Review of approaches to reducing adverse impacts of road deicing on groundwater in Finland

An increase in groundwater chloride concentrations was first reported 20 years ago in Finland. This discovery coincided with a sharp rise in the rate of road-salt application – the annual amount of NaCl consumed had increased from 50 t a−1 in the late 1970s to 140 t a−1 10 years later. To reverse these trends, research and development projects aimed at the reduced application of sodium chloride and improved protection of valuable groundwater resources were initiated. Several innovations, methods and practices, including the use of brine and pre-wetting, preventive anti-icing, advanced devices for salt spreading, utilization of meteorological online data and rewarding the private contractors for accurate, timely and scarce anti- and deicing, has resulted in a decline of 35% in the amount of salt applied since the early 1990s. Research on the fate and behavior of road salt in groundwater aquifers, predictions of future chloride concentrations and risk assessment have guided the risk management actions taken. Campaigns with reduced salting, use of geomembranes and recent progress on alternative deicing agents provide attractive options for further work towards sound deicing at valuable groundwater areas.