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(258) Sediment characteristics other than TOC affect the desorption and bioavailability of non-polar chemicals. Kukkonen, Jussi1,2, Landrum, Peter2, 1 2 ABSTRACT- Desorption of benzo(a)pyrene (BaP) and 2,2',4,4',5,5'-hexachlorobiphenyl (HCBP) was measured in seven different natural sediments using the consecutive Tenax extraction. Chemicals were spiked to the sediments at the same molar concentration in each case. The fraction of rapidly, slowly and very slowly desorbing chemical was calculated as well as rate constants for the desorption from these fractions. The rapidly desorbing fraction probably represents the fraction of sorbed organic compound that determines the bioavailable portion of chemical by organisms and also poses actual risks for transport to (ground)water. The sediments were characterized by total organic carbon content (TOC), total organic nitrogen content (TON), soot carbon content, particle size distribution. After a short contact time with sediment, the rapidly desorbing fraction (Frap) of BaP varied from 7% of total to 26% of total. The Frap of HCBP varied from 31% of total to 55% of total. The Frap of HCBP was 1.5 to 7.1 times larger that the one of BaP in the same sediment. Similarly the desorption rate of HCBP was either the same or higher than the one for BaP. This phenomenon could partly explain the noticed difference in the bioavailability of these two chemicals. The TOC content, soot particles or TON content of the sediment did not explain the variation between the sediment. Bioavailability measurements with benthic invertebrates and better characterization of the sediments are in progress and the results will be discussed in the context of measured desorption of the chemicals. Key words: Sediments, Organic chemicals, Desorption, Bioavailability |
