The role of earthworm Lampito mauritii (Kinberg) in amending lead and zinc treated soil.

A laboratory experiment was carried out to determine the effect of earthworm (Lampito mauritii) activity on mobility of Pb2+ and Zn2+ in the soil (DTPA-extractable) and its composting potential in presence of these metals. Well clitellate earthworms collected from an uncontaminated site were exposed to different concentrations (75, 150, 300mgkg(-1)) of Pb2+ and Zn2+ separately for 30 days. It was observed that the metal burden in the earthworm tissue increased with the increase in metal treatment. L. mauritii elevated the soil pH of all the metal treated beds and lowered the soil C/N ratio in the cast by reducing the organic carbon and fixing additional nitrogen. Earthworm activity significantly increased the availability of phosphorous, potassium and decreased the amount of DTPA-extractable Pb2+ and Zn2+ in the cast, which implies the immobilization of metals in soils. These findings suggest the use of L. mauritii in amelioration of metal contaminated soil.