Potentially Toxic Elements in Spring Water of the Northern Ladoga Region: Speciation, Migration Intensity, and Sources

The abundant water resources of the Northern Ladoga region are subject to anthropogenic pressures and geogenic influences associated with the distinctive geochemistry of the bedrock. Spring water is widely used for domestic purposes, including drinking. These waters are characterized by low salinity with a dominant Ca–HCO3 facies often enriched in SO42−. Geochemical signatures reflect sulfide and fluorite mineralization, particularly in springs near Pitkäranta, and are associated with elevated concentrations of Zn, Mn, Rb, Y, Cd, Mo, U, and Cu. NICA-Donnan speciation modeling indicates extensive complexation by dissolved organic matter (DOM) of Fe, Ni, Cd, Cu, Pb, U, Th, Co, and Al, with particularly stable complexes of Cu, Pb, U, and Th. Positive matrix factorization (PMF) modeling indicated that mining and its associated industrial heritage are the primary sources of potentially toxic elements, followed, to a lesser extent, by transport and road infrastructure, as well as natural sources.