BIOCONCENTRATION AND BIOKINETICS OF HEAVY-METALS IN THE EARTHWORM

This study examines the steady, state and non-steady state kinetics of five metals, cadmium, copper, lead, nickel, and line in earthworms. T he steady state kinetics are based on field studies in which worms fro m contaminated and uncontaminated sites were collected and measurement s were made of concentrations in the earthworms and soils. For each of the metals, evidence suggests that bioconcentration depends on the me tal concentrations in the soil, bioconcentration is greater at lower s oil concentrations. The studies of non-steady state kinetics involve u ptake and elimination experiments in which worms are transferred from an uncontaminated soil to a contaminated soil (uptake studies) or from a contaminated soil to an uncontaminated soil (elimination studies). The voiding time is shown to be an important experimental variable in determining the measured levels of metal in earthworms because experim ental measurements are usually made on a worm-soil complex (i.e. the s oft tissue of the worm and the soil in the gut of the worm). Thus, for metals that are bioconcentrated in worm tissue, increasing the voidin g period increases the concentration of the metal in the worm-soil com plex. Conversely, for metals that are not bioconcentrated, increasing the voiding time leans to a decrease in concentrations in the worm-soi l complex.