Comprehensive geochemical characterization and multi-index ecotoxicological appraisal of heavy metal contamination in soils impacted by open waste disposal practices

Abstract

This study provides an integrated geochemical characterization of the contamination extent, ecotoxicological impacts, and pollution profiles of selected heavy metals in soils underlying open waste disposal sites. An integrative suite of eight pollution indices: Contamination Factor, Geo-accumulation Index, Pollution Load Index, Modified Degree of Contamination, Heavy Metal Pollution Index, Metal Index, Potential Ecological Risk Index, and Carcinogenic Risk, were used to evaluate the spatial distribution, contamination intensity, and ecological implications of potentially toxic metals across the sites. The sites included those used for abattoir, paint processing, and auto mechanic wastes disposal. Results revealed alarming levels of Pb and Cd in several sites, with Contamination Factor and Geo-accumulation Index values suggesting significant anthropogenic enrichments. The Pollution Load Index values exceeded the critical threshold in all sites, indicating overall soil degradation. Pearson correlation analysis was applied to quantify the strength and direction of linear relationships between pairs of heavy metals in the dataset. To strengthen source apportionment, Principal Component Analysis (PCA) was employed to extract dominant contaminant patterns. The primary contributor to overall variability in Principal Component 1 was Pb in automobile waste, and Principal Component 2’s dominant factor was Pb in paint processing waste. The significance of this research lies in its multi-index analytical framework, which not only quantifies contamination levels but also reveals patterns of anthropogenic enrichment and ecological risks that are often masked in conventional single-index studies. This research advances the field of environmental and earth sciences by presenting a replicable and robust model for multi-metric contamination assessment.