TOXICITY AND BIOACCUMULATION OF A MIXTURE OF HEAVY-METALS IN CHIRONOMUS-TENTANS (DIPTERA, CHIRONOMIDAE) IN SYNTHETIC SEDIMENT

This research investigated toxicity and bioaccumulation of a mixture o f Cd, Cu, Pb, and Zn in Chironomus tentans in synthetic sediment, and compared predicted to measured steady-state bioaccumulation factors (B AFs). In a toxicity test, C. tentans were exposed to various dilutions of a base concentration (1.0 X) of a mixture of the four metals (5 mu g/g Cd, 10 mu g/g Cu, 70 mu g/g Pb, and 300 mu g/g Zn) in synthetic s ediment. Mortality ranged from 17 to 100%. To measure bioaccumulation of the metals, C. tentans were exposed to 0.35 X the base concentratio n for a period of up to 14 d in two uptake tests. Bioaccumulation of a ll four metals increased over the 14-d uptake phases. Concentrations o f metals in chironomids were significantly correlated with exposure ti me in the uptake phases. Only concentrations of copper approached back ground levels after 7 d depuration. Uptake rate coefficients and elimi nation rate constants were determined for each metal. Bioaccumulation factors were highest for Cd and lowest for Pb. With the exception of P b, steady-state BAFs were within a factor of about two of those calcul ated using the first-order kinetic model. The high BAFs calculated may indicate greater bioavailability in synthetic sediment. Studies compa ring toxicity and bioaccumulation of natural and synthetic sediments a re necessary before the use of synthetic sediments is widely adopted.