Cu accumulation by Lumbricus rubellus as affected by total amount of Cu in soil, soil moisture and soil heterogeneity

To investigate the effect of soil heterogeneity on accumulation of pollutants in a contaminated soil by earthworms, we performed experiments under laboratory conditions with soil from a Cu-contaminated site, followed by experiments under field conditions. The first experiments were set up as a preliminary investigation for the latter experiments. Also the effect of soil moisture on uptake of Cu under laboratory conditions was investigated. In the laboratory experiments, earthworms (Lumbricus rubellus) were added to homogeneously mixed Cu-contaminated soil and a reference soil. The total Cu content in the soil varied from 10 up to 130 mg kg−1; soil pH was around 5; the soil moisture was set to 25, 35 and 45% of the pore volume for each treatment. The tissue Cu concentration was determined by sampling five earthworms after 1, 3, 7, 14, 28 and 56 d. At the field experiment, 500 earthworms were introduced in two differently Cu-contaminated plots. After 14, 28 and 70 d, 25 earthworms were sampled to determine the tissue Cu concentration. Under laboratory conditions, soil Cu contents significantly affected the Cu uptake, whereas under field conditions this could not be shown. Soil moisture did not significantly affect Cu uptake. In the field experiment soil temperature affected the Cu accumulation considerably. Variance of tissue Cu concentration of earthworms from both experiments differed significantly after 14 d, but did not significantly differ after 28 d.