Arsenic Contents in Buried Valley Aquifers In

Date: 11/15/2005

I, Alejandra Bonilla______, hereby submit this work as part of the requirements for the degree of: Master of Science in: Geology It is entitled: Geochemistry of Arsenic and Sulfur in Southwest Ohio: Bedrock, Outwash Deposits and Groundwater.

This work and its defense approved by:

Chair: Dr. Barry J. Maynard

Dr. David B. Nash

Dr. Warren D. Huff

“Geochemistry of Arsenic and Sulfur in Southwest Ohio: Bedrock, Outwash Deposits and Groundwater”

A thesis submitted to the

Division of Research and Advanced Studies

of the University of Cincinnati

in partial fulfillment of the

requirements for the degree of

MASTER OF SCIENCE

in the Department of Geology

of the College of Arts and Sciences

2005

Alejandra Bonilla Ramos.

B.S., Universidad Nacional Autónoma de México, 2002

Committee Chair: Dr. Barry J. Maynard

ABSTRACT

Located in southwest Ohio, the Mason and also the Lebanon Correctional Institute (LeCI)

drinking water distribution systems obtain their water from the Shaker Creek “buried

valley” Aquifer. The Pleistocene valley contains glacial outwash material and some lake

clays incised into the limestone-shale bedrock. Analyses were done in water, aquifer

material and bedrock samples. The results of arsenic in water ranged from 4-18 µg/L,

and show that many of these samples are above the USEPA MCL. Thus, both systems

have concerning arsenic levels. Arsenic analyses in the bedrock and glacial outwash

material ranged from 4-40 ppm. Therefore, arsenic in the groundwater could be sourced

from the glacial aquifer material and/or from the surrounding bedrock.

The bedrock geology of the area of study consists of Upper Ordovician-Lower

Silurian limestones and shales of southern Ohio and northern Kentucky. The bedrock

formation studied and that partly influence the water chemistry in the Shaker Creek

buried aquifer is the Kope Formation. Stable isotope analysis of sulfur was used for this

study. Many of the geochemical characteristics of arsenic are analogous to those of

sulfur, because both elements occur in reduced and oxidized forms and the oxidation states change as a result of biological processes. Biogenic reduction is the dominant form

of sulfur fractionation in nature and is mainly a product of sulfur reducing bacteria.

The present thesis is focused in two main parts. First part covers the study of arsenic in solids and sulfur isotopes were used to calculate sedimentation rates in the

Kope Formation. Second part includes the study of arsenic in groundwater and its source in the Shaker Creek Aquifer. This study presents a model of the possible sources and mechanisms of arsenic in groundwater. Sulfur isotopes were used to provide a chemical

i assessment and a comparison of sulfur isotopes in the bedrock with dissolved sulfur in the aquifer as a test for arsenic release by pyrite dissolution.

ii ACKNOWLEDGMENTS

I want to express my deepest gratitude to the Department of Geology, University of Cincinnati for all the financial and moral support for my Masters project through the Wycoff Scholarship and summer URC. The laboratory expenses for this project were supported from Sigma Xi and Geological Society of America. The Mexican government trough the Secretaria de Educaciόn Pública (SEP) and Consejo Nacional de Ciencia y Tecnologia (CONACYT), which granted with a complementary scholarship. Such support makes possible that Mexican students are able to study abroad. I thank my advisor, Dr. Barry Maynard, for his guidance and support. Since our first communication he showed that even his multiples occupations he is always assisting and encouraging his students in all kind of aspects. I thank the members of my committee: Dr. David Nash and Dr. Warren Huff for their valuable suggestions and comments to the present thesis. My appreciation for their patience and invaluable time for correcting and suggestions to my writings and proposals: Susie Taha, Dr. Warren Huff, Dr. Tammie Gerke and Phil Hart. This project was also possible with the help and assistance for collecting and processing samples: Erika Elswick, Indiana University, Greg Davis, Lebanon Correctional Institute, Bruce Whitteberry, Greater Cincinnati Water Works and Dr. Carl Brett, University of Cincinnati. A special thanks to Ana Londoño not only for her great friendship but for all her moral and academic support during my studies. My thousand thanks to my friends who made an unforgettable and amazing experience my life in Cincinnati: Chie Suzuki, Pablo Rosales, Orla Keyes, Hari Prashadan, Xavier Beteta, Giovanni Contreras, Jorge Jaramillo, Zheng Wang, Arjun Santhanam, Carmen Espinoza, Utku Solpuker and John Byron Baena. All my love and gratefulness to my family: my dad Arturo, Adriana, Carla, Ernesto, Claudia and Alicia.

iii TABLE OF CONTENTS

Abstract ii Acknowledgments iii Table of Contents iv List of Figures vi List of Tables ix

INTRODUCTION 1

PART I Geochemistry of Arsenic and Sulfur of the Kope Formation 4 in Southwestern Ohio 1.1. Introduction 5 1.2. Geology 10 1.2.1 Submembers of the Kope Formation 11 1.2.2 Paleogeography and genesis of the bedding in the Kope Formation 11 1.3. Methods 14 1.3.1 Geochemistry 14 1.3.1.1 Solids 14 1.3.1.2 Sulfide analyses 15 1.4. Results 19 1.4.1 XRF Results 30

1.5. Interpretations 33

1.6. Conclusions 41

PART II The Kope Formation as a Source of Arsenic and Sulfur 42 in Groundwater in Southwestern Ohio.

2.1. Introduction 43

iv 2.1.1 Statement of the problem 46 2.1.2 Background 49 2.1.3 History of glaciations and associated deposits 53 2.1.4 Shaker Creek Aquifer 53

2.2. Arsenic chemistry 55 2.2.1 Arsenic in groundwater 58 2.3. Methods 59 2.3.1 Solids 59 2.3.2 Groundwater sampling 59 2.3.3 Sulfide analyses 60 2.3.3.1 Sulfate precipitation 60

2.4. Results 64 2.4.1 Sulfur isotopes results 79

2.5. Sulfur isotopes 82

2.6. Interpretations 86

2.7. Conclusions 94

References 96

v LIST OF FIGURES

Figure No. Page No

Part I

1.1. Location of the area of study and bedrock sampled 7

1.2. Diagram of the generalized Upper Ordovician stratigraphy of southwestern

Ohio and northern Kentucky known as the Cincinnatian Series 8

1.3. Geologic map of Southwest part of Ohio conformed by Butler, Warren,

Hamilton and Clermont Counties 9

1.4. The Kope Formation with the respective five submembers: Snag Creek,

Alexandria, Grand View, Grand Avenue and Taylor Mill 13

1.5. Diagram of the sulfur extraction system used in the geochemistry laboratory

in the Department of Geology 17

1.6. Peaks of arsenic concentrations in the Kope Formation in the outcrop

at Kentucky route 445 20

1.7. Arsenic results obtained from the Clermont County well 21

1.8. Arsenic levels in the Rapid Run Creek Section 29

1.9. Aluminum concentrations versus δ34S in samples from the Kope Formation 31

1.10. Calcium concentrations versus δ34S in samples from the Kope Formation 32

1.11. Range of δ34S in different shales, limestone, biogenic pyrite and sea water 35

1.12. Diagram of sulfur fractionation 36

1.13. Relationship of the sulfur fractionation and rate of sulfate-pyrite

reduction by bacteria in marine sediments 40

vi Figure No. Page No

Part II

2.1. Map of United States showing locations and arsenic concentrations

for groundwater sampled by the USGS and state agencies 45

2.2. Map of the area of study and sampling areas in Ohio and Kentucky. 48

2.3. Surficial geology of the southwesterm part of Ohio 51

2.4. Geology of the Shaker Creek Aquifer 52

2.5. pE-pH diagram for predominant arsenic species in groundwater systems 56

2.6. Molecular difference between arsenate [As5+] and arsenite [As3+] 57

2.7A. Bowser-Morner using a rotosonic rig in the LeCI prior to the drilling 62

2.7B. Sample of aquifer material recovered and packed in a box 62

2.8. Diagram of the sulfur extraction system used in the geochemistry

laboratory in the Department of Geology for solids 63

2.9. Recovered log from the Lebanon Correctional Institute 66

2.10. Arsenic concentrations in the Lebanon Correctional Institute

aquifer material 67

2.11. Average Oxidation Potential Reduction of Shaker Creek Aquifer wells and its relation with time 72

2.12. Iron increased with time from 1997 to 2004 in LeCI and Mason wells 73

2.13. Manganese increased with time from 1997 to 2004 in LeCI and Mason wells 74

2.14. Relationship between arsenic and total ORP in LeCI and Mason monitoring wells 75

2.15. Relations between sulfate and arsenic in LeCI and Mason monitoring wells 76

vii Figure No. Page No

2.16. Chloride and sodium relationship in the Mason and LeCI wells 77

2.17. Range of δ34S in different shales, limestone, biogenic pyrite and sea water 84

2.18. Isotopic systematics of sulfur fractionation in groundwater 85

2.19. Scheme of the Shaker Creek Aquifer and the chemical reactions

occurring within 88

2.20. Diagram of the possible interactions between δ34S isotopes and

redox conditions occurring in the aquifer depending on the time with pyrite 89

2.21. Possible interactions in the aquifer between δ34S isotopes, redox

conditions with time for arsenopyrite 90

2.22. Hydrograph of monthly fluctuations in water-table elevation from a well of the Shaker Creek Aquifer 93

viii LIST OF TABLES

Table No Page No

Part I

1.1. Relation of majors from XRF analysis and sulfur isotopes relation from bedrock samples of the Kope Formation in the section area of KY route 445 22

1.2. Whole-rock chemistry of trace elements and arsenic concentrations of the Kope Formation in the area of Kentucky Route 445 23

1.3. Analysis of total carbon, sulfur and arsenic of the bedrock samples from the Kope Formation in the Kentucky Route 445 24

1.4. Relation of majors from XRF analysis and sulfur isotopes relation from bedrock samples of the Rapid Run Creek 25

1.5. Relation of majors from XRF analysis and sulfur isotopes relation from bedrock samples of the Kope Formation corresponding to the Rapid Run Creek section 26

1.6. Sedimentation rate obtained with the relationship from modern sediments for the samples from Rapid Run Creek section 27

1.7. Sedimentation rate calculated for the Kope samples obtained in Kentucky Route 445 28

Table No Page No

Part II

2.1. Water chemistry of Shaker Creek wells during 1997 68

2.2. Water chemistry from LeCI and Mason wells during 1999 69

2.3. Data for redox-sensitive species from Mason Production Wells during

2002-2003 70

2.4. LeCI and Mason chemical parameters in groundwater from wells and monitoring wells from 2004 71

2.5. Sulfur isotopes results in water, glacial outwash fill material and bedrock samples from Mason and LeCI 80

2.6. Average δ34S values from bedrock, glacial outwash material and groundwater samples 81

x INTRODUCTION

Elevated levels of naturally-occurring arsenic have been identified in regional patterns within the United States and are attributed to geochemistry, geology, climate, and glacial history (Welch et al., 2000). In 2001, the U.S. Environmental Protection

Agency (US EPA) recommended a maximum contaminant level (MCL) of 10 μg/L for

arsenic in US public drinking water supplies scheduled to go into effect in 2006 (US

EPA, 2001).

In southwestern Ohio, elevated arsenic levels have been detected in some

groundwater supplies, including many in Warren County that draw their water from the

Shaker Creek Aquifer. This aquifer occupies a Pleistocene buried valley system cut into

Ordovician bedrock. The bedrock geology is dominated by the upper Ordovician Kope

Formation, which is composed of interbedded limestone and shale and occurs throughout

the southwestern part of Ohio and Northern Kentucky. Arsenic occurs in small amounts

in Silurian carbonates and Ordovician shales in southwestern Ohio, and these units may

be the source of the arsenic found in the groundwater. To test this idea, two water

systems, the Lebanon Correctional Institution were investigated: a prison operated by the

State of Ohio's Department of Corrections and Rehabilitation, and the Mason, Ohio

system, operated by the Greater Cincinnati Water Works. Both draw their water from the

Shaker Creek Aquifer,

An important tool used in this study is stable isotope analysis of sulfur. Many of

the geochemical characteristics of arsenic are analogous to those of sulfur, because both

elements occur in reduced and oxidized forms and the oxidation states change as a result

of biological processes. Therefore finding the source of sulfur in the groundwater can

1 also reveal the source of arsenic. Stable isotopes have extensive application in geological

and environmental studies as tracers of biological and geochemical processes. In nature,

isotopic variations occur because substances such as minerals, water, and gases preferentially concentrate one isotope over another, or because organisms can more

efficiently metabolize one isotope than another. Thus, natural isotopic variations can

arise from numerous common chemical and physical processes, such as cooling of

hydrothermal fluids during mineral deposition, the evaporation or condensation of water,

mixing of two or more sources of fluid, or the metabolic activity of organisms. The study

of the stable isotopes of carbon, nitrogen, oxygen and sulfur can provide powerful

insights into these processes. Sulfur is an abundant element in nature, and is found in

different forms in nature due to its oxidation state. It is present in many global processes

and sulfur isotopes can be used for determining the geochemical processes occurring in

either groundwater or solid materials. The sulfur associated with sedimentary processes

generally reflects the composition of biogenic sulfide produced by bacteria reduction of

marine sulfate (Sharp, 2005).

The present study is divided in two parts. The first part covers the origin and the

source of the arsenic in both glacial outwash fill material and bedrock shale (Kope

Formation). Arsenic was found in both cases, and is likely the source of arsenic detected in the groundwater. In addition to the study of arsenic in solids, sulfur isotopes were used as a tool to evaluate sedimentation rates in the Kope Formation. The sedimentary events represented by the Kope Formation represent an ordered succession of mudstone units having different episodes in which the terrigenous shales were rapidly deposited while the calcareous shales represent periods of low and slower sediment deposition.

2 The second part focuses on the study of arsenic in groundwater in the Shaker

Creek Aquifer in southwestern Ohio. It includes both the possible geochemical mechanisms occurring within the aquifer and a general model proposing the behavior of arsenic and other related elements. Arsenic is possibly being leached into the groundwater from the dissolution of arsenopyrite (AsFeS2) in the outwash glacial aquifer material and/or local bedrock. Sulfur isotopes were used to provide a chemical assessment and a comparison of sulfur isotopes in the bedrock with dissolved sulfur in the aquifer as a test for arsenic release by pyrite dissolution. Since arsenic tends to follow sulfur in its behavior, finding the source of the sulfur will give a likely source for the arsenic. Thus, this study provided a geochemical tool in which sulfur isotopes can be used to trace the source of arsenic in groundwater.

PART I GEOCHEMISTRY OF ARSENIC AND SULFUR OF THE KOPE FORMATION IN SOUTHWEST OHIO.

4 1.1 INTRODUCTION

The Lebanon Correctional Institute (LeCI) and Mason well systems draw their water

from the Shaker Creek Aquifer, which is a Pleistocene buried valley aquifer cut into

Ordovician bedrock (Figure 1.1). These water systems have moderate arsenic levels,

which prompted this investigation of the aquifer. In addition to conducting chemical

analyses of water from the Shaker Creek Aquifer a study of the bedrock surrounding the

LeCI and Mason wells was conducted to form a more complete understanding of

potential arsenic sources. The geology of this area consists of Late Pleistocene glacial

outwash-fill and bedrock material formed from a series of limestones and shales (Figure

1.2). The levels of this bedrock correspond to the upper Ordovician Kope and Fairview

Formations, which are units composed of interbedded limestone and shale, which occur throughout the southwestern part of Ohio and Northern Kentucky (Figure 1.3). Previous arsenic studies in the bedrock of southwest Ohio have been done so far by the United

States Geological Survey (USGS). These studies show that high arsenic concentrations

were detected in Silurian carbonates and in the underlying Ordovician shales (Thomas,

2003). Arsenic is commonly found in black shales, principally because of the pyrite

content (Smedley and Kinniburgh, 2005). However, such black shales are absent from

southwest Ohio, so this study has focused instead on gray shales.

The chemical behavior of arsenic is strongly related to that of sulfur. The highest

arsenic concentrations have a tendency to occur in sulfide minerals, of which pyrite is the

most abundant (Smedley and Kinniburgh, 2005). Thus, as part of the arsenic study, a

study of sulfur isotopes in the bedrock of the Kope Formation was conducted. Sulfur

isotopes can be used to determine reaction paths for sulfur and hence for arsenic. Arsenic

5 is chemically very similar to sulfur, thus analyses of these sulfur isotopes can be used to evaluate hypotheses of arsenic hosts in the bedrock in Southwestern Ohio. Also, sulfur isotopes can be used as a tool to understand more about the sedimentation regime occurring in the bedrock during its deposition by analyzing rates of sulfate reduction.

The objectives in this part of the study are:

1) To provide a comprehensive chemical assessment of a section of bedrock (Kope

Formation) as a potential arsenic source for the Shaker Creek Aquifer in the area

around Mason, Ohio.

2) To characterize the chemistry of the Kope Formation in different levels to explore

stratigraphic controls on rock chemistry.

3) Comparing sulfur isotopes of sulfides in the bedrock with dissolved sulfur in the

aquifer to test for arsenic release by pyrite dissolution.

4) To have a better picture of the rates of sulfate reduction in the Kope depositional

environment in order to evaluate sedimentation rates that occurred in the Kope.

Figure 1.1. Location of the bedrock sampled from the Kope Formation. The samples correspond to core recovered in Clermont County core, Rapid Run Creek and KY Route 445 sections.

Figure 1.2. Diagram of the generalized Upper Ordovician stratigraphy of southwestern Ohio and northern Kentucky known as the Cincinnatian Series (From: Caster et al., 1955).

Figure 1.3. Geologic map of Southwest part of Ohio conformed by Butler, Warren, Hamilton and Clermont Counties. The host rocks are Silurian-Ordovician age (From Ohio Department of Natural Resources).

9 1.2 GEOLOGY

Greater Cincinnati is located on the west flank of the Cincinnati Arch. The predominant bedrock includes limestone and shale beds. The geology of the area of study consists of Upper Ordovician-Lower Silurian limestones and shales of southern

Ohio and northern Kentucky (Figure 1.2 and 1.3). The three main Ordovician bedrock formations that influence the water chemistry in the Shaker Creek buried aquifer are the

Point Pleasant Formation, the Kope Formation and the lower Fairview Formation.

The Point Pleasant is the oldest exposed formation in the Cincinnati region. The local outcrops approximately are 100 feet thick and consist mainly of coarse-grained limestones (medium to coarse-grained wackestones and packstones) interbedded with medium-gray shales (Potter, 1996).

The Upper Ordovician Kope Formation is exposed throughout northern Kentucky, southwest Ohio, and southeast Indiana. The Kope Formation is the most frequently exposed formation by natural erosion in the greater Cincinnati area. The Kope formation consists of up to 200 feet of varying proportions of shale and interbedded limestone

(Holland et al, 2000). The Kope was deposited in an offshore environment on a northward-dipping storm-dominated ramp (Tobin and Prayor, 1983; Jennette and Pryor,

1993). Shale comprises roughly two-thirds of the Kope, with the remainder consisting of very thin to medium beds of calcisiltite, skeletal packstone, and skeletal grainstone, all deposited as storm beds.

The Fairview Formation (70-100 feet) is composed of roughly 50-60 percent blue-gray shale with continuous interbeds of fossiliferous limestone (Potter, 1996). It represents a transition between deep and shallow marine waters.

10 Samples were collected from outcrops along Kentucky Route 445 at its

intersection with Kentucky Route 8; from outcrops along Rapid Run Creek in Delhi

Township, Hamilton County Ohio; and from a core in Union Township, Clermont

County, Ohio. Several typical meter-scale cycles in the Kope are shown in Figure 1.4.

1.2.1 Submembers of the Kope Formation

Brett and Algeo (2001) assigned detailed subdivisions to the Kope Formation

based on the occurrence of repetitive sedimentary units. The Kope Formation displays a

uniform pattern of meter-scale cycles in the mudrocks that are systematically repeated.

The submembers of the Kope Formation are distinctive by faunal elements, trace fossils

horizons, taphonomic features and sedimentary structures. The samples studied in this

research correspond to the Snag Creek, Alexandria, Grand View, Grand Avenue and

Taylor Mill submembers (Figure 1.2 and 1.4). The submembers are composed of

interbedded mudrocks alternating with calcisiltite, packstone and grainstone units (Brett and Algeo, 1999).

1.2.2 Paleogeography and genesis of the bedding in the Kope Formation

According to Scotese (1990), the Kope Formation was deposited at about 20-25

degrees south latitude during Late Ordovician time. There are two major structural

features of the region formed by the Lexington Platform, a carbonate-producing high to

the southeast of Cincinnati, and the Sebree Trough, a narrow, elongate basin to the north

and northwest (Mitchell and Bergström 1991; Ettensohn 1999; Ettensohn et al. 2002).

The depositional setting of the Kope Formation was formed between these two features.

11 The genesis of the mudrock and limestone meter-scale cyclicity in the Kope

Formation has been explained using three different models: sea level fall in which eustatic fluctuations constrained the effect of storms on the sea floor (Jennette and Pryor,

1993); variation in storm intensity, which explains winnowing and deposition of removed muds controlled by changes in storm intensity over time (Holland et al., 1997), and changes in silicilastic sedimentation proposed by Brett and Algeo (2001) suggesting that variation in siliciclastic sediment influx to the Kope ramp was the primary control on lithology.

Figure 1.4. The Kope Formation with the respective five submembers: Snag Creek, Alexandria, Grand View, Grand Avenue and Taylor Mill. The diagram displays a uniform pattern that is classified as a “meter-scale cycle” in the mudstones that are uniformly repeated (Modified from Kirchner, 2005).

13 1.3 METHODS

1.3.1 Geochemistry

Because the Kope Formation is not exposed in the Mason area, the strategy for identifying sources of arsenic required the collection of bedrock samples from the Kope

Formation along the Ohio River that corresponded to the same stratigraphic sequence as

that in the subsurface at Mason, and from well samples from Clermont County. The two

sections sampled from the Kope Formation were along Route 445 in Brent, Kentucky and

Rapid Run Creek area, both along the Ohio River. Also a bedrock core from Clermont

County was sampled, which has a stratigraphic elevation similar to the previous locations

(Figure 1.1).

1.3.1.1 Solids

At the Route 445, Rapid Run Creek area and Clermont County exposures of the

Kope Formation samples were taken vertically through the section approximately every 3 feet. The samples taken from Rapid Run Creek were done in different meter cycles from the base to the top of the Kope Formation (Figure.1.4) The purpose of this systematic sampling was to have an accurate location of the stratigraphic level for arsenic contents.

A total of 100 samples were collected and bagged in Ziploc bags for subsequent analyses in the Geology Department, University of Cincinnati.

The outcrop sampling of the Kope Formation was designed to enable whole rock analysis. The samples were dried and the crushed using a tungsten carbide ball mill prior to X-ray fluorescence analyses (XRF). Solids were pressed into thin pellets using a Spex

3624B X-Press 20-ton press. The trace and major element chemistry of the solids was

14 determined with a Rigaku 3070 XRF spectrometer at the University of Cincinnati.

Samples were analyzed for SiO2, TiO2, Al2O3, Fe2O3 (total iron), MnO, MgO, CaO, K2O,

P2O5, Mo, Zr, Sr, U, Rb, Th, Pb, Br, Zn, Cu, Ni, Co, Mn, Cr, V and Ba. Volatiles were

estimated as Loss On Ignition (LOI). In this determination, two grams of each sample

were heated to 1000 °C for approximately one hour to determine the LOI values. The

XRF intensities obtained were recalculated and converted to parts per million (ppm) or

weight percent using USGS rock standards and LOI values. Arsenic was determined by

sodium peroxide fusion at XRAL laboratories in Toronto, Canada by Atomic Absorption spectroscopy.

1.3.1.2 Sulfide analyses

Twenty-eight bedrock samples from the Kope Formation were chosen for sulfur

extraction. A multi-step sulfur analysis scheme was used to isolate reduced sulfur species

(pyrite + acid volatile sulfur + elemental sulfur) according to the original procedures

established by Canfield (1986).

Sulfur extractions were performed following the laboratory procedures from the

Geology Department, University of Cincinnati (Figure 1.5; Elswick, 2001). First, native

sulfur was obtained. Approximately 2 grams of sample in a cellulose thimble were

weighed on an analytical balance and placed into a soxhelt extraction glassware vessel.

Cleaned copper shot was placed into a 250 ml flask filled with 250 ml of

dichloromethane. The loaded flasks were placed on hot plates inside condensers for ~10

hours. Once the sample cooled and dichloromethane evaporated, the copper shot was

saved and poured into a three neck reaction glassware vessel in the Geology Department

sulfide extraction apparatus. Under N2, 50 ml of 12N HCl was poured into the glassware.

15 H2S was released from copper shot and collected in test tubes filled with 50 ml of

AgNO3. The precipitated Ag2S was then collected on a 1.2 µm glass fiber filter. Each

filter was dated, weighed and recorded.

Figure 1.5. Diagram of the sulfur extraction system used in the geochemistry laboratory in the Department of Geology. This consists of a multi-step sulfur analysis to isolate reduced sulfur species (Elswick, 2001).

17 Acid Volatile Sulfur (AVS) extractions were done with approximately 2 grams of powered sample in the three neck glassware vessel. 50 ml of 6N HCl was added followed by heating and agitation in the extraction apparatus. N2 sealed had to flow constantly through the system until the reaction took place. After 4 or 5 hours H2S reacted with

AgNO3 and precipitated Ag2S into test tubes. The remaining solid sample was extracted to the next step in the sulfur extraction. The Ag2S obtained was filtered in a previously weighed 1 μ glass fiber filter and dried in the 50° C oven.

Chrome-Reducible Sulfur was extracted using the sample remaining from the

AVS. It was added to 40 ml of CrCl3 and 40 to 50 ml of 6N HCl. In this step, iron di- sulfides were reduced, releasing H2S, which was then reacted with AgNO3 to produce

Ag2S, again filtered and weighed in the 1 μ filter. After drying the percent of sulfide in each sample was calculated with the formula:

⎜⎛ ⎟⎞ ⎡ Native Sulfur (g) ⎝32.07⎠ ⎤ ⎢ ⎥ %S = ⎢ (32.07 + 2(107.87) ⎥ × 100 ⎢ Weight dry sample (g)⎥ ⎣⎢ ⎦⎥

Dried samples were kept in small vessels and sent to Indiana University for sulfur isotope analysis of δ34S values using the methods reported in Studley et al. (2002).

18 1.4 RESULTS

Three different areas were selected for sampling bedrock samples from the Kope

Formation exposures. The first round of sampling was taken along the Route 445 in

Brent, Kentucky. The second sampling comes from Rapid Run Creek and the third one, a

core from the Clermont County. As stated previously, bedrock is not well exposed in the

Mason area, so samples were obtained from the nearest pertinent outcrop sites. All the areas have a stratigraphic elevation similar to that of the walls of the buried valley at

Mason that corresponds to the Kope Formation. The sampling of bedrock revealed a zone of elevated arsenic in the Snag Creek submember (Brett and Algeo, 2001) of the

Kope Formation along Route 445 with values from 3.9 to 39.9 ppm (Figure 1.6). The sampling taken in Clermont County has a lower range of arsenic of 4.2-15.8 ppm (Figure

1.7). The last samples taken from the Kope Formation were from the Rapid Run Creek area and have a range of arsenic from 5.5-13 ppm (Figure 1.8). Neither the Clermont

County core nor the Rapid Run section showed the arsenic spike in the Snag Creek submember found in the Kentucky Route 445 outcrop.

19 Arsenic contents in the Kope Formation (Kentucky route 445)

160

140

120

100

Feet abovethe base 20

-20

-40

-60 0 5 10 15 20 25 30 35 40 45 As (ppm)

Figure 1.6. Peaks of arsenic concentrations in the Kope Formation in the outcrop at Kentucky route 445.

20 Arsenic concentrations in Clermont County's core

180

160

140

120

100

60 feet above theKope Fm. 40

-20 0 5 10 15 20 25 30 35 40 45 As (ppm)

Figure 1.7. Arsenic results obtained from the Clermont County well. The arsenic values obtained are lower than the Brent outcrops, and lack the prominent spike at 120 feet.

21 Table 1.1. Relation of majors from XRF analysis and sulfur isotopes relation from bedrock samples of the Kope Formation in the section area of KY route 445. 34 Sample Feet FeO3 MnO TiO2 SiO2 Al2O3 CaO K2O P2O5 MgO Na2O3 LOI δ S above the (%) (%) (%) (%) (%) (%) (%) (%) (%) (%) (%) (‰CDT) base K02 10 4.36 0.05 0.44 42.71 38.13 1.19 1.62 0.11 2.67 1.32 8.40 10.76 K07 35 2.58 0.07 0.30 39.14 4.55 17.50 1.29 0.27 5.07 0.35 27.31 6.14 K10 50 3.35 0.06 0.49 39.32 7.40 13.48 2.17 0.16 7.44 0.31 24.59 -12.43 K12 60 2.39 0.03 0.31 52.11 5.48 13.52 1.55 0.15 6.29 0.66 16.37 5.52 K14 70 2.01 0.04 0.30 52.72 5.14 10.97 1.36 0.19 3.84 0.67 21.69 13.65 K15 75 4.45 0.05 0.45 42.54 38.13 1.18 1.60 0.13 2.72 1.37 8.40 31.21 K16 80 3.54 0.06 0.35 37.81 5.25 18.36 1.39 0.14 8.30 0.35 22.97 -13.20 K18 90 3.86 0.08 0.57 48.45 6.51 9.72 1.57 0.16 5.00 0.50 22.62 14.46 K19 95 3.43 0.07 0.57 50.77 9.15 10.01 2.29 0.17 5.03 0.45 17.27 14.06 K27 130 3.76 0.08 0.35 33.49 3.98 21.97 1.34 0.28 8.21 0.26 24.60 -1.24

Table 1.2 Whole-rock chemistry of trace elements and arsenic concentrations of the Kope Formation in the area of Kentucky Route 445. Sample Feet Above Sr Rb U Th Pb Zn Cu Ni Co Cr V Br Mo Zr As The (ppm) (ppm) (ppm) (ppm) (ppm) (ppm) (ppm) (ppm) (ppm) (ppm) (ppm) (ppm) (ppm) (ppm) (ppm) Base K02 10 293.3 134.9 2.1 14.6 11.2 72.1 8.4 17.2 19.5 68.6 90.4 3.6 0.3 171.9 11.0 K03 15 212.0 147.6 1.9 16.0 14.8 74.3 7.0 16.4 18.2 75.5 109.6 2.6 0.2 180.6 6.9 K05 25 304.5 141.8 1.4 14.3 8.4 75.8 7.5 20.0 17.9 129.6 81.4 1.6 0.1 153.0 8.7 K06 30 245.9 85.0 2.8 12.3 16.5 48.2 8.0 10.2 16.7 111.0 78.1 2.2 0.4 225.4 6.4 K07 35 224.2 150.4 1.2 14.7 10.6 79.0 7.7 15.7 18.3 72.8 92.0 0.8 0.2 156.6 12.0 K08 40 221.9 149.7 1.7 15.2 17.2 79.0 7.7 22.1 16.8 74.2 99.7 1.6 0.0 178.6 6.5 K10 50 262.1 137.0 3.6 14.5 16.8 73.3 7.0 19.5 18.7 86.0 91.1 1.6 0.0 169.3 5.7 K11 55 198.3 163.5 1.5 15.8 6.9 82.8 10.1 26.4 20.8 109.8 128.2 0.5 0.2 161.2 6.3 K12 60 226.4 136.6 1.5 15.3 6.5 75.0 8.4 29.1 18.1 105.6 110.5 0.9 0.1 175.9 5.2 K15 75 673.7 65.9 1.2 10.1 7.1 40.5 6.0 6.3 10.7 63.2 67.9 2.9 0.2 154.9 25.4 K16 80 186.7 154.4 3.7 15.7 12.5 77.7 7.2 17.9 15.3 72.6 102.5 0.2 0.0 155.1 39.9 K17 85 198.0 155.6 1.3 14.5 7.2 78.7 8.5 30.2 21.0 121.9 116.7 0.1 0.1 155.1 8.6 K18 90 176.0 160.5 2.6 14.3 7.1 79.3 8.2 22.6 20.0 84.1 126.5 1.4 0.1 148.8 11.2 K19 95 207.8 143.8 1.5 14.2 8.8 74.3 7.8 18.9 18.3 68.0 93.1 0.9 0.1 166.9 5.7 K27 130 225.1 128.7 2.0 14.4 9.9 70.4 9.1 15.4 18.5 73.2 91.1 2.4 0.2 196.7 13.0

23 Table 1.3. Analysis of total carbon, sulfur and arsenic of the bedrock samples from the Kope Formation in the Kentucky Route 445. Sample Feet from the base As %C %S (ppm) K- 1 5 5.5 2.07 0.81 K- 2 10 11.0 1.83 0.68 K- 3 15 6.9 1.27 1.00 K- 4 20 4.2 1.21 0.22 K- 5 25 8.7 2.02 0.82 K- 6 30 6.4 2.27 1.12 K- 7 35 12.0 1.44 0.66 K- 8 40 6.5 3.35 1.08 K- 9 45 5.2 1.94 1.04 K-10 50 5.7 1.82 0.74 K-11 55 6.3 1.16 0.55 K-12 60 5.2 1.23 0.42 K-13 65 7.6 1.24 0.42 K-14 70 14.1 1.46 0.52 K-15 75 25.4 3.67 0.40 K-16 80 39.9 1.23 0.28 K-17 85 8.6 0.93 0.43 K-18 90 11.2 1.07 0.49 K-19 95 5.7 1.53 0.46 K-20 100 3.2 3.34 0.19 K-22 105 3.8 1.53 0.53 K-23 110 5.4 1.55 0.50 K-24 115 4.1 2.88 0.46 K-25 120 5.0 2.32 0.46 K-26 125 8.4 2.24 0.80 K-27 130 13.0 1.15 0.26 K-28 135 9.4 1.07 0.55 K-29 140 5.9 1.05 0.52 K-30 145 6.0 2.39 0.28

Table 1.4. Relation of majors from XRF analysis and sulfur isotopes relation from bedrock samples of the Rapid Run Creek. 34 Sample Feet from FeO3 MnO TiO2 SiO2 Al2O3 CaO K2O P2O5 MgO Na2O3 LOI δ S the base (%) (%) (%) (%) (%) (%) (%) (%) (%) (%) (%) (‰ CDT) SC1 127 7.09 0.08 0.87 55.70 15.63 4.10 4.21 0.14 3.44 0.75 8.02 -12.57 SC3 129 7.24 0.08 0.90 55.86 15.99 3.41 4.34 0.14 3.49 0.71 7.92 15.92 SC7 136 7.74 0.08 0.91 56.07 17.46 2.44 4.75 0.14 3.53 0.74 6.43 0.99 SC12 143 7.32 0.08 0.94 56.50 16.35 2.71 4.47 0.15 2.99 1.28 7.39 12.17 SC13 144 6.46 0.09 0.95 57.92 15.26 3.42 4.13 0.18 2.96 1.35 7.25 8.98 SC15 147 7.24 0.08 0.93 56.71 16.54 3.70 4.49 0.13 2.88 1.41 6.13 8.86 SC18 151 6.87 0.09 0.85 53.68 14.31 3.95 4.19 0.14 2.88 1.16 11.52 4.11 SC20 153 8.27 0.07 0.98 56.08 16.89 2.09 4.68 0.14 3.04 1.26 6.91 -0.5 Alx 2 156 7.42 0.08 0.97 57.73 16.77 1.98 4.69 0.13 2.98 1.20 6.42 -6.19 Alx 4 159 7.61 0.07 0.97 57.17 15.90 3.09 4.43 0.18 2.92 1.40 6.69 0.39 Alx 6 161 7.38 0.08 1.00 57.30 16.18 2.63 4.62 0.14 3.04 1.31 6.61 12.5 Alx 8 167 7.53 0.08 0.96 56.58 16.34 2.89 4.54 0.13 2.99 1.27 6.95 -4.41 C 25-26 170 7.71 0.08 0.93 56.11 16.93 3.03 4.82 0.19 2.75 1.52 6.15 11.06 C 28-29 183 7.35 0.08 0.97 57.35 16.78 2.58 4.66 0.27 2.71 1.57 5.95 8.4 C 30-31 190 7.54 0.08 0.98 56.36 16.36 1.91 4.72 0.19 2.93 1.34 7.77 10.68 C 33-34 210 7.49 0.08 0.95 56.42 15.93 2.59 4.56 0.21 2.84 1.38 7.77 1.98 C 38-39 237 7.21 0.09 0.94 55.38 16.31 4.22 4.58 0.21 2.99 1.51 6.66 11.37 C 40-41 250 7.32 0.07 1.03 57.23 17.34 1.07 4.97 0.20 2.91 1.30 6.90 2.67

25 Table 1.5. Relation of majors from XRF analysis and arsenic concentrations from bedrock samples of the Kope Formation corresponding to the Rapid Run Creek section.

Samp Sr Rb U Th Pb Zn Cu Ni Co Cr V Ba As (ppm) (ppm) (ppm) (ppm) (ppm) (ppm) (ppm) (ppm) (ppm) (ppm) (ppm) (ppm) (ppm) SC1 114.5 147.7 0.95 13.68 8.1 51.3 28.4 35.7 25.6 68.5 62.7 258.7 9.0 SC2 133.0 138.2 2.15 14.83 5.4 48.3 31.5 31.4 18.0 67.1 66.3 282.0 9.8 SC3 220.4 122.5 2.86 11.51 11.3 48.1 24.9 33.0 20.2 81.9 74.6 247.1 9.6 SC4 158.7 143.5 2.77 13.46 9.2 50.8 32.2 35.3 21.9 73.3 79.8 294.2 7.9 SC5 140.6 148.5 2.47 14.06 9.6 51.8 29.1 37.5 22.8 78.1 94.0 283.7 12.6 SC6 148.1 152.5 1.92 14.04 6.9 51.7 32.0 34.5 21.8 67.7 86.8 337.9 10.0 SC7 188.0 146.7 5.02 13.05 5.6 50.9 28.9 32.7 15.8 62.8 84.7 299.7 5.5 SC8 302.1 104.2 1.19 10.15 11.4 43.8 21.0 27.0 19.4 57.5 48.1 204.0 12.8 SC9 92.6 153.5 3.69 13.59 18.2 53.0 30.1 38.1 23.8 68.0 85.3 305.9 12.3 SC10 124.5 146.8 5.52 12.98 11.9 52.1 32.3 36.1 21.7 79.6 100.5 272.0 11.6 SC11 92.3 157.3 1.64 14.51 4.5 54.0 35.0 38.5 25.2 72.9 85.8 258.7 9.6 SC12 90.1 156.1 1.95 13.71 8.0 53.6 32.2 38.6 23.4 88.7 87.7 251.3 10.8 SC13 104.9 137.7 2.87 12.89 11.3 48.1 32.8 39.8 22.4 71.9 79.9 197.7 9.0 SC14 109.5 151.0 3.41 13.28 5.6 51.9 31.6 41.1 23.1 69.0 81.3 214.6 10.9 SC15 102.2 151.8 0.61 14.35 6.5 52.3 29.1 37.0 20.4 71.7 94.5 264.7 7.7 SC16 107.1 151.7 2.49 13.77 7.0 53.2 29.2 38.0 21.0 68.3 101.4 219.7 10.7 SC17 108.7 150.7 3.80 13.99 8.2 54.7 30.5 38.2 22.0 77.6 63.5 278.5 12.8 SC18 112.6 153.3 1.83 14.46 10.8 58.8 28.9 43.2 25.1 66.5 67.2 313.0 11.3 SC19 128.9 149.4 2.36 14.48 9.3 51.0 29.1 41.9 19.3 63.8 112.5 290.7 10.8 SC20 125.8 155.2 4.27 14.58 7.8 55.3 31.2 42.5 25.2 71.7 105.1 306.6 11.7 ALX1 149.5 151.2 0.73 12.93 11.3 49.7 25.6 43.1 22.3 68.1 89.1 298.6 12.4 ALX2 133.0 146.9 0.42 12.92 8.8 51.5 26.0 43.0 20.1 67.1 94.0 272.1 11.3 ALX3 82.7 169.4 2.14 15.17 8.1 56.0 25.3 46.3 25.7 70.1 83.8 298.5 10.2 ALX4 114.5 147.7 0.95 13.68 8.1 51.3 28.4 35.7 25.6 68.5 62.7 258.7 11.2 ALX5 133.0 138.2 2.15 14.83 5.4 48.3 31.5 31.4 18.0 67.1 66.3 282.0 10.2 ALX6 220.4 122.5 2.86 11.51 11.3 48.1 24.9 33.0 20.2 81.9 74.6 247.1 9.7 ALX7 158.7 143.5 2.77 13.46 9.2 50.8 32.2 35.3 21.9 73.3 79.8 294.2 8.2 ALX8 140.6 148.5 2.47 14.06 9.6 51.8 29.1 37.5 22.8 78.1 94.0 283.7 6.9 C25- 26 148.1 152.5 1.92 14.04 6.9 51.7 32.0 34.5 21.8 67.7 86.8 337.9 8.5 C28- 29 188.0 146.7 5.02 13.05 5.6 50.9 28.9 32.7 15.8 62.8 84.7 299.7 12.2 C30- 31 302.1 104.2 1.19 10.15 11.4 43.8 21.0 27.0 19.4 57.5 48.1 204.0 10.9 C33- 34 92.6 153.5 3.69 13.59 18.2 53.0 30.1 38.1 23.8 68.0 85.3 305.9 10.0 C38- 39 124.5 146.8 5.52 12.98 11.9 52.1 32.3 36.1 21.7 79.6 100.5 272.0 8.1 C40- 41 92.3 157.3 1.64 14.51 4.5 54.0 35.0 38.5 25.2 72.9 85.8 258.7 13.0

26 Table 1.6. Sedimentation rate obtained with the relationship from modern sediments 34 34 34 34 calculated with the relationship: log ω = 1.33 – 0.042 Δδ S and Δδ S = δ Ssulfate - δ Ssulfide- pyrite for the samples from Rapid Run Creek section. The bedrock samples correspond to the 34 Rapid Run Creek Section and the Kentucky Route 445. The δ Ssulfate value for the Ordovician-Silurian is 22 ‰ CDT (Strauss, 1997)

Above the base Stratigraphic 34 Sample of the Kope δ Ssulfide-pyrite Sedimentation Submember of Formation rate the Kope feet ‰ CDT cm/yr C 40-41 250 2.67 3.2 Taylor Mill C 38-39 237 11.37 7.6 Taylor Mill C 33-34 210 1.98 3.1 Grand Avenue C 30-31 190 10.68 7.1 Grand View C 28-29 183 8.4 5.7 Alexandria C 25-26 170 11.06 7.4 Alexandria Alx 8 167 -4.41 1.6 Alexandria Alx 6 161 12.5 8.5 Alexandria Alx 4 159 0.39 2.6 Alexandria Alx 2 156 -6.19 1.4 Alexandria SC20 153 -0.5 2.4 Snag Creek SC18 151 4.11 3.7 Snag Creek SC15 147 8.86 6.0 Snag Creek SC13 144 8.98 6.0 Snag Creek SC12 143 12.17 8.2 Snag Creek SC7 136 0.99 2.8 Snag Creek SC3 129 15.92 11.8 Snag Creek SC1 127 -12.57 0.7 Snag Creek

Table 1.7 Sedimentation rate calculated for the Kope samples obtained in Kentucky Route 34 34 34 34 445 with the relation: log ω = 1.33 – 0.042 Δδ S and Δδ S = δ Ssulfate - δ Ssulfide-pyrite 34 Sample Base of the Kope δ Ssulfide-pyrite Sedimentation rate feet ‰ CDT cm/yr K02 10 10.76 7.210 K07 35 6.14 4.612 K10 50 -12.43 0.765 K12 60 5.52 4.344 K14 70 13.65 9.535 K15 75 31.21 52.098 K16 80 -13.20 0.711 K18 90 14.46 10.311 K19 95 14.06 9.920 K27 130 -1.24 2.259

Arsenic contents in the Kope Formation submembers

260.0

250.0

240.0 Taylor Mill 230.0

220.0 Grand Avenue 210.0

200.0 Grand View 190.0

180.0

170.0 Alexandria

160.0 ft above the base of the Kope Fm. Kope the of base the above ft 150.0

140.0 Snag Creek 130.0

120.0 0 5 10 15 20 25 30 35 40 45 As (ppm)

Figure 1.8. Arsenic levels in the Rapid Run Creek Section. The graph includes each submember of the Kope Formation in which samples were taken.

29 1.4.1 XRF Results

Major and trace elements were studied from a total of approximately 100 samples of the

Kope Formation. The XRF analyses were performed for samples from the Clermont County,

Route 445 in Brent, Kentucky and Rapid Run Creek. The purpose of these analyses was to

determine weather a chemical correlation exists between arsenic, major and trace elements and

sulfur isotopes. Chemical correlations could also indicate any probable pattern between the

elements present in the bedrock and the sedimentation regime occurring in the Kope Formation.

The results obtained by XRF were negative with respect to the arsenic relationships with trace or major elements. From the results obtained it is clear that arsenic does not correlate with any

other elements, nor with sulfur isotopes (Tables 1.1-1.6).

There is, however, a relationship between the contents of aluminum and calcium in the

Kope Formation and the sulfur isotopes. Figure 1.9 and 1.10 show a reciprocal relation. High

aluminum has a weak association with heavy sulfur; high calcium has stronger association with

light sulfur.

35.00

30.00

25.00

20.00

15.00

10.00

34S(‰) 5.00 δ

0.00

-5.00

-10.00

y = 0.5554x + 0.0218 -15.00 R2 = 0.3225

-20.00 0.00 5.00 10.00 15.00 20.00 25.00 30.00 35.00 40.00 45.00 Al (ppm)

Figure 1.9. Aluminum concentrations versus δ34S in samples from the Kope Formation in the Kentucky Route 445.

31 35.00

30.00

25.00

20.00

15.00

10.00

34S (‰) 5.00 δ

0.00

-5.00

-10.00 y = -1.4031x + 23.436 2 -15.00 R = 0.5129

-20.00 0.00 5.00 10.00 15.00 20.00 25.00 Ca (ppm)

Figure 1.10. Calcium concentrations versus δ34S showing a reversal pattern as the aluminum in the previous figure.

32 1.5 INTERPRETATIONS

The principal objective of this research is to acquire a broad chemical evaluation

of bedrock (Kope Formation) as part of the arsenic study in the Shaker Creek Aquifer in

Mason, Ohio. A possible source of arsenic was found in different stratigraphic levels

from the Kope Formation with moderate values ranging bewteen 2.5-40 ppm. By

contrast, average shales have about 5-13 ppm in the Rapid Run Creek section and 4.2-

15.8 ppm in the Clermont County core. The highest value found was from an isolated horizon from the section in KY route 445. The reason for these elevated values is not yet well understood because these values were not repeated in other section of the Kope

Formation. Possibly, the changes in concentration of arsenic in the Kope Formation reflect different accumulation of arsenic in different sections of the bedrock at varying rates of deposition during sedimentation.

The major minerals that adsorb arsenic in sediments are metal oxides, particularly those of iron, aluminum, and manganese (Smedley and Kinninburgh, 2005). Arsenic could be concentrated when hydrous iron, aluminum and manganese oxides are present in the rock. After analyzing our samples by XRF we find no relationship of arsenic to iron, aluminum or manganese. There is likewise no relation to organic carbon or to total sulfur

(Table 1.3).

The second objective of this study is to compare sulfur isotopes of sulfides in the bedrock with dissolved sulfur in the aquifer to test for arsenic release by pyrite dissolution and also to understand in terms of whole rock chemistry the sedimentation rates occurring in the Kope.

33 Sulfur isotope fractionation occurs by two processes in nature. First, there is

equilibrium fractionation during inorganic reactions between sulfur bearing ions,

molecules and solids. In this case, 34S is concentrated in the compounds with the highest

oxidation state or the greatest bond strength (Figure 1.11; Bowen, 1988). Second is

fractionation due to the reduction of sulfate ions (Figure 1.12). This can occur by

inorganic processes or by biogenic processes. This fractionation occurs because the 32S

forms weaker bonds than the 34S and therefore the reduced product tends to be depleted in 34S (Clark and Fritz, 1997). The amount of inorganic reduction fractionation is

dependent upon external factors affecting the system. These factors will vary with the

rate at which S-O bonds in sulfate are broken (Bowen, 1988). The reduced sulfur species

produced by this process can be depleted in 34S by up to 73‰ from the starting sulfate

(Clark & Fritz 1997).

Biogenic reduction is the dominant form of sulfur fractionation at the Earth’s

surface. Biogenic fractionation is mainly a product of sulfur reducing bacteria such as

Desulfovibrio desulfuricans. These bacteria live in the ocean and in lake sediments. The

bacteria are able to achieve greater rates of sulfate reduction because the process is

enzyme catalyzed. Depletions of up to 50‰ in 34S have been reported for reduced products (Krouse and Mayer, 2000). Negative δ34S values are typical of diagenetic

environments where reduced sulfur compounds are formed (Krouse, 1980). The most

common reaction product is pyrite, which is present in many shales or other organic-rich

sedimentary rocks and is formed by bacteria reducing seawater sulfate in marine

sediments. Because of its similarity to sulfur, arsenic is also incorporated in these

biogenic pyrites.

Figure 1.11. Range of δ34S in different shales, limestone, biogenic pyrite and sea water. The isotopic values of sedimentary rocks varies from -45 ‰ < δ34S < +42 ‰ (Modified from Krouse, 1980).

Figure 1.12. Diagram of sulfur fractionation. Dissolution/precipitation of sulfate 2- - minerals produces no fractionation. Reduction of SO4 isotopes to HS produces a large - 2- fractionation, however oxidation of HS back to SO4 produced no fractionation (Modified from Krouse and Mayer, 2000).

36 Sulfur is removed from the oceans in either the oxidized form, sulfates, or the

reduced form, sulfides (Sharp, 2005). The fractionation between the oxidized form and

dissolved sulfate in ocean water is very small, while that between dissolved sulfate and

reduced sulfides is large and positive. Removing large amount of sulfide from the ocean

will increase the δ34S value of the dissolved sulfate.

Sulfate reducing bacteria are a group of microorganisms that use electron donors to reduce sulfate by dissimilatory sulfate reduction (Hsu and Maynard, 1999). The degree of separation of the sulfur isotopes is a function of the sedimentation rate of the mud: the faster the sedimentation rate, the faster the bacteria work, and less they fractionate sulfur isotopically (Potter et al., 2005). The reduction rate for sulfate in marine sediments can be estimated from:

Log R= -0.084 Δδ34S + 0.36

where R is the reduction rate R in moles/(liter of pore water × year) (Figure 1.13;

Maynard, 1980) and Δ34S is the isotopic fractionation given by:

34 34 34 Δδ S = δ Ssulfate - δ Ssulfide

The Kope δ34S values ranged from -12.57 to + 31.21 ‰ CDT. These values indicate that the pyrite was originally formed at the same time the sediments were deposited. The correlation obtained in the oxides with aluminum and calcium (Figure 1.9 and 1.10) show two different types of shales in the Kope Formation and also show the reaction of the sulfate bacteria in the sediments. The plots show that the higher the calcium values the lower the values in δ34S and the slower the rate in sedimentation. In

the same way, the contents of aluminum show a higher content in clay material, the

higher δ34S values and the higher the rate of sedimentation.

37 The variation in δ34S values can be explained as the result of variation in bacterial

reduction rate. This phenomena was observed previously by Hsu and Maynard (1999)

stating that slow-growing bacteria having slow rates of reduction and a larger degree of

isotope fractionation between the sulfate in original sea water and sulfide; in contrast, the

fast growing bacteria have a fast rate of reduction with a smaller degree of isotope

fractionation. This is applicable between the sulfate and sulfide in pyrite in the shales of

the Kope Formation. The variability of δ34S of evaporates has been recorded from the

Precambrian to the present. The δ34S for the Upper Ordovician-Lower Silurian period

34 was about 22 ‰ CDT (Strauss, 1997), which is the δ Ssulfate. The data obtained

34 represents the δ Ssulfide-pyrite from the bedrock. The data can be used to determine the

sedimentation rate during this period with the following (Potter et al., 2005):

Log ω = 1.33 – 0.042 Δδ34S

34 34 34 where ω is the sedimentation rate in cm/yr and Δδ S = δ Ssulfate – δ Ssulfide-pyrite.

The values summarized in Table 1.6 and 1.7 show a significant variation in the sedimentation episodes occurred in the Kope Formation. The rate varies from 0.7-52 cm/yr, having a total average of 6.8 cm/yr for all sequences studied in the Kope.

As stated before, the genesis of the Kope Formation has been controversial, having three different interpretations: sea level fall, variation in storm intensity and changes in silicilastic sedimentation. The variation in sediment rates occurring in the

Kope, from the data obtained, shows that during formation of calcareous mudstone there was low net input of siliciclastics. In contrast, the non-calcareous (aluminum-rich shales) were deposited much more rapidly, and the sulfur fractionation rate was faster. This supports the idea that the events occurring in the Kope represents an ordered succession

38 of mudstone units having different episodes in which the terrigenous shales were rapidly deposited while the calcareous shales represent periods of low and slower sediment deposition. The pure limestones were not tested and could be rapidly deposited by storms. The variations in sedimentation rate reveal the differences between events that occur locally and on regional scales, even when corresponding to the same stratigraphic level but in different locations. The data obtained from the sulfur isotopes show instantaneous rate of a particular pack of mud during a brief period of time. This thesis presents the data from different cycles and not a series for a single cycle. A more detailed sampling in one cycle can determine the progression in the sedimentation. The sequential sampling in one or more cycles can give important information about the depositional events occurring in the Kope.

According to Brett et al. (2003) the correlations in the Kope Formation are recognized by distinctive faunal assemblages, taphonomic features, trace fossils, sedimentary structures and other characteristics. The present work proposes the use of sulfur isotopes as a tool for calculating the sedimentation rates occurring in the Kope

Formation. Preliminary data support that Brett et al. (2003) model of rapidly deposit terrigenous mudstones.

Figure 1.13. Relationship of the sulfur fractionation and rate of sulfate-pyrite reduction by bacteria in marine sediments. R is the reduction rate for sulfate in marine deposits and 34 34 34 Δδ S is defined as δ Ssulfate – δ Spyrite (From Maynard, 1980).

40 1.6 CONCLUSIONS

1. There appears to be an accumulation of arsenic, probably as arsenopyrite, in

shales in the Snag Creek submember, approximately 60-80 feet above the base of

the Kope Formation. The anomaly was found in the section of the Kope

Formation along the Route 445, and reaches values as high as 39.9 ppm,

compared to 8.38 ppm in typical Kope shale samples.

2. The arsenic concentrations are not located in the same stratigraphic horizon in all

the sections studied so far in this research.

3. The stable isotopic analyses in the bedrock of the Kope show two types of shales.

The calcium-rich shales with lower δ34S values had a slower rate of

sedimentation. The aluminum-rich shales showed higher δ34S values and thus a

higher rate of deposition.

4. The data presented in this study suggests that the Kope Formation was formed

during different episodes of siliciclastic sedimentation in which the input of the

terrigenous shales was faster than that of calcareous shales.

5. Arsenic does not correlate to the stratigraphy of the Kope Formation but whole

rock chemistry and sulfur isotopes contribute as a proxy for sedimentation rates in

the Kope.

6. Sulfur isotopes are a complementary tool for calculating sedimentation rates, not

only in the Kope but other siliciclastic units with measurable sulfur content in the

bedrock.

PART II

THE KOPE FORMATION AS A SOURCE OF ARSENIC AND SULFUR IN GROUNDWATER IN SOUTHWEST OHIO.

42 2.1 INTRODUCTION

Naturally occurring arsenic in public water supplies is a worldwide problem and

one of the most widespread environmental/public health problems with groundwater that

we face as a society. Contamination by human activities, such as mining is one source of

arsenic in groundwater. Another source is the groundwater’s host material, since high

concentrations of arsenic are also commonly found in some rocks, unconsolidated

sediments and soils. The intake of arsenic in drinking water has been shown to adversely

affect human health. Arsenic has been verified through epidemiological evidence as one

of the most carcinogenic and toxic substances in surface and groundwater (Welch et al.,

2000); who indicate that arsenic is linked to cancer of the skin, bladder, lungs, kidney,

nasal passages, liver and prostate. There is also a strong proven link between arsenic and

damage to the cardiovascular, pulmonary, immunological, neurological and endocrine

systems (National Research Council, 1999). According to this same study, an arsenic

concentration of 50 ppm, gives a 1/100 lifetime chance of developing cancer. For many

years the United States Environmental Protection Agency (U.S. EPA) Maximum

Contaminant Level (MCL) for arsenic in drinking water was 50 micrograms per liter

(µg/L). The National Research Council suggested lowering the MCL to 5 µg/L.

Subsequently, in 2001, the U.S. EPA established a 10 µg/L MCL. However, arsenic levels exceeding this standard of 10 μg/L are present in numerous supply wells. This new standard will be enforced from January 2006 requiring all groundwater systems in the United States to comply with a lowered MCL.

Concentrations of naturally occurring arsenic in groundwater are known to vary regionally owing to the combination of climate and geology (Welch, et. al 2000).

43 Compared with the Western region of the U.S., the Midwest typically has lower levels of

arsenic in the groundwater (Figure 2.1). However, most of the groundwater used in the

Midwestern region is produced from glacially-formed buried valley aquifers, and this is one of the most frequently cited occurrences of elevated arsenic concentration. Elevated concentrations of arsenic are often associated with wells developed in the sand and gravel units in Ohio, (Ohio EPA, 2002). Some groundwater systems in southwestern Ohio present arsenic levels above the currently recommended MCL.

Figure 2.1. Map of United States showing locations and arsenic concentrations for 31,350 wells and springs sampled by the USGS and state agencies between 1973 and 2000 (Ryker, 2001). The state of Ohio shows wells with very low to moderate contents of arsenic in groundwater.

45 2.1.1 Statement of the problem

Two drinking water distribution systems located in southwestern Ohio that present

arsenic elevations above the maximum contaminant level in their source water are Mason

and the Lebanon Correctional Institute (LeCI; Figure 2.2). Both systems obtain their

water from the Shaker Creek Aquifer, which is classified as a buried valley aquifer

(Debrewer et al., 2000). The aquifer geology consists of a sequence of glacial outwash

fill material (sands, gravels and some finer-grained lake deposits), filling a Pleistocene

valley incised into the limestone-shale bedrock. The source of the arsenic in this area is

not yet understood. A potential source could be an anthropogenic one, but regional

patterns suggest that arsenic comes from the glacial aquifer material and/or from the

surrounding bedrock (Matisoff, 1982; Korte, 1991; Slattery, 2001; Thomas 2003). More

specifically, arsenic could come from dispersed pyrite in the glacial fill or from thin lake

deposits interbedded with the glacial outwash or from the underlying bedrock. Other

concerns include the action of iron oxides, which absorb arsenic in some aquifers with

these same geological features, whereas in others does not.

An understanding of geochemical processes such as arsenic release and removal

mechanisms is needed to develop groundwater resources in buried-valley aquifers. In

order to have a better understanding of arsenic release in groundwater in the Shaker

Creek Aquifer the present study will pursue the following objectives:

(1) To determine the source(s) and mechanism(s) of mobilization of arsenic into the

groundwater supply for Mason and LeCI.

46 (2) To develop a geochemical model of aquifers like Shaker Creek that shows the cycling of arsenic in groundwater. This model can then be applied to other areas of the United

States that have similar geology and help mitigate arsenic in the groundwater supply.

Figure 2.2. Map of the area of study and sampling areas in Ohio and Kentucky. The samples were taken from the Lebanon Correctional Institute and Mason both in Warren County.

48 2.1.2 Background

An enormous interest has developed within the scientific and medical community

surrounding the considerable health effects caused by arsenic. Arsenic found dissolved

in water is generally in the arsenate [As5+] or arsenite [As3+] state (Welch et al., 1988).

However, recent studies have shown that ingested As5+ can be reduced to As3+

(Stollenwerk, 2003). Both As5+ and As3+ have serious toxicological effects for human

beings (National Research Council, 1999).

Welch et al. (2000) published a study illustrating the occurrence and geochemistry

of arsenic in 31,150 wells throughout the United States (Figure 2.1). High arsenic

concentrations in groundwater appear to be more frequent in the western United States

and in east Texas than in eastern-most states (Figure 2.1; Korte, 1991). Some arsenic

does occur in Ohio, however. Studies suggest several potential sources of this arsenic.

Matisoff et al. (1982), studied aquifers in Pennsylvanian-age sandstones and in glacial

outwash in glacially buried valleys with elevated levels of arsenic in northeastern Ohio.

This research attributes the arsenic found in the groundwater to the adsorption of arsenic

onto ferric oxyhydroxides in the rock and subsequent release under reducing conditions.

Additionally, Korte (1991) studied different groundwater sites in northern Ohio with

elevated arsenic levels and concluded that the arsenic was released into the aquifer by

bacterial reduction of sorbent iron minerals and oxidation-reduction systems in the

sediments.

Thomas (2003) provided data showing 24 percent of wells tested in southwest

Ohio had a detectable arsenic content, of which 9 percent were above the Maximum

Contaminant Level (MCL for arsenic = 10 μg/L). Both the Mason and Lebanon

49 Correctional Institute (LeCI; Figure 2.2) water supplies come from the Shaker Creek

Aquifer, a typical buried valley aquifer, which was formed by Late Pleistocene fluvial

and glacial outwash deposits (Figure 2.2 and 2.3; Debrewer et al., 2000). The Pleistocene

valley, incised into the limestone-shale bedrock, contains glacial outwash material and

some lake clays.

Both the Mason and LeCI water systems have reported elevated arsenic levels in

their groundwater supply. The groundwater supplies in this area are supervised by the

LeCI water division and by the Greater Cincinnati Water Works (GCWW). In 2002-

2004 GCWW made intensive investigations of two Mason wellfield, but they have since

decided to close the operation. LeCI continues to use their wellfield. The University of

Cincinnati, Department of Geology has been monitoring the aquifer since 1997 and has

developed or adapted well-head protection plans for both wellfields. In the process, monitoring of the water chemistry has been carried out (e.g. University of Cincinnati,

2001).

Figure 2.3. Surficial geology of the southwest part of Ohio. The Lebanon Correctional Institute is located in the Shaker Creek Aquifer composed of glacial and alluvial material, clays and comprised loamy till deposits (From: Brockman,et al., 2004).

Figure 2.4. Geology of the Shaker Creek Aquifer (SCA). The main lithologies are alluvial material, ground moraine and complex (defined as a combination of glacial deposits, alluvium and sediments). The main cities are shown with the production wells that use the SCA as a supplier and extends from the Little Miami River at South Lebanon, Ohio to Great Miami River at Middletown, Ohio (Modified, University of Cincinnati, 2001).

52 2.1.3 History of glaciations and associated deposits

There have been different episodes of glaciation throughout the geologic history of the Greater Cincinnati area. Kansan glaciation took place 300,000 years ago, Illinoian between 130,000 and 300,000 years ago and Wisconsinan glaciation 7,000 to 19,700 years ago. The result of these glaciations was a diverse and complex landscape in the

Tri-State area (Kentucky, Ohio and Indiana). Unsorted and unstratified material was deposited by ice producing glacial till. A large quantity of glacial sediment deposited by melt water streams formed from gravels, sands and lake-clay deposits (Potter, 1996). The outwash and alluvial deposits in the area of study represent the principal remnants of glacial deposits

2.1.4 Shaker Creek Aquifer

The geologic settings and distribution of Ohio’s major aquifer types are composed of sand and gravel, sandstone, and carbonates. The sand and gravel aquifer system, which is superimposed on the bedrock of the eastern, central, and southwestern portions of the state, comprise Ohio’s most productive and sensitive aquifers (Ohio EPA, 2002).

These buried valley aquifers are composed of bands of permeable unconsolidated sand and gravel (20 to 200 + feet thick) filling old river valleys which were cut by glacial meltwater and preglacial streams. The carbonate bedrock aquifer is found in the western half of the state and can be thick (up to 600 feet).

The surficial geology of the Shaker Creek Aquifer (SCA) corresponds to ice contact deposits of Wisconsian age next to and overlying loamy till deposits (Figure 2.3).

The SCA is classified as a buried valley aquifer, which is the product of alluvial material

53 deposited in a valley by rapidly moving water that transports and deposits coarse material

(gravel and sand), which can form permeable aquifer deposits when buried (Figure 2.3 and 2.4; UC, 2001). The hydrogeologic setting of the aquifer system consists of a thin upper discontinuous aquifer and a thicker, lower more continuous aquifer (UC,

Department of Geology, 2001). The SCA contains about 200 feet of glacially-derived sands and gravels with some finer-grained lake deposits that fill a Pleistocene-age valley incised into the limestone-shale bedrock (Figure 2.3).

According to the study of the Geology Department, University of Cincinnati

(2001), the basin area of Shaker Creek is 21,974,000 m2. This study also reports that

Lebanon Correctional Institute (LeCI) average pumped water was ~ 39 millions of gallons from 1994-1997. The Mason Plant operational data reported in 2004 by the

GCWW states that 553,529,000 gallons of raw water is pumped every year, 535,818,600 gallons of finished water is delivered for consumption and 25,697,000 gallons of filtered water is used in washing filters. The Mason and LeCI wells are located in a confined aquifer that lacks any connection with surface streams. This lack of connection creates a particular drainage that is subject to a strong drawdown with pumping and does not have a direct source of recharge. In addition, the high content of shales makes this aquifer particularly rich in H2S. H2S is crucial in the geochemical behavior of sulfides and arsenic.

54 2.2 ARSENIC CHEMISTRY

Arsenic [As0] is a semi-metallic element present in nature forming 0.00005 % of

the earth’s crust. All rocks contain some arsenic, typically 1-5 ppm (Smedley and

Kinniburgh, 2002). Higher than average concentrations are found in some igneous and

sedimentary rocks. Arsenic is present in aquatic systems in four different states of

oxidation. The most common of these are the trivalent (arsenite) [As3+] and pentavalent

(arsenate) [As5+]. The predominant species of arsenic in raw water that falls between the

- 2- - pH ranges from 5 to 9 are: H2AsO4 , HAsO4 , H3AsO3, H2AsO3 (Figure 2.5). The

factors that allow mobility and easy speciation of arsenic are: adsorption/desorption

reactions, oxidation/reduction, precipitation/dissolution and biological transformation

(Stollenwerk, 2003). Arsenates have a better capability of ionization than arsenites due to the presence of a double-bonded oxygen (Figure 2.6). Reduction of arsenate to arsenite can promote arsenic mobility because arsenite is generally less strongly adsorbed

5+ than is arsenate (Manning and Goldberg, 1997). As (as H3AsO4) is stable in water with

high levels of oxygen where the pH range is between 2 and 13. Under anoxic conditions,

even with a pH higher than 7, arsenic is stable in non-ionic species (Figure 2.6). Thus,

arsenates and arsenites are dissociated in different ranges of pH.

Figure 2.5. pE-pH diagram for predominant arsenic species in groundwater systems. - -2 The species fall between the pH ranges of 5 and 9 are: H2AsO4 , HAsO4 , H3AsO3, - H2AsO3 .

Figure 2.6. Molecular difference between arsenate [As5+] and arsenite [As3+] (Vance, 1995).

57 2.2.1 Arsenic in groundwater

Arsenic behavior is generally related to oxides of iron, aluminum and manganese, which are generally found in aquifer sediments (Stollenwerk, 2003). The majority of all arsenic found in well-oxygenated water and sediments is present in the stable form of arsenate. Depending on the surrounding Eh/pH conditions, arsenic speciation and concentration of competing ions, it is possible for arsenic to be released from the water and sediments in which it is present (Figure 2.5; Stollenwerk, 2003).

Regarding the presence of arsenic in groundwater, wells containing water with high arsenic content in the Midwest are generally associated with deeper, less-oxygenated aquifers (Thomas, 2003). High arsenic content is related to high levels of redox-sensitive elements in the water. Arsenic has an affinity for iron-manganese oxides that are also released under reducing conditions. Therefore, the release of iron-manganese oxides further heightens the likelihood of the release of arsenic (Moore et al., 1988; Welch et al.,

2001; and Stollenwerk and Kinninburg, 2002). Another important factor affecting the release of arsenic and oxide minerals is the role of sulfate-reducing bacteria. Zobrist

(2000) studied the anaerobic growth of bacteria using iron and arsenate as electron acceptors. He concluded that a change from oxidizing conditions to reducing conditions in an aquifer will cause bacteria to dissolve these oxides and lead to release of the sorbed arsenic. It is likely that arsenic concentrations will vary depending on the geology of an area, its microbial activity, its redox environments and the speciation of elements in the aquifer.

58 2.3 METHODS

2.3.1 Solids

Previous work was done during 1997 and 1999 by the University of Cincinnati,

Geology Department. The Department participated in a well head protection plan for the

LeCI (UC, Department of Geology, 2004). A monitor well of 225 feet deep was opened and the core was taken by Bowser-Morner using a rotosonic rig (Figure 2.7 A). The

material obtained in this drilling included coarse-grained glacial outwash, sands and

gravels filling a valley cut into bedrock. The material recovered was boxed in 10 ft intervals (Figure 2.7 B). Once in the Geology Department the core was repacked and sampled at one foot intervals.

2.3.2 Groundwater sampling

To better assess the behavior of arsenic in this aquifer, we conducted a survey of

water chemistry in production and monitor wells, representative aquifer solids and

production scales.

Geochemical data were collected from the Mason and LeCI production and

monitor wells in the Shaker Creek Aquifer. Field measurements were made with a sensor

for measuring temperature, conductivity, pH and ORP (Oxygen Reduction Potential).

Samples for cations and metal analysis were filtered at <0.2 μ and preserved with nitric

acid. Analyses were conducted by Cincinnati Water Works facilities, Belmont and

Brookside Laboratories.

59 2.3.3 Sulfide analyses

Sulfur extractions were performed following the laboratory procedures from the

Geology Department, University of Cincinnati (Figure 2.8; Elswick, 2001) and the original procedures established by Canfield (1986). The methodology for sulfur

extraction is explained in more detail in Section I of this thesis.

2.3.3.1 Sulfate precipitation

Water samples were taken from LeCI and Mason monitor wells and kept in 100

ml clean bottles. Sulfate was then recovered using precipitation with BaCl2 (Standard

Methods, 1999, page 4-137). Each water sample was filtered with a membrane filter to remove organic matter. Iron, which interferes with sulfate recovery, was precipitated by adding tablets of NaOH until the sample reached a pH of 8 and filtered again to remove precipitated iron oxides.

To minimize co-precipitation of BaCO3, the samples were acidified below pH 4 with a

few drops of NO3. A BaCl2 solution was prepared by dissolving 100 g of barium

chloride in 1 liter of distilled water. Drops of this solution were added to each water

sample while stirring until no further white precipitated formed. Solutions were then

heated at 80-90 °C for approximately 2 hours to increase grain size of the BaSO4 precipitated. Membrane filters were weighed and then used for water samples filtered for precipitated BaSO4 and dried in a petri dish inside the 70 °C oven. Dried samples were

2- weighed in the analytical balance and mg of SO4 were calculated with the following

formula:

2- mg Ba SO4 × 411.6 mg SO4 /ml = ml sample

60 Precipitated sulfate was kept in glass vials and sent for sulfur isotope analysis by the mass spectrometer at Indiana University (Studley, et al., 2002).

61 A B

Figure 2.7. A) Bowser-Morner using a rotosonic rig prior to the drilling in the LeCI. B) 10 feet of aquifer material recovered and packed in a box.

Figure 2.8. Diagram of the sulfur extraction system used in the geochemistry laboratory in the Department of Geology for solids. This system consists of a multi-step sulfur analysis to isolate reduced sulfur species (Elswick, 2001).

63 2.4 RESULTS

Glacial outwash samples and bedrock samples were sent to XRAL laboratories for arsenic analysis by atomic absorption spectroscopy. The arsenic values obtained in the glacial outwash material were relatively low and ranged from 2.9-12.0 parts per million (ppm; Figure 2.10).

The first results of water chemistry data analysis were compiled by the

Department of Geology, University of Cincinnati during development of a well head protection plan from 1997 and 1999 (Table 2.1 and 2.2). Table 2.3 presents a round of chemical parameters collected by the Greater Cincinnati Water Works (GCWW) during

2002-2003. Many of the results obtained for arsenic are above the USEPA MCL. As part of the field work for the University of Cincinnati project, samples were collected in

May of 2004, from Lebanon Correctional Institute (LeCI) and Mason wells (Table 2.4).

The results obtained in the groundwater sampling showed complex geochemical conditions within the aquifer. The results for arsenic ranged from 5.2 to 18.0 µg/L, and show that many of these samples are also above the USEPA MCL (10 µg/L).

The water chemistry results from different wells in the Shaker Creek Aquifer showed considerable variation. The chemistry of these wells differs depending on the location and depth but in general the chemical trends change with time, the age of the water and probable reactions with bedrock and aquifer materials. Additionally, GCWW have a continuous monitoring plan in Mason to keep a good quality system of the wells and provided data that was used for a better correlation in the oxidation-reduction potential during time (Table 2.3, Figure 2.14). Subsequently, during the most recent well head protection plan (UC, Department of Geology, 2004) the data obtained for the LeCI

64 and Mason wells show in general a similar chemistry with increasing trends with time in redox sensitive elements such as manganese and iron increase. The results obtained for iron show an increase trend with time from 1997 to 2004 in LeCI and Mason wells, responding to the lowered oxygen in the wells (Figure 2.12). At the same time the increase is also present in manganese but the trend is less obvious as it is with iron

(Figure 2.13). The production wells at both LeCI and Mason show a strong linear relationship between sodium and chloride that suggests mixing of waters from two distinct sources (Figure 2.16). This was suggested by the Well Head Report from UC in

2004. Overall, the results suggested that the groundwater in LeCI and Mason’s fairly old and has reacted extensively with aquifer solids.

Figure 2.9. Recovered log from the Lebanon Correctional Institute showing the variety in lithologic material of the ~ 228 feet recovered by the Department of Geology, University of Cincinnati (Courtesy of Thomas Lowell).

66 Arsenic contents in aquifer material

250

200

150

100 LCI monitorwell deep (feet)

0 0 5 10 15 20 25 30 35 40 45 As (ppm)

Figure 2.10. Arsenic concentrations in the Lebanon Correctional Institute aquifer material.

Table 2.1. Water chemistry of Shaker Creek wells during 1997*

- 2- 3- Well pH ORP** Ca Fe Mg Mn K Si Na HCO3 Cl SO4 NH3 PO4 mV ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm LCI #2 7.37 155 116 2.85 36 54 bdl nd 19 333 36 51 bdl bdl Mason, combined 8.07 nd 129 1.05 34 140 nd nd 16 314 38 108 bdl bdl LCI Pig Farm 7.15 145 132 4.49 39 99 bdl nd 13 344 50 93 bdl 0.09 Monroe #4 7.22 120 150 5.45 99 92 bdl nd 48 333 144 91 bdl bdl Warren Co #2 7.31 155 144 5.67 39 86 bdl 5.5 13 336 26 115 bdl bdl Otterbein #2 6.82 300 98 Bdl 25 bdl bdl 2.5 27 248 56 43 1.96 bdl Rahm Farm 7.2 44 83 0.658 35 194 4 3.9 46 291 49 58 bdl bdl Berns Field 7.67 330 93 0.22 27 15 3 nd 31 228 54 76 1.54 bdl Berns Nursery 7.28 397 101 0.084 25 14 3 3.4 27 249 48 53 2.23 bdl Shaker Creek 8.11 307 52 Bdl 14 bdl bdl bdl 12 139 24 24 1.4 0.1 bdl. Below the detection limit nd. Not determined *Parameters taken in the field: pH and oxidation reduction potential (ORP) by the UC, Department of Geology. ** Eh add +200 mV. Data provided by Brookside Laboratories

Table 2.2. Water chemistry from LeCI and Mason wells during 1999* - 2- 3- Well pH ORP** Ca Fe Mg Mn K Si Na HCO3 Cl SO4 NH3 PO4 mV ppm ppm ppm ppm ppm ppm ppm ppm ppm Ppm ppm ppm LCI #2 6.9 81 100 2.8 31 40 1 6.6 18 349 39 59 bdl bdl LCI #2 7.3 66 110 2.8 32 50 1 6.7 19 341 37 70 bdl bdl LCI MW -1 7.15 67 94 2.1 29 1 6.5 13 285 48 109 bdl bdl (shallow) 60 LCI MW -2 7.37 76 85 2.4 36 2 7.5 9 341 15 52 bdl bdl (deep) 60 Mason, 7.24 82 120 2.4 32 130 2 6.3 21 328 48 164 bdl bdl combined bdl. Below the detection limit nd. Not determined *Parameters taken in the field: pH and oxidation reduction potential (ORP) by the UC, Department of Geology ** Eh add +200 mV. Data provided by Brookside Laboratories

69 Table 2.3. Data for redox-sensitive species from Mason Production Wells during 2002-2003. 2- Date Well ORP* As Ba Fe SO4 mV ppb ppm ppm μg/l 10/09/02 1 14 476 2700 04/16/03 1 -102 18 3280 121 10/09/02 2 10 586 3100 04/16/03 2 -104 11.6 3200 189 10/09/02 5 6.3 95.9 3320 04/16/03 5 -47 8.4 3300 42 10/09/02 6 5.2 183 2840 04/16/03 6 -61 10.1 3220 117 10/09/02 7 10.6 196 3250 04/16/03 7 -64 8.9 2560 135 10/09/02 8 9.0 151 3090 04/16/03 8 10.6 3030 38 * Eh add +200 mV. Data from the Greater Cincinnati Water Works (GCWW).

70 Table 2.4. LeCI and Mason chemical parameters in groundwater from wells and monitoring wells from 2004* 2- LeCI wells T Cond. pH ORP** Ca Fe Mg Mn K Na HCO3 Cl SO4 As °C μS/cm mV mg/l mg/l mg/l μg/l mg/l mg/l mg/l mg/l mg/l μg/l LeCI-P1 17.5 1022 7.4 -55 137 4.5 40 98 1.5 28 469 56 113 7.5 LeCI-P2 16.9 774 7.3 -97 107 3.3 36 71 1.9 18 367 32 71 5.1 LeCI-P3 16.7 768 7.6 -32 111 4.7 40 59 1.1 15 398 23 56 16.3 LeCI-P4 16.7 1105 7.4 -46 152 6.8 42 81 1.5 46 442 71 116 9.5 LeCI-P5 17.0 766 7.6 -95 107 2.7 37 37 1.2 18 408 39 30 6.0 LeCI-P6 16.4 919 7.4 -89 130 4.4 39 66 1.2 22 430 51 67 8.8 LeCI-P7 16.3 118 7.3 -45 175 5.4 44 141 1.5 26 488 46 135 <2.5 LeCI-MW7 (shallow) 12.6 837 7.2 -82 122 2.3 32 n.d <0.6 21 382 59 80 <2.5 LeCI-MW8 (deep) 13.2 748 7.61 -118 115 3.1 39 n.d <0.6 8 470 3 70 15.9 MAS-P1 12.69 674 7.10 -96.9 101 2.2 35.1 110 1.57 14.8 350 34 51.3 13.1 MAS-P2 12.70 684 7.12 -94.7 103 3.0 33.0 55 1.34 14.8 338 32 47.3 8.46 MAS-P5 12.48 867 6.87 -54.8 151 2.7 41.1 185 1.68 11.9 350 31 190 4.65 MAS-P6 12.51 842 7.03 -71.1 129 2.9 35.9 199 1.68 27.9 324 74 116 5.36 MAS-P7 12.72 862 7.11 -63.2 134 2.9 36.5 125 1.70 20.5 328 65 128 5.67 MAS-P8 12.62 795 7.44 -69.5 126 2.5 36.6 188 1.26 12.4 360 33 111 7.90 MAS-MW1 12.65 694 6.91 -103 114 3.4 31.8 66 1.02 9.45 Error 45 42.0 7.18 MAS-MW2 12.54 654 6.95 -87.1 109 2.0 31.2 111 1.38 9.73 Error 32 88.7 3.84 LeCI -Lebanon Correctional Institute wells MAS Mason Monitoring Wells MW -Monitor Wells n.d. not determined *Temperature (T), conductivity (Cond), pH and oxidation reduction potential (ORP) are parameters taken in the field. ** Eh add +200 mV. Analyses obtained from Brookside laboratories.

71 ORP relation versus time

200

150

100

50 ORP (mV)

-50

-100 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 Time (year)

Figure 2.11. Average Oxidation Potential Reduction of Shaker Creek Aquifer wells and its relation with time. The data corresponds to Tables 2.1-2.4.

72 5

4.5

3.5

3 LeCI wells

2.5 Fe (ppm)

Mason wells 1.5

0.5

0 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 Year

Figure 2.12. Iron increased with time from 1997 to 2004 in LeCI and Mason wells, responding to the lowered oxygen in the wells.

73 160

Mason wells 140

120

100

80 Mn (ppm)

60 LeCI wells

0 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 Year

Figure 2.13. Manganese concentrations also increased with time, but not as much as was seen with iron.

74 Arsenic versus Oxidation Potential Reduction

20 Mason wells 2003 18 Mason wells 2004 LeCI wells 2004 16

10 As (ppb) As 8

0 -120 -100 -80 -60 -40 -20 0 ORP (mV)

Figure 2.14. Relationship between arsenic and total ORP in LeCI and Mason monitoring wells. The pattern indicates an increasing concentration of arsenic at lower ORP conditions.

75 18.0

Group I 16.0

14.0

12.0

10.0

As, ppm 8.0

6.0

4.0

2.0 Group II

0.0 0 20 40 60 80 100 120 140 160 180 200 Sulfate, ppm

Figure 2.15. Relations between sulfate and arsenic in LeCI and Mason monitoring wells. There are two main groups of relatively high arsenic and low sulfate and the opposite relation with high sulfate and low arsenic concentrations.

76 Mason and LeCI wells

50 2004 45 1999 1997 40 Shaker Creek

Sodium (ppm) 20

10 y = 1.5639x + 12.26 R2 = 0.5839 5

0 0 1020304050607080 Chloride (ppm)

Figure 2.16. The chloride and sodium values show a correlation in the Mason and LeCI wells, suggesting a mixing of two different sources for the water.

77 All the chemical parameters of the groundwater in the Mason and in the LeCI wellfields are similar, but chemistry changes through time. Arsenic correlates with redox at LeCI and Mason groundwater. Also, arsenic concentrations are higher with depth with arsenic being absent from the shallow aquifer (Table 2.3 and 2.4; Figure 2.14).

Groundwater arsenic concentrations are spatially heterogeneous in the Lebanon

Correctional Institute (LeCI) and Mason groundwater supplies from the 2002-2003 sampling (Table 2.4). Arsenic values ranged from 5.2 ppb to 18 ppb with 7 of the 12 samples at or exceeding the MCL. However, the chemical data show few correlations of arsenic to other water quality parameters. Arsenic and iron oxides are usually found to be chemically related (Stollenwerk, 2003; Gotkowitz et al., 2004). However, both Mason and LeCI showed no relation between iron and arsenic.

2- A better relationship is seen in the plot of arsenic versus sulfate (SO4 ), as shown

2- in Figure 2.15. High arsenic samples are associated with low SO4 values and vice versa, although the correlation is poor. This antithetical relationship of the high arsenic and

2- SO4 concentrations suggests that sulfate reduction by bacteria is an important control on arsenic release to the aquifer. Another factor that is suggesting this is the increase of manganese and iron as arsenic values increase with time (Figures 2.12 and 2.13). As stated before, oxides of iron and manganese are potentially the most important source for arsenic in aquifer sediments because of their chemistry, widespread occurrence, and tendency to coat other particles (Stollenwerk, 2003).

78 2.4.1 Sulfur isotopes results

Arsenic is possibly being leached into the groundwater from the dissolution of arsenopyrite (AsFeS2) in the outwash glacial aquifer material and/or local bedrock. To test this, sulfur was extracted from groundwater and aquifer samples from Mason and

LeCI water supplies. The sources of sulfur were characterized using sulfur isotope mass spectrometry at Indiana University (Table 2.5). Sulfur isotope data shows signatures in rock (sulfide) and water (dissolved sulfate) samples from the area of study. Table 2.5 presents the sulfur isotopic composition (δ34S) of pyrite from the Mason monitoring wells, and LeCI water samples. The groundwater samples ranged from δ 34S -4 to -16 ‰, averaging -11.1 ‰. Pyrite in the bedrock was found to average +6.8 ‰, compared to glacial outwash pyrite, which was -41 ‰ (Table 2.6).

Table 2.5. Sulfur isotopes results in water, glacial outwash fill material and bedrock samples from Mason and LeCI.

Sample Method δ34S (‰ CDT*) MMW 1, 16' aquifer -48.0 material MMW 2, 21' aquifer Solids -33.6 material (Ag2S) MMW 2, 136' (bedrock) -4.8 LeCI, P#1 -13.2 LeCI, P#4 -12.5 LeCI, P#7 groundwater -15.1 LeCI, MW-7 (BaSO4) -3.9 LeCI, MW-8 -7.6 Mason P#5 -15.8 Mason P#6 -9.2 * CDT. Canyon Diablo Troilite

80 Table 2.6. AVERAGE Δ34S VALUES FROM BEDROCK, GLACIAL OUTWASH MATERIAL AND GROUNDWATER SAMPLES. *CDT =CANYON DIABLO TROILITE. Sample δ34S (‰ CDT*) Bedrock pyrite n=28 +6.8

Groundwater sulfate n=7 -11.1

Glacial outwash material n=2 -41

81 2.5 SULFUR ISOTOPES

Arsenic has many similarities in its geochemical behavior to sulfur. Therefore, tracking sulfur behavior can give clues about arsenic behavior. Sulfur is a major element in both marine sediments and sea water with four main oxidation states ranging from +VI to –II (Clark and Fritz, 1997), which makes it an easy electron acceptor and donor in redox reactions. Sulfur has 4 main stable isotopes 32S, 33S, 34S and 36S with 95.02%,

0.75%, 4.21% and 0.02% abundance, respectively. Sulfur isotopes are considered stable isotopes because they are not involved in any radioactive decay scheme. A primary research application of stable isotopes is to understand the source of water and processes that have affected the water since it was formed.

As a form of shorthand the δ (delta) notation is used to express the difference between a sample and a reference, such as the Canyon Diablo Troilite (an iron sulfide meteorite). The reference calculation is expressed as:

A δ value that is positive signifies that the sample is enriched relative to the reference in

34S and a sample that has negative values, indicates relative depletion.

Sulfur in nature varies from δ34S -50 to +50 ‰ (Figure 2.17; Krouse, 1980). δ34S in pyrite in modern marine sediments varies over a wide range from –35 to +4 ‰

(Goldhaber and Kaplan, 1974). The variation in δ34S is due partly to the fractionation factor and partly to the fact that pyrite does not grow directly from sea water but from interstitial water in sediments, and is highly fractionated between sulfur compounds due to biological cycling (Drever, 1988). In the case of this study, the sulfur isotope

82 composition of groundwater sulfate depends upon the process affecting its generation and removal (Figure 2.18; Krouse and Mayer, 2000).

Where sulphide-bearing rocks are exposed to oxygen, oxidation of pyrite and other sulphide minerals can contribute considerable amounts of sulfate to groundwater

(Clark and Fritz, 1997). The reaction can be visualized as follows:

2+ 2- + FeS2 + 3½ O2 + H2O Æ Fe + 2SO4 + 2H

This process, however, results in the no fractionation of sulfur isotopes, but it is the process by which much of sulfate in groundwater is produced.

Sedimentary rocks are usually the most important source of groundwater sulfate, since they typically contain large amounts of oxidized and/or reduced sulfur minerals

(Krouse and Mayer, 2000). Most fine-grained sedimentary rocks contain significant

34 amounts of reduced inorganic sulfur in the form of pyrite (Fe2S). Commonly found δ S values for pyrite in sedimentary rocks vary between -30 and 5 ‰ (e.g., Migdisov et al.,

1983; Strauss, 1997). Therefore, sulfate in groundwater derived from pyrite oxidation will have a similar δ34S distribution. In contrast, sulfate derived from dissolution of sedimentary sulfates like gypsum will have seawater-like values, around +20 ‰.

Thus sulfur isotopes can be used to trace the source of sulfur in groundwater.

Because arsenic tends to follow sulfur in its behavior, finding the source of the sulfur will give a likely source for the arsenic.

Figure 2.17. Range of δ34S in different shales, limestone, biogenic pyrite and sea water. The standard is a native iron monosulfide FeS; it is known only in meteoritic irons (Modified from Krouse, 1980).

Figure 2.18. Isotopic systematics of sulfur fractionation in groundwater. Dissolution/precipitation of sulfate minerals produces no fractionation. Reduction of 2- - - SO4 isotopes to HS produces a large fractionation, however oxidation of HS back to 2- SO4 produces no fractionation (Modified from Krouse and Mayer, 2000).

85 2.6 INTERPRETATIONS

The ultimate goal of this thesis is to determine the source(s) and mechanism(s) of mobilization of arsenic into the groundwater supply coming from Mason and LeCI. I propose that arsenic is released into the groundwater in the glacial outwash material from the Ordovician bedrock and introduced into the aquifer during recharge.

From the data collected, it appears that higher than expected concentrations of arsenic in the groundwater can be attributed to more than one cause. The reasons for arsenic release into the groundwater are functions of varying groundwater chemistry, as well as bedrock and/or sediment in the aquifer, resulting in the presence of multiple redox conditions (Figure 2.19). A commonly cited source of arsenic in groundwater is oxidation of arsenic-bearing pyrite:

2- 2- + FeAsS + 7/2 O2 + 4 H2O Æ Fe(OH)3 + SO4 + HAsO4 + 4H … (A)

Pyrite can also be dissolved by reduction:

2+ - - 2FeAsS + H2 Æ 2Fe + 2HS + 2As …(1)

- + 2As + 6H2O + 2H Æ 2H3AsO3 + 4H2 …(2)

Giving the overall reaction:

+ 2+ 2FeAsS + 6H2O + 4H Æ 2Fe + H2S + 2H3AsO3 + 3H2 … (B)

Note that both reactions will yield dissolved sulfur with negative δ34S values identical to those of the source of pyrite. Reductive dissolution of the pyrite in different intervals within the aquifer and the bedrock is likely the more important reaction because of the association of hydrogen sulfide (H2S) encountered in deeper wells in the Shaker Creek

Aquifer (SCA) with arsenic.

86 The reactions show that a reductant, such as hydrogen or methane, produced by bacterial decomposition of organic matter, reduces the sulfur and arsenic in pyrite to soluble forms and releases them to the water in the adjacent aquifer.

According to Smedley and Kinninburgh (2005), anaerobic sulfate reduction is an important microbial process in groundwater. It is an alternative source for the relatively

- high concentrations of hydrogen sulfide (H2S and HS ) present in the groundwater in the in the Shaker Creek Aquifer:

2- - 2R(CH2O) + SO4 Æ H2S + 2HCO3 + 2R … (C)

R (CH2O) represents metabolizable organic matter (Leventhal, 1983). This reaction has the potential of producing fairly heavy δ34S, depending on the rate of reduction and the

34 2- δ S of the parent SO4 (see Section I). The H2S produced in reactions B and C is cycled back to sulfate at the oxic-anoxic interface:

2- + H2S + 2O2 Æ SO4 + 2H … (D)

Note that no fractionation occurs in this step.

The results of our analyses using sulfur isotopes suggest different reactions occurring in the aquifer. The most positive values are in the parts of the aquifer where oxidizing conditions occur. At the same time, there is a possible horizon of arsenopyrite

(FeAsS; Figures 2.20 and 2.21; reaction A & B) reacting in the bedrock and incorporating the arsenic in the water.

Figure 2.19. Scheme of the Shaker Creek Aquifer and the chemical reactions occurring within. The reducing reactions are occurring in the deepest part of the aquifer, meanwhile the oxidizing are in the shallowest area. The reactions occurring are different in each part of the aquifer depending on the type of conditions and lithology involved.

Figure 2.20. Diagram of the possible interactions between δ34S isotopes and redox conditions occurring in the aquifer depending on the time. The fractionation occurs not also depending on time but on the redox conditions within the aquifer. (Fractionation between the oxidized form and dissolved sulfate in ocean water is very small, while that between dissolved sulfate and reduced sulfides is large and positive).

2- Figure 2.21. Under moderately reducing conditions, HAsO4 begin to dissolve releasing adsorbed arsenate into groundwater. Arsenate is reduced to arsenite by bacteria in reducing sediments, and if sulfur is abundant, as in the case of most marine sediments, most of the arsenic reacts with sulfides to form arsenopyrite.

90 Table 2.5 summarizes the δ34S values from glacial outwash fill material at 16’,

21’ and 136’ depth which δ34S values are -48, -33.66, -4.87 ‰, respectively. Table 2.6

34 34 summarizes the average values of δ Ssulfate in groundwater and δ Ssulfide-pyrite in bedrock and glacial outwash material. The value in groundwater is -11.1 ‰ indicating that pyrite in the aquifer is not the major source of sulfur, and hence of arsenic. The values of 6.8‰

2- for bedrock and -41‰ for the glacial outwash material suggest that SO4 in the water in the SCA is a mixture of bedrock and aquifer material sources in proportions of approximately 60% bedrock and 40% glacial outwash material. Alternatively, all the

2- sulfur could be coming from the bedrock and being then cycled between SO4 and H2S.

Reactions B and C show that the arsenic is moving back and forward depending on the redox conditions occurring within the aquifer. The fractionation occurring in the bedrock and in the aquifer is depending on the redox reactions and this is maybe increased or accelerated due to the pumping in the aquifer. Data reported from the

Malcom Pirnie report (2000) there is a 35-45% of the recharge from bedrock to the aquifer. Also this report presents data for the discharge in the SCA as 7.2 million gallon per day (mgd) +/- 15% and a recharge of 8.8 mgd +/- 30%. This same report compares water pumped during the early 1960’s of 2.7 mgd. Subsequently, during 1990’s it increase to 4.4 mgd and by 2000 it reached 10.9 mgd. This indicates that there is a overdrawing in the aquifer due to the over-pumping and perhaps an increase in flow out of the bedrock.

The Mason wellfields were closed during 2005 for drinking water purposes due to the poor water quality. The water levels for the area show the water pumped in the last decades in the SCA caused a drawdown of the aquifer (Figure 2.22). This drawdown

91 matches the trend in ORP, manganese and iron (Figures 2.11-2.13). Also, arsenic is present in the groundwater and it is possible it would increase if the water continued to be pumped at the previous rate.

0 0 50 100 150 200 250 300 350 400 450

-10

-20

-30

-40 Depth to water (feet)

-50

-60 y = -0.0748x - 26.365 R2 = 0.7417 -70 Time, months

Figure 2.22. Hydrograph of monthly fluctuations in water-table elevation from a well of the Shaker Creek Aquifer.

93 2.7 Conclusions

1. The present study proposes a geochemical model of the release of arsenic into

groundwater from pyrite dissolution from the bedrock. It is likely that arsenic is

leaching into the groundwater from reduction of pyrite in bedrock.

2. This model would only apply to aquifers like Shaker Creek that have dissolved

2- sulfate (SO4 ) and hydrogen sulfide (H2S) in the deep groundwater.

3. The Kope Formation sampled for this study is in a stratigraphic elevation similar

to that exposed in the walls of the buried valley at Mason, Ohio. Arsenic

concentrations in the bedrock were considerably higher than in the glacial

outwash fill material, and thus bedrock is the more likely source of arsenic in the

groundwater.

4. Sulfur isotopes showed that sulfate in the groundwater is close in composition to

sulfur in pyrite in the bedrock, but far from pyrite in glacial outwash fill material.

The values suggest that both the bedrock and the glacial outwash fill material can

be sources of the sulfur as well as the arsenic in the groundwater, but that the

bedrock source is dominant.

5. The geochemical trends in different redox-sensitive indicators like iron,

manganese, oxidation reduction potential and arsenic in groundwater from the

Shaker Creek Aquifer show falling oxidation states over the last decade. This

trend would continue and water quality would continue to deteriorate if the water

from the aquifer were to be pumped at the same rate, with consequent lowering of

water level and transfer of older and older water to the well screens. However,

94 Mason has recently stopped withdrawing water and the system may rebound in both water level and water quality.

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