MODEL OF BIOTA-SEDIMENT ACCUMULATION FACTOR FOR POLYCYCLIC AROMATIC HYDROCARBONS

Abstract

A model of the BSAF is constructed for PAHs using a steady-state representation of a benthic food web of a small creek. Analyses of the data collected by others on sediment, crayfish and sunfish PAH indicate that for the crayfish, the BSAF (kg org C kg lipid−1) range over log Kow is relatively narrow between 0.01 and 0.1. For the sunfish, a marked decline occurs in the station average BSAF with increasing log Kow to values ranging from 0.00001 to 0.005. A separation also occurs in the behavior of the PAH groups, with the unsubstituted PAHs constituting an approximate lower bound on the entire set of PAHs. Model calibration to crayfish and sunfish BSAF is accomplished through assignment of PAH (Kow) functions derived from laboratory data. The substituted naphthalenes in contrast to the unsubstituted PAHs are calculated to behave similarly to PCBs but lower by about one order of magnitude. Analyses of the model calibration indicate that (1) relative to the sunfish, the crayfish appear to exhibit reduced metabolism and higher gut assimilation efficiencies resulting in BSAFs different from sunfish BSAFs; (2) for the sunfish, the BSAF for unsubstituted PAHs declines rapidly with increasing Kow primarily because of low gut assimilation efficiency and increased metabolism and not because of reduced bioavailability of sediment PAH; and (3) the relative contribution of the food route and water route to the BSAF varies with Kow.