Degradation of humus-bound metabolites generated from toluene and o-xylene in soil

We investigated the fate of 14C-labeled toluene and o-xylene in soil. Some of the metabolites of toluene and o-xylene were bound to the humic matrix rather than mineralized or incorporated into biomass. The distribution of the bound radioactive metabolites from toluene and o-xylene were respectively, 33.4% and 32.1% of original radioactivity. Most of the humus-bound metabolites (83.5–85.4%) from toluene and o-xylene were found in the humin fraction and less than 10% were incorporated to fulvic and humic acid, respectively. The bound metabolites from radioactive toluene and o-xylene were not extracted with various solvents, and they showed slow biodegradation. The mineralization rates of bound metabolites generated from toluene and o-xylene did not differ significantly, and the turnover times ranged between 3.9 and 4.6 years.