Sorption and biodegradation of phthalic acid esters in freshwater sediments

Pathalic acid esters (PAEs) have been used as plasticizers in many products so that they could enter the aquatic environment. Three freshwater sediments in Taiwan were selected to explore the sorption and biodegradation processes of PAEs. Results indicated that di-n-butyl phthalate (DBP) and di-2-ethylhexyl phthalate (DEHP) are the only detectable PAEs which ranged in 24.9-68.3 mg/kg and 39.1-71.9 mg/kg in this study. The adsorption capacities of DBP and DEHP were identified by Kf values of the nonlinear Freundlich model associated with R2 values more than 0.90. This is expected that partition is the main mechanism controlling the transfer of PAEs between water and sediment phases. After 30 days contact, much of DBP and DEHP were removed immediately within 1 day in the desorption process. Because microorganism is as the major routes of breakdown of PAEs in the environment, much lower degraded amounts of DBP and DEHP occurred in the sterilized sediment than those in the unsterilized sediments.