Mobility and chemical fate of antimony and arsenic in historic mining environments of Kantishna Hills, Denali National Park and Preserve, Alaska

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Author
Ritchie, Vanessa J.
Keyword
gold mines and mining
Alaska
Kantishna Hills
antimony
arsenic
acid mine drainage
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URI
http://hdl.handle.net/11122/11371
Abstract
Oxidative weathering processes of acid-forming sulfide minerals, such as pyrite (FeS₂), and associated arsenopyrite (FeAsS) and stibnite (Sb₂S₃), can have a significant impact on water quality associated with current and legacy mining operations. Concentrations of toxic metals and metalloids, such as antimony (Sb) and arsenic (As), in acid mine drainage can exceed drinking water quality standards by orders of magnitude. This study provides a detailed hydrogeochemical assessment of the mobility and chemical fate of antimony and arsenic in streams draining from historic antimony mines within Denali National Park and Preserve, Alaska. Antimony and arsenic concentrations in stream water reach up to 720 parts per billion (ppb) and 239 ppb, respectively. Aqueous phase antimony and arsenic speciation was determined using liquid chromatography coupled to an inductively coupled plasma mass spectrometer. Antimony in all water samples is predominantly found as Sb⁵ whereas arsenic was detected as mixtures of As³ /As⁵⁺ . Elevated antimony concentrations extend over 8 km downstream from the source, whereas arsenic quickly attenuates within 1.5 km. High correlation between antimony/arsenic and iron concentrations in fine-fraction streambed sediment indicates that sorption and (co)precipitation with iron (hydr)oxides is an important pathway for the attenuation of antimony and arsenic in natural waters.
Description
Thesis (M.S.) University of Alaska Fairbanks, 2011
Table of Contents
1. Introduction and objectives -- 1.1. Sources and impacts of antimony and arsenic contamination -- 1.2. Geochemistry of acid mine drainage from sulfidic mine tailings -- 1.2.1. Acidic water formation -- 1.2.2. Controls on drainage chemical composition -- 1.3. Antimony and arsenic in natural waters -- 1.4. Antimony aqueous geochemistry -- 1.4.1. Thermodynamic equilibrium predictions for antimony -- 1.4.2. Kinetic influences on antimony speciation -- 1.4.3. Antimony mobility -- 1.5. Arsenic aqueous geochemistry -- 1.5.1. Thermodynamic equilibrium predictions for arsenic -- 1.5.2. Kinetic influences on arsenic speciation -- 1.5.3. Arsenic mobility -- 1.6. Research objectives -- 1.7. Outline of presented work -- References -- 2. Field study: site description, experimental methods, results and discussion -- Abstract -- 2.1. Introduction -- 2.2. Study area -- 2.3. Methods -- 2.3.1. Field sampling and in situ measurements -- 2.3.2. Analytical methods -- 2.4. Results and discussion -- 2.4.1. Major/minor element aqueous chemistry -- 2.4.2. Aqueous speciation and redox potentials -- 2.4.3. Mobility and attenuation of Sb and As -- 2.5. Summary -- Acknowledgements -- References -- 3. Conclusions and future work -- Appendix.
Date
2011-05
Type
Thesis
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