Road Salt Runoff in Freshwater Constructed Wetlands: A Year in the Life
Road salts, brines, and other de-icers are used to melt snow and ice on roads and sidewalks. The runoff resulting from this process is high in salt ions such as sodium, chloride, calcium, magnesium, and potassium. These ions end up in our waterways, and contribute to the problem of increasing salinity in freshwater ecosystems. In this study, two constructed freshwater wetlands near Kent State University were monitored for one year by measuring conductivity with in situ conductivity probes, concentration of road salt ions in surface water samples, and salt content in plant tissue. This data set allowed us to assess seasonal trends in road salt runoff as well as to estimate a mass balance for road salt ions in these systems. We found that the wetlands were a considerable sink for road salt ions over the course of the year. Moreover, the degree to which each wetland retained the ions was not the same. The wetland with continuous flow and comparatively less pore space retained less of the ions than the intermittently flowing, deeper wetland. This notable imbalance in the salt budget of these wetlands, despite their differences in flow regime, is symptomatic of unsustainable road salt practices in these and similar watersheds. Should this pattern continue, there could reach a point where the wetlands could no longer store the influx of salt ions each year, resulting in a large release of saline water into downstream freshwater ecosystems. Long term studies like this are critical to addressing these issues, and these findings can be used to inform management decisions not only in Kent, Ohio, but also in any city to better balance ecosystem function with public safety.
Weatherholt, Riley M. and Kinsman-Costello, Lauren E.(2019). Road Salt Runoff in Freshwater Constructed Wetlands: A Year in the Life. Environmental Science & Design Research Initiative. Paper 52.