Heavy metal pollution and health risk assessment in upland and riparian soils of the Ganga River basin

Riparian zones act as crucial sinks for heavy metals (HM), with spatial distribution influenced by landscape positioning and land-use practices. This study investigated the mineralogical composition, HM contamination, and associated risks in the upland and riparian soils of the Ganga River basin. A total of 56 composite soil samples (0–20 cm depth) were collected from five land-use types: uplands (undisturbed forest: CALref; conventional agriculture: CAL) and riparian zones (reservoir: RSRZ; river: RRZ; uncultivated: RZref). Statistical analysis revealed significantly (P < 0.05) higher concentrations of HM in cultivated soils (CAL, RSRZ, RRZ) compared to reference soils (CALref, RZref). Pollution indices (Igeo, EF, and CF) revealed high soil contamination by Cd > As > Ga, particularly in riparian soils. Ecological risk assessment identified high potential risks (PERI > 600) in the cultivated riparian soils (RSRZ: 766, RRZ: 620) than in other soils, primarily contributed by Cd (> 85%). Health risk assessment revealed that cultivated riparian soils pose significant non-carcinogenic (THI: 1.55–1.73) and carcinogenic risks (TCR: 1.06 × 10–4–1.13 × 10–4) for children, primarily due to Cr and As exposure. The dominant exposure pathway of the HM was ingestion (> 88%), which was higher for children than adults. Source apportionment analysis identified mixed anthropogenic sources (36.2%), geogenic origins (26.5%), and specific agricultural inputs (9.8%) as primary factors controlling the HM distribution. The study emphasizes the impact of agricultural-induced land use changes on HM contamination in riparian soils, increasing the risk of exposure and toxicity to local communities dependent on riparian resources.