Biodegradation of Di-n-Butyl Phthalate and Di-2-Ethylhexyl Phthalate in Freshwater Hydrosoil

Abstract

The phthalic acid esters di-2-ethylhexyl phthalate (DEHP) and di-n-butyl phthalate (DBP) which are used as plasticizers and recovered in routine chemical analysis of freshwater fish, were incorporated into freshwater hydrosoil in the laboratory. Samples containing about 1 mg/liter of these two esters, 14C (carbonyl) labelled, were incubated aerobically and anaerobically for 1, 5, 7, 14, and 30 days. Differences in the rates and conditions of degradation of the two esters were marked. Under aerobiosis, 53% of the radio-labelled DBP was degraded within 24 h, and 98% within 5 days; DEHP, in contrast, was only 50% degraded after 14 days. Under anaerobiosis degradation of both esters was retarded. DBP was degraded only one-sixth as fast in hydrosoil overlayed with nitrogen whereas degradation of DEHP was not detected. Our evidence from both thin-layer chromatography and radiorespirometry suggests that the esters undergo decarboxylation after initial hydrolysis, probably to the 1,2-dihydroxybenzene molecule.