National Research Program


Microbiological Discoveries
Potential for Environmental Remediation I

Initial discovery and isolation of bacteria that can convert ferric iron to magnetite in the absence of oxygen was of great significance because it helped to explain the formation of magnetite in deep ancient sediments where no oxygen was available. Subsequent investigations led to findings that imply a great potential for remediation activities. For example the isolated bacteria have been found to: cause changes in a variety of organic compounds that frequently contaminate ground water; reduce the soluble, oxidized form of uranium into an insoluble form that precipitates; and, consume freon compounds from the atmosphere (a discovery recognized as a possible important, previously unrecognized, sink for freon (a greenhouse gas) as well as being a potential mechanism for the destruction of freon.) As an example of how such efforts are potentially of great importance to the bioremediation of contaminated ground water is the 1994 report in Nature that adding organic ligands increases the bioavailability of Fe (III). Ground water containing aromatic hydrocarbons (common in petroleum contamination) is often found under anoxic conditions in which microbial degradation is slow; however, Fe (III) oxides are generally abundant in shallow aquifers. Adding organic ligands to anoxic aquifer sediments gave rates of degradation of aromatic hydrocarbons that were comparable to those in oxic sediments. The results indicate that adding suitable ligands to increase the bioavailability of Fe (III) provides an alternative to adding oxygen (a procedure that can be technically difficult and expensive) in order to stimulate biodegradation in petroleum contaminated aquifers.

Reference:

Lovley, D.R., Woodward, J.C., and Chapelle, F.H., 1994, Stimulated anoxic biodegradation of aromatic hydrocarbons using Fe (III)ligands: Nature, v. 370, no. 6485, p. 128-131.

Microbiological Discoveries
Potential for Environmental Remediation II

Agricultural wastewaters which drain seleniferous soils in the western United States contain toxic selenium compounds and thus pose a serious environmental problem. In studying this problem, USGS made a major discovery of a bacterial process which converts toxic selenium compounds to non-toxic elemental selenium. Because follow-up studies showed that the rate of removal of the toxic selenium compounds from water was rapid, the procedure has great potential for treating irrigated waters that have been contaminated with selenium. This bacterium has more recently been found to also convert toxic arsenic compounds into a more mobile form which would enable a biotreatment mechanism to decontaminate arsenic-polluted soils located around pesticide factories and smelters.

Reference:

Oremland, R.S., 1994, Biogeochemical transformations of selenium in anoxic environments, in Frankenberger, W.T., Jr., and Benson, S., eds., Selenium in the Environment: Marcel Dekker, N.Y., p. 389-419.

For additional information and references, see the project description, Microbial Biogeochemistry of Aquatic Environments or contact Ronald S. Oremland, roremlan@usgs.gov

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