Equilibrium Model of Fate of Microcontaminants in Diverse Aquatic Food Chains

Abstract

Biocencentration and bioaccumulation factors of PCB [polychlorinated biphenyls], 239Pu and 137Cs were compiled from the literature as a function of organism size. The distribution of field-observed bioaccumulation factors varied between each substance but similarly to order of magnitude within each substance across diverse food chains. PCB levels in top predators were due primarily to food chain transfer. A steady state compartment food chain model was derived for estimation of the relative effect of uptake directly from water vs. food chain transfer. The model food chain transfer number f, given by .alpha.C/K + G for .alpha. = chemical absorption efficiency, C = specific consumption, K = excretion rate and G = net organism growth rate indicated the degree of food chain accumulation. For f > 1, food chain transfer was significant; for f < 1, uptake from water was more significant. Application of the model suggested that PCB body burden in top predators was due almost entirely to consumption of contaminated prey, for 239Pu all body burden was due to uptake from water only and observed 137Cs concentration factors were due principally to food chain transfer with a high dependence on the salinity-dependent phytoplankton adsorption.