Seasonal dynamics of Potentially Toxic Elements (PTEs) in a riverine ecosystem in a developing country: a baseline study

This study evaluates seasonal variations in sediment and water quality of the Sugondha River across three distinct monitoring sites. Water parameters, such as pH, total dissolved solids (TDS) and dissolved oxygen (DO), generally met the Department of Environment (DoE) standards; however, elevated chemical oxygen demand (COD) and biological oxygen demand (BOD) indicated persistent organic pollution. Potentially toxic elements (PTEs)–cadmium (Cd), arsenic (As), lead (Pb) and chromium (Cr)–exceeded WHO and USEPA thresholds. Sediment analysis revealed moderate organic matter enrichment and substantial accumulation of Cd and Cr. Pearson correlation matrices showed strong positive associations between metal concentrations (Cd-Cr: r = 0.82; Pb-As: r = 0.76), confirming co-occurrence likely driven by industrial effluents and urban runoff. Principal component analysis (PCA) and cluster analysis further identified anthropogenic activities as dominant contamination sources. Contamination indices (Igeo, CF, CD and PLI) categorized sediment pollution levels as moderate to high, with cadmium as the principal pollutant. The Nemerow pollution index (NPI) further confirmed elevated comprehensive pollution levels, particularly during the dry season, with values exceeding critical thresholds at all sites. These findings underscore the ecological vulnerability of the Sugondha River and highlight the urgent need for integrated basin-wide management for sediment remediation.