We all know the salt-isfying feeling of spreading salt on our frozen driveways and sidewalks and watching our worr-ice melt away. What most of us don’t consider, though, is where that salt ends up. As the snow melts and the salt dissolves the briny solution enters our storm drains, infiltrates our soils, and in some cases flows directly into our streams. As salt leaves the impervious surfaces we use for transportation it no longer serves the purpose of melting snow and ice, but rather as-salts our natural systems including damage to our urban forest.
Here are just a few ways salt can harm the environment:
– In solution with water salt breaks into its constituents: Sodium (Na) and Chloride (Cl). Of the two, chloride is more mobile and harmful. Chloride can cause significant decreases in survival rates of aquatic species. In significant concentrations, Chloride interferes with sodium regulation and uptake in most aquatic organisms, and allows more salt-tolerant non-native species to out-compete less tolerant species.
– The other component of salt, sodium, enters the soil in tree pits, tree lawns, and other vegetated areas. The sodium in the soil reduces the roots capacity to absorb water and can draw water away from, and even out of the tree roots in some cases. Eventually rain will flush the tree pits of excess sodium; however the damage may already have been inflicted by the time the spring thaw and April showers come around to flush the sodium from the soil. Still, sodium continues through other systems like our groundwater where it can continue to have negative impacts.
– The briny solution of salt and water also flows into our storm drains and streams where it raises the salinity of the water. In some streams, salinity has increased by more than 100% since the middle of the 20th century, an increase which can largely be attributed to the increasing use of road salt. These changes in salinity can put pressure on ecosystems by decreasing habitability for native species.
– Dissolved road salt is often left behind on roads and sidewalks, where it can be mobilized by wind and blown onto tree limbs and leaves. The fine salt powder draws moisture from the leaves and branches, stunting growth and causing them to become disfigured. This can cause health and structural problems, but also makes for less attractive trees.
Salt is necessary for keeping our roads and walkways clear and safe, and we recognize that majority of salt is used on our public roads.
Still, there are ways to mitigate the negative impacts at your doorstep:
– Shovel or sweep snow before it becomes compacted, it makes shoveling easier and ice is less likely to form.
– Before you salt your sidewalks consider that the salt you put down this winter will enter our streams and waterways sooner rather than later.
– Apply salt in advance of a coming snow or ice storm. The pre-placed salt will become a brine more quickly and reduce the chances of ice forming in the first place.
– Use only the recommended quantities of salt when spreading salt. Adding more is unlikely to speed up the melting process, will cost you more money, and will increase the amount of salt spread to the natural environment.
– Use salt which is mixed with sand, sawdust, or other gritty components to increase traction in areas where the salt does not melt completely.
– Use an alternative to sodium chloride, such as calcium chloride, magnesium chloride, calcium magnesium acetate, or ‘pet-safe’ de-icers, which contain lower quantities of sodium, chloride, and cyanide.
– If the typical spring rain is late, you can flush tree pits, lawns and flower beds by watering them thoroughly.
To learn more about local use of road salt, and the cost of using more environmentally friendly road salts, see our blog post from January 2018 by clicking here.