Effect of cadmium on reductive dechlorination of trichloroaniline

Abstract

Abstract The effect of a transition metal, cadmium (Cd), on reductive dechlorination of a model chlorinated organic, 2,3,4-trichloroaniline (2,3,4-TCA), was determined in the laboratory in three anaerobic, flooded soils with varying properties. Dechlorination of 2,3,4-TCA was inhibited over a continuum of pore-water-soluble Cd concentrations (10–200 μg/L) in mineral-dominated rice paddy and bottomland hardwood soils. In organic-dominated marsh soil, however, a critical inhibitory level of pore-water-soluble Cd (200 μg/L) was observed. Lower-chlorinated aniline metabolites differed with soluble Cd concentration. Different metabolites (2,3-dichloroaniline and 2-chloroaniline) were observed in some soils as Cd neared the completely inhibitory concentration. Speciation of soluble Cd was necessary to predict whether inhibition would occur, particularly in the presence of high concentrations of organic ligands such as humic acids. Selective extractions and measurement of acid-volatile sulfides provided additional information but did not adequately predict inhibition of dechlorination. These results demonstrate the importance of quantification and speciation of pore-water metal concentrations in predicting potential inhibition of anaerobic biodegradation reactions such as reductive dechlorination.