Evaluation of physicochemical properties and distribution of Pb, Cd, Cr and Ni in soils and growing plants around refuse dumpsites in Akure, Nigeria

Abstract

The physicochemical properties and distribution of Pb, Cd, Cr and Ni in soils and growing plants around refuse dumpsites in Akure, Southwestern Nigeria were evaluated to ascertain the impact of the wastes on these soil quality indices and edible plants. The soils close to the dumpsites were more acidic (pH, 5.50) compared with the soils away (25.0 m) from the sites. Also there were corresponding increases in the organic carbon and cation exchange capacities of the soil indicating measurable levels of biodegradability of the wastes. Pb, Cd, Cr and Ni have maximum concentrations of 23.00, 2.91, 9.00 and
24.00 mg/kg respectively in the soils. The amount of Cd determined in the soils was consistent with the critical level obtained for agricultural soils. Results obtained from the plant tissues analysed showed
that 0.84 mg/kg Pb was detected in the root of Zea mays, while 0.25 mg/kg Ni was obtained in the root of Sorghum vulgare. Talinum triangulare and Amaranthus crucantus did not possess detectable levels of these metals. The present study has justified the need to continually assess the quality of soils, and the concentration of certain heavy/toxic metals in growing plants around refuse dumpsites.