PW20 New Approaches to Determining Soil and Sediment Exposures
Exhibit Hall
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(PW293) A solid phase dosing and sampling technique to determine partitioning coefficients of very hydrophobic chemicals in complex matrices.

ter Laak, T1, Durjava, M2, 3, Struijs, J3, Hermens, J1, 1 Utrecht University, Utrecht, The Netherlands2 Institute of environmental protection and public health, Maribor, Slovenia3 National Institute of Public Health and the Environment, Bilthoven, The Netherlands

ABSTRACT- Accurate partitioning coefficients to dissolved organic carbon (DOC) are of great importance to perform proper environmental and biological fate modeling and risk assessment. However, the determination of partitioning coefficients becomes more difficult with increasing hydrophobicity (logKOW > 5-6) because of problems with spiking test solutions, separating the matrix from the aqueous solution and decreasing free concentrations. To overcome these problems, a glass fiber with a 30 um polydimethylsiloxane (PDMS) coating was applied to dose 6 PAHs (logKOW 4.5 - 6.8). The fiber was exposed in pure aqueous solutions and in solutions containing increasing amounts of humic acids. The depletion of the fiber was used to calculate partitioning coefficients to the PDMS-coating as well as the DOC. In the first experiment, fibers were exposed to different volumes of water, and PDMS-water partitioning coefficients were calculated from decrease of the fiber concentration. In the second experiment Aldrich humic acid was added at concentrations ranging from 0.5 to 100 mg/L, and the depletion of the fiber concentration was used to calculate the partitioning coefficient to this DOC. The obtained PDMS-water partitioning coefficients and the DOC-water partitioning coefficients showed a clear relationship with logKOW. The PDMS water partitioning coefficients were comparable to literature but the DOC-water partitioning coefficients of the more hydrophobic PAHs were considerably higher than literature values. In conclusion, this technique seems to be simple and accurate tool to determine partitioning coefficients of very hydrophobic chemicals to various complex hydrophobic phases.

Key words: PAHs, DOC-sorption, Solid phase dosing and sampling technique

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