A proxy-based restriction scoring approach using soil physico-chemical properties to assess potentially toxic element risk in agroecosystems

Agricultural intensification, particularly in developing countries, has led to widespread soil pollution and potentially toxic element (PTE) contamination due to excessive use of synthetic fertilizers and pesticides. This study assesses the spatial variability of HM contamination risks in the Mehrgard Catchment (1275.59 km²), Isfahan Province, using soil physico-chemical properties as proxies. Soil samples from 134 locations revealed significant heterogeneity in organic carbon (OC, 0.5–6.9%), alkaline phosphatase activity (ALP, 0.59–15.67 µmol/g/l), and texture (sand 54.9–78.8%). Principal component analysis (PCA) identified three components explaining ~80% of the variance, emphasizing the dominant roles of OC, ALP, and texture in regulating PTE dynamics. OC and nutrient-related parameters were key to PTE retention, while sandy soils and carbonate content increased contamination risks. A restriction score (RS, ranging from -1.132 to 0.676) was calculated for each location using PCA-derived weights and adjusted soil properties. Hotspot analysis (Getis-Ord Gi*) identified northern areas as high-risk zones (49 locations across three clusters), where soil properties elevated PTE accumulation risks. The findings advocate for site-specific strategies, such as organic amendments for sandy soils and precision irrigation for carbonate-rich areas, to mitigate PTE contamination, highlighting the inadequacy of uniform agricultural practices for sustainable land use.