Formation of humus-bound residues in the course of BTX biodegradation in soil

초록

To examine whether the xylene component of BTX (benzene, toluene, xylene) mixture is co-metabolized and residues are produced in soil, 14C-labeled-o-xylene was added to sandy loam in combination with unlabeled benzene and toluene. After 4 weeks of incubation in a sealed system connected to an oxygen reservoir, 55.1% of the radiocarbon was converted to 14CO<inf>i</inf>, 3.0% was solvent-extracted, and 33-35% was recovered by wet combustion of the extracted soil, adding up to 95.8% radiocarbon recovery. Biomass incorporation of o-xylene radiocarbon which was detected by fumigation/extraction was usually low (5.6%), but 32.1% radiocarbon became associated with soil humus. Most of the humus-bound radiocarbon was found in humin fraction. In addition to o-xylene, p-xylene and toluene also showed similar results. The evidence shows that some of their reactive methylcatechol biodegradation intermediates attach to the humic matrix in soil in preference to mineralization and biomass incorporation.

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