BIOLOGICAL AND CHEMICAL DEGRADATION OF IONIC ETHYLLEAD COMPOUNDS IN SOIL

Degradation rates and formation of organolead metabolites of ionic triethyllead (TREL) and diethyllead (DEL) in nonsterile and autoclaved surface and subsurface soil samples of Arredondo fine sand were determined using C-14-labeled chemicals. Both [C-14]TREL and [C-14]DEL in nonsterile and autoclaved soils initially declined rapidly, and both chemicals initially disappeared more rapidly from the surface samples (0 to 15 cm depth) than from the subsurface samples (30 to 45 cm depth), with the exception of the surface sample treated with [C-14]DEL. In this soil, [C-14]DEL in the autoclaved sample disappeared more rapidly than that in the nonsterile sample. The [(14)]DEL was briefly detected in [C-14]TREL-treated soil samples, and [C-14]DEL remained in the autoclaved samples longer than in the nonsterile samples. Both [C-14]TREL and [C-14]DEL in nonsterile surface and subsurface samples were initially mineralized rapidly, and at the end of 31 and 28 d of incubation, 15 to 16% and 18 to 19% of the applied C-14 was mineralized, respectively. Mineralization was not observed in autoclaved soil samples. It was concluded that both biological and chemical degradation of TREL and DEL in soil occurred, and chemical degradation was probably the major factor contributing to the disappearance of TREL and DEL in soil. The exact extent of chemical degradation is not known. Chemical and physical properties of soil could be altered significantly by autoclaving, and may account for the increase in chemical degradation rates.