For Melting Ice and Protecting Waterways, Less is More
Salt, or sodium chloride, lowers the freezing point of water. On its own, water freezes at 32 degrees Fahrenheit. When salt is applied, it lowers that freezing point to about 15 degrees. This sodium chloride along with chlorides containing magnesium, calcium, or potassium are typically used as deicers. When these compounds are done doing their job of melting snow and ice, they dissolve and run off hard surfaces with the ice and snow melt to accumulate in nearby soils or the local waterbody. The various compounds, but particularly the chloride, can be toxic to aquatic life in freshwater. In saltwater environments like the brackish Chesapeake Bay, animals aren’t likely to react as negatively to additional chloride, but for the critters in our rivers and steams, it can spell bad news.
A study published in the Proceedings of the National Academy of Sciences suggests that salt ions are changing the chemistry of freshwater streams across the nation. The study, which analyzed five decades of data from U.S. Geological Survey river and stream monitoring sites, found that salt ions increased in 37 percent of the study sites. Salty, alkaline soils and freshwater not only pose issues for wildlife—they can cause big problems by corroding bridges and pipes, polluting drinking water supplies, leaching metals and nutrients, and even decreasing carbon sequestration. Salt that stays on the land can be harmful to plants as evidenced by dead or dying, seemingly burned-out vegetation found along many roadways. This affects the ability of these plants to support valuable wildlife.
The salt you add to your sidewalk can have a cascade of negative impacts.
So what can you do you do to avoid an icy fall down your front steps? Less is more.
According to the Salt Smart initiative, the first step is shoveling, clearing all snow before it turns to ice. Then twelve ounces of salt—about as much as would fill a coffee mug—is enough to treat a 20-foot-long driveway or about 10 squares of sidewalk. Make sure to distribute salt evenly, not in clumps. And when the snow clears, you can even sweep up left over salt and reuse during the next freeze!
While alternatives to chloride-based ice melts like calcium magnesium acetate (CMA) exist, they may come with their own negative environmental impacts. Be aware that store-bought salt products may include additives or impurities that include trace metals that can also be toxic. Some salts may also contain an anti-caking device such as forms of cyanide, another toxic chemical. So read the label. Know what’s in the products you chose to use and apply them according to their directions.
Sand is a popular go-to alternative to salt for improving traction on slick surfaces. But it can also find its way into streams where it can smother habitat important to fish and other aquatic life.
Regardless of which type of snow or ice melt you choose, proper application is key to preventing damage to vegetation and polluting nearby waters. As with the use of fertilizers, using just enough ice melt to get the job done, at the right time and in the right locations, is the key.
