Geogenic and anthropogenic sources of heavy metals in soil: An ecological and health risk assessment in the granitic terrain of South India

Abstract

Heavy metals (HMs) contamination in soils poses significant ecological and human health risks, particularly in regions with complex geogenic and anthropogenic influences. This study investigates the levels, distribution, and sources of heavy metals in Chromic Luvisols (Toxic) of a granitic terrain in South India. Total of 44 soil samples were collected and analyzed for various heavy metal content using the XRF technique. The concentrations of the elements ranged between 3.4–19.6 mg/kg for As, 370.2–1710.6 mg/kg for Ba, 0.3–89.6 mg/kg for Co, 8.7–543.4 mg/kg for Cr, 7.7–96.6 mg/kg for Cu, 0.2–12.4 mg/kg for Mo, 5.4–168 mg/kg for Ni, 4–66 mg/kg for Pb, 29.6–223 mg/kg for Rb, 134.6–437.9 mg/kg for Sr, 39.8–162.8 mg/kg for V, 10.9–268.3 mg/kg for Y, 1–478.3 mg/kg for Zn and 141.2–8232.3 mg/kg for Zr with higher concentrations observed in the northwestern region. The Geo-accumulation index (I_geo) indicates the soil is moderately contaminated. Enrichment Factor (EF) mean values for As in most samples is > 2 indicating minimal enrichment or involvement of anthropogenetic activities in the area. Principal component analysis suggested anthropogenic activities, such as pesticide and fertilizer use, as key contributors to soil contamination. The non-carcinogenic risk for children and adults via ingestion, dermal, and inhalation pathways in almost all the samples is found to be HI < 1 indicating no noteworthy chronic risk of metals in the study area. Total Carcinogenic Risk (TCR) showed 90.91 % and 4.45 % of samples exceeding the limit for children and adults, respectively. Children face particularly high carcinogenic risks from Cr and As through ingestion, which could lead to cancer with prolonged exposure. Heavy metals like Cr and As showed very high values via ingestion pathway that may cause carcinogenic risk to the people of the study area. The Ni and Cr via dermal pathway also showed some carcinogenic risk which should also be taken seriously.