The scientists used historical records over the last 30 years and direct measurements to quantify changes in baseline salinity and predict what would happen if trends of urbanization and deicer use continue. By accumulating in groundwater and aquifers, some water in the northeastern U.S. already exceeds the recommended standard for the protection of aquatic life of 250 mg/l of chloride. In developed areas of Baltimore, chloride concentrations were already high enough to induce mortality in aquatic animals and alter wetland plant composition. During the winter months chloride in urbanized areas can increase in waterways to as high as 5 g/l which is equivalent to 25% of seawater concentrations.
Dr. Kaushal of the University of Maryland Center for Environmental Science Appalachian Laboratory said, "There is a direct connection between the rate of construction of new roadways and parking lots and the quality of our fresh water. In particular, we have not paid enough attention to rapid changes in human development and deicer use in watersheds that supply our drinking water and provide habitats for many species of aquatic life."
Dr. Peter Groffman, of the Institute of Ecosystem Studies, notes, "It is surprising and significant that the long-term record shows that salinity concentrations are going up, even in places where the amount of salt applied has not increased. Concentrations are high in the summer, not just in the winte r when salt is applied to melt snow, suggesting that salt is accumulating in the environment."
If current trends continue over the next century, many surface waters could become unfit for human consumption and toxic to some aquatic life throughout the region. Reversing the problem involves reducing the creation of new roads and subsequent use of deicers. Despite being a major aquatic pollutant, road salt is not currently regulated as a fresh water contaminant.