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COLLABORATIVE RESEARCH: IN SITU MITIGATION OF MERCURY CONTAMINATED GROUNDWATER IN KAZAKHSTAN
Citation:
DEVEREUX, R., W. J. DAVIS-HOOVER, S. A. ABDRASHITOVA, M. A. ILYUSHCENKO, W. FREEMAN, D. FRIEDMAN, AND L. S. WILLIAMS. COLLABORATIVE RESEARCH: IN SITU MITIGATION OF MERCURY CONTAMINATED GROUNDWATER IN KAZAKHSTAN. Presented at EPA Science Forum, Washington, DC, May 16 - 18, 2005.
Description:
Abstract for EPA Science Forum.
The EPA Office of International Affairs is managing a U.S. State Department -funded project to redirect former Soviet Union biological weapons scientists. Scientists in countries of the former Soviet Union receive funding through the International Science and Technology Center (ISTC) for collaborative research with scientists from the EPA Office of Research and Development. This research program will enable countries of the former Soviet Union to develop the scientific infrastructure capable of addressing their environmental problems. This project (K-756) has investigated the feasibility of using biotechnological approaches to mitigate mercury contaminated ground water associated with a chloralkali plant in Pavlodar, Kazakhstan.
The chloralkali plant operated from 1970 to 1990. High-levels of mercury contamination exist within the confines of the plant and in a large plume of ground water moving towards a nearby village and threatening contamination of a major river. In order to meet the possible challenge of containing the plume, it was proposed to develop biofilters containing (i) mercury-resistant aerobic bacteria capable of sequestering the mercury or (ii) mercury-resistant anaerobic bacteria that would precipitate the mercury.
As a first step, mercury-resistant bacteria were isolated from contaminated soils and sediments at the site and characterized for their potential use in the biological treatments. Characterization of the isolates, in particular, addressed two concerns related to mercury contamination; mercury volatilization and methylation. A high percentage of the isolated aerobic bacteria were resistant to mercury chloride concentrations up to 0.1 nM. These bacteria effectively removed mercury from culture media with little volatilization. Of special note, the bacteria grew as well or better at 4 C as they did at 25 C. These bacteria are therefore well adapted to the cold temperatures of the site and could be useful in other applications in cold environments.
Among the anaerobic bacteria, obligately anaerobic sulfate-reducing bacteria were obtained that efficiently precipitated mercury with sulfide without forming significant levels of methyl mercury. One facultative anaerobic bacterial isolate produced sulfide but mercury in the medium was not precipitated. Potential mobilization of mercury by facultative anaerobic bacteria has important implications for better understanding mercury transport in aquatic ecosystems.
These mercury-resistant microorganisms are being further characterized for their potential use for in situ biological mitigation at this site. While mercury contaminated ground water in Kazakhstan and elsewhere throughout the world is widespread, there are few options available for mitigating the contamination. This line of research could lead to the development of alternative, cost-effective approaches.