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of water. As we all know, ice forms when water reaches a temperature of 32° Fahrenheit; when salt is added to the water, that temperature drops. A 10% salt solution freezes at 20° F, and a 20% solution freezes at 2° F. When you sprinkle salt on a sidewalk or roadway, the salt dissolves into the liquid water in the ice and lowers its freezing point, so the ice melts.
This may be all well and good, but are you aware of how much salt we use annually? According to the EPA, over 11 million tons of salt are thrown on our streets and highways every year. The real problem arises when the ice melts, since its primary destination is, by default, our ground and surface water. Salt also acts as a desiccant – stressing salt-intolerant vegetation, and as a corrosive – effecting both metal and concrete. As salt is extremely soluble, it is easily transported with stormwater along with melted snow and ice runoff into our public water supply, much of which comes from ground and surface water.
Since most of us aren’t that fond of drinking salt water, it would behoove us to start looking for some alternate solutions to salting our roads and sidewalks. There are five chemicals commonly used as de-icers – and the alternatives that claim to be environmentally friendly are usually a combination of these, blended to minimize environmental risk while optimizing performance and remaining cost friendly. Understanding their properties will help you make informed decisions on melting ice in your own backyard. Calcium chloride (CaC12) often outperforms other products at lower temperatures. Producing an exothermic reaction, it gives off heat as it melts and attracts moisture directly from its surroundings, enabling it to dissolve ice faster. Sodium chloride (NaCl), also known as rock salt, has been used as the de-icer of choice since the 1940s, but loses its effectiveness when temperatures drop below 25° F. This is the culprit seeping into our groundwater. Potassium chloride (KCl) is a naturally occurring material also used as a fertilizer and a salt substitute for food. Its high salt index gives it the potential to burn foliage and inhibit rooting, so its use is limited. Urea (NH2CO2 NH2) is synthesized from ammonia and carbon dioxide and is primarily used as a fertilizer. As a de-icer, it has a lower burn potential than potassium chloride. Calcium magnesium acetate is a salt-free melting agent made from dolomitic limestone and acetic acid. It does not harm plants or concrete and is effective in environmentally sensitive areas.
Any de-icer can be mixed with equal parts sand to minimize the adverse environmental effects and provide grit for added traction. Check the ingredients on your de-icer of choice to see how environmentally friendly it is, or better yet, let’s hope for a milder winter this year.
KIM FRISBIE, Freelance Writer
