Bioavailability in soil or sediment: exposure of different organisms and approaches to study it

Soil and benthic organisms may be exposed to contaminants via different rou tes: (pore) water, soil or sediment, and food. Depuration of the contaminan t from the organisms may take place via the same routes and, additionally, via biotransformation, reproduction, etc. Whereas uptake from and depuratio n to water can be predicted well, predictions for soil or sediment are less accurate. One of the reasons may be the reduced bioavailability of the con taminant in the soil or sediment. In biomimetic approaches, such as solid p hase micro-extraction (SPME) or measurements with C18-discs, the freely dis solved concentration in the (pore) water is determined. The SPME-fiber or C 18-disc may serve as a surrogate organism, but sometimes underestimates, an d sometimes overestimates bioavailability. The soil (or sediment) availabil ity ratio (SARA) method, that uses organisms to study the uptake of freshly added and 'aged' chemicals, is proposed to study the magnitude of the redu ction in bioavailability. SARA also includes the organism-specific exposure and depuration routes. (C) 2000 Elsevier Science Ltd. All rights reserved.