Road salt chloride retention in wetland soils and effects on dissolved organic carbon export

ABSTRACT

Deicing salt runoff is a cause of freshwater salinisation in many regions. Studies in uplands indicate that soil properties affect storage and movement across the landscape of salt and dissolved organic carbon (DOC). Wetlands have unique soil properties, act as buffers between uplands and aquatic ecosystems, and are major sources of DOC to surface waters, yet less is known about these dynamics in wetlands. Soil cores from three wetlands differing in vegetation and soil organic matter (SOM) were flushed with road salt treatments of 0, 2.5, and 5.0 g chloride L⁻¹ followed by no-salt flushes. Leachate was analysed for chloride (Cl_in), DOC concentration and quality (as specific UV absorbance (SUVA)), and Cl_in accumulation in soils was measured. Soils retained 3.6–41% of the added Cl_in, and there was a significant positive relationship between SOM and Cl_in retention. Salt treatment significantly reduced DOC export from only one of the three soils and had no effect on SUVA. Our findings suggest that the ability of wetland soils to buffer downstream aquatic systems against salt pollution is highly variable and likely limited to low salt concentrations, and that soil Cl_in accumulation may have negative impacts on wetland flora, fauna and biogeochemistry.

KEYWORDS:

• Deicing salts
• dissolved organic carbon
• DOC export
• freshwater salinisation
• road salt pollution
• salt retention

Acknowledgements

Parts of the text have been published before in partial fulfilment of the academic degree (M.Sc.) for author Kayla McGuire at Eastern Michigan University (EMU). Funding for this project was provided by awards to K.M. by the Eastern Michigan University (EMU) Department of Biology and the EMU Graduate School. We thank the Michigan Department of Transportation Detroit Office for providing deicing salt.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Notes on contributors

Kayla M. McGuire received her M.S. in Ecology, Evolution, and Organismal Biology at Eastern Michigan University.

Kristi E. Judd is a Professor of Biology at Eastern Michigan University. Her research interests include wetland biogeochemistry.