Enzymatic coupling of 2,4-dichlorophenol to stream fulvic acid in the presence of oxidoreductases

The coupling 14C-ring-labelled 2,4-dichlorophenol (2,4-DCP) to stream fulvic acid was investigated in the presence of several oxidoreductases including tyrosinase, peroxidase, and laccases of Rhizoctonia praticola and Trametes vesicolor. During 12-h incubation of the oxidoreductases with 14C-2, 4-DCP and stream fulvic acid, a substantial amount of the radioactivity was incorporated into fulvic acid. Chromatographic analysis indicated that although a large portion of the radioactivity remained in solution, no unbound 14C-2,4-DCP was present in the supernatant. The effects of pH, temperature, concentration of fulvic acid, and concentration of enzyme on the coupling processes were studied. The results of this research provide evidence that the enzymatic coupling of certain xenobiotic pollutants to humic substances is an important natural process which must be considered in studies of the fate, reactivity, and persistence of these organic compounds in soils and stream waters