Assessment of Seasonal Variation on Heavy Metal Concentration in the Soil of Ugwuaji Solid Waste Dump Sites

Abstract

Open dump site has become a major challenge in maintaining a pollution free environment in most rural and suburban areas. The present study was aimed toward investigating the effect of seasonal variation on metal (Pb, Cd, Cu, Cr, Hg, and Zn) concentration in soil obtained from Ugwuaji solid waste dump sites in Enugu state. Standard procedures and techniques were employed in the study. Using circular plot method, soil samples were collected from the study area at depth 0 to 15 cm, 15 to 30 cm, and 30 to 45 cm during the dry (November, December, January) and wet (April, May, June) season. The results of the findings showed reduction in soil pH, CEC, SOM and moisture content during the dry season [5.65 pH.H2O, 11.8 cmol/kg, 388.2 g/kg, and 8.12 % respectively] compared to the wet season [6.75 pH.H2O, 13.8 cmol/kg, 458.2 g/kg, 16.1 %]. The concentration of metals increased progressively during the period of assessment in the order: November> December>January>April>May>June. During the dry season metal concentration was highest in soil sample from depth 0 to 15 cm and least in soil sample from depth 30 to 45 cm. In contrast, during the wet season metal concentration was highest in soil sample from depth 30 to 45 cm and least in soil sample from depth 0 to 15 cm. The concentration of all the metals investigated were above WHO maximum permissible limit for both seasons. The concentrations of the metals investigated were observed in the following order Zn > Pb > Cu > Cr > Hg > Cd. The research study has indicated that soil from the study area (Ugwuaji waste dumpsite) are polluted by the heavy metals.