Aeration effects on the partitioning of a PCB to anoxic estuarine sedimentpore water dissolved organic matter

Pore water dissolved organic matter (DOM) plays an important role in the di stribution, mobility, and bioavailability of hydrophobic organic chemicals (HOCs) in sediment environments. The effect of aeration on the partitioning of 2,2',4,4'-tetrachlorobiphenyl (TeCB) to anoxic pore water DOM from thre e estuarine sites was investigated. Pore water DOM was fractionated into mo lecular size and polarity fractions by ultrafiltration and XAD-8 resin chro matography. Total organic carbon analysis was utilized to determine shifts in molecular size and polarity distributions. Changes in functional groups and aromaticity were evaluated for whole and fractionated pore waters by sp ecific UV absorbance at 254 nm (SUVA(254)) The solubility enhancement metho d was used to determine the partitioning of TeCB to whole and fractionated pore water DOM. At two sites, the overall TeCB-DOM distribution coefficient decreased by an order of magnitude after aeration. The higher molecular si ze and all polarity fractions exhibited a decrease in partitioning behavior upon aeration. The aromaticity and TeCB-DOM distribution coefficient of th e lowest molecular size fraction (<1000 Da) decreased upon aeration. The hi ghest (>10 000 Da) and lowest (<1000) molecular size fractions contributed the most to overall partitioning. The observed aeration effects in anoxic e stuarine sediment pore waters differed significantly from those previously reported in freshwater systems.