AbstractThe fate of the carcinogen 3,3′‐dichlorobenzidine (DCB) in soil was evaluated with regard to persistence and binding. A Brookston clay loam soil was amended with 4 or 40 ppm14C‐DCB and incubated under aerobic conditions for 32 weeks or under anaerobic conditions for 1 year. Mineralization occurred very slowly in aerobic soil and did not occur in anaerobic soil. Total14C radioactivity in soil remained essentially constant during the incubations, demonstrating that volatile losses of DCB or DCB decomposition products did not occur in our incubation system. DCB was shown to bind strongly to soil. After 32 weeks of incubation, approximately 90 of the applied radioactivity remained in soil after extraction with ethyl acetate and methanol. The loss of solvent‐extractable DCB occurred mostly in the first several weeks of incubation and was accompanied by an increase in alkali‐extractable DCB. These data strongly suggest the formation of covalent linkages between DCB and soil humic components as the primary fate of DCB in the Brookston soil. The significance of humus‐bound DCB residues as potential sources of future contamination is essentia
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