Road deicers and salts are changing the major ion composition and total salt content in freshwater systems, especially in areas of human-dominated land use. Dissolved salts can exceed toxicity thresholds for aquatic biota and are hypothesized to disrupt nutrient retention processes in wetland sediments. Evaluation of nutrient removal capacity of urban wetlands is important for the management of eutrophication in freshwater systems. Over 23,000 acres in the Cleveland Metroparks (CMP) are embedded within the major metropolitan area of Cleveland, Ohio, including over 3,500 acres of wetlands. The proximity of CMP to urban areas provides a unique opportunity to investigate the effect of surrounding impervious surface cover on surface water chemistry in wetlands.
In the fall of 2017, surface water samples were collected from 15 urban wetlands throughout the Cleveland, Ohio metropolitan area prior to the first road salt deicer applications of the season, and analyzed for major ion concentrations. The objective of the study was to quantify major ion concentrations in wetland surface water in correlation to catchment impervious surface cover. By sampling multiple urban wetlands throughout the Cleveland metropolitan area, the study provides a survey of wetland surface water ion composition and evidence of freshwater salinization in the region.
Results/Conclusions
As the result of anion analysis, chloride and sulfate were found in elevated concentrations in most sampling sites. The average chloride concentration was 68 mg/L and the highest observed concentration was 274 mg/L. The average sulfate concentration was 66 mg/L and the highest observed concentration was 349 mg/L. Preliminary analyses suggest that percent impervious surface cover within a 500-meter buffer area is positively correlated to elevated chloride and sulfate concentrations.
These results show that chloride and sulfate concentrations are elevated in wetland surface water months after the last application of salt deicers from the previous winter. This suggests that salts may be stored in wetlands long term or alternatively, salt inputs from various sources contribute to freshwater salinization in the region. These data are single sampling moments and therefore represent a snapshot of water chemistry in the study sites. A future study will sample pore water ion concentrations to obtain a better understanding of background ion concentrations in the study sites, as well as experimentally test the biogeochemical implications of elevated ion concentrations on the phosphorus retention in sediments.