Hold the salt for the sake our lakes

Get out the shovels and snowblowers!  Most of Minnesota received 6-12 inches of snow in the past week, which means the season of snow removal from our roads, driveways and sidewalks is here. 

To make the roads and sidewalks safer, we usually use some form of road salt and/or gravel.  When salt is applied to ice and snow it creates a brine that has a lower freezing temperature than the surrounding ice or snow.  Salt is good for de-icing because it is readily available, inexpensive, easy to spread.  Salt is also necessary for winter travel in Minnesota.

So what happens to that salt after the ice on the road melts?  Because chloride from dissolved road salt is not removed from water by chemical or biological processes, all of the chloride applied as road salt is expected to reach surface water or groundwater. Once chlorides enter the ground or surface water, they never go away.

The chloride in road salt is toxic to aquatic life in moderate to high concentrations. In low concentrations, it can interfere with reproduction and survival of young.  When dissolved in water, anticaking agents in the road-salt mixture dissociate and release a form of cyanide that is extremely toxic to aquatic creatures and interferes with a fish's breathing mechanism.

Chloride also is toxic to plants, both aquatic and terrestrial.  In soil, salts reduce the availability of water to plants, and significantly increase water stress during spring and summer months. This effect has been referred to as chemical drought. Salts deposited directly on foliage may also burn and kill the affected parts, or the entire plant.  This is commonly observed where salts from winter maintenance damage evergreen trees and shrubs adjacent to roadways.

Monitoring of surface and ground water continue to show increasing trends in chloride and sodium levels although the levels are not yet a human health hazard.  Storm water monitoring in Madison, WI and Canada during snowmelt has identified surges of extremely high levels of chloride. These surges have the potential of harming fish and other aquatic organisms as they enter local lakes and rivers.

So what can you do about this issue?  The first step is to be aware of the effects of chloride in the environment.  This issue is applicable whether you live on a lake or in town.  It is important to understand that the water that flows through storm sewers in town typically does not get treated before entering the natural environment.  Also, think about the parking lots where you work.  If you work at a private business, the business probably has the responsibility to keep its own parking lot and sidewalks free of ice.

Salt is still the cheapest de-icer to use, and is necessary for driving and getting around in Minnesota winters.  When you salt your driveway and sidewalk try and use as little as you can.  As much as possible, try to sweep up residue and dispose of it at the Becker County Transfer Station.  When the roadside snow piles melt in the spring, it's better to spread the sand and grit on turf than to sweep it off the curb into the street.

Until next week, enjoy the lakes!

Moriya Rufer is the Lakes Monitoring Program Coordinator for RMB Environmental Laboratories in Detroit Lakes, 218-846-1465, lakes.rmbel@eot.com.