BIOACCUMULATION KINETICS AND TOXICITY OF LEAD IN HYALELLA-AZTECA (CRUSTACEA, AMPHIPODA)

Accumulation and depuration of Pb in Hyalella azteca were rapid and fi t a one-compartment first order kinetics model. The elimination rate c onstant was 0.76 or 0.52/day, estimated during accumulation or elimina tion, respectively. Body size had only a weak negative effect on the P b concentration in Pb-exposed H. azteca. One-week-old H. azteca were a pproximately twice as sensitive to Pb in 8-day toxicity tests as 10- t o 16-week-old amphipods. LC(50)s and whole body LD(50)s were 97.3 nM a nd 349 nmol/g for the 1-week-old and 216 nM and 728 nmol/g for the 10- to 16-week-old H. azteca. Pre-exposure of 1-week-old H. azteca for 4 weeks to 100 nM Pb solutions resulted in a small but nonsignificant in crease in resistance to Pb. Estimates for LC(50)s and LD(50)s were 114 nM and 434 nmol/g for the control nonexposed and 132 nM and 490 nmol/ g for the Pb pre-exposed group. Pb was accumulated as a nonlinear func tion of water concentration in H. azteca in both toxicity studies. The relationship was described equally well using a log-log regression or a one-compartment saturation kinetics model. At low aqueous Pb concen trations the saturation model reduces to the one-compartment saturatio n kinetics model.