Heavy Metals Concentration In Soils And Bioaccumulation In Earthworm (Lumbricus Terrestris) At Lemna Solid Wastes Dumpsite, Calabar, Cross River State

Abstract

This study investigated the concentrations of heavy metals and their bioaccumulation in earthworm in Lemna solid wastes dumpsite in Calabar, Cross River State, Nigeria. Three composite samples of the depth of 30 cm each were collected from Lemna dumpsites and control from the University of Calabar Botanical garden, making a total of four composite soil samples, while samples of earthworms were collected at each sampling point. The samples were analysed for Pb, Cd, Zn and Cu. The result showed that the levels of heavy metals were all higher in dumpsite and significantly different from the control. The respective means of metal concentrations from both Lemna and control were Pb(323.99mg/kg , 89.88mg/kg),  Cd(1.12 mg/kg, 0.072 mg/kg), Zn(281 mg/kg, 7.60 mg/kg) and Cu(21.58 mg/kg, 4.89 mg/kg). Pb, Cd, Zn and Cu were also higher in earthworm of dumpsite than earthworm of the control soil. Correlation between Cadmium and Zinc concentration in soil and Cadmium and Zinc concentration in earthworm displayed strong and positive relationship while weak and negative correlation was observed between Cu and Pb concentrations in soil and Cu and Pb concentrations in earthworm. Bioaccumulation of the heavy metals by earthworm was in the order of Zn (0.382) > Cd (0.170) > Pb (0.076) > Cu (0.020). The dumpsite soil was found to be contaminated with Cd, Pb and Zn as their concentrations were high above maximum permissible limits except Cu.  For safe consumption of crops from Lemna dumpsite soil, remediation of heavy metals in the soil in advocated.