Uptake of trace metals by the earthworm Lumbricus terrestris L. in urban contaminated soils

The bioaccumulation of the trace metals Cu, Pb, and Zn by the earthworm Lumbricus terrestris L. was studied in 12 field-collected urban contaminated soils from the Montreal area. The soils studied contained between 22 and 2900 mg Cu kg(-1), 30 and 7100 mg Pb kg(-1), and 40-14,600 mg Zn kg(-1). A preliminary experiment showed that the metal tissue concentrations in L. terrestris reached an equilibrium within 2-3 weeks of exposure to a single contaminated soil. Incubation of the earthworms resulted in tissue concentrations varying from 8 to 74 mg Cu kg(-1), <0.2 to 37 mg Pb kg(-1) and 166 to 480 mg Zn kg(-1). Despite the high levels of soil metal contamination, there was no significant earthworm mortality in any of the soil samples tested. Nevertheless, the earthworms bioaccumulated Cu, Pb and Zn in their tissue following a linear relationship to the log 10 of the soil total metal content (with an R-2 of 0.674 and 0.71 for Cu and Pb (P < 0.001), and an R-2 of 0.329 for Zn (P < 0.1)). The low metal bioavailability and absence of toxic effects are attributed to the chemical characteristics common to the urban soils studied (mainly alkaline pH). (C) 2002 Elsevier Science B.V. All rights reserved.