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A Geochemical, Isotopic, and Petrologic Study of a Watershed with Arsenic-Enriched Ground Water in Northport, Maine Gail Elizabeth Lipfert

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A Geochemical, Isotopic, and Petrologic Study of a Watershed with Arsenic-Enriched Ground Water in Northport, Maine Gail Elizabeth Lipfert The University of Maine DigitalCommons@UMaine Electronic Theses and Dissertations Fogler Library 2006 A Geochemical, Isotopic, and Petrologic Study of a Watershed with Arsenic-enriched Ground Water in Northport, Maine Gail Elizabeth Lipfert Follow this and additional works at: http://digitalcommons.library.umaine.edu/etd Part of the Environmental Indicators and Impact Assessment Commons Recommended Citation Lipfert, Gail Elizabeth, "A Geochemical, Isotopic, and Petrologic Study of a Watershed with Arsenic-enriched Ground Water in Northport, Maine" (2006). Electronic Theses and Dissertations. 107. http://digitalcommons.library.umaine.edu/etd/107 This Open-Access Dissertation is brought to you for free and open access by DigitalCommons@UMaine. It has been accepted for inclusion in Electronic Theses and Dissertations by an authorized administrator of DigitalCommons@UMaine. A GEOCHEMICAL, ISOTOPIC, AND PETROLOGIC STUDY OF A WATERSHED WITH ARSENIC-ENRICHED GROUND WATER IN NORTHPORT, MAINE By Gail Elizabeth Lipfert B.S. University of Maine, 1997 M.S. University of Maine, 1999 A THESIS Submitted in Partial Ful¯llment of the Requirements for the Degree of Doctor of Philosophy (in Earth Sciences) August, 2006 Advisory Committee: Andrew S. Reeve, Associate Professor of Earth Sciences, Advisor Martin G. Yates, Lab Manager/Instructor, Earth Sciences Robert G. Marvinney, Maine State Geologist, Maine Geological Survey Robert A. Ayuso, U.S. Geological Survey Stephen A. Norton, Professor of Earth Sciences LIBRARY RIGHTS STATEMENT In presenting this thesis in partial ful¯llment of the requirements for an advanced de- gree at the University of Maine, I agree that the Library shall make it freely available for inspection. I further agree that permission for \fair use" copying of this thesis for scholarly pyrposes may be granted by the Librarian. It is understood that any copying or publication of this thesis for ¯nancial gain shall not be allowed without my written permission. Signature: Date: A GEOCHEMICAL, ISOTOPIC, AND PETROLOGIC STUDY OF A WATERSHED WITH ARSENIC-ENRICHED GROUND WATER IN NORTHPORT, MAINE By Gail Elizabeth Lipfert Thesis Advisor: Dr. Andrew S. Reeve An Abstract for the Thesis Presented Partial Ful¯llment of the Requirements for the Degree of Doctor of Philosophy (in Earth Sciences) August, 2006 High mean arsenic concentrations up 26.6 ¹mol/L (1990 ¹g/L) occur in ground water within a watershed at Kelly's Cove, Northport, Maine, USA. The Kelly's Cove water- shed is a fractured-bedrock system composed of sul¯dic schist with granitic to dioritic intrusions. Arsenic is enriched in these rocks up to 1050 mg kg¡1 (average: 68 mg kg¡1). The distribution of arsenic in the bedrock appears to be controlled by the pres- ence of arsenopyrite and arsenian pyrite, that occur primarily in post-metamorphic, tourmaline + quartz § carbonate veins and the Kelly's Cove granite. Based on the metamorphic signature of the tourmaline chemistry and the similarity in ±34S val- ues of the sul¯des, these veins probably derived from hydrothermal remobilization of surrounding metamorphic rock. Chemical analyses of water from 35 bedrock wells throughout the watershed re- veal spatial clustering of wells with high arsenic concentrations. Sti® diagrams and box plots distinguish three distinct water types; calcium bicarbonate-dominated wa- ter with low arsenic concentrations (CaHCO3 type), sodium bicarbonate-dominated water with moderately high arsenic concentrations (NaHCO3 type), and calcium bicarbonate-dominated water with very high arsenic concentrations (High-As type). Di®erences in recharge area, ground-water evolution, and possibly bedrock composi- tion contribute to the chemical distinctions within the watershed's ground water. Lack of correlation of aqueous arsenic concentrations with pH indicates that des- orption of arsenic is an insigni¯cant control on arsenic concentration. Correlations of aqueous arsenic concentrations with increasing Fe(II)/Fe(III) and decreasing Eh indi- cates that reductive dissolution of ferric oxyhydroxides plays a role in the occurrence of high arsenic concentrations in the NaHCO3 and High-As type water. Ground water with high arsenic concentrations contains sulfate with enriched 34 18 sulfur and oxygen isotopes. The range of ± S[SO4] and ± O[SO4] values at the Kelly's Cove watershed (+3.4 to +4.9 and -2.01 to +6.72 , respectively) are strikingly similar to that of another Maine watershed (+3.7 to +4.6 and -2.56 to +7.47 , respectively), that has di®erent oxidizing ground-water conditions. The association 18 of high arsenic concentrations and high ± O[SO4] is not due to oxidizing conditions or reduction of sulfate, but may be related to paleo-aeration of iron oxyhydroxides that are now reducing and releasing arsenic. Preface This thesis is the continuation of a hydrogeologic study by Michael Horesh for his Master's thesis (Horesh, 2001), which was prompted by concerned inhabitants of the Kelly's Cove area who discovered exceptionally high arsenic in their drinking water. His work revealed a cluster of wells in the Northport area that centered at Kelly's Cove and concluded the arsenic in the ground water originated from the bedrock. The main questions that this current work strives to answer are: What is the distribution of arsenic in the bedrock? How did the arsenic get enriched in the bedrock at Kelly's Cove? What is the distribution of arsenic throughout the watershed? What are the controls of arsenic in the ground water? Can isotopes be used to determine sources of arsenic and explain processes releasing it to the ground water? How does this site compare with that of Goose River, another coastal Maine watershed, but with lower arsenic concentrations in the ground water? Chapter Two of this thesis has been published (Lipfert et al., 2006). It is expected that Chapters One and Three will be submitted to Chemical Geology in 2006. ii Acknowledgements This project was funded by the U.S. Environmental Protection Agency through co- operative agreement #82956101 with the Maine Geological Survey. I wish to thank William C. Sidle of the U.S. Environmental Protection Agency and Robert Marvin- ney for without their e®orts in securing these funds, this project would not have been possible. I would also like to thank the residents of Northport who allowed us to collect water samples and install wells on their property. I am indebted to my advisor, Andrew S. Reeve for his guidance, clarity and level-headedness, my other committe members, Martin Yates, for his exceptional patience, Robert Marvinney, for providing the opportunity, Robert A. Ayuso, for his thorough reviews and illu- minating comments, and Stephen A. Norton for being willing to jump in at the last minute with his able red pen. I would like to make special ackowledgement of the late Charles V. Guidotti and the endless wisdom, humor, support, and appreciation of geology that he gave me throughout my undergraduate and graduate career at the University of Maine. His presence is sorely missed. I would like to thank Marc C. Loiselle from the Maine Geological Survey for his encouragement of me and this project, Adrian Boyce from the Scottish Universi- ties Environmental Research Center, for an enjoyable data-collection experience in Scotland, Jean MacRae from the Civil Engineering Department at the University of Maine, for illuminating discussions on microbial activity, Aria Amirbahman from the Civil Engineering Department at the University of Maine, for suggesting new ways of thinking about geochemistry. I would like to also thank Jennifer Weldon, Eric Rickert, Benjamin Morton, and Kirsten for their assistance in the ¯eld. I would like to thank the whole Earth Sciences Department at the University of Maine, particularly the graduate students I have encountered during my stay, for making the whole graduate experience enjoyable and rewarding. iii I am particularly appreciative of the unagging support of this endeavor by my life companion, Elaine Malkin, who made working on a doctorate pleasurable. Thank you, all. iv TABLE OF CONTENTS PREFACE ........................................................................................................ ii ACKNOWLEDGEMENTS ............................................................................... iii LIST OF TABLES ............................................................................................ viii LIST OF FIGURES .......................................................................................... x Chapter 1. REMOBILIZED ARSENIC WITHIN A SULFIDIC, CARBONACEOUS SCHIST, NORTHPORT, MAINE, USA ....................................................... 1 1.1. Abstract............................................................................................ 1 1.2. Introduction ...................................................................................... 3 1.3. Regional geology ............................................................................... 6 1.4. Local geology .................................................................................... 6 1.5. Methods............................................................................................ 7 1.6. Site description ................................................................................. 10 1.7. Results.............................................................................................. 12 1.7.1. Whole rock analysis ............................................................. 12 1.7.2. Petrographic and microprobe
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