Sewage Sludge Application on Soil: Effects on Two Earthworm Species
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Some biological effects of soilfertilisation with sewage sludge were investigated aftersoil reclamation in an opencast mining area. Two earthwormspecies (Allolobophora chlorotica chloroticaand Nicodrilus caliginosus meridionalis) inhabitingthe reclaimed soil were tested for their response to twohigh doses of sludge (75 and 150 g kg-1 of dry sludgein dry sieved soil). The metal concentrations in thesludge amended soils were below that which worm mortalitywould be expected. Mean annual density of the earthwormswas higher in the plots where the sludge was applied (435and 335 ind. m-2) than in control (115 ind. m-2).We verified the accumulation of Cd and Zn by the twoearthworm species at any dose of sludge, and metalaccumulation was higher in N. caliginosus than inA. chlorotica. Zn, Pb, Cr, Cu and Ni were moreconcentrated in the earthworm egesta than in the bulk soil.
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