Accumulations of Cr, Cu, Zn and Pb in sediments under cage trout farms of Lake Ladoga

This study presents an environmental assessment of the accumulation levels of trace metals (Cr, Cu, Zn, and Pb) in the sediments of Lake Ladoga near three cage trout farms. Samples were collected at the end of an intensive fish feeding period from both the cage and reference sites. Using ICP-MS, acid-soluble and labile metal forms were analyzed. The results show that Zn had highest accumulation levels, which can be attributed to organic waste from the farms. The labile forms of Zn (up to 53%) pose serious risks of secondary pollution in the water column. However, no significant input of Cu and Pb from the trout farms was found. Elevated Cr concentrations (up to 133 mg/kg) were observed in both the cage and reference sites, mainly due to natural factors such as geochemical features of the surrounding bedrocks. The integrated Pollution Load Index (PLI) indicated moderate pollution levels, ranging from 1.0 to 1.2. These results highlight the need for monitoring Zn content under cage farms, development of sediment quality guidelines, and assessment of hydrological and geochemical conditions in aquaculture planning.