Metal Contamination in Littoral Sediments: Ecological Risks in Mining-Impacted Lakes | Metallförorening i sediment i litoralzonen: Ekologiska risker i gruvpåverkade sjöar
2025
Sundström, Ellen
Mining activities have long lasting impacts on freshwater ecosystems, with legacy contamination from mine tailings posing ongoing risks even after they’ve been closed down. This study investigates metal contamination in littoral sediments of lakes in northern Sweden near the former Laisvall lead (Pb) and zinc (Zn) mine, comparing three polluted and three reference lakes. Sediment samples were analysed for metal concentrations, organic matter (OM), and grain size, and ecological risk was assessed using the Probable Effect Concentration Quotient (PEC-Q). In addition to this, relationships between PEC-Q values and benthic macroinvertebrate indices including Ephemeroptera, Plecoptera, and Trichoptera taxa (%EPT), %Chironomidae, average score per taxon (ASPT) and the Shannon Index were made. The results in this study showed significantly elevated metal concentrations in contaminated lakes, with PEC-Q values exceeding the threshold for probable biological effects (PEC-Q>2) in both normalized and non-normalized forms. High PEC-Q values were also associated with high abundances of EPT taxa, while Chironomidae dominated in reference sites with lower risks. This suggests that habitat factors, such as coarse substrate and OM content, may mediate biological responses. Although TOC normalization adjusted PEC-Q scores, it did not alter the correlation with biological indices, which is likely due to the overall magnitude of contamination. These findings highlight the value, but also the limitations of PEC-Q as a risk assessment tool. Metal concentrations alone may not fully explain community composition, which emphasizes the need for integrating habitat data and biological assessments when evaluating ecological risk in metal-contaminated lake systems.
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