Tracking soil health and potentially toxic elements (PTEs) across land-use types using physico-chemical, magnetic, and geochemical proxies: a case study from Manipal, Southwestern India

This study investigates spatial variations in soil quality across five distinct land-use types-forest, roadside, agricultural, industrial, and residential-in the Manipal region of southern India. Ten surface soil samples from each land-use category were analysed for physico-chemical properties, geochemical composition, and environmental magnetic parameters to evaluate soil degradation and identify potential pollution sources. Marked variations were observed in electrical conductivity, pH, and salinity, with industrial and roadside soils exhibiting elevated values indicative of anthropogenic impact. Concentrations of potentially toxic elements (PTEs), including Pb, Cr, Cu, and Zn, were significantly higher in roadside and industrial areas, frequently exceeding recommended safety thresholds. Environmental magnetic measurements, such as low-frequency magnetic susceptibility (χ_lf) and frequency-dependent susceptibility (χ_fd%), effectively differentiated between anthropogenic and pedogenic magnetic inputs. Principal Component Analysis (PCA) highlighted distinct contamination patterns and revealed strong correlations between magnetic parameters and PTE concentrations. Pollution indices-including the Pollution Load Index (PLI), Enrichment Factor (EF), and Contamination Factor (CF)-identified notable contamination in industrial soils (PLI > 1.3). Overall, the findings underscore increasing environmental pressures on soil systems in rapidly urbanizing regions and demonstrate the value of environmental magnetism as a cost-effective, non-destructive tool for early detection and long-term monitoring of soil pollution. These insights can inform sustainable land management strategies and guide policy frameworks aimed at safeguarding soil health and ecological resilience.