Controlling factors of heavy metal distributions in granitoid-derived soils and their environmental risks

In this study, the weathering degrees of the outcropping magmatic rocks in the northeastern part of Aksaray province, as well as the heavy metal variations in the resulting granitoid-derived soils and their associated environmental risks, were evaluated. The calculated weathering indices vary as follows: Ruxton Ratio (RR) 5.88–8.51, Chemical Index of Alteration (CIA) 49.58–66.33, Chemical Index of Weathering (CIW) 60.45–80.18, Weathering of Parker Index (WIP) 48.32–76.79, and Plagioclase Index of Alteration (PIA) 64.33–83.79. These values indicate that the granites in the study area are moderately weathered. To assess the environmental risks of heavy metals (HMs) in the granitic soils, the Geo-accumulation Index (Igeo), Contamination Factor (CF), Pollution Load Index (PLI), and Potential Ecological Risk (PER) were calculated, ranging from -4.58 to 0.99, 0.06 to 2.98, 0.36 to 0.97, and 0.124 to 23.818, respectively. The ecological indices, which show similar distributions with increasing weathering degrees, indicate the absence of significant heavy metal pollution in the area and suggest that any minor contamination originates from the lithology, with no anthropogenic pollution observed.