Abstract: The use of deicing agents during the winter months is one of many stressors that impact stream ecosystems in urban and urbanizing watersheds. In this study, a long-term dataset collected by citizen scientists with the Missouri Stream Team was used to evaluate the relationships between watershed urbanization metrics and chloride metrics. Further, these data were used to explore effects of elevated chloride concentrations on stream invertebrate communities using quantile regression. While the amount of road surface in a watershed was a dominant factor in predicting the maximum chloride measurement, the median chloride concentration was also strongly related to the amount of medium-to-high density development in the watershed, suggesting that non-municipal salt use is an important contributor to increases in baseflow chloride concentrations. Additionally, chloride concentration appears to be one of the many factors that impact invertebrate density and diversity measurements, with decreases in invertebrate diversity corresponding with the U.S. EPA water quality criteria. Our findings suggest that the use of chloride-based road salt on municipal roads as well as in non-municipal settings is contributing to a loss of diversity and density of aquatic invertebrate communities in urban regions.

Abstract: The use of deicing agents during the winter months is one of many stressors that impact stream ecosystems in urban and urbanizing watersheds. In this study, a long-term dataset collected by citizen scientists with the Missouri Stream Team was used to evaluate the relationships between watershed urbanization metrics and chloride metrics. Further, these data were used to explore effects of elevated chloride concentrations on stream invertebrate communities using quantile regression. While the amount of road surface in a watershed was a dominant factor in predicting the maximum chloride measurement, the median chloride concentration was also strongly related to the amount of medium-to-high density development in the watershed, suggesting that non-municipal salt use is an important contributor to increases in baseflow chloride concentrations. Additionally, chloride concentration appears to be one of the many factors that impact invertebrate density and diversity measurements, with decreases in invertebrate diversity corresponding with the U.S. EPA water quality criteria. Our findings suggest that the use of chloride-based road salt on municipal roads as well as in non-municipal settings is contributing to a loss of diversity and density of aquatic invertebrate communities in urban regions.

Abstract: The use of road salt to increase roadway safety during winter storms releases high concentrations of chloride into urban and suburban stormwater. This stormwater flows into nearby streams, resulting in concentrations of chloride that can exceed water quality standards intended to protect aquatic life. As chloride pollution is not readily filtered by soil or plants, mitigation will require reductions in the amount of salt used. In this study, cities in St. Louis County, Missouri, U.S., were used as a test case for brining as a best management practice (BMP) to reduce salt use relative to the standard practice of spreading solid rock salt. The practice of brining involves the dissolution of road salt in water and the application of the resulting brine solution to roadways in advance of a forecasted winter storm. During the winters of 2016-17 and 2017-18, stormwater runoff from residential areas was monitored in paired cities to determine if the availability of brining as a BMP for salt application on residential roads would result in a decrease of chloride in stormwater and, therefore, a decrease in chloride reaching urban streams. The use of brining by city governments resulted in a 45% average reduction of chloride loads conveyed to streams, demonstrating that brining is a highly viable BMP for local municipal operations. Publication DOI: https://doi.org/10.1021/acs.est.9b02864

Abstract: The use of road salt to increase roadway safety during winter storms releases high concentrations of chloride into urban and suburban stormwater. This stormwater flows into nearby streams, resulting in concentrations of chloride that can exceed water quality standards intended to protect aquatic life. As chloride pollution is not readily filtered by soil or plants, mitigation will require reductions in the amount of salt used. In this study, cities in St. Louis County, Missouri, U.S., were used as a test case for brining as a best management practice (BMP) to reduce salt use relative to the standard practice of spreading solid rock salt. The practice of brining involves the dissolution of road salt in water and the application of the resulting brine solution to roadways in advance of a forecasted winter storm. During the winters of 2016-17 and 2017-18, stormwater runoff from residential areas was monitored in paired cities to determine if the availability of brining as a BMP for salt application on residential roads would result in a decrease of chloride in stormwater and, therefore, a decrease in chloride reaching urban streams. The use of brining by city governments resulted in a 45% average reduction of chloride loads conveyed to streams, demonstrating that brining is a highly viable BMP for local municipal operations. Publication DOI: https://doi.org/10.1021/acs.est.9b02864