Uptake and elimination of cadmium and zinc by Eisenia andrei during exposure to low concentrations in artificial soil.

Bioaccumulation factors (BAFs) are often used in the risk assessment process to estimate trophic transfer of contaminants such as metals from soil. BAFs can be derived from laboratory studies through the determination of steady-state concentrations or kinetic estimation methods. In this study, bioaccumulation tests were performed with artificial soil spiked at low levels with cadmium or zinc to determine uptake and elimination kinetics of both metals by the compost worm Eisenia andrei. The metal-amended soils were acclimated for 21 days prior to the test, after which worms were individually incubated in the soils. The uptake phase comprised 0-21 days, after which the test organisms were transferred into clean soil and the elimination phase continued for an additional 21 days. Subsamples of soil and earthworms (whole body) were collected from independent replicates throughout the uptake phase and elimination phase and analyzed for total metal concentrations. Uptake of Cd in E. andrei increased linearly with time and did not reach steady state within the testing period. Cd uptake and excretion were described by a one-compartment first-order kinetics model. Zn concentrations rapidly increased in E. andrei after 1 day of exposure but subsequently decreased to background levels throughout the remainder of the uptake phase; internal Zn concentrations did not change from background levels during the elimination phase. Kinetic BAFs were calculated for Cd and Zn. Cd is a nonessential metal that is bioaccumulated at a relatively rapid rate, while Zn is an essential metal, and as such, it is regulated by E. andrei. Metal essentiality and concentration significantly impact bioaccumulation of metals by terrestrial invertebrates.