Biodegradation of phthalate esters in False Creek sediments

Phthalate diesters (DPEs) are a family of industrial chemicals used in a vast array of consumer products. Because of their broad commercial applications, many DPEs have become ubiquitously distributed in the environment. An in vitro test was conducted to measure the biodegradation rate of seven DPEs in temperate marine sediments. Low molecular weight congeners degraded rapidly with sediment half-lives ranging from 3.0 and 8.0 days, while high molecular weight congeners exhibited slow (2-ethyl-hexyl phthalate sediment half-life of 340 days) or no significant biodegradation. While previous studies show that the high molecular weight congeners are inherently biodegradable, in the current study they were recalcitrant in natural sediments. A mechanistic biodegradation model was developed based on the premise that all phthalates are inherently biodegradable, but only the freely dissolved fraction of the chemical concentration in sediments is bioavailable for microbial degradation. The model showed good agreement with empirical observations.