BIOLOGICAL AND CHEMICAL DEGRADATION OF IONIC ETHYLLEAD COMPOUNDS IN SOIL

Degradation rates and formation of organolead metabolites of ionic tri ethyllead (TREL) and diethyllead (DEL) in nonsterile and autoclaved su rface and subsurface soil samples of Arredondo fine sand were determin ed using C-14-labeled chemicals. Both [C-14]TREL and [C-14]DEL in nons terile and autoclaved soils initially declined rapidly, and both chemi cals initially disappeared more rapidly from the surface samples (0 to 15 cm depth) than from the subsurface samples (30 to 45 cm depth), wi th the exception of the surface sample treated with [C-14]DEL. In this soil, [C-14]DEL in the autoclaved sample disappeared more rapidly tha n 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 autocl aved samples longer than in the nonsterile samples. Both [C-14]TREL an d [C-14]DEL in nonsterile surface and subsurface samples were initiall y 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, respectivel y. Mineralization was not observed in autoclaved soil samples. It was concluded that both biological and chemical degradation of TREL and DE L in soil occurred, and chemical degradation was probably the major fa ctor contributing to the disappearance of TREL and DEL in soil. The ex act 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.