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African Journal of Biotechnology

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Levels of toxic elements in soils of abandoned waste dump site

NE Okoronkwo, SA Odemelam, OA Ano

Abstract


The soils of an abandoned waste dumps sites which has been presently used for crop cultivation was investigated. Three points on the location of the waste dump site were selected and three pits of 100 cm
depth were dug at selected points. Soils samples were collected at an interval of 10 cm from the three pits. The physico-chemical properties and toxic heavy metal (As, Cd, Cr, Ni and Pb) levels were determined. The results of the study showed that the mean percentage of sand, silt and clay were 75.01±2.31, 12.87±0.93 and 10.45±1.47, respectively, while the mean pH was 6.89±0.01. The mean percentage organic matter content were high and was 3.47±0.41. The mean exchangeable Ca, Mg, K and Na in meq/100 g of soil were 4.20±0.42, 3.41±0.32, 0.31±0.004 and 0.47±0.006, respectively. The mean exchangeable acidity (EA) and exchangeable AI were 0.23±0.002 and 0.69±0.004, respectively. Of all the five toxic elements studied, the highest mean concentration (mg/kg) of 133.74±10.60 was recorded for Pb followed by Cr (22.27±3.03), Ni (8.14±0.33) and As (5.97±0.32) in the soils while the least mean concentration of 1.64±0.11 was recorded for Cd. The toxic elements were examined for dependency upon some soil factors through the use of correlation analysis, sand, organic matter and effective cation exchange capacity (ECEC) correlated significantly and positively with Cr and Pb indicating that these factors largely control the concentration of these elements in the soils.



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