PARENT SESSION

HA7 Phthalate Esters: Fate and Effects
201 Oregon Ballroom
8:00 AM - 12:00 PM, Thursday

() Sediment-water distribution of phthalate esters and PCBs in a marine ecosystem.

Mackintosh, C¹, Maldonado, J¹, Gobas, F¹, Ikonomou, M², ¹ Simon Fraser University, Burnaby, British Columbia, Canada² Institute for Ocean Sciences, Sidney, British Columbia, Canada

ABSTRACT- Dialkyl phthalate esters are widely used industrial chemicals with octanol-water partition coefficients ranging between 10^1.61 for dimethyl phthalate to 10^9.46 for di-iso-decyl phthalate, indicating a propensity to sorb to organic matter. Thirteen dialkyl phthalate esters (DPEs) (dimethyl, diethyl, di-iso-butyl, di-n-butyl, butylbenzyl, di(2-ethylhexyl), di-n-octyl, di-n-octyl, di-iso-hexyl (C6), di-iso-heptyl (C7), di-iso-octyl (C8), di-iso-nonyl (C9), and di-iso-decyl (C10)) and ten polychlorinated biphenyls (PCBs) (PCB-18, -16/32, -53, -73/52, -110, -149, -132/153, -187/182, -180, and -194) were measured in the sediments and seawater of a marine inlet, providing a direct comparison between the partitioning characteristics of the two classes of chemical. To measure ambient aqueous concentrations, a two-step extraction method using 0.45-m glass fiber filters (GFF) and C18 bonded extraction disks (C18) was applied and distinguished between large diameter-sorbed chemical and operationally defined freely dissolved chemical. Sediment-water distribution coefficients (K_OC) of DPEs in bottom sediments, based on total water concentrations, did not correlate well with log K_OW. The relationship with K_OW improved substantially when K_OC was determined using freely dissolved water concentrations, indicating that particulate matter in the water phase may misrepresent the inherent sorptive capacity of DPEs. Sediment-water distribution coefficients (K_OC) of DPEs and PCBs followed different relationships, with Koc values for DPEs being lower than those for PCBs of similar hydrophobicity. The latter suggests that DPEs have a somewhat lower sorption capacity than PCBs. Sediment-water distribution coefficients (K_OC) of the lower molecular weight were greater than expected based on their Kow. This apparent disequilibrium may increase the importance of bottom sediments as a route of DPE exposure to sediment dwelling organisms.

Key words: PCBs, phthalate esters, sediment-water partition coefficient, marine