Soil heavy metal contamination analysis: A representative case study in New Zealand

The study conducts a geospatial analysis of soil Heavy Metal (HM) contamination within the diverse landscapes of Clutha, Dunedin, and Gore in New Zealand. Recognizing the critical impact of soil pollutants on environmental and public health. The research aims to map the distribution and concentration of Potentially Toxic Elements (PTE) using advanced interpolation techniques and assess their ecological risks. The study employed the Inverse Distance Weighting (IDW) method for spatial interpolation, a geo-statistical tool that helps visualize contamination dispersion based on proximity and intensity. In this study, 158 soil samples were collected from location A=0-30cm depths and 155 samples from location B=50-70cm depths. This stratified sampling covered both topsoil and subsoil, ensuring a comprehensive spatial analysis of soil heavy metal contamination. Each sample was analyzed using the heavy metal pollution index (HPI) and Igeo, where 35 % of sites showed an Igeo classification of ≥ 5. Cobalt concentrations were notably high, averaging 234.48 ppm. The HPI analysis revealed pervasive contamination of Zn, Co, and Cr, 70.21 ppm, 234.48 ppm, and 23.06 respectively. While Igeo showing extreme HM levels and reaching the highest categories. The study indicates an urgent need for targeted environmental interventions and policy reforms to reduce PTE emissions and remediate contaminated sites. Using geospatial mapping and IDW interpolation has proven indispensable in delineating contamination hotspots, offering a valuable tool for environmental scientists and policymakers in planning effective pollution control measures.