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Heavy metals and physico-chemical characteristics of top and subsoils of refuse dumps at the University of Nigeria, Nsukka


C.B. Okebalama
M.F. Udeh

Abstract

Disposal of waste on the soil surface affects both the physico-chemical properties and the concentrations of heavy metals in the soil. Following a field reconnaissance at the University of Nigeria, Nsukka Southeastern Nigeria, two representative dumpsites and adjacent control sites at Odim-gate and Faculty of Engineering (FOE) were selected to assess some soil physico-chemical properties, including heavy metals concentrations, at 0-20 and 20-40 cm depths. The soil data obtained from the sites were arranged in a 2 x 2 x 2 factorial and analyzed. Results showed that the soils were generally sandy loam, slightly acidic to slightly alkaline, with a high available P content, while the concentrations of organic carbon (OC), total N, Ca2+, Na+ and K+ , including effective cation exchange capacity, were low. Saturated hydraulic conductivity and OC content were significantly higher at the Odim-gate, while soil pH, available P, Al3+ and H+ concentrations were significantly lower than at the FOE location. Soil bulk density, and concentrations of Al3+ and H+ were significantly lower, while total porosity, pH, OC, Ca2+ and Na+ concentrations increased in the dumpsite compared to the control. The OC, Ca2+ , Na+ and K+ were significantly higher in the topsoil (0-20 cm), while Al3+ was significantly lower. Heavy metals Fe and Pb concentrations in the soils were low, although the Fe concentration at the Odim-gate location and the control site was significantly higher than their corresponding counterparts. The high Zn concentration at both locations, particularly at 0-20 cm depth at the FOE dumpsite, poses a potential risk to the environment and human health as Zn accumulates to toxic levels.