When it snows it pours: Increased chloride concentrations in the Cuyahoga River during the last half century

Road salt (NaCl, halite) use in areas with substantial snowfall has increased dramatically since the mid-20th century. However, few studies on chloride loading to the Laurentian Great Lakes or Ohio rivers have been conducted. To that end, we analyzed long-term (1972–2019) chloride data across 10 watersheds obtained as part of the Heidelberg Tributary Loading Program (HTLP) for the Lake Erie, Ohio River, and Grand Lake St. Marys watersheds and found that the Cuyahoga River, which has the greatest percent urban land use, had the highest watershed yield and mean concentrations of chloride for any of the HTLP rivers. Further, we apportioned the data seasonally to determine if river chloride levels were greater during seasons of road salt application (Winter) and snowmelt (Spring). Seasonally, winter levels of chloride exceeded the USEPA chronic water quality criteria concentration of 230 mg/L in more than half of the years of the 21st century, compared to only 1 year exceeding this value in the late 20th century. Further, road salt application is increasing with time in the Cuyahoga, Maumee, and Sandusky River watersheds. This increase is significantly and positively related to winter, spring, and fall mean chloride concentrations in the Cuyahoga River and winter mean chloride concentrations in the Maumee River. Finally, chloride-to-sulfate mass ratios (CSMR) for the Cuyahoga River almost always exceeded the 0.5 value that promotes corrosivity of metal pipes and are increasing with time. Ways to minimize the use of or even replace road salt as a deicer are warranted.