Arsenic is a common metal contaminant found in groundwater from both natural and anthropogenic sources. In particular, natural arsenic contamination of groundwater poses a major human health threat in many parts of the world. Arsenic in groundwater may be removed or sequestered by adsorption or co-precipitation on sulfide bio-minerals if they form naturally or can be ?engineered? to precipitate. The proposed research includes educational and research activities for undergraduate and graduate students. The research will expose students from an EPSCoR state to field, laboratory, and modeling research on a significant environmental health problem. The results will be of great interest to the broad fields of mineralogy/geochemistry, hydrology, geomicrobiology, bioremediation, and environmental health. The results will have significant implications for mitigation of arsenic problems at both natural and industrial sites. The results will provide critical information to industry as they plan and implement cost-effective remediation strategy for the large number of arsenic (and other metals) contaminated industrial and military sites. Moreover, because natural As-contamination is a pressing problem worldwide, the optimized cost-effective bioremediation technology we develop in US may benefit many arsenic-affected developing countries (Bangladesh, Vietnam, Cambodia, India, etc.).
The overarching objective of this study is to assess how bacterial activity, biomineralization, and geochemical sorption work together to remove arsenic from groundwater at the field scale. To achieve the research goal the research team will conduct long-term field injection experiments at an industrial site amended by labile water-soluble organic carbon and electronic acceptors; and, characterize contaminant assimilative capacity of sulfide biominerals formed in a natural aquifer setting. The team will integrate field experiments with lab-based studies and geochemical modeling to assess the key microbial activities and biogeochemical reactions that control arsenic mobility and groundwater geochemistry under changing redox conditions. This research offers an unparalleled opportunity to monitor the natural attenuation processes and evaluate a potential remediation tool. To address critical gaps in the understanding of key biogeochemical processes of arsenic sequestration in natural aquifers, the proposed study will center around three questions: 1) What is the main mechanism causing arsenic to be removed? 2) Can the proposed biostimulation technology be optimized so that the Fe-sulfide biominerals continue to sequester arsenic by sorption after bacterial metabolism ceases? 3) How does the natural microbial community structure change in response to biostimulation in the field? The proposed research will characterize sorption and attenuation (both biotic and abiotic) of metal contaminants, will develop a greater understanding of the effect of chemical and biological processes and their associated rates on contaminant behavior, will develop tools to estimate the natural contaminant assimilative capacity of natural aquifers, and also will develop geochemical methods to determine whether natural attenuation processes are still occurring after biostimulation (and will likely to continue into the future).
