Spatial variability and health risk assessment of potentially toxic elements in mountain catchment soils across land-use classes

Abstract

Potentially toxic elements (PTEs) in rural mountainous soils may pose environmental and health concerns due to direct human exposure, particularly for children. This study evaluated the concentrations, spatial distribution, and associated health risks of Cd, Co, Cu, Mn, Ni, Pb, and Zn in 428 surface soil samples collected from a non-industrial mountainous micro-catchment in Eastern Türkiye. Mean concentrations followed the order Zn > Ni > Mn > Pb > Cu > Co > Cd, with average values of 74.94, 23.19, 19.96, 10.53, 4.51, 1.70, and 0.038 mg kg⁻¹, respectively. Although mean concentrations generally indicated low to moderate contamination levels, localized threshold exceedances were detected for Ni, Pb, and Zn. Non-carcinogenic risks remained below the critical threshold of 1 for both adults and children, with mean HI values of 8.66 × 10⁻³ and 7.14 × 10⁻², respectively. Pb and Ni were the main contributors to non-carcinogenic risk. Mean total carcinogenic risk values were within the tolerable range for adults and children; however, maximum TCR values exceeded 1 × 10⁻⁴ at limited sampling locations, mainly due to Ni. Land use significantly influenced cumulative HI and TCR values, with degraded forest soils showing comparatively higher risk values. Overall, the study area presents low non-carcinogenic risk and generally tolerable mean carcinogenic risk, but localized Ni-related risk elevations indicate the need for periodic monitoring and source-oriented evaluation.