Fluoranthene KDOC in sediment pore waters

When calculating concentrations of truly dissolved hydrophobic organic contaminants (HOCs) in sediment pore water, a common assumption is that the partition coefficient between pore water and colloidal plus dissolved organic carbon (KDOC) equals the partition coefficient between pore water and sediment total organic carbon (KOC). This study examined the KDOC of fluoranthene in pore water from 11 sediments. Truly dissolved fluoranthene was separated from DOC-associated fluoranthene by partitioning on C-18 Sep Paks. Measured values of KDOC were not constant over the 11 sediments examined, and were over or underestimated by assuming that KDOC = KOC. Current models used to predict the fate of HOCs may require modification to account for the observed difference between KDOC and KOC.