PT02 Soil Toxicology and Risk Assessment
Exhibit Hall
8:00 AM - Tuesday, 11 November 2003
(PT025) Dynamics of Soil Microbial Communities When Exposed to Pb and 2,4,6-Trinitrotoluene Mixtures.
Shuler, S.1, Xia, K.1, Williams, M.1, 1 Department of Crop and Soil Sciences, The University of Georgia, Athens, GA, USA
ABSTRACT- Large tracts of land within military and recreational shooting ranges and military munition facilities are contaminated with heavy metals and explosive organic compounds, especially Pb and 2,4,6-trinitrotoluene (TNT). Research has shown that Pb and TNT can significantly affect the activity of certain soil enzymes, but the combined influence of Pb and TNT mixtures on soil microbial community dynamics have not been explored. In this study, community based microbial dynamics in two Pb and TNT contaminated soils were investigated by extracting soil fatty acids. Two soils were spiked with Pb2+ and TNT separately at 4 concentration levels up to 150 mg/kg and 500 mg/kg, respectively. The soils were also spiked with Pb2+ and TNT mixtures at similar concentration levels. The spiked soils were incubated aerobically at two moisture contents for 4 and 12 hours, and 2, 10, and 30 days. Soil CO2 production was measured throughout the study and at the end of each incubation period, soil microbial biomass was determined using the fumigation extraction method. Total and bioavailable Pb and TNT were measured. Fatty acids from the soil were quantitatively extracted, methylated and analyzed by GC/MS. In general, within two-day of exposure Gram-negative and Gram-positive bacteria and actinomycete biomarkers declined with increasing contaminant concentrations. The fungal biomarkers increased with increasing concentration when TNT was present but were largely unaffected by the presence of Pb. Our results indicate that members of the eubacterial microbial community are sensitive to both Pb and TNT and that many organisms turnover (die) with exposure to these contaminants. Fungi appear to be resilient to Pb and grow in the presence of TNT.
Key words: FAME, trinitrotoluene, microbial community, mixture