Mechanism of biomagnification in fish under laboratory and field conditions

摘要

While biomagnification of certain organic contaminants in food chains has been observed in field studies, the mechanism of the biomagnification process is still unresolved. Knowledge of the mechanism by which contaminants are absorbed andbiomagnified in food chains is important in environmental risk assessment and studies of chemical bioavailability. In this study, we hypothesize a fugacity based model of the gastrointestinal absorption of contaminants. We test the model in a 73 daylaboratory, gastrointestinal magnification study of 2,2',4,4',6 6'-hexachlorobiphenyl in adult rainbow trout (Oncorhynchus mykiss) and in a field study of the gastrointestinal magnification of PCB congeners in rock bass (Ambloplites rupestris). Bothstudies show that the fugacity of the test chemicals in the gastrointestinal tract (GIT) can increase to levels up to 7-8-fold greater than those in the consumed food. The fugacity increase in the GIT is the result of a drop in the chyme's fugacitycapacity for the test chemicals (i.e. approximately 4-fold in this study) and an increase in chemical concentration due to food absorption in the GIT (i.e. approximately 2-fold in this study). Food digestibility and absorption are found to be criticalfactors controlling biomagnification factors and dietary uptake efficiencies under laboratory and field conditions.