Contamination and health risks of trace metals in water and sediments of May Sieley stream, Ethiopia

Abstract

The Stockholm Convention underpins the significance of monitoring the toxic trace metals in ecosystems. This study was conducted in May Sieley stream, North Ethiopia, in 2020. The main aim was to assess the spatial-temporal variation of trace metals in water and sediments using the ICP-OES technique and further evaluate their health risks. PCA and correlation analysis identified the sources of pollution, mutual dependence, and identical behavior of trace metals. Except for Hg, the Cu, Zn, Ni, As, Cr, Cd, and Pb were high in water during the post-rainy season. The trace metals concentrations were lower in dry season sediment than in post-rainy season except for Cu and Zn. The post-rainy season showed a higher upstream concentration than the rest. There was a strong positive correlation (0.84 < r < 0.93, p < 0.01) between Ni–Cr–Cd–Pb, suggesting that the same factors influenced these trace metals. Hg correlated negatively with all other trace metals suggesting that this trace metal tends to move in a different direction. The water's Cr, Cd, Pb, and As exceeded WHO standards during the post-rain season. However, Hg and As exceeded those standards in the dry season. Pb, As, Cd, and Hg showed unacceptable non-carcinogenic levels in both groups (Q > 1). All trace elements assessed displayed unacceptable carcinogenic risk levels in both groups. The findings are significant to the policymakers in framing water quality control strategies at the river basin level.