Modelling the properties and stability of meromixis induced by saline mine waters in two boreal lakes

Mine waters are a significant point source stressor for aquatic environments. Acid mine drainage has long been considered a big environmental issue, but recent studies suggest that the salinity of mine waters may also be harmful particularly to small, dimictic lakes which are abundant in the boreal region. The denser saline mine waters may cause a shift in the mixing regime of a lake, leading to a permanent stratification of the water column, ie meromixis. As the demand for raw materials increases, mining companies, policy makers, and environmental regulators need to be more aware of these harmful effects of saline mine waters. In this study, two lakes receiving drainage waters from closed copper-nickel mines are investigated. Lake Valkeinen and Lake Sortavalanjärvi are situated in Eastern Finland near the mines Kotalahti (active 1959-1987) and Laukunkangas (active 1986-1994), respectively. The waters from …