Glittering landscapes; days filled with sledding, skiing, snowboarding, and tubing; cozy nights spent nestled be the fire with a good book… With all of the glorious activities and sights to experience, one might questions what there is to suggest that winter is not the perfect wonderland that we hold it to be in our minds. However, we all know of the storms that frequent the northern portions of the North American continent, blanketing the region with freezing rain, ice, and snow, and we are equally aware of the losses of power and mobility which result from these mighty displays of weather. We stock up on bread, milk, and toilet tissue; gather together our shovels; and prepare countless bags of road salt and deicing chemicals for treatment of our driveways and roads.
Once the storm hits, we either hunker down and cozy up to wait out the storm or brave the whirling tempest to clean off travelways- and finally let loose those tons of road treatment compounds we use none-too-gingerly. Yes, the road salts may splash onto your shoes and vehicle, but these compounds make further splash in our waters, where they impact aquatic life, as well as drinking. ground, and surface water quality.
Sodium Chloride
One of our most popular food amendments has another use sourced in the treatment of roads in instances of wintry conditions. Sodium chloride is predominantly used for the melting of snow on roads and walkways and has for long been used in states across the United States. Because the compound dissolves entirely when introduced to water, its components, the sodium and chloride ions, separate from one another completely and remain within their water source. The prolonged effects of these ions result from their difficulty of removal from water sources. The Minnesota Stormwater Manual explains that the chloride ion is not easily extracted from its solvent and therefore does not willingly participate in selective precipitation, which is used as a primary mode of water treatment.
As prior stated, melted wintry weather makes its way into runoff and groundwater upon melting, and from there heads into local bodies of water and drinking water sources. Of immediate concern are the high concentration of ions present within close proximity to treated roadways. Even over brief amounts of time, soil substrates are altered by the presence of sodium and chloride ions such that their permeability and density are affected such that increased erosion occurs. This creates the issue of loose soil presence in groundwater sources in addition to that of difficult-to-treat compound contaminants. Once present within drinking water, these seemingly-benign ions wreck havoc, contaminating drinking wells for long durations and endangering the health of those who cannot consume large quantities of sodium.
While slightly less issue is posed by the dissolved ions in running streams, their impact is more heavily felt in stiller bodies, like ponds and lakes. Of particular note is the effect of sodium chloride in the turning process of lakes; because the compound is much more massive than the water molecule by itself, a heavy “saline layer” forms at the body’s bottom. This results in the inability of the body’s convection current from pulling this bottom-most layer of liquid from its depths, and further causes issues for lakebed-dwelling organisms which are smothered by the lack of oxygen and high ion concentration within the water. (For more information about the effects of deicing compounds in lake waters, please head to The Minnesota Stormwater Manual’s article “Environmental impacts of road salt and other de-icing chemicals” and scroll to the section entitled “Surface Waters,” or AskSmithsonian‘s article entitled “What Happens to All the Salt We Dump On the Roads?“)
Further pressures are felt by biotic life beyond the stagnation of lake current. Many organisms which reside in aquatic conditions require highly balanced and distinct environments that are thrown askew by increases in salinity and toxic metal release catalyzed by the presence of chloride ions. Alterations begin at the very bottom of the food chain with bacteria and other microorganisms on which fish and higher-order predators rely and slowly creep their way through the hierarchy. This further permits the possible harm of humans by way of consumption of fish or other aquatic organisms.
Other Deicing Agents
Sodium chloride is clearly not the only chemical utilized in the treatment of road and pathways in events of winter weather. Other popular compounds include those that are acetate- or carbohydrate-based.
Acetate-based compounds, in particular calcium-magnesium acetate, dissolve when introduced to water in a process which uses oxygen; this deprives organisms inhabiting the water source from the resource and can inspire asphyxiation.
Due to the natural inefficiency of carbohydrates themselves in deicing measures, they are often combined with other compounds to ensure effective treatment; however, many of the carbohydrates utilized are founded in more natural sources (like beet juice). While little formal research has been completed, there is speculation that the decay of the carbohydrates (once they are unleashed into the environment) can contaminate waters and other environmental pieces by way of produced nutrients.