Ref ID : 6856
Steve C. Sheppard, William G. Evenden, and Teresa C. Cornwell; Depuration and Uptake Kinetics of I, Cs, Mn, Zn and Cd by the earthworm (Lumbricus terrestris) in radiotracer-spiked litter. Environmental Toxicology & Chemistry 16(10):2106-2112, 1997
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The relative depuration and uptake kinetics of contaminants should be known to interpret appropriately the use of organisms such as earthworms in environmental bioassays and monitoring. For example, 14-day earthworm bioassays should be interpreted with the knowledge that some contaminants will continue to accumulate in tissues for months. The radiotracers [125]I, [134]Cs, [54]Mn, [65]Zn, and [109]Cd were applied to deciduous litter and specimens of Lumbricus terrestris were exposed, either to litter alone or to litter on the top of soil columns. Depuration was monitored for 120 days and uptake, in a separate experiment, for 20 days. Both depuration and uptake were described using two-phase, first-order statistical models. Gut clearance had a mean half-time of 1.4 days. The mean half-time for physiological depuration decreased from I (210 days) > Cd (150 days) > Zn (69 days) > Mn (40 days) > Cs (24 days). Both the depuration and the uptake experiment were necessary to resolve even partially the multiphase processes. Earthworm/soil dry weight concentration ratios decreased from Cd > Zn > I >/_ Cs >/_ Mn. The very slow kinetics indicate that tissue concentrations will increase continuously for a long time, with important implications for subsequent food-chain transfers.