Road Salting Induces Regional-Scale Losses of Base Cations from Forested Watersheds

Water, Air, & Soil Pollution, 232:1-10

Dan Kelting & Corey Laxson

Road salt (NaCl) and acid deposition co-occur across much of North America and Europe. One such region is the Adirondack Park (AP) in New York, USA, where the effects of acid deposition have been widely studied and the effects of road salt have not. Road salt delivers 3560 Mmolc of Na to AP roads each year, which has significant potential to displace soil base cations and exacerbate ecosystem recovery from acidification. Our objective was to estimate the effect of road salt on soil base cation export for the AP. We used a simple steady state model based on estimated runoff and cation concentrations from lakes in watersheds with (n=84) and without (n=68) paved roads to estimate watershed export of Ca, Mg, K, and Na. Road salting resulted in significantly higher export for all cations, with 28, 15, 2, and 83 mmolc/m2/year more of Ca, Mg, K, and Na released, respectively, compared to watersheds without paved roads. Mineral weathering rates are insufficient to replace these lost cations and thus watershed recovery from acidification will be slower in the presence of road salt. Road salt should be included as a co-occurring stressor when assessing the impacts of pollutants on ecosystem health, not only in the AP but wherever road salt is applied.