Spatial Assessment of Some Selected Heavy Metals and Soil Physicochemical Properties in Open Dumpsites in Owerri North Nigeria

Abstract

The rising demand for food and other essentials due to increase in urban population had perpetuate a rise in the amount of waste generated daily by each household. In this study, soil physicochemical parameters (pH, SOM, TN, Exchangeable bases of Ca, Mg, Na, K, CEC) and heavy metal (Cu, Pb, Cr, Cd) concentration in two dumpsites in Owerri North were assessed and compared with the control soils from the same terrain using standard analytical methods. The results show that the both the dumpsites and the control sites had high % sand (>80.0%) with lower clay and silt contents. Soil mean pH varied between 5.08±0.01 in the control of Nekede and 8.20±0.02 in the main dumpsite of Egbu. The SOM ranged from 0.619±0.57 to 2.410±0.85% with the Nekede dumpsite having clear variation of SOM with its control comparable to Egbu dumpsite SOM. Total nitrogen (N) content ranged from 0.112±0.08 to 0.196±0.08%. Available P ranged from 14.92±0.99 to 85.81±0.76 mg/kg. Cation exchange capacity (CEC) varied between 19.6±0.97 to 25.2±1.24 Cmol/kg. Exchangeable Ca, Mg, K and Na, were far above the critical levels set by FAO for agricultural soil. Cu concentration ranged from 0.92±0.20 to 1.67±0.25. Pb was found in trace amount (<0.0001±0.01 mg/kg) in both dumpsites and control sites. Mean concentration of Cr in the dumpsite soils varied between 1.89±0.58 and 3.77±2.26 mg/kg in the two dumpsites, while Cd was found to be higher than the soil permissible limit. It ranges from 2.08±0.80 to 4.51±1.86 mg/kg. Conclusively, the concentrations of heavy metals studied in the soil were found to be lower than the maximum permissible limit except Cd. However, the dumpsite though high in soil nutrients and low in evaluated heavy metals might be unsafe for human consumption due to but high concentration of Cd in the study area.