in the water in the Dillon Reservoir. The point labeled DR indicates the average concentrations of major elements in the Dillon Reservoir. The DR water is enriched in Na by 25.6%, Mg by 2.7%. and Ca by 25.1%, but it is depleted in K by 7.7% (Table 8.4) relative to the predicted concentrations. Because of analytical errors and uncertainties in interpolating the concentrations based on discharge, any element whose observed concentration differs by less than 10% from the predicted concentration is considered to be in balance within error and no attempt to explain the difference is required. In general, if the increases in the concentrations were due to evaporation, as show n in Figure 8.5, the point representing the composition of DR would move along the dashed line that passes from the origin through point P. If the concentrations of elements 131 evaporation TMC D fl' ^ C o 2 c BR 03O c • p . o o c '(/) CO 03 DA O c dilution 0 SR 0 increasing concentration Figure 8.4. Effect of evaporation and dilution on the composition of water in the Dillon Reservoir (DR) relative to the predicted composition (P). in the Dillon Reservoir were diminished by dilution, point DR would lie on the dashed line in Figure 8.6 between point P and the origin. Therefore, if the water of DR does not lie on the trajectory indicating evaporation or dilution, other inputs or sinks for the elements must be considered. 132 6000 5500 - TMC 5000 4500 BRDR CT 4000 3500 3000 2500 SR 2000 1000 2000 3000 4000 5000 6000 N a ppb 54000 TMC' 49000 44000 39000 DR g; 34000 O 29000 24000 BR 19000 14000 SR 9000 500 1500 2500 3500 4500 5500 6500 K ppb Figure 8.5. Three-component mixing of the predicted concentrations o f Na. Mg (a). Ca. and Mg (b) in the water o f the Snake River (SR). Blue River (BR). Tenmile Creek (TMC). The weighted average concentrations derived by mixing of the stream water are represented by point P. whereas DR is the average chemical composition of the outflow water, which represents the water in the Dillon Reservoir. 133 The point representing the Dillon Reservoir (DR) in Figure 8.5a lies outside the mixing triangle because the water has a higher concentration o f Na than predicted. The enrichment of the water in Na is not explainable by evaporation but may be caused by the use of road salt by the town of Dillon and by other municipalities from November to May. The town of Dillon uses 150 to 200 tons of a 57c salt and sand mixture annually. Consequently, the increase in Na (and Ca) concentrations in the Dillon Reservoir is attnbutable to the dissolution of halite (NaCl), anhydrite (CaSOj), and possibly CaCF. wliich arc used to lower the freezing point of water. Other anthropogenic sources of Na. such as municipal wastewater, are not likely to be important because the concentrations of P in the three rivers and the reservoir are below the detection lim it of 50 ppb. Phosphorus is used in detergents and fertilizers and therefore, if there is significant contamination of the reservoir by the local communities, it should be reflected by an increase in the P concentration. 8.3.2 Trace Elements The trace elements Zn. Mo. Cu. Ni. Cd. Se. and U have detectable concentrations m the water of the major rivers of the Dillon Reservoir. The weighted average concentrations for the trace elements were determined using the same procedure as that lor the major elements in section 8.3.1. Unlike the major elements discussed above, the relationship between concentration of trace elements and discharge is not necessarily the same in every stream. Figure 8.7 indicates that the Zn concentrations decrease with increasing discharge in the Snake River, but increase with increasing discharge in the Blue River. The Zn concentration in Tenmile Creek is variable at low discharge but increases slightly at high 134 Snake River ^ 200 100 0 100 Blue River 80 Q. 60 Q. N 40 20 0 80 Tenmile Creek 60 20 0 0 100 200 300 400 500 600 700 800 discharge cfs Figure 8.6 Zn concentrations as a function of average monthly discharge for water samples collected from the mouths of the Snake River, Blue River, and Tenmile Creek. The period of time represented is September 1998 through October 2000. discharge. The patterns of other trace elements vary similarly suggesting that the concentrations of trace elements do not decrease with increasing discharge in all cases. The concentrations of the trace metals are decreased by sorption but may also be increased by leaching of soil and tailings piles during high discharge events, which may flush metal-rich fluids into the streams. 135 8.3.2.1 Molybdenum Elevated concentrations of Mo occur in the water o f Tenmile Creek and in the Dillon Reservoir, but Mo is below the detection lim it in the Snake River and the Blue Riser. In addition, the data in Figure 8.8 indicate that the average weighted concentration of Mo in the reservoir is greater than the measured concentration by about 18.6% (Table 8.4). 250 TMC 200 Q. DR BR SR 0 50 100 150 200 250 Zn ppb Figure 8.7. Three component mixing of the predicted concentrations of Mo in water in Dillon Reservoir and the actual concentration in the water (lowing out of the reservoir in the Blue River below the dam. 136 log CR acid log CR acid Sediment soluble sediment soluble sediment sample and overflow and pore water water DR-1 3.4 3.9 DR-2 3.7 DR-3 3.6 2.6 DR-4 3.3 DR-5 3.1 DR-7 3.2 DR-8 4.1 DR-9 3.5 DR-10 3.7 DR-11 3.4 DR-12 4.2 2.0 D R-13 4.3 2.2 D R-14 3.9 DR-15 3.1 DR-16 4.3 DR-17 3.8 DR-18 3.7 = 0.2 2.3 r 0.4 average Table 8.5 Log CR for Mo in the acid soluble sediment, water in the Dillon Reservoir, and pore water. The errors are 2 standard deviations o f the mean. 137 The high concentrations of Mo in the sediment of the Dillon Reservoir (Chapter 7 ) indicate sorption of MoO;"'^ to hydroxides of Fe and Al. Therefore, the deficiency of Mo in the water of the Dillon Reservoir compared to the predicted concentration is also attnbutable to sorption of Mo to the sediment. To test this hypothesis further, the concentration ratios (CR) (ratio of the concentration of Mo in the acid-soluble sediment to the concentration in the water) o f Mo were calculated for the water in the reservoir and the pore water of the sediment at the bottom of the reservoir. The results in Table 8.5 indicate that the log CR values for Mo in solution in the water of the reservoir range between narrow limits and have a mean of 3.7 ± 0.2. whereas the log CR values relative to Mo in the pore water have an average of 2.3 ± 0.4. .Although the pH of water in the Dillon Reservoir ranges from 6.9 to 7.3. it is likely that the pH of the pore water in the sediment is at least one half pH unit lower than in the water of the reservoir. Therefore, the high average log CR value of Mo relative to the water in the reservoir is consistent with sorption of M oO:‘ * at near neutral pH whereas the lower average log CR o f the pore water may reflect the more acidic conditions in the sediment at the bottom of the reservoir. In addition. Mo may also occur as the M oO ;' ion in the oxygenated surface water of the reservoir. However, if this ion is dominant over MoO:'*. Mo should desorb from the sediment with increasing pH. 8.3.3.2 Zinc, Copper, Nickel, and Cadmium Three-component mixing triangles were produced for Zn. Cu. Ni, and Cd to determine the average composition of water in the Dillon Reservoir assuming it to be a mixture of the water entering from its three principal tributaries. .All of the 138 2.5 2 TMC 1.5 0.5 BR SRDR 0 1.5 BR DR SR Q. 0.9 0.8 TMC 0.7 0.6 50 100 150 200 250 Zn ppb Figure 8.8. Three component mi.xing o f average weighted river water to determine the concentrations of Zn, U, and Se in the water in Dillon Reservoir. The actual concentrations in the water were measured in water flowing out o f the reservoir below the dam. Abbreviations are the same as in Figure 8.4. 139 TMC SR -Q Q. Q. z DR 0.5 0 1 0.8 TMC SR 0.6 O 0.4 BR 0.2 DR 0 3.5 3 SR 2.5 Q. Q. 2 3 o 1.5 1 DR 0.5 TMCBR 0 0 50 100 150 200 250 Zn ppb Figure 8.9. Three component mixing of the predicted concentrations of Zn. Cu. Cd. and Ni in the water in Dillon Reservoir and the actual concentrations in the water tlowing out of the reservoir in the Blue River below the dam. .Abbreviations are the same as in Figure 8.4. 140 concentrations of trace elements in the Dillon Reservoir are lower than the predicted concentrations (Figure 8.8 anH s.9'! with die e.xception of Se. which is only 4.8% higher than predicted (Table 8.4). As with the major elements, any trace element whose concentration is within 10% of the predicted concentration is assumed to be within the margin of error. There may be several possible e.xplanations for the lower than predicted concentrations of trace elements in the water of the Dillon Reservoir. 1 ) dilution due to ineteonc precipitation exceeding evaporation. 2) sorption onto hydroxides of Fe and .Al. clay minerals, and dissolved organic matter, and 3) uptake by aquatic organisms. None of the trace element concentrations is explained by dilution due to meteoric precipitation. In addition, the concentrations of the conservative major elements are also not attributable to dilution and therefore dilution does not control the trace element concentrations either. Instead, the existence of elevated concentrations of trace elements in the acid-soluble fraction of sediment in the reservoir supports the hypothesis that the trace metals are removed from the water by sorption to Fe and Al hydroxides and to other sorbents such as suspended organic matter and by absorption as micronutrients by organisms in the water. The importance of the effect of pH on the concentrations of trace elements in the water is indicated by the fact that the concentrations of Zn and Mo in the Dillon Reservoir water decrease with increasing pH (Figure 8.10). The concentrations of Cu. Ni. and Cd also decrease as a function of pH. but the data points are more scattered because of the low concentrations of these elements. The dependence of the trace-metal concentrations on the pH supports the hypothesis that the loss of the trace metals from the 141 100 80 & 60 ♦ Q. N 40 ♦ 20 0 100 J3 a . Q. O 2 6.0 6.5 7.0 7.5 8.0 8.5 9.0 PH Figure 8.10. Zinc and Mo concentrations as a function of pH in the water of the Dillon Reservoir. 142 *Dd> (/)o • o U 4 4.2 4.4 4.6 4.8 5 5.2 5.4 5.6 5.8 6 6.2 6.4 6.6 6.8 7 7.2 7.4 7.6 7.8 8 pH Figure S. II. Sorption curves derived from neutralization of Snake River water. The area outlined in the bo.\ is shown at larger scale in Figure 8.12 in order to determine the percent sorbed at near neutral pH. 99.8 99.4 98.6 98.2 <13 97.8 .Q Cu -H O 97.4 pH Figure 8.12. Portion of the sorption curve for Cu outlined in Figure 8.11 used to determine the percent of Cu sorbed at near neutral pH values. 143 Dillon Reservoir is due to sorption. To test this hj'pothesis further, the sorption curves for Zn and Cu derived from the experiment described in Chapter 5 were used to determine the ACu/AZn ratio of the water in the Dillon Reservoir assuming that the pH increased in increments of 0.2 in the water entering the reservoir. In order to carry out this test, the ratios of the amount sorbed of Cu and Zn (ACu/AZn) were calculated for 0.2 increments of the pH from 5.8 to 7.6 using the sorption curves in Figure 8.11 and 8.12. The increase in the pH was determined from the sorption curves in Figure 8.11 and 8.12. The values of ACu and AZn were calculated as the change in the concentration of each element in P corresponding to the increase of the fraction sorbed. The resulting \ allies of ACu and AZn are listed in Table 8.6 and the calculated ACu/AZn ratios were plotted vs pH in Figure 8.13. These ratios are equal to the slope representing the difference between the predicted concentrations of Cu and Zn in the reservoir (P) and the measured concentrations (DR). The slope of the vector joining point P to point DR in Figure 8.9 is: ACu/AZn = (1. 3-0.9)/ (85-27) = 0.4/58 = 0.007. The vanation of the ACu/AZn ratio with increasing pH in Figure 8.13 indicates that ACu/AZn ratio of 0.007 corresponds to a change in pH form 5.8 to 6.0. Since these pH values are not unreasonable for stream water entering the Dillon Reservoir, the sorption hy pothesis to explain the observed deficiencies of trace metals in the Dillon Reservoir is l iable. The sorbent is not restricted to hydroxide particles of Fe and Al suspended in the water, but probably includes organic particles and dissolved organic matter which may complex trace metals. In addition, some of the trace elements are micronutrients (e.g. Zn and Cu) and may also be assimilated by planktonic organisms in the Dillon Reservoir. 144 pH interval %Zn sorbed %Cu sorbed AC u ppb AZn ppb ACu/AZn 5.8 - 6.0 12 6 0.078 10.2 7.65E-03 6.0 - 6.2 14 2 0.026 11.9 2.18E-03 6.2 - 6.4 16 2 0.026 13.6 1.91 EE-03 6.4 - 6.6 12 0.5 0.0065 10.2 6.37E-04 6.6 - 6.8 11 0.05 0.00065 9.35 6.95E-05 6.8 - 7.0 10 0.05 0.00065 8.5 7.65E-05 7.0 - 7.2 6 0.05 0.00065 5.1 1.27E-04 7 .2 -7 .4 2.5 0.01 0.00013 2.125 6.12E-05 7.4 - 7.6 1 0.01 0.00013 0.85 1.53E-04 Table S. 6. Percent Cu and Zn sorbed for each pH interval and the resulting change in Cu and Zn concentrations from the predicted (P) concentrations in the water of the Dillon Reservoir 145 7.6 5 6.5 6.2 ♦ O.OOE-00 1.00E-03 2.00E-03 3.00E-03 4.00E-03 5.00E-03 6.00E-03 7.00E-03 8.00E-03 9.00E-03 ACu/AZn Figure 8.13. pH interval as a function of the ACu/AZn ratio. 146 8.4 Conclusions The average weighted chemical compositions of water in the Snake River. Blue River. Tenmile Creek, and the Dillon Reservoir differ from each other in terms of major and trace element concentrations reflecting differences in the geology of each basin. The Tenmile Creek is characterized by high concentrations of Na. K. Mg. Ca. Mo, U. and Ni. the Snake River has the highest concentrations of Zn and Cu due to the acid drainage from Peru Creek, and the Blue River has the highest concentration of Se. The major elements vary systematically with discharge such that there is a decrease in concentration as the discharge increases. The concentrations of trace elements do not vary systematically with discharge and the patterns vary from stream to stream. The water in the Dillon Reservoir differs in composition from the predicted concentrations of the major and trace elements. The concentrations of Na and Ca are higher than predicted, most likely due to the use of road salt in the winter in the suiTounding communities. The concentrations of trace elements in the Dillon Reser\oir are all lower than predicted, which is attributable to sorption to hydro.xides of Fe and .A.I and by organic material, as well as to uptake by aquatic organisms. The water in Tenmile Creek and the Dillon Reservoir contains significant concentrations of Mo. In addition, the acid-soluble sediment in the reservoir (Chapter 7) has elevated concentrations of this element. The concentration ratio of Mo for the sediment and pore water is lower than that for Mo in the sediment and water in the reser\oir. Molybdenum may exist both as MoO^"' and M oO :'*. but M oO:'^ appears to be the dominant species judging by the evidence that Mo is sorbed in cationic form by hydroxides in the sediment. 147 The concentrations of trace metals in the Dillon Reservoir are lower than the predicted concentrations in this study. According to the sorption curves derived for Cu and Zn for water in the Snake River, the deficiency in the concentrations of trace elements of water in the Dillon Reservoir can be accounted for by sorption to hydro.xides of Fc and .A! and by organic matter that is suspended in the water. The sorption occurs due to small increases in the pH that occur when the water of the tributary streams enters the Dillon Reservoir. 148 CHAPTER 9 SUMMARY OF CONCLUSIONS The research done in this dissertation has resulted in several conclusions. • The chemical composition of the water entering the Dillon Reservoir is controlled by the geology and ore deposits of each basin, but varies seasonally because of natural fluctuations in pH and discharge. • The Snake River is acidic and metal-rich due to contamination by natural acid rock-drainage. which results from the o.xidation of pyrite and other sulfide minerals within the underlying bedrock of the drainage basin. The concentrations of the trace elements in the Snake River decrease as a function of distance downstream due to neutralization of the acidic water by tributaries. For example, the Snake River mixes with Deer Creek, causing the pH to rise and leading to the precipitation of chemically active .Al-hydroxysulfate w hich sorbs trace metals. o Experimental neutralization of water from the Snake River indicates that Pb, Cu, Zn, and Ni are sorbed with increasing pH, whereas sulfate is initially removed from the water at low pH and is subsequently released as the pH increases. In addition, the neutralization experiment confirmed that there is a preferred sorption sequence such 149 thaï Pb is removed at the lowest pH followed by Cu. Zn. and Xi. Sorption of trace metals at low pH is enhanced by the presence of anions such as SO4, o The changes in pH in the Snake River control not only the formation and the composition of the sorbent, but also the partitioning of trace elements between water and the precipitates. The progressive downstream depletion of trace metals in the Snake River limits the amount of trace metals available for sorption farther downstream and results in an improvement in the water quality by natural processes. • The weathering experiments indicated that the major variable that controls the concentrations of elements in solution over time is the pH w hich is controlled by: I ) the release of H" ions during the formation of Fe and A1 hydroxides by hydrolysis; and 2) the presence of carbonate minerals that have a buffering effect on the pH of the solutions. The pH controls the spéciation of trace metals in solution, the formation of inorganic sorbents, the polarity of surface sites on these sorbents, and the sorption coefficients of trace elements. o The water draining from the Pennsylvania Mine has a low pH and elevated concentrations of major and trace elements. As this water mixes with water in Peru Creek, the pH rises causing the formation of Fe-. .A1-. and SO 4- rich precipitates including schw ertmannite. Trace metals are then sorbed to these precipitates. • The sediment accumulating in the Dillon Reservoir contains elevated concentrations of Fe. At. and Mn and various trace elements such as Pb. Cu. 150 Zn. Ni. Cd. Co. Ag and Mo. There is an overall correlation such that the higher concentrations of elements occur where the water depth increases and in general with increasing distance from the mouths of the streams. In addition, the acid-soluble fraction of sediment is mechanically separated from the coarse-grained detrital material because the acid-soluble fraction has a lower density. The amount of acid-soluble sediment is positively correlated with the concentrations of Fe and .A1 and with the total concentration of trace metals in the sediment, which confirms that the trace metals are sorbed to hydroxides of Fe and Al. o The sediment in the Tenmile Creek arm has anomalously high concentrations of Mo as does the main body of the Dillon Reservoir. This observation indicates that the Mo must be present as the M o O f* because only cations are sorbed under near-neutral conditions. Therefore, even though water from the tailings of the Climax Molybdenum Mine is being treated to remove metals, some Mo is getting into the sediment of the Dillon Resetwoir. o The metals in the acid-soluble fraction of sediment in the Dillon Reservoir have commercial value and can be used to off-set expenses when the reservoir must be dredged in the future. • The pH and concentrations of trace metals in the water o f the Dillon Reservoir vary seasonally and therefore the water withdrawn from the reservoir does not always have the same composition. 151 o The water in the Dillon Reservoir differs in composition from the predicted concentrations o f the major and trace elements. The concentrations of Na and Ca are higher than predicted, most likely due to the use of road salt in the winter in the surrounding communities. The concentrations of trace elements in the Dillon Reservoir are all lower than predicted, which is attributable to sorption by hydro.xides of Fe and Al and by organic material, as well as to uptake by aquatic organisms. o The water in Tenmile Creek and the Dillon Reservoir also contains significant concentrations of Mo. The concentration ratio of Mo in the sediment and pore water is lower than that for Mo in the sediment and w ater in the reservoir perhaps because the pore wacr has a lower pH than the water in the reservoir, o .According to the sorption curves derived for Cu and Zn for water in the Snake River, the deficiency in the concentrations o f trace elements of water in the Dillon Reservoir can be explained by sorption to hydroxides of Fe and .Al and to organic matter suspended in the water. Calculations indicate that sorption occurs due to small increases in the pH that occur when the water of the tributary streams enters the Dillon Reservoir. This dissertation provides new methods of solving some of the problems associated w ith water and sediment contaminated by .AMD and ARD. The results of the experiment in Chapter 5 demonstrated that the sorption o f trace elements 152 can be effectively investigated by neutralizing natural water samples in the laboratory: thereby developing a unique set of sorption curves for the trace metals dissolved in the water. In addition, the sorption curves were useful in explaining the loss of trace elements from the water of the Dillon Reservoir (Chapter S). The laboratory weathering experiments in Chapter 6 provided insights into the production and compositional evolution of acid mine-water that cannot be determined from natural water samples alone. These and other methods dc\eloped in this dissertation can be applied to other drainage basins throughout the world, which are contaminated by AMD and ARD. 153 APPENDIX A 154 Appendix A. Elements analyzed and detection limits for ICP-MS and ICP-OES. Detection limit Detection Element Method Method (PPb) (PPb) ICP-MS ICP-OES Antimony Sb MS 0.1 ICP 50 Aluminum Al ICP 50 Arsenic As MS 0.1 ICP 30 Barium Ba MS 0.01 ICP 10 Beryllium Be MS 0.1 ICP 5 Bismuth Bi MS 0.01 ICP 50 Cadmium Cd MS 0.01 ICP 10 Calcium Ca ICP 50 Cerium Ce MS 0.01 Cesium Cs MS 0.01 Chromium Cr MS 0.1 ICP 10 Cobalt Co MS 0.1 ICP 10 Copper Cu MS 0.1 ICP 5 Dysprosium Dy MS 0.01 Erbium Er MS 0.01 Europium Eu MS 0.01 Gadolinium Gd MS 0.01 Gallium Ga MS 0.01 Hafnium Hf MS 0.01 Hclmium Ho MS 0.01 Indium In MS 0.01 Iron Fe ICP 50 Lanthanum La MS 0.01 ICP 10 Lead Pb MS 0.01 ICP 30 Lutetium Lu MS 0.05 Magnesium Mg ICP 50 Manganese Mn MS 0.1 ICP 5 Mercury Hg MS 0.2 Molybdenum Mo MS 1 ICP 10 Neodymium, Nd MS 0.01 Nickel Ni MS 0.1 ICP 10 Niobium Nb MS 0.01 Phosphorus P ICP 50 Potassium K ICP 100 Praseodymium Pr MS 0.01 Rubidium Rb MS 0.1 Scandium Sc MS 0.1 ICP 1 Selenium Se MS 0.1 Samarium Sm MS 0.01 155 Appendix A. (cont.) Silver Ag ICP 1 Sodium Na ICP 50 Strontium Sr MS 0.01 ICP 1 Tantalum T a MS 0.01 Tin Sn MS 0.01 ICP 50 Tellurium Te MS 0.1 Terbium Tb MS 0.01 Thallium Th MS 0.01 Thulium Tm MS 0.01 Titanium Ti ICP 10 Tungsten W MS 0.01 ICP 50 Uranium U MS 0.01 Vanadium V MS 0.1 ICP 10 Ytterbium Yb MS 0.01 Yttrium Y MS 0.01 ICP 5 Zinc Zb MS 0.1 ICP 5 Zirconium Zr MS 0.1 ICP 10 156 APPENDLX B 157 Appendix B. Sample locations. Samples in Appendix C. ______Location SR-DC-98-1 Snake River S R -D C -98-2 Snake River S R -D C -98-4 Snake River S R -D C -98-5 Snake River SR-DC-98-6 Snake River SR-98-1 Snake River SR -98-2 Snake River SR -98-6 Snake River SR -98-7 Snake River SR -98-8 Snake River SR-PC-98-1 Snake River RiverSnake below confluence with Peru Creek PC-98-3 Peru Creek just downstream from Pennsylvania Mine (1st crossroad) PC-98-4 Holding pond at Pennsylvania Mine PC-98-5 Minp effluent draining into Peru Creek at Pennsylvania Mine PC-98-6 Grave site along road to Pennsylvania Mine PC-98-7 Peru Creek above confluence with Snake River Samples in Appendix D. water 1W Snake River/Deer Creek confluence 2W Snake River/Deer Creek confluence 3W Snake River/Deer Creek confluence 4W Snake River/Deer Creek confluence 5W Snake River/Deer Creek confluence 6W Snake River/Deer Creek confluence 7VV Snake River/Deer Creek confluence see map Chapter 5 Figure 5.1 IPS Appendix B. (cont.) precipitate IP Snake River/Deer Creek confluence 2P Snake River/Deer Creek confluence 3P Snake River/Deer Creek confluence 4P Snake River/Deer Creek confluence 5P Snake River/Deer Creek confluence GP Snake River/Deer Creek confluence 7P Snake River/Deer Creek confluence see map Chapter 5 Figure 5.1 Samples in Appendix E. Location Ground water GW-1 Water well, Montezuma Mercantile store G W -2 Water well, Dave Hannin home, Montezuma G W -3 Water well. Grannies Bed and Breakfast, Montezuma G W -4 Natural seep, above the portal of the New York Mine Mine effluent Burke-Martin Mine, upper portal. Snake River valley, 0.5 km upstream MW-1 of Montezuma M W -2 Burke-Martin Mine, lower portal M W -3 Saints John Mine, Saints John Creek Valley M W -5 Spring, ferricrete deposit, upper Snake River M W -6 Horse Shoe Mine, upper Peru Creek (Argentine District) Meteoric precipitation (snow) SS-1 Pennsylvania Mine, Peru Creek SS-2 Deer Creek SS-3 New York Mine, Montezuma, Snake River Water samples SR-1 Snake River well above confluence with Deer Creek SR-2 Snake River near confluence with Deer Creek SR-3 Snake River above Burke-Martin Mine SR-4 Snake River above confluence with Saints John Creek SR-5 Snake River above confluence with Peru Creek SR-6 Snake River below Peru Creek SR-7 Snake River downstream from SR-6 SR-8 Snake River downstream from SR-7 SR-9 Snake River at entry to Dillon Reservoir DC-1 Deer Creek, upper 159 Appendix B. (cont.) DC-2 Deer Creek, lower PC-1 Peru Creek, upper PC-2 Peru Creek, lower SJC-1 lower Saints John Creek Samples in Appendix G. DR-1 Bluer River arm DR-2 Bluer River arm DR-3 Bluer River arm DR-4 Bluer River arm DR-5 main body DR-7 Snake River arm DR-8 Snake River arm DR-9 Snake River arm DR-10 Snake River arm DR-11 Snake River arm DR-12 main body DR-13 main body DR-14 main body DR-15 Tenmile Creek arm DR-16 Tenmile Creek arm DR-17 Tenmile Creek arm DR-18 Tenmile Creek arm see map Chapter 7 Figure 7.2 Sample m Appendix H. SR INFLOW 98W mouth of Snake River SR 699W mouth of Snake River SR INFLOW 999W mouth of Snake River SR INFLOW 1099W mouth of Snake River SR INFLOW 0700W mouth of Snake River SR INFLOW 100GW mouth of Snake River BRI 699W mouth of Blue River BRI INFLOW 999W mouth of Blue River BRI INFLOW 1G99W mouth of Blue River BRI INFLOW G7GGW mouth of Blue River 160 Appendix B. (cont. BRI INFLOW 1000W mouth of Blue River BRO 699W Blue River dam outflow BR OUTFLOW 999W Blue River dam outflow BR OUTFLOW 1099W Blue River dam outflow BR OUTFLOW 0700W Blue River dam outflow BR OUTFLOW 1000W Blue River dam outflow TMC INFLOW 98W mouth of Tenmile Creek TMC 699W mouth of Tenmile Creek TMC INFLOW 999W mouth of Tenmile Creek TMC INFLOW 1099W mouth of Tenmile Creek TMC INFLOW 0700W mouth of Tenmile Creek TMC INFLOW 1000W mouth of Tenmile Creek 161 APPENDIX C 162 Appendix C. Chemical analyses and pH of water samples from the Snake River, Deer Creek and Peru Creek collected in 1998. Method SR-DC-98-1 S R -D C -98-2 SR -D C -98-4 SR-DC-98-5 SR-DC-9E pH 3.1 3.2 3.7 4.5 4.9 SO: gravimetric 91.17 90.96 67.09 66.06 51.45 Na ICP 2550 2530 2380 2160 2140 K ICP 800 790 770 710 730 Mg ICP 5090 5070 4640 4170 4150 Ca ICP 9170 9160 9620 10340 10500 Ba ICP 30 29 30 28 26 Fe ICP BD BD BD 67 63 Al ICP 4090 4080 3420 1950 1770 Mn ICP 964 967 835 677 668 As ICPBDBD BD BD BD Mo ICP BDBDBD BD BD Ag ICPBDBD BD BDBD Cd ICPBDBD BD BDBD p ICP BDBDBD BD BD Be ICP BDBD BD BDBD Sc ICP BDBD BD BDBD Ti ICPBD BDBD BD BD V ICPBDBD BD BD BD Cr ICPBD BD BD BDBD Co ICP 13 BD BD BD 16 Ni ICP 10 15 18 13 21 Cu ICP 15 15 14 10 10 Zn ICP 579 578 501 409 404 Y ICP 5 6 6 BD 5 Zr ICP BDBD BD BDBD Sn ICP BDBD BD BDBD Sb ICP BD BD BD BD BD Sr ICP 70 71 67 63 63 La ICPBDBD BD BD BD W ICPBDBD BD BDBD Pb ICPBDBD BD BDBD Bi ICP BDBDBD BD BD Rb MS 2.9 2.7 2.7 2.3 2.3 Sr MS 61.5 56.8 60.3 51.8 52.1 Mn MS 964 968 866 679 687 Be MS 0.8 0.8 0.8 0.7 0.7 Sc MS 3.6 3.5 3.4 3.2 3.1 Cu MS 13.7 12.4 10.8 9.7 9.5 Pb MS 0.71 0.69 1.17 1.89 1.35 163 Appendix C (cont.) Method SR-DC-98-1 SR -D C -98-2 SR -D C -98-4 SR-DC-98-5 SR-DC-9 Co MS 8.2 8.2 7.5 5.9 5.7 Zn MS 499 455 457 345 341 V MS BD BDBD BDBD Ni MS 15.9 15.7 14.3 12 10.7 U MS 0.29 0.27 0.27 0.28 0.25 Or MS BD BDBD BDBD Ga MS 0.14 0.12 0.12 0.08 0.08 As MSBD BDBD BDBD Se MS 1.2 1 1 1 0.6 Y MS 4.14 3.7 3.27 3.04 2.72 Zr MSBD BDBD BD 0.2 Nb MSBD BD BDBD BD Mo MSBD BD BDBD BD Cd MS 3.13 2.59 2.52 2.11 2.07 In MS BD BD BDBD BD Sn MSBD BD BDBD BD Sb MS BD BDBD BDBD Te MS BD BD BDBD BD Cs MS 0.15 0.13 0.13 0.09 0.09 Ba MS 27.8 24 26.7 23.2 22.3 La MS 1.5 1.33 1.23 1.18 1.07 Ce MS 1.96 1.62 1.39 1.33 1.18 Pr MS 0.3 0.24 0.21 0.21 0.18 Nd MS 1.8 1.56 1.37 1.35 1.2 Sm MS 0.81 0.77 0.7 0.7 0.67 Eu MS 0.11 0.08 0.07 0.07 0.05 Gd MS 0.95 0.87 0.8 0.79 0.74 Tb MS 0.67 0.66 0.66 0.64 0.64 Dy MS 0.98 0.86 0.79 0.8 0.76 Ho MS 0.68 0.67 0.65 0.65 0.64 Er MS 0.71 0.66 0.62 0.62 0.18 Tm MS 0.04 0.04 0.03 0.03 0.02 Yb MS 0.62 0.2 0.16 0.16 0.14 Lu MSBD BD BD BDBD Hf MS BD 0.04 0.04 0.03 0.03 Ta MSBD BDBD BDBD VV MSBDBD BD BDBD Hg MS BDBD BD BDBD TI MS 0.04 0.04 0.04 0.03 0.02 Bi MS BDBDBD BD BD Th MS BD 0.09 0.09 0.09 0.09 164 Appendix C. (cont.) Method SR-98-1 SR-98-2 SR-98-6 SR-98-7 SR-PC-98-1 SR-98-1 pH 5.9 5.4 5.1 6.3 5.9 6.6 SO, gravimetric 75.12 65.44 63.39 51.45 50.63 53.10 Na ICP 2210 1940 2010 2350 2010 2870 K ICP 900 670 670 720 690 890 Mg ICP 4100 3600 3780 4310 3440 3130 Ca ICP 17770 11810 11680 9650 14340 14640 Ba ICP 68 23 72 26 33 49 Fe ICP BD BD 54 103 BD BD Al ICP 140 86 160 2760 68 BD Mn ICP 349 464 535 743 599 236 As ICPBD BD BD BD 51 BD Mo ICP BDBD BD BD BD BD Ag ICP BD BD BD 3 BD BD Cd ICPBD BD BD BD BD BD P ICP BD BD BD BDBD BD Be ICP BDBD BD BD BD BD Sc ICP BD BD BD BD BD BD Ti ICP BD BDBD BDBD BD V ICP BD BDBD BDBD BD Cr ICP BD BDBD BD BD BD Co ICP 11 BD BD 16 BD BD Ni ICP BD BDBD 15 BD BD Cu ICP BD BD BD 19 14 9 Zn ICP 314 271 316 445 733 238 Y ICP BDBD BD BDBD BD Zr ICP BD BD BD BD BD BD Sn ICP BD BD BD BD BD BD Sb ICP BD BDBD BDBD BD Sr ICP 74 60 62 65 110 108 La ICP BD BD BD BDBD BD W ICP BDBD BD BDBD BD Pb ICP BD BDBD BDBD BD B: ICPBD BD BD BD BD BD Rb MS 2.4 1.9 2.2 ND ND ND Sr MS 64.8 47.9 50 ND ND ND Mn MS 337 443 540 ND ND ND Be MSBD BD BD ND ND ND Sc MS 2.8 2.5 2.8 ND ND ND Cu MS 1.8 1.9 3.2 ND ND ND Pb MS 0.15 0.09 0.1 ND ND ND Zn MS 276 219 266 ND ND ND Ni MS 6 12.8 9 ND ND ND Co MS 2.6 3.9 4.5 ND ND ND 165 Method SR-98-1 SR-98-2 SR-98-6 SR-98-7 SR-PC-98-1 SR-98- Cr MSBDBDBDNDND ND V MSBDBDBDNDND ND U MS 0.1 0.03 0.03 NDNDND Ga MS 0.03 0.04 0.06 NDND ND As MSBDBDBDND NDND Se MS 0.6 0.8 0.9 NDNDND Y MS 0.61 0.61 0.91 NDND ND Zr MSBDBDBDNDNDND Nb MS BDBDBDND NDND Mo MS BDBDBDNDND ND Cd MS 1.4 1.48 1.6 NDNDND In MS BD BDBDNDND ND Sn MSBDBDBDND NDND Sb MS 0.1 BDBDNDNDND Te MS BD BDBDNDND ND Cs MS 0.12 0.07 0.09 ND ND ND Ba MS 58.8 19.6 58.7 NDND ND La MS 0.06 0.07 0.65 ND NDND Ce MS 0.08 0.07 0.3 NDND ND Pr MS 0.01 0.01 0.04 NDND ND Nd MS 0.06 0.05 0.22 ND ND ND Sm MS 0.02 0.02 0.05 NDND ND Eu MS 0.02 0 0.03 ND ND ND Gd MS 0.01 0.01 0.06 NDND ND Tb MSBDBD BDND NDND Dy MS 0.02 BD 0.05 NDND ND Ho MSBDBD 0 ND NDND Er MSBDBD 0.02 NDND ND Tm MS 0.88 BDBD NDNDND Yb MSBD 0.01 0.01 NDND ND Lu MSBDBDBDNDND ND Hf MS 0.03 BD BDNDND ND Ta MS BD BDBDNDND ND W MSBD BDBDNDNDND Hg MS BD BDBDNDND ND TI MS 0.01 BD 0.02 NDND ND Bi MS BD BDBDNDND ND Th MS 0.09 BD BDNDND ND 166 Appendix C. (cont.) Method PC-98-3 PC-98-4 PC-98-5 PC-98-6 PC-98-7 pH 6.3 2.8 4.5 4.2 5.6 SO 4 gravimetric 29.84 711.44 68.74 90.14 44.45 Na ICP 1350 4460 1740 2250 1920 K ICP 480 910 590 780 740 Mg ICP 2620 28450 4700 4630 3150 Ca ICP 9950 84020 15950 16010 13610 Ba ICP 36 10 37 46 33 Fe ICP 50 13650 81 85 BD Al ICP 50 23140 1490 3170 96 Mn ICP 42 25950 1960 1700 751 As ICP BD BD BD BD 31 Mo ICP BDBDBDBDBD Ag ICP BD 10 BD BDBD Gd ICP 10 166 14 12 10 P ICP BD 109 BDBDBD Be ICP BD BD BD BD BD Sc ICP 1 3 BDBDBD Ti ICP BD BD BD BDBD V ICP BD BD BD BD BD Cr ICP 10 17 10 10 10 Co ICP 10 86 10 10 10 Ni ICP 10 217 16 16 10 Cu ICP 5 7230 454 207 56 Zn ICP 9 42250 3050 2060 1030 Y ICP BD 76 BD 7 BD Zr ICP BDBDBDBDBD Sn ICP BDBDBDBDBD Sb ICP BDBDBDBDBD Sr ICP 125 803 184 166 131 La ICP BD 35 BDBDBD W ICP BD BDBDBDBD Pb ICP 30 51 30 30 30 Bi ICP BDBDBDBDBD 167 APPENDIX D 168 Appendix D. Major and trace element concentrations for water samples in the Snake River below the confluence with Deer Creek reported in pg/L. Major elements measures by ICP-OES and trace elements by ICP-MS. Sample 1W 2W 3W 4W 5W 6W 7W Blank pH 3.6 5.9 6.3 5.2 5.2 5.3 5.2 - distance (m)“ 7 15 17 37 41 48 54 • Al 4380 BDBD 2040 2030 4690 1130 BD Fe 124 BDBD 238 272 514 130 BD SO 4 (ppm) 49.2 31.1 32.8 10.7 42.1 46.8 29.4 - Mn 1700.0 226.0 116.0 714.0 714.0 508.0 516.0 0.2 Na 2740 1780 1620 2240 2250 2220 2280 BD K 1230 690 540 850 790 790 830 BD Ca 11370 13090 13150 12550 12600 12510 12500 BD Mg 6210 3260 2780 4590 4490 4530 4520 BD Rb 8.0 1.6 1.3 2.4 2.1 2.3 2.5 BD Sr 70.70 46.10 50.80 71.20 69.00 67.10 57.40 0.2 Cu 20.6 8.4 5.2 24.3 19.1 22.2 16.3 0.3 Pb 2.71 0.37 0.61 2.13 1.43 2.22 1.10 0.02 Zn 614.0 186.0 136.0 487.0 426.0 467.0 429.0 2.0 Ni 21.3 8.1 5.8 17.3 14.4 15.0 15.7 0.1 Cd 2.81 0.73 0.47 1.86 1.49 1.69 1.38 0.02 Co 14.1 2.2 1.3 6.5 5.5 5.6 6.0 BD Cr 0.7 0.7 0.5 1.0 0.5 0.6 0.6 BD BD = below detection limit 169 Appendix D. Major and trace element concentrations of precipitates in the Snake River channel below the confluence with Deer Creek reported in pg/g or weight % acid-soluble precipitate. Major elements measures by ICP-OES and trace elements by ICP-M S. Sample IP 2P 3P 4P 5P 6 P 7P pH 3.6 5.9 6.3 5.2 5.2 5.3 5.2 distance (m) 7 15 17 37 41 48 54 Al °o 12.7 19.4 19.9 20.5 22.5 27.9 20.5 Fe =0 7.1 2.9 2.4 2.8 3.6 2.6 3.1 O C °o 13.5 10.2 9.8 6.5 5.3 5.4 5.8 SC^°o 12.9 8.5 2.4 9.7 13.6 11.2 10.7 Mn 180.8 231.5 86.2 41.9 54.1 40.4 135.8 Na 543 491 410 465 569 517 927 K 410 728 373 429 616 709 1399 Ca 1862 724 591 608 3060 752 701 Mg 556 356 289 326 401 425 431 Rb 3.4 1.3 0.7 0.9 1.3 1.5 3.0 Sr 19.78 7.74 5.69 4.44 4.35 4.63 4.85 Cu 181.2 322.0 402.6 150.2 96.1 142.9 89.2 Pb 220.15 268.29 336.98 89.24 120.64 123.82 105.79 Zn 807.8 11414.6 6593.8 542.7 660.9 765.7 718.4 Ni 19.4 106.6 196.7 19.9 14.3 11.2 22.4 Cd 2.11 2.32 3.92 2.71 0.79 0.69 1.55 Co 1.5 1.5 1.1 0.6 0.5 0.4 1.1 Mo 11 2 4 8 10 6 11 Cr 168.7 165.9 132.4 89.4 159.7 96.1 138.7 W 4.78 89.18 339.55 235.07 62.50 53.36 21.46 170 Appendix D (cont.) Chemical analyses o f hard coatings on the Snake River and Deer Creek streambeds. Element Method SR-DC-98-1 R DC-SR-98-1R Be ICP 7 4 Na ICP 2473 751 Mg ICP 5995 44762 Al ICP 57509 56510 P ICP 17679 11695 K ICP 5154 1793 Ca ICP 33815 41504 Sc ICP 3 6 Ti ICP 637 145 V ICP 240 143 Cr ICP 104 111 Mn ICP 1088 114158 Fe ICP 392570 154981 Co ICP 57 487 Ni ICP 77 464 Cu ICP 365 210 Zn ICP 1128 6403 As ICP BDBD Sr ICP 69 133 Y ICP 55 85 Zr ICP BD 10 Mo ICP 33 51 Ag ICP 15 14 Cd ICP 47 54 Sn ICPBDBD Sb ICP 71 39 Ba ICP 343 5968 La ICP 69 82 W ICP BD BD Pb ICP 983 714 Bi ICPBDBD BD = Below Detection 171 APPENDIX E 172 Appendix E. Ground water, mine water, snow melt, and stream water samples collected in 1996. (samples collected by Douglas Pride and Charles S. Robinson) Method GW-1 G W -2 G W -3 G W -4 MW-1 MW-2 MW-3 MW-5 MW -6 pH 7.01 7.54 6.37 7.28 7.81 7.87 6.37 4.24 3.34 Mg ICP 7.62 5.19 3.72 7.24 9.51 10.4 19.5 7.8 7.62 Na ICP 4.04 6.04 2.25 4.25 4.08 4.31 8.71 2.9 4.29 Al ICP BDBD BD BD BD BDBD 5090 1060 S ICP 44.9 28.4 19.9 26.2 51.6 60.9 127 43.4 102 K ICP 2.5 2 1.3 1.4 2.7 2.5 1.2 1.3 0.7 Ca ICP 40.5 42.7 15.1 56.9 47.9 58.8 142 49.8 49.5 Mn ICP 926 994 66 1060 1000 962 5850 594 32200 Fe ICP BD 170 150 BD 407 227 BD 2130 1940 Zn ICP 693 133 2090 853 2820 2560 3730 444 10400 Sr ICP 242 275 100 471 129 216 218 58 1370 Ba ICP 26 23 16 BD 15 13 14 13 19 Method SS -1 SS-2 SS-3 SR -1 SR-2 SR-3 SR-4 SR-5 SR-6 pH 5.85 5.45 5.51 3.7 3.78 6.08 6.58 7.12 6.56 Mg ICP 0.06 BD BD 4.35 5.17 3.82 3.97 4.01 3.68 Na ICP 0.44 0.46 0.48 2.28 2.48 2.02 2.12 2.08 2.07 Al ICP BDBD BD 3420 4050 575 301 448 233 SICP 0.41 0.35 0.15 25.3 29.5 18.5 19.1 20.2 18.6 K ICP 0.8 1 0.3 0.8 0.9 0.8 0.8 0.9 0.8 Ca ICP 0.54 0.5 0.17 6.99 9.42 11.8 13.3 17.8 15.8 Mn ICP 27 14 6 600 948 462 412 390 628 Fe ICP BD BD BD 610 320 140 100 180 80 Zn ICP 7 19 9 252 554 223 289 474 725 Sr ICP 3 BDBD 54 73 65 72 71 107 Ba ICP 11 17 BD 29 26 20 23 23 25 Method SR-7 SR -8 SR-9 DC-1 DC-2 P C -1 PC-2 SJC-1 pH 6.88 7.29 7.39 7.94 7.61 6.95 5.28 7.42 Mg ICP 3.41 3.04 3.14 2.06 2 2.78 3.48 4.22 Na ICP 2.11 2.56 2.58 0.96 1.19 1.11 1.7 1.74 Al ICP 260 304 255 BDBD BD 1200 BD SICP 16.8 11.7 11.6 2.45 4.45 11.8 20.6 21.1 K ICP 0.9 0.9 0.9 0.5 0.5 0.5 0.7 0.8 Ca ICP 15.5 14.4 14.7 10.7 11 10.7 13.6 27.4 Mn ICP 457 259 255 BD 10 240 1010 547 Fe ICP BD 170 140 150 100 BD 254 190 Zn ICP 602 310 308 8 12 133 1360 311 Sr ICP 105 101 104 38 41 144 129 60 Ba ICP 22 24 23 19 17 31 23 44 173 APPENDIX F 174 Appendix F. Chemical analyses of solutions from the experimental weathering of the ore from the Shoe Basin Mine (SBM) and the Pennsylvania Mine (PM). sample SBM-2-1 SBM -2-2 SBM -2-3 SBM -2-4 SBM -2-5 days elapsed 1 2 4 10 22 pH Method 6.6 6.5 6.1 5.8 5.1 Be ICP BD BD BD BD BD Na ICP 1020 4290 8800 9860 11980 Mg ICP 2920 4140 6560 11930 11710 AI ICPBD BD 92 185 115 P ICP BDBDBD 246 261 K ICP 1000 500 660 1420 6400 Ca ICP 10750 11740 13790 18830 16340 Sc ICP 2 2 2 1 2 Ti ICP BD BDBDBD BD V ICP BDBDBD BD BD Or ICP BD 12 BDBD 17 Mn ICP 12090 18740 44680 102780 111280 Fe ICP BD 548 6300 12730 59 Co ICP BDBDBD BD 19 Ni ICP 25 47 113 237 231 Cu ICP 16 230 1590 1550 1000 Zn ICP 35 168 688 1110 954 As ICP BDBDBD BD BD Sr ICP 200 228 229 256 207 Y ICP BD BDBDBDBD Zr ICP BD BD BD BD BD Mo ICP BD BD BD BD BD Ag ICP BD 1 4 9 10 Cd ICP BDBDBD BD BD Sn ICP BDBDBD BD BD Sb ICP BD BDBDBDBD Ba ICP 49 53 50 40 28 La ICP BDBDBD BD BD W ICP 57 57 BD BD BD Pb ICP 42 141 587 383 83 Bi ICP BD BD BD BD BD BD = below detection 175 Appendix F. (cont.) Method PM-1 PM-2 PM-3 PM-4 PM-5 PM -6 PM-7 PM -8 PM-9 days 1 2 5 10 15 25 35 45 60 elapsed pH 4.6 4.3 4.2 3.9 3.5 3.3 3.1 3.1 2.9 As MS 0.2 0.2 0.3 0.4 0.7 0.8 2.2 3.6 4.1 Ba MS BD 101 82.9 102 69.2 69.2 71.8 44.3 32.6 Be MS BD BD BD BD 0.1 0.1 BDBD BD Bi MS BD BDBD BDBDBD 0.11 0.34 0.08 Cd MS 88.7 98.2 103 70.3 70.7 155 179 208 163 Ce MS 9.53 11.3 14.8 13 18.6 58.7 35.1 107 123 Co MS 1 1 1.1 0.8 12.7 102 BDBD BD Cr MS 0.2 0.2 0.1 0.2 0.3 0.3 0.3 BD 16.4 Cs MS 0.07 0.04 0.07 0.03 0.03 0.08 0.05 BD BD Cu MS 27.4 31.7 73 29.1 79.2 108 150 2460 159 Dy MS 0.06 0.06 0.14 0.07 0.12 0.33 0.17 0.4 0.5 Er MS BD 0.02 0.03 0.02 0.04 0.1 0.05 0.1 0.15 Eu MS 0.11 0.1 0.13 0.1 0.13 0.41 0.23 0.7 0.76 Ga MS 0.05 0.07 0.09 0.08 0.12 0.3 0.2 0.53 0.52 Gd MS 0.14 0.18 0.29 0.23 0.29 0.78 0.5 1.29 1.51 Hf MS BD BD BD BDBD 0.01 0.23 BD BD Hg MSBDBDBD BDBDBDBD BD BD Ho MSBD BD 0.02 0.01 0.02 0.04 0.03 0.06 0.05 In MSBDBDBD BDBD 0.01 0.02 BD BD La MS 5.41 6.34 8.16 7.11 10.2 31.6 19.7 56.8 65.2 Lu MSBD BD BD BDBDBD BDBD BD Mn MS 0.136 0.168 0.178 0.102 0.175 0.145 0.156 0.097 0.065 Mo MS BD BDBD BDBDBDBD BD BD Nb MS BD BDBD BD BDBD 0.02 BD BD Nd MS 2.14 2.6 3.52 2.94 4.24 13.9 8.2 26.6 30.5 Ni MS 11.7 8.1 6.2 5.6 14.7 54.5 BDBD BD Pr MS 0.83 1.03 1.34 1.15 1.62 5.47 3.2 9.93 11.2 Rb MS 5.6 4.9 4.8 2.7 3.1 4.6 3.9 6.1 8.8 Sb MS 6.2 6.9 4.5 4.2 7.7 11.8 17 1 0.8 Se MS 0.1 0.3 0.2 0.8 0.6 0.7 0.7 0.7 1.8 Sm MS 0.25 0.25 0.41 0.35 0.45 1.27 0.8 2.61 2.91 Sn MS BD 0.01 BD BDBD 0.02 0.15 BD BD Sr MS 44 47.2 41.4 24.4 35.9 35.6 40.2 66.8 35.3 Ta MS BD BD BD BD BDBD BDBD BD Tb MS 0.02 0.02 0.03 0.03 0.03 0.1 0.05 0.16 0.18 Te MS BDBDBD BD 0.1 0.2 BD BD BD Th MS BDBDBD . BD 0.08 0.2 0.51 0.29 0.13 TI MS 0.1 0.07 0.08 0.04 0.04 0.08 0.07 0.06 0.07 Tm MS BDBDBD BDBDBDBDBD BD 176 u MS 0.06 0.07 0.12 0.12 0.19 0.35 0.18 0.38 0.45 V MSBD BDBDBD BD BD 0.1 BDBD w MS 0.02 0.1 0.13 -0.01 0.03 0.05 0.93 BD BD Y MS 0.2 0.24 0.42 0.26 0.44 1.05 0.62 1.48 1.43 Yb MSBD BD 0.02 0.02 0.02 0.09 0.06 0.07 0.09 Zn MSBDBD BDBDBD BDBDBDBD Zr MSBD BDBDBD 0.1 1.4 9.9 BDBD Ag ICP BD 2 4 BDBD 3 BD 2 BD A! ICP 142 140 246 257 413 723 670 2730 2190 As ICP BDBDBDBD BD BDBDBDBD Ba ICP 432 129 104 127 85 81 86 55 38 Be ICPBDBDBDBD BD BDBDBDBD Bi ICPBD BDBDBD BD BDBD BDBD Ca ICP 1630 1480 1520 734 1440 1060 2250 651 356 Cd ICP 103 117 124 81 85 170 196 228 181 Co ICP BDBDBDBD BD 114 2510 35350 33550 Cr ICP BDBD BDBDBD BDBDBD 17 Fe ICP 648 575 235 550 1540 2980 1500 3500 4900 K ICP 4560 4690 4220 2500 3740 5640 9620 8520 5140 La ICPBDBD 13 14 13 39 30 69 79 Mn ICP 147 188 200 109 187 159 168 114 73 Mo ICPBDBD BDBD BD BDBDBDBD Na ICP 4120 7210 3560 5550 10950 11650 18540 9490 4080 Ni ICP BDBDBD BD BDBD 1100 18160 9190 P ICP BDBD BDBD BD BDBDBDBD Pb ICP 6860 8430 10800 5860 6310 5560 3020 937 906 Sb 'CPBD BDBDBD BD BDBDBDBD Sc ICP 1 BD BDBD BDBD 1 1 1 Sn ICPBD BDBDBD BD BDBDBDBD Sr ICP 58 62 56 32 47 44 54 80 42 Ti ICP BDBD BDBD BDBD BD BDBD V ICPBD BDBDBD BDBD BD BDBD w ICP BDBDBD BDBD BDBDBDBD Y ICP BDBDBDBD BD BDBDBDBD Zn ICP 18470 20550 21100 14450 14770 29520 35330 40160 33590 Zr ICPBDBD BDBD BDBD BDBD BD BD = below detection 177 APPENDIX G 178 Appendix G. Chemical analyses of the acid-soluble fraction of sediment of the Dillon Reservoir, reported in pg/g of total sediment. Method DR-1 DR-2 DR-3 DR-4 DR-5 DR-7 DR-8 Be ICPBDBDBD 2.1 BD 1.3 1.3 Na ICP 34.3 58.4 68.7 102.3 79.8 76.6 73.4 Mg ICP 1301.2 1464.2 1220.4 3600.9 1279.8 2369.4 1724.1 Fe ICP 8948.4 18286.1 14060.2 30404.5 17504.6 19915.5 21194.9 AI ICP 3697.8 6125.5 5455.7 13201.6 8081.8 8865.3 9263.3 P ICP 452.4 720.5 581.9 966.3 716.4 640.4 627.8 K ICP 650.6 762.2 723.5 1811.8 734.2 1239.8 1134.2 Ca ICP 2607.5 3871.3 3710.1 4852.0 4000.1 3376.0 4157.0 Sc ICP BD 0.2 BD 0.3 0.3 0.3 0.3 Ti ICP 103.7 127.9 81.6 193.3 102.0 156.3 184.6 V ICP 11.2 17.4 16.2 31.6 17.8 22.0 20.0 Cr ICP 7.9 10.2 8.0 21.8 8.7 11.8 12.2 Mn ICP 353.3 2200.9 2986.6 3528.5 7781.0 2328.4 5645.6 Co ICP 4.1 10.0 12.4 20.8 13.5 11.3 13.7 Ni ICP 7.6 19.0 19.6 35.5 32.6 25.6 30.1 Cu ICP 31.0 77.8 71.1 106.4 61.4 79.4 128.4 Zn ICP 912.4 1980.8 1897.5 3068.5 2605.5 1992.8 2339.2 As ICPBD BDBDBD BD BD BD Sr ICP 13.7 24.1 25.0 33.4 29.1 24.3 26.8 Y ICP 6.9 13.2 12.6 19.5 15.3 13.1 23.0 Zr ICPBD 3.0 3.1 BD 4.6 2.6 BD Mo ICP 4.3 23.9 13.6 22.9 7.6 4.4 6.6 Ag ICP 0.8 1.6 2.1 2.8 2.8 1.5 4.6 Cd ICP 5.6 13.7 10.6 14.9' 11.2 9.0 9.1 Sn ICPBDBDBD BD BDBD BD Sb ICPBDBDBD BD BD BDBD Ba ICP 101.9 182.1 216.3 357.2 364.6 256.1 263.3 La ICP 7.1 15.3 12.1 19.3 16.3 14.9 26.8 W ICP BD BDBDBD 16.8 19.7 19.7 Pb ICP 64.0 148.0 156.5 239.3 148.6 145.7 263.3 Bi ICPBDBDBD BD BDBD BD 179 Appendix G. (cont.) Method DR-9 DR-10 DR-11 DR-12 DR-13 DR-14 DR-15 Be ICP 1.3 1.5 1.3 1.5 BD 1.3 1.6 Na ICP 76.7 87.7 53.8 104.0 87.9 88.4 66.6 Mg ICP 1788.5 4086.9 1871.6 3342.5 1254.9 1237.0 1258.7 Fe ICP 17669.1 31810.7 21359.3 27315.0 16200.3 18076.6 17054.3 AI ICP 8059.6 13806.6 9219.6 12952.5 8158.1 8906.7 6153.5 P ICP 546.5 699.6 702.5 847.5 785.9 794.8 717.4 K ICP 1198.3 2062.8 1153.7 1687.5 770.5 881.7 852.1 Ca ICP 3925.9 4351.9 3740.6 4580.0 5207.7 5246.9 3377.2 Sc ICP 0.3 0.3 0.3 BD BD 0.3 0.3 T i ICP 199.1 326.6 229.2 191.0 91.7 95.6 96.3 V ICP 17.2 29.1 18.7 31.3 17.5 18.7 16.3 Cr ICP 14.9 23.1 10.3 20.0 7.5 9.7 7.8 Mn ICP 3992.6 2546.3 1971.6 4752.5 11621.3 14171.4 1471.0 Co ICP 8.5 17.2 9.7 19.8 13.7 22.5 9.3 Ni ICP 23.6 32.9 19.5 39.5 43.5 51.4 15.8 Cu ICP 120.3 195.7 180.8 119.0 106.4 117.1 72.0 Zn ICP 1693.5 2183.6 2022.9 3217.5 2710.8 2957.0 2227.3 As ICP BD BD BD BDBD BD BD Sr ICP 24.1 28.8 24.4 31.5 36.1 39.9 21.0 Y ICP 20.3 27.0 23.8 21.8 17.5 17.9 14.2 Zr ICP 3.1 2.6 2.8 BDBD 2.6 BD Mo ICP 40.0 18.5 20.8 13.5 56.7 72.3 20.7 Ag ICP 4.6 6.9 5.4 3.8 3.6 3.3 1.8 Cd ICP 7.7 9.5 9.7 14.5 10.8 12.8 9.6 Sn ICPBD BD BDBD BD BD BD Sb ICPBD BD BD BDBD BD BD Ba ICP 211.2 259.8 225.1 342.5 363.3 465.1 203.6 La ICP 25.7 32.2 25.6 20.8 17.5 17.1 12.4 W ICPBD BD 14.6 BD 15.7 BD BD Pb ICP 261.7 401.2 361.5 265.0 167.2 172.3 156.2 B i ICPBD BD BDBDBD BD BD 180 Appendix G. (cont.) Method DR-16 DR-17 DR-18 Be ICP 1.5 1.3 1.5 Na ICP 93.9 59.3 51.1 Mg ICP 3565.9 2132.1 1956.3 Fe ICP 27853.2 25712.4 14465.2 AI ICP 10780.1 7106.3 6764.5 P ICP 800.1 725.1 628.4 K ICP 1615.7 1092.7 859.9 Ca ICP 3591.6 4137.5 4515.6 Sc ICP 0.3 0.5 0.5 Ti ICP 280.4 201.8 143.5 V ICP 25.0 18.0 15.8 Cr ICP 20.1 13.4 11.7 Mn ICP 2076.3 943.1 602.9 Co ICP 13.9 9.6 4.6 Ni ICP 26.0 17.0 13.7 Cu ICP 86.2 90.0 58.3 Zn ICP 1968.2 2142.3 1592.6 As ICPBD BDBD Sr ICP 22.9 19.5 19.8 Y ICP 14.2 15.2 14.8 Zr ICP 3.3 BD BD Mo ICP 9.3 83.2 18.1 Ag ICP 1.5 2.0 2.3 Cd ICP 10.8 12.7 12.0 Sn ICPBDBD BD Sb ICPBDBD BD Ba ICP 257.0 162.5 115.8 La ICP 16.7 15.2 15.3 W ICP 15.2 BD 14.0 Pb ICP 164.1 299.2 229.7 Bi ICPBD BDBD 181 Appendix G (cont.) X-ray fluorescence analyses for bulk sediment o f the Dillon Reser\oir. Sample Detection Method DR-3 DR-10 DR-13 DR-14 DR-16 Ident Limit(%) SiO: XR F100 0.01 65 61.5 61.7 62.3 62.7 AI2O 3 XR F100 0.01 14.7 16.5 14.8 14.3 13.4 CaO XR F100 0.01 0.56 0.81 0.5 0.56 0.97 MgO XRF100 0.01 0.91 0.9 1.09 1.1 1.24 Na.O XR F100 0.01 1.1 1.38 0.8 0.74 1.45 K 20 XR F100 0.01 2.95 3.21 2.96 2.83 3.03 Fe.O ] XRF100 0.01 2.84 2.96 3.69 3.79 4.02 ,MnO XR F100 0.01 0.08 0.04 0.27 0.44 0.07 TiO; XRF100 0.001 0.672 0.851 0.631 0.617 0.722 P ;0 ; XRF100 0.01 0.11 0.11 0.18 0.17 0.12 XRF100 0.01 -0.01 -0.01 -0.01 -0.01 -0.01 LOI XRF100 0.01 11.4 11.8 13.7 13.5 12.4 Sum XR F100 0.01 100.2 100 100.4 100.3 100.2 182 APPENDIX H 183 Appendix H. Chemical analyses of water samples collected around the Dillon Reser\oir. SR SR SR SR SR INFLOW SR 699W INFLOW INFLOW INFLOW INFLOW 98W 999W 1099W 0700W 1000W f collection 9/23/98 6/20/99 9/9/99 10/20/99 7/4/00 10/13/00 large cfs 31 431 48 32 101 26 pH 6.6 7.1 7.7 7.4 7.2 7.4 Method Cu MS 9.8 4 3 1.2 2 1.3 Zn MS 241 147 284 284 192 323 Ni MS 2.3 1.5 2.9 3.4 2.2 3.7 Cd MS 0.76 0.59 1.22 0.81 0.74 1.32 Mo MSBDBDBD BDBDBD U MS 0.09 0.14 0.18 0.12 0.12 0.2 Se MS 0.2 1.3 1 1 1.4 0.8 Na ICP 2750 1770 3020 3380 2280 3590 Mg ICP 3410 2030 3760 3970 2810 4390 Ca ICP 15040 8640 16390 17140 12260 18850 K ICP 820 790 890 1100 840 1220 Sr MS 89.9 55.6 97.6 105 76.1 121 Be MSBDBDBD BDBD BD Sc MS 2.3 1.8 2.5 2.3 2 2.6 V MS 0.1 BD BD BDBD BD Pb MS 0.25 0.56 BD BD BD 0.04 Cr MS 0.5 0.3 0.4 0.5 0.5 0.4 Mn MS 0.227 0.073 0.25 0.174 0.007 0.281 Co MS 0.8 0.2 0.9 0.7 BD 1.1 Ga MS 0.02 0.02 0.04 0.02 0.01 0.04 As MSBDBDBD BD BD BD Rb MS 0.5 BD 0.4 0.3 0.3 0.6 Y MS 0.09 0.11 0.12 0.08 0.07 0.03 Zr MSBDBDBD BDBD BD Nb MS BDBDBD BD BD 0.01 in MSBD BD BD BDBD BD Sn MSBDBDBD BD BDBD Sb MS 0.1 BD 0.3 0.2 0.2 0.3 Te MSBDBDBD BD BDBD Cs MS 0.02 BD BD BD BDBD Ba MS 41 116 43.8 24 19.9 28.7 La MS 0.06 0.07 0.07 0.04 0.04 0.03 Ce MS 0.08 0.09 0.1 0.04 0.03 0.03 Pr MS 0.02 0.03 0.02 0.01 0.02 BD 184 Nd MS 0.11 0.1 0.12 0.07 0.06 0.02 Sm MS 0.05 0.05 0.02 0.05 0.07 0.01 Eu MS 0.02 0.04 0.01 0.02 0.02 0.01 Gd MS 0.06 0.07 0.05 0.04 0.04 0.05 Tb MS BD 0.01 BD BD BD BD Dy MS 0.02 0.03 0.05 0.03 0.01 0.02 Ho MS BD BD 0.01 BDBDBD Er MS 0.02 0.03 0.03 0.02 0.01 0.03 Tm MS BD BD BDBDBD BD Yb MS 0.03 0.02 0.02 0.02 0.02 0.03 Lu MS BD BD BDBDBDBD Hf MS 0.02 0.01 BD 0.04 0.04 0.04 Ta MS 0.01 0.02 BD 0.02 0.01 0.01 W MS BD 0.03 0.02 0.02 0.03 0.05 Hg MS BDBDBDBDBDBD TI MS 0.02 0.03 0.03 0.04 0.04 0.02 Bi MS BDBDBDBD BD BD Th MS BDBDBDBDBDBD BI) = Bolou Detection AppcntJix H. (com.) BRI BRI BRI BRI BRO BRI 699W INFLOW INFLOW INFLOW INFLOW 699W 999W 1099W 0700W 1000W ' collection 6/20/99 9/9/99 10/20/99 7/4/00 10/13/00 6/20/99 large cfs 543 59 46 136 51 1550 pH 7.2 7.9 8.1 8.1 8.7 6.9 Method Cu MS 0.8 0.3 0.5 0.5 0.3 0.6 Zn MS 92.2 69.5 39.6 59.7 23 25.3 Ni MS 0.7 0.6 0.7 0.6 0.7 1.2 Cd MS 0.52 0.44 0.36 0.25 0.22 0.21 Mo MS BD 1 BD 1 2 80 U MS 0.17 0.11 0.29 0.1 0.12 0.23 Se MS 1.6 1.5 1.1 1.5 1.7 2.3 Na ICP 1900 2710 2860 2770 3420 5050 Mg ICP 3590 4780 5090 4400 5440 4480 Ca ICP 16770 22350 23590 19930 24360 41120 K ICP 920 1020 980 1010 1210 3080 Sr MS 81.6 112 112 104 126 131 Be MS BD BD BDBDBDBD Sc MS 1.7 2.1 1.9 1.9 2.4 1.6 V MS 0.1 0.4 BD 0.5 1 0.7 Pb MS 0.27 BDBDBDBDBD Cr MS 0.5 1.1 0.4 1.7 3.7 2.3 185 HCDHX?Hxr- C/3C/)C/5C/)C/)C/)C/îC/J(/J{/)C/)C/)C/)C/)C/)C/)C/JC/)CnC/>CnC/)C/)C/)C/)C/)C/>C/îC/)C/)C/)C/)(y)C/)C/) o o o 0 0 0 0 0 0 0 —1 0 CD CDCDCDCDCDCDCD^ CD S g b o o o OOOOOOOf'J O o ^ to o -tvcotnto-^ooco-c^^ DDOOOOOg ro 1 o o o o O o o o O O o p p CD CD 03 CD CD CD CD CD CD CD cn CD CD O CD CD CD CD O Ô CD CD b b o o o O o o o o b OO oo o o o CO g O CO O OOO g 8 8 s o a o o o O a Ov O o o o o o o o o o o O p p CD CD CD 03 03 03 03 CD CD CD CD O CD CD CD CD O CD CD CD b b b b b b b b b D D o to s O O 8 a ro o CO s g OO CO D O b o DOO ■- O 8 O a o o o o o 03 CD CD O SS^ScDOaCDferoCDOCDOOCDCDS CD CD b b 8 8 2 0 0 0 0 0 0 0 0 b §§i g 2 g O O O w CO S':' ^ r \) o ro O O o o o o o o o o o O o O O CD CD CD CD CD 03 03 03 03 g CD CD p CD CD P CD CD b b b b b b b b b O D O CO o tn s O a 8 a ro O 8 cn OO ro O O CO cog U CO 2 O o o o o p CD CD 03 CD CD CD cdcdcd P cd P cd - CD b b P cd P ° ° ° cdcdcd ^ o o s O g cn s OOO 8 o g g g g o o o _ o o o g o R oro P BR BR BR BR TMC TMC OUTFLOW OUTFLOW OUTFLOW OUTFLOW INFLOW 699W 999W 1099W 0700W 1000W 98W date of 9/9/99 10/20/99 7/4/00 10/13/00 9/23/98 6/20/99 collection discharge cfs 119 358 202 70 42 679 pH 8.3 6.2 7.2 7.3 6.4 7 Method Cu MS 1 1.2 0.9 0.8 0.3 1.2 Zn MS 19.1 37.2 31.2 21.1 14.7 26.9 Ni MS 1.2 1.5 1.8 1.7 2.9 2.2 Cd MS 0.28 0.33 0.27 0.21 0.64 0.6 Mo MS 36 56 63 68 331 83 U MS 0.37 0.58 0.55 0.29 0.57 1.18 Se MS 0.9 1.1 1.1 0.8 0.6 0.8 Na ICP 3490 4050 4520 4420 4400 4660 Mg ICP 3880 4090 4330 4310 4880 4630 Ca ICP 30040 35190 39370 39080 48570 43950 K ICP 1820 2370 2740 2770 4390 5270 Sr MS 107 114 125 127 276 126 Be MSBD BD BDBD BD BD Sc MS 1.5 1.7 1.4 1.7 1.6 1.4 V MS 0.2 0.2 BD 0.6 0.5 0.1 Pb MSBD BD BDBDBD BD Cr MS 0.5 0.3 0.4 2 1.7 0.5 Mn MSBD BD BDBD BDBD Co MS 0.1 0.1 0.2 0.2 0.4 0.2 Ga MS 0.02 0.02 0.01 0.01 0.01 0.02 As MSBD BD 0.2 0.2 BDBD Rb MS 2.2 3.6 3.9 4.5 22.1 5.7 Y MS 0.02 0.03 0.02 0.02 BD 0.05 Zr MS BDBD BDBD BD 0.2 Nb MS 0.01 BD BD 0.02 0.01 BD In MSBDBD BDBD BD BD Sn MSBDBD BD 0.02 BDBD Sb MS 0.2 0.2 0.2 0.2 BD BD Te MS BD BD BDBD BDBD Cs MSBD BD BD BD 0.04 BD Ba MS 34.5 35.3 36.6 34.7 60.8 87.9 La MS 0.01 0.02 0.03 0.02 BD 0.03 Ce MSBD BD 0.01 BD BD 0.03 187 Pr MS BD 0.01 BDBD BD 0.01 Nd MS 0.02 0.04 0.03 0.02 0.04 0.07 Sm MS 0.07 0.05 0.04 0.01 0.02 0.02 Eu MS 0.01 0.03 0.02 0.02 0.02 0.02 Gd MS 0.08 0.05 0.03 0.02 0.03 0.03 Tb MS BDBD BDBD BDBD Dy MS 0.04 0.02 BD 0.02 0.03 0.03 Ho MS BDBD BDBD BDBD Er MS 0.03 0.02 0.01 0.02 0.02 BD Tm MS BD 0.01 BDBD BDBD Yb MS 0.02 BD 0.02 0.01 BD 0.01 Lu MS BD BD BDBD BDBD Hf MS 0.1 0.09 0.08 BD 0.03 0.14 Ta MS 0.01 BD BD 0.06 0.02 0.02 W MS 0.04 BD BD 0.03 0.08 0.01 Hg MS BDBD BDBD BDBD TI MS 0.02 0.02 0.03 0.05 0.07 0.04 Bi MS BDBD BDBD BDBD Th MS BDBD BDBD BDBD BD = Below Detection TMC TMC TMC TMC INFLOW INFLOW INFLOW INFLOW 999W 1099W 0700W 1000W date of 9/9/99 10/20/99 7/4/00 10/13/00 collection discharge cfs 62 41 137 25 pH 7.7 7.4 7.9 8.2 Method Cu MS 0.6 0.3 0.4 0.3 Zn MS 44 37.9 14.2 22.2 Ni MS 4.5 5.1 2.6 3.8 Cd MS 0.97 1.14 0.53 1.06 Mo MS 303 437 182 415 U MS 5.61 4.78 1.93 1.67 Se MS 0.9 1.3 1.2 0.8 Na ICP 4760 4850 4760 8040 Mg ICP 5970 5290 5880 6290 Ca ICP 60640 57130 43030 116570 K ICP 5480 5500 5670 8120 Sr MS 339 398 232 332 Be MS BDBDBD BD Sc MS 1.8 2 1.7 2.2 V MS 0.2 0.2 BD 0.8 188 Pb MSBDBD BD BD Cr MS 0.4 0.9 0.6 3 Mn MS 0.041 0.027 0.009 0.222 Co MS 0.6 0.7 0.3 0.5 Ga MS BD 0.02 0.03 0.03 As MS BDBD BD BD Rb MS 24.2 29.8 11.9 20.6 Y MS 0.05 0.02 0.02 0.01 Zr MS 0.3 BD BD BD Nb MS BDBD BD 0.01 In MS BD BDBDBD Sn MS BD BDBDBD Sb MS 0.2 0.2 0.2 0.2 Te MS BD BDBDBD Cs MS 0.06 0.09 0.02 0.02 Ba MS 64.7 59.4 51.3 53 La MS 0.05 0.02 0.02 0.01 Ce MS 0.02 BD 0.02 BD Pr MS BD BDBDBD Nd MS 0.04 0.03 0.03 0.04 Sm MS 0.04 0.04 0.03 0.04 Eu MS 0.02 0.01 0.02 0.01 Gd MS 0.07 0.05 0.03 0.03 Tb MSBDBD BDBD Dy MS 0.02 0.02 0.01 0.02 Ho MS BD BDBDBD Er MS 0.02 0.01 0.03 0.01 Tm MSBDBD BD BD Yb MS 0.01 0.02 0.01 0.02 Lu MS BD BDBDBD Hf MS 0.21 0.07 0.08 0.05 Ta MS 0.02 0.03 0.02 0.02 W MS 0.03 0.03 0.03 0.04 Hg MS BD BDBDBD TI MS 0.06 0.06 0.04 0.04 Bi MSBDBD BDBD Th MS BD BDBDBD BD = Below Detection 189 LIST OF REFERENCES Adriano. 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(Eds.), Water Resource Problems Related to .Mining. .American Water Resources Association. Minneapolis. Minnesota, pp. 158-173 Proc. No. 18. Winland. R.L.. Traina. S.J.. and Bigham. J..M.. 1991. Chemical composition of ocherous precipitates from Ohio coal mine drainage. J. of Environmental Quality 20- 2. 452-460. Zuyi. T.. Taiwei. C.. Jinzhou. D.. XiongXin. D.. and Yingjie. G.. 2000. Effect of fulvic acids on sorption of U(VI). Zn. Yb. I and Se(IV) onto oxides of aluminum, iron and silicon. .Appl. Geochem. 15. 133-139. 192