Winter Wonderlands are pretty to watch and enjoy with a lot of waterproof and warm clothes, but they also have their little challenges. For example, lots of snow can lead to a lot of compacted snow, that turns into ice, making Winter Wonderlands turn into Winter Slipperylands with all the accidents and issues that ensue. A common practice to reduce ice and its dangers is the use of de-icing salts. In this post, I want to talk about de-icing salts and how their excessive use can lead to unwanted consequences in our natural spaces and the organisms that inhabit them.
What are de-icing salts?
De-icing salts are most commonly sodium chloride salts, a non-food-grade version of the salts we use in our kitchens. Because high concentrations of sodium chloride in the soil lead to many environmental issues, alternatives exist, including potassium chloride, calcium chloride, magnesium chloride, and calcium magnesium acetate (CMA). Note, however, that although these alternatives are considered more environmentally friendly, they are just less environmentally harmful than sodium chloride.
All these salts generally reduce the freezing temperature of water, leading to water (ice) melting at temperatures at which it would have been frozen in the absence of the salt. Although this is a very simple and effective way of reducing or preventing ice formation, the intense use of salts leads to accumulation in the soil and water table, which is worrisome in many ways.
What happens if salts accumulate in the soil and water?
As we apply salts, they eventually dissolve in the water we are trying to de-ice, in moisture in the soil, and/or with precipitation. This salt then accumulates in the soil and in the water bodies into which the area drains. Both these processes can have strong effects on the health of the environment and the survival of many species.
Soils with high salt content are generally more toxic for plants (herbaceous and woody) that are not otherwise adapted to salty environments, leading to a negative effect on plant health and survival in regions where salts are applied intensely and regularly. For example, high salt content in the soil reduces the ability of plants to capture water and other nutrients and to tolerate low temperatures and drought. Further, when exposed to these high concentrations, plant tissues can also become enriched in salts, which can lead to cell dehydration and an inability to perform photosynthesis.
Reductions in plant diversity and health can also lead to other, more indirect effects. They can affect the ability of insects or other animals to find appropriate host plants to develop on and nest in and can lead to an increase in pest outbreaks, which are associated with reductions in the general diversity of the plant communities.
Besides accumulating in the soil, salts can also dissolve in the water and end up in the water bodies close to where the salts were applied. When salt use is very intense, it can lead to a significant accumulation of salts in lakes, streams, and rivers, which has demonstrated negative impacts on their organisms. Fishes, amphibians, insects, aquatic plants, and microorganisms display specific ranges of salt tolerance, and given that freshwater is not normally enriched in salts, the rise in its concentration leads to an inability for these organisms to survive under those conditions. Further, because some of the de-icing salts have phosphates, their runoff into the Chesapeake Bay can increase phosphate pollution and its negative effects on the survival of Bay ecosystems. Finally, it has been shown that high salt concentrations in water promote the survival of salt-tolerant organisms, one of which is mosquitoes. This can lead to larger mosquito populations in areas where there is intense and regular use of de-icing salts.
Does this mean that I can’t use de-icing salts anymore?
No, this means that because salts are not neutral to our environment, we should use them thoughtfully and cautiously. For example, shoveling or plowing snow before it becomes packed and icy is a great way to maintain ice- and salt-free spaces. Also, only applying salts when you’re sure that a storm will arrive is another way to reduce salt applications and its negative effects on the environment. Finally, if salts are needed, a good strategy is to apply them lightly and only to high-traffic areas. Don’t treat areas where there is no traffic. It has been shown that de-icing salt grains spaced 3 inches apart can readily and efficiently remove ice. Applying salts more heavily does not improve the de-icing action but increases salt concentration in the soil and water bodies.
Finally, if you do need to use salts on a regular basis, consider planting native salt-tolerant plants. For ideas, refer to this Salt-Tolerant Native Plants page from Virginia Cooperative Extension Master Gardeners in Northern VA. These plants will grow in Maryland, increase the biodiversity of your green space, and, in some cases, capture some of the salts in the soil, further reducing salt runoff.
To learn more:
- Maryland Department of the Environment: learn other strategies to reduce salt use.
- U. of Minnesota Extension: learn how to prevent or adapt to high salt concentration in soils.
- Chesapeake Bay Program: learn how de-icing salts affect the health of the Chesapeake Bay.
By Anahà EspÃndola, Associate Professor, Department of Entomology, University of Maryland, College Park. See more posts by AnahÃ.
Anahà also writes an Extension Blog in Spanish! Check it out here, extensionesp.umd.edu, and please share and spread the word to your Spanish-speaking friends and colleagues in Maryland. ¡Bienvenidos a Extensión en Español!