THE BIOACCUMULATION OF POLYNUCLEAR AROMATIC-HYDROCARBONS BY BENTHIC INVERTEBRATES IN AN INTERTIDAL MARSH

Biota-sediment accumulation factors (BSAF; concentration in organism l ipid/concentration in sediment on an organic carbon basis) of polyarom atic hydrocarbons varied with season and along an intertidal gradient in a coastal marsh in San Francisco Bay. The BSAFs were lowest during the local rainy season. During the dry season, BSAFs were lowest in th e high intertidal zone closest to shore. Significant differences among species groups were also observed; BSAFs were lowest in polychaetes a nd highest in the asian clam (Potamocorbula amurensis), varying over a lmost three orders of magnitude (0.0069-5.4 g sediment organic C/g lip id). The BSAFs decreased with increasing percent fines in the sediment s and with PAH concentrations on an organic carbon basis. We suggest t hat a determining variable is the content of highly aromatic soot part icles, which increases during periods of surface runoff and which is e xpected in the dry season to be highest in the high intertidal zone wh ere these finer particles preferentially accumulate. Correlations of B SAFs with the ratio of the logarithm of the activity coefficients in p orewaters to those in sediments were generally stronger than with log K-ow indicating a limitation of octanol as a surrogate for sediment or ganic carbon or organism lipid. These observations qualify but also st rengthen the concept of equilibrium partitioning as the determining fa ctor in bioaccumulation by benthic organisms of nonpolar organic compo unds from sediments; the assumption that ''organic carbon'' can be con sidered in generic terms without allowance for aromaticity and probabl y other factors as well, must, however, be reconsidered.