Environmental modelling of soil quality, heavy-metal enrichment and human health risk in sub-urbanized semiarid watershed of western India

Natural chemical structure of soil is triggered due to tremendous emissions from industrial, mining, domestic effluents, overuse of agricultural pesticides and chemical fertilizers. Hence, the chemical analysis of this resource is necessary to understand the chemical changes and the concentration of heavy metals. In this regard, 25 representative soil samples in Shivganga watershed were collected from the surface to 15 cm depth for the detection of heavy metals viz., cadmium, copper, lead, zinc, cobalt, molybdenum, nickel, chromium and arsenic. These soil samples were also examined for physio-chemical parameters and further subjected to X-ray fluorescence spectrometer. The analysed elements were normalised using upper continental crust and standard basalt values. The pollution index (PI) was calculated to identify the enrichment of heavy metals in study area soils. The PI value ranges from 0.44 to 9.55 wherein the highest contribution is from cadmium, up to considerable level from copper and molybdenum and moderate contamination by zinc, arsenic and lead. The study revealed that there is a considerable concentration of heavy metals mainly due to the anthropogenic sources viz. the chemical fertilizers that are used in agricultural practices and the transportation in main roads (highways) with high traffic density. Considering the higher concentrations of heavy metals in the study region, health risk assessment model was generated for adults and children. It is observed that the hazard quotient and hazard index values for these heavy metals are well within acceptable range for adults as compared to children showing low health risk by ingestion of heavy metals.