M5 PM Marine Environmental Chemistry of Organic Pollutants
Monday, 14 November 2005: 1:50 PM - 5:30 PM in 321-323

(WIT-1117-679614) Using Solid Phase Microextraction to evaluate the bioavailability of PAHs in sediments of the western Baltic Sea.

Witt, Gesine¹, Liehr, Gladys¹, Thiele, Rajko¹, ¹ Baltic Sea Research Institute, Seestrasse 15, D-18119 Rostock, Rostock, Germany

ABSTRACT- The risk of PAHs binding to sediment strongly depends on their mobility and consequently their bioavailability. In this study a partitioning based sampling technique was applied as tool to estimate the mobility of 9 PAHs in sediments of the western Baltic Sea focussing on a highly contaminated former dumping area. The freely dissolved PAH porewater concentration was measured using matrix solid-phase microextraction (SPME). It is shown that SPME is a very powerful method for the determination of truly dissolved PAHs. Only a minimum fraction of PAHs were presented as freely dissolved molecules in the porewater (9-192 ng/L). Based on these results it was possible to calculate the fraction of the total measured PAH sediment concentration that was available for equilibrium partitioning (0.01-25.8%). Furthermore elevated solid water distribution coefficients of the PAHs were calculated (log K_OC between 4.5 and 9.2) and compared to data from the literature. The elevated partitioning coefficients of the sediment-porewater systems could be explained through the distribution model which included the soot-partitioning. Furthermore a comparison of the different sampling sites shows that no linear relationship exists between the sediment and freely dissolved porewater concentration. A particulate phase exists to which PAHs sorb more readily at the dumping site compared to the other stations in the western Baltic Sea. These findings indicate that soot carbon was not the primary sorption material for PAHs at the dumping site. The results are particularly important to predict the mobility and bioavailability of the PAHs in environmental samples of different origin.

Key words: PAH mobility, solid phase microextraction, porewater, soot