MODELING EQUILIBRIUM CONCENTRATIONS OF MICROCONTAMINANTS IN ORGANISMS OF THE RHINE DELTA - CAN AVERAGE FIELD RESIDUES IN THE AQUATIC FOODCHAIN BE PREDICTED FROM LABORATORY ACCUMULATION

To explore the validity of extrapolation of laboratory bioaccumulation ratios to field conditions, we collected values from experiments and compared these to ratios observed in the field surveys carried out in the Rhine delta. For some major chemical groups and taxa, we concluded that: (1) Fat weight corrected concentrations of more persistent organics in (a) organic suspended solids, freshwater plants and pelagic invertebrates tended to be similar, both in laboratory experiments and field surveys, (b) fish from the Rhine delta were about twice as high as those in the invertebrates and those expected from laboratory studies, and (c) birds were one order of magnitude or more above those in their invertebrate and fish prey, whereas accumulation in laboratory experiments with common birds and mammals did not exceed their food level by more than 10; (2) Fat weight corrected concentrations of less persistent organics can be substantially lower than those of more persistent isolipophilic compounds; for instance, accumulation of some polycyclic aromatic hydrocarbons in short-term laboratory experiments was similar to that of more persistent compounds but held levels were 30 (in invertebrates) to more than 1000 (in fish) times lower than expected; (3) Dry weight corrected concentrations of cadmium, copper, mercury and zinc in (a) freshwater plants and invertebrates from the Rhine delta were 0.2 to 0.3 times the concentrations in suspended solids, as more or less expected from literature, (b) fish were lower than for invertebrates both for literature and Rhine delta data, and (c) kidneys and livers of laboratory and field birds or laboratory mammals are at most 10 times those in their food. The pattern of bioaccumulation of mercury is similar to that of extremely persistent organics.