Contamination of Arable Soil with Toxic Trace Elements (Tes) around Mine Sites and the Assessment of Associated Human Health Risks

Abstract

ABSTRACT Soil contamination with TEs around mining areas without monitoring and risk assessment has serious human health implications. Soil samples were collected around the Abakaliki Pb-Zn mine sites. Lead (Pb), zinc (Zn), copper (Cu), iron (Fe), manganese (Mn), chromium (Cr), barium (Ba), rubidium (Rb), strontium (Sr) and major oxides were analyzed by X-ray fluorescence technique. Acidity (pH), redox potential (Eh), electrical conductivity (EC) and total dissolved solids (TDS) were analyzed using pH/conductivity meter. The mean value of pH (6.4) reflects moderately acidic soils, while means of 422, 182 and 295 mg kg− for EC, TDS and Eh, respectively, indicated less conductive soils. Zn obtained the highest mean (42023 mg kg−) and Cr the least (14.8 mg kg−). Silicon (iv) oxide (SiO2) recorded the highest mean of 44.7 mg kg− while chromium oxide (Cr2O3) had the least mean (0.02 mg kg−). Strong positive correlation among Pb, Zn and Mn indicated that they had a common source. Principal component analysis (PCA) indicated that sources of elements are from weathering of galena and sphalerite deposits. Pb means for contamination factor (Cf), geo accumulation index (Igeo), potential ecological risk (EiR) and potential ecological risk index (IR) are 726, 4.8, 3632 and 4120, respectively. The results show that the soil in the region has reached the heavily extremely contaminated level and very high risk level. Ingestion is the major pathway for non-carcinogenic risk, and children are more vulnerable to carcinogenic risk than adults. Hazard quotient (HQ) and total hazard index (HI) values in few locations showed the possibility of humans contracting cancer. Lifetime average daily dose (LADD) values of carcinogenic risk (9.12 × 10−6, 2.3 × 10−6 and 3.92 × 10−5) exceeded the upper and lower limits of 1 × 10−4 and 1 × 10−6. This study is invaluable in assessing ecological and health risk in agricultural soils around mining areas.