Biodegradation of Di-<i>n</i>-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, 14 C (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.