Integrating geostatistics and pollution indices to delineate chromium contamination hotspots and risk zones in an industrial landscape

Chromium (Cr) contamination in soils poses a major ecological and human health concern in industrial landscapes, particularly in tannery clusters. In this study, geostatistical methods and pollution indices were integrated to delineate Cr contamination hotspots and ecological risk zones in the Walaja block, Tamil Nadu, India. Sixty-eight surface soil samples were collected in September, 2024 and analysed for physicochemical properties and total Cr concentrations using standard protocols. The contamination factor (CF), geo-accumulation index (Igeo) and ecological risk index (Er) were computed. Spatial interpolation was performed using inverse distance weighting (IDW) and hotspots were identified with the Getis–Ord Gi* statistic. Soil Cr concentrations ranged from 129 to 2625 mg/kg (mean ≈ 601 mg/kg), which is over 27 times the natural background level. Contamination factor (CF) and Igeo values indicated severe to extreme contamination in the northwestern industrial corridor, whereas Er values were mostly in the low-to-moderate risk category due to Cr’s relatively low toxicity factor. Spatial analysis confirmed statistically significant Cr hotspots in tannery zones and cold spots in agricultural areas. Integrated risk zonationclassified approximately 20 % of the study area as high risk, 35-40 % as moderate risk and 40-45 % as low risk. These findings indicate that the high-risk areas coincide with tannery belts, underscoring the urgent need for soil remediation and stricter land-use regulation. The combined geostatistical-index approach provides a robust tool for policymakers to prioritize monitoring and mitigation efforts in industrial regions.