Long-term trends in sodium and chloride in the Mohawk River, New York: the effect of fifty years of road-salt application

Ecological studies have demonstrated the adverse effects of road-salt, primarily NaCl, on water quality, flora, and fauna. In this study, we quantified changes in ionic composition and solute flux of water draining the Mohawk River Basin (9103 km(2)) in New York State, from 1952 to 1998. Using various statistical, graphical, and modeling techniques, we showed that concentrations of Na+ and Cl- have increased by 130 and 243 %, respectively, while other constituents have decreased or remained constant. The use of de-icing salt on roads within the watershed, which we estimate at 39 kg km(-2) day(-1), appears to be the primary mechanism responsible for reported increases, accounting for the increase in NaCl export from 16 to 46 kg km(-2) day(-1) over the 47-year period. Moreover, despite population decline within this rural upstate watershed, increased environmental stewardship, and The Clean Water Act, concentrations of Na+ and Cl- still increased during the 1990s. (C) 2003 Elsevier Science Ltd. All rights reserved.