Potentially toxic metal contamination in semi-arid agricultural soils: sources, risk analysis, and spatial distribution.

The increased demand, driven by a growing population and changing dietary habits, has created immense pressure on agroecosystems throughout the globe. In semi-arid areas, this increased pressure has led to excessive use of agrochemicals in agriculture, which poses a threat of potentially toxic metal (PTM) contamination in agricultural soils. PTMs in agricultural soils result in significant environmental and health threats for humans and livestock. The current study aimed to evaluate the risks associated with five PTMs-nickel (Ni), lead (Pb), chromium (Cr), cadmium (Cd), and cobalt (Co)-in agricultural soils of the semi-arid South Punjab region of India. The study area included sites from district Bathinda of Punjab (3385 km). Among the PTMs analyzed, the concentration of Cd (0.65-1.85 mg/kg) in several agricultural soil samples was above the international permissible limits (1.0 mg/kg). Principal component analysis (PCA) pointed to parent rock materials as the main sources for Cr, Co, Ni, and Pb, while for Cd, agricultural sources (phosphatic fertilizers) can be a prominent contributor. The values observed for Pollution Load Index (PLI: 0.93-1.64) and Ecological Risk Index (RI: 206.66-584.03) indicated that soil samples were significantly contaminated with the tested PTMs, posing considerable ecological risks. Analysis of other physicochemical characteristics showed that soil samples were alkaline and saline, with low levels of soil organic matter. The human health risk assessment pointed to minimal non-carcinogenic (NCR) and carcinogenic risks (CR) associated with the presence of PTMs in the soil. Spatial distribution analysis revealed a higher level of metallic contamination in the eastern part of the district. Thus, adequate steps must be taken to control the increase in levels of these PTMs in the soils of the study area.