Environmental Assessment of Heavy Metal Pollution around Industrial Area in Southwestern, Nigeria

Abstract

This study investigated heavy metal contamination around an industrial district in Obajana, Southwest Nigeria. The study region lies between latitudes 7°54′N to 7°56′N and longitudes 6°24′E to 6°27′E. Thirty samples each for groundwater and soil and twelve plant samples were collected from the study area. All samples were collected in triplicate. The physical and chemical parameters of the groundwater, soil, and plant samples were measured. The average pH level of the groundwater samples is 7.2 which falls within the Nigerian Standards for Drinking Water Quality (NSDWQ). The ranges of the other physical parameterssuch as electrical conductivity (EC), total dissolved solids (TDS) and total hardness (TH) are also within the acceptable limits. The mean concentrations of heavy metals in groundwater samples for Mn (0.020 mg/L), Zn (0.010 mg/L), Ni (0.010 mg/L), Cr (0.130 mg/L), Cu (0.020 mg/L), and Fe (0.090 mg/L) are within the allowable limit, with the exception of Pb (0.090 mg/L) that is above the recommended level. According to the index of geo-accumulation (Igeo), the soil and plant samples are not polluted with respect to the heavy metals tested. The analysis of the human risk assessment reveals that the values for the carcinogenic risk are within acceptable bounds; however, the values for the non-carcinogenic risk are substantially above the acceptable bounds. This demonstrates that non-carcinogenic health impacts are a threat to the broader population. This study suggests continuous monitoring of groundwater, soil, and plant in the study area.