Trace Metals in Fish From a Reservoir Receiving Runoff From a Developing Watershed
The objective of this research was to measure the concentrations of the cadmium, chromium, copper, lead, mercury and zinc in bass and carp taken from the Occoquan Reservoir in Virginia with three purposes in mind. First, to determine whether the amounts of metals present represent any hazard to humans when the fish are used as food. Second, to assess the degree of change in the concentrations over time when compared with a previous study. Third, to discover whether the geographical patterns of metal concentrations point to source areas of elevated stream contamination.
Fish were collected from three stations. Liver and fillet samples were prepared using wet digestion techniques and analyzed using an atomic absorption spectrophotometer. Average concentration in the edible fillet of all fish sampled for all metals studied were below published action levels. Eleven out of sixty-four bass had levels of lead in the fillet above a US FDA action level of 0.25 Âµg/g. Zinc and copper in bass livers, and zinc in carp livers were significantly higher than in fish sampled in the earlier study. However these increases could be caused by seasonal variations, and not be indicative of a long-term increase in metals levels. Bass from the arm of the reservoir that passes through the most highly developed area of the watershed were found to have significantly higher liver copper levels and fillet mercury levels, than did bass taken from the other stations.