Abstract:
Heavy metals have been widely studied today. Its occurrence has been influenced lately by various anthropogenic activities particularly in urban areas. It has been a source of threat to human health due to its non-biodegradability property particularly in soils. This research is carried out to determine the spatial distribution and possible health effect of selected heavy metals in urban soil around Akure metropolis, Ondo state, Nigeria.
Akure metropolis was divided into grid cells of 1.97x2.07sqkm and composite samples were taken at depth of 0-15cm in each of the grid. Physicochemical properties (pH, % organic carbon, % organic matter, CEC, EC, and soil texture) were carried out using standard methods. Soil samples were digested using aqua regia HCl: HNO3 (3:1) in order to extract the heavy metals and analysed using Buck scientific Atomic Absorption Spectrophotometer (210). The result obtained was treated with statistical and Geographic Information System (GIS) software.
The results of the physicochemicals (% Silt, % sand, % clay, pH, EC, %OM and %OC) obtained are 7.91, 61.95, 28.15, 7.80, 325.13, 3.40, 2.10 and 21.94, respectively. The results of the concentration of selected heavy metal (Cu, Cr, Ni, and Mn) are 24.27, 31.60, 20.96 and 242.78, respectively in mg/kg. The results show that the soil is sandy clay loam in texture, slightly alkaline, rich in organic matter and contain good amount of inorganic salt. This is an indication that the soil will enhance solubility, mobility and retainability of metals. The spatial distribution shows that the places with high industrial activities have high concentration of heavy metals and it was also found out that heavy metals are concentrated at high elevated region. The enrichment values of the heavy metals in the soil for Cu, Cr, Ni, and Mn are 1.98, 2.36,2.12 and 1.64 respectively. The heavy metals are all enriched in the soil following the order Mn < Cu < Ni < Cr; showing that the presence of the heavy metal in the soil is anthropogenic. Constant check should be carried out in order to monitor the availability of the metals and their persistency in the soil.
