Ecological risk assessment of heavy metal pollution in reservoir sediments from major climatic zones of Sri Lanka

Ranathunga H, Ileperuma OA, Yatigammana SK, Chandrajith R. 2025. Ecological risk assessment of heavy metal pollution in reservoir sediments from major climatic zones of Sri Lanka. Lake Reserv Manage. 41:180–193.Trace element contamination in sediments and water poses a significant risk to human and ecological well-being. These elements often accumulate in sediments, acting as the primary repository for heavy metals in aquatic settings. Enrichment Factor (EF) quantifies the impact of both natural and human sources on trace element levels in reservoirs. Surface sediments (0–5 cm) were collected from 67 non-urban, shallow, and small-scale village reservoirs across Sri Lanka’s 3 main climatic zones (Wet, Dry, and Intermediate). Using an Inductively Coupled Plasma Mass Spectrophotometer (ICPMS), trace element concentrations were determined and compared with standard reference levels to assess sediment contamination. Overall, the average concentrations of trace elements fell within recommended sediment quality guidelines across all climatic zones, suggesting no significant anthropogenic impact from various sources. However, sediment EF analysis revealed variable values ranging from insignificant to extremely severe enrichment. Specifically, elements such as Cr, Mn, Ni, Zn, Cd, and Hg exhibited enrichment in select investigated reservoirs. This situation may stem from both natural phenomena and human activities like soil erosion, agriculture, and domestic practices. The study indicates a potential moderate to very high ecological risk based on the ecological risk potential index. Given that many reservoirs are situated in regions with intensive agricultural activities, the use of agrochemicals likely contributes to trace element accumulation in reservoirs and sediment. This research offers valuable background insights into environmental stresses, aiding future contamination assessments.