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TRANSFORMATION OF CHIRAL POLLUTANTS IN SOIL AND SEDIMENT MICROCOSMS
Citation:
O'Niell, W. L., W J. Jones, A Whittemore, AND J Avants. TRANSFORMATION OF CHIRAL POLLUTANTS IN SOIL AND SEDIMENT MICROCOSMS. Presented at 22nd Annual Society of Environmental Toxicology and Chemistry Meeting, Baltimore, MD, November 11-15, 2001.
Impact/Purpose:
Elucidate and model the underlying processes (physical, chemical, enzymatic, biological, and geochemical) that describe the species-specific transformation and transport of organic contaminants and nutrients in environmental and biological systems. Develop and integrate chemical behavior parameterization models (e.g., SPARC), chemical-process models, and ecosystem-characterization models into reactive-transport models.
Description:
The transformation rates and enantiomeric ratios of several chiral pollutants were determined in laboratory microcosms (25oC). Aerobic and anaerobic agricultural soil slurries were separately dosed with the following chiral pesticides: o,p'-DDT, o,p'-methoxychlor, cis-chlordane, trans-chlordane, heptachlor, heptachlor epoxide, and -HCH. In addition, microcosms prepared anaerobically with lake sediment were seprately dosed with a polychlorinated biphenyl mixture (Arochlor 1260) and the chiral PCB congeners 2,2',3,4',5',6-hexachlorobiphenyl and 2,2',3,3',4,4',5,6-octachlorobiphenyl. Experimental treatments consisted of live (natural) slurries, live slurries dosed with an organic nutrient mixture, and autoclaved controls.
The concentrations of the chiral pollutants in the experimental microcosms were analyzed by enantioselective high-resolution GC/MS and data were modeled to determine transformation rates. Enantiomer concentrations in transformed and unaltered (control) microcosms were compared to one another to assess enantioselective transformation of the compounds. Transformation was absent or insignificant in cis-chlordane, heptachlor epoxide, Arochlor 1260, and 2,2',3,3',4,4',5,6-octachlorobiphenyl dosed microcosms. However, appreciable losses of the parent compounds were observed in microcosms dosed with 2,2',3,4',5',6-hexachlorobiphenyl, o,p'-DDT, o,p'-methoxychlor, trans-chlordane, heptachlor, and -HCH. The addition of an organic nutrient mixture to the microcosms generally enhanced transformation rates, and transformation was greater in microcosms incubated under anaerobic conditions for all degraded compounds except -HCH. Statistically significant enantioselective transformation was not observed in most of the samples after 100 days incubation, but differences in enantiomeric ratios were observed in selected samples dosed with o,p'-DDT.