Bioaccumulation of PCB congeners by Diporeia spp.: Kinetics and factors affecting bioavailability

The toxicokinetics of four polychlorinated biphenyl (PCB) congeners were determined for the amphipod Diporeia spp. exposed to selected PCB congeners through both water and sediment to determine the effect of temperature and organism size (mass). For compounds with log K-ow 6 or greater, the water-only uptake coefficient (k(u)) was inversely proportional to the size of the organism at all temperatures. For monochlorobiphenyl, k(u) was directly proportional to organism mass only at 16 degreesC. Increasing temperature resulted in increasing uptake rare coefficients for all compounds except hexachlorobiphenyl (HCBP) where k(u) did not appear to depend on temperature. The hydrophobicity of the contaminants did not contribute significantly to changes in uptake rate from water. The elimination rare constant (k(e)) was inversely proportional to organism size bur was not significantly affected by temperature. The elimination rare constant declined e;exponentially with increasing log K-ow. As log K-ow increased, the effect of organism mass on k(e) was greatly reduced. The uptake from sediment was affected by temperature and the congener log K-ow. At lower temperatures, the uptake coefficient from sediment (k(s)) declined with increasing log K-ow while at higher temperatures, it exhibited a slight upward trend. Smaller animals had much higher uptake rates from sediment than large or medium size animals. Small animals exhibited very high biotasediment accumulation factors (5.4 to 20.8) over 4 to 16 degreesC for HCBP (BSAF, concentration in the organ ism normalized to the lipid content divided by the concentration in the sediment normalized to the organic carbon content). The relationship between BSAF and log K-ow was exponential for both laboratory and field data.