Effects of high copper concentrations on soil invertebrates (earthworms and oribatid mites): : Experimental results and a model

Data in the literature on the toxicity and uptake of copper by soil invertebrates are contradictory. Copper toxicity and bioaccumulation studies were therefore performed using earthworms and oribatid mites. Field-simulating experiments in soil-filled plastic containers showed that earthworms try to escape moderately toxic situations and that they are much more sensitive than oribatid mites to temporary high Cu²⁺ concentrations in soils. The total copper concentration in the bodies of the earthworm species Octolasium cyaneum was measured in experiments with different soil types and different amounts of added CuSO₄. The copper concentrations in the earthworms increased in response to the higher concentrations of the copper fraction extractable with 2.5% acetic acid in the soil. Furthermore, internal copper concentrations showed a slight tendency to oscillate. The worms died when the concentrations within their bodies exceeded about 100-120 ppm, calculated on a dry weight basis. To interpret the experimental results, a compartment model is proposed which describes the dynamics of different fractions of copper in worms living in varying soil environments. Applying this model, the different reports on toxicity and uptake of copper in the literature no longer contradict each other.