EFFECT OF MUNICIPAL SOLID WASTES ON HEAVY METAL CONTENT OF FARMLAND SOILS IN BAUCHI METROPOLIS, BAUCHI STATE, NIGERIA

Abstract

The level of heavy metal pollution (Cd, Cr, Pb, Ni, and Zn) in farmland soils treated with Municipal Solid Waste (MSW) and Inorganic fertilizer (NPK) in Bauchi metropolis, Bauchi state, Nigeria was evaluated. Soil samples were collected at a depth of 0-30cm from three farmland locations fertilized with municipal solid waste (MSW 1 treated soil, MSW 2 treated soil and MSW 3 treated soil), one with inorganic fertilizer (NPK), and one from uncultivated land. The soils were subjected to physicochemical and heavy metal analysis using standard procedures. The results showed that MSW treated soils had significantly more sand and less silt and clay than the NPK and control soils. Texturally, the MSW-fertilized soils were classified as loamy sand, while the NPK-treated and control soils were classified as sandy loam. The soil pH was neutral for MSW 2 and 3 treated soils and slightly acidic for the MSW 1 treated soils, NPK treated soils, and the control. Soils treated with MSW had significantly (P≤0.05) higher levels of organic carbon, nitrogen, Cation Exchange Capacity (CEC), exchangeable bases, and Electrical Conductivity (EC) than NPK-treated soils and the control. Heavy metals concentration (Cd, Cr, Pb. Ni, and Zn) were also significantly (P≤0.05) higher in MSW treated soils, followed by NPK treated soils, and the lowest concentrations were found in the control soils. The pattern of accumulation of the heavy metals were Zn > Ni> Pb > Cr > Cd in MSW fertilized soils and Zn > Pb > Ni > Cr > Cd in NPK treated soils and control. Heavy metal levels in NPK treated and the control soils were within the FAO/WHO recommended limits in soil. The concentration of Zn, Pb, and Cd in the MSW treated soils exceeded FAO/WHO permissible limits while Cr was within the permissible limits. Nickel concentrations were within the range for MSW 3 treated soil but exceeded the limit in MSW 1 and MSW 2 treated soils. The study concluded that fertilizing farmland soils with MSW increased heavy metal contamination of the soils thus, posing a serious risk to environmental sustainability. Based on the result of this study, effective implementation of the National and State policies on solid waste management by the relevant institutions is recommended.