Chloride Pollution

salt

Last week we all had to deal with the rather large amount of snow that fell on the metro area. Whether you walk, drive, or bike, slippery roads and sidewalk affected you in one way or another. As a native of the state commonly referred to as “Minnesnowta” I am familiar with the ubiquitous solution of applying salt to increase the coefficient of static friction. But what happens to the salt once it has successfully melted the ice were does it go and what effects does this consistent use have on important pieces of our natural environment and infrastructure?

Sodium chloride or salt is the states current solution to ice. A recent study by the University of Minnesota engineering department calculated that over 350,000 tons of salt is poured on roads, sidewalks, and parking lots in the Twin Cities metropolitan in an average winter. This number is on the rise because of the increasing number of roads and the move away from the use of sand, which was clogging storm drains in some areas. Chloride is a natural pollutant that is harmful to Minnesota wildlife and contaminates one of our states most valuable natural resources water. When chloride is poured onto our roads it melts the snow as long as it’s above fifteen degrees. After this melting has occurred the chloride travels with the water eventually entering rivers and lakes. Chloride unlike other pollutants, which eventually end up in the gulf, sinks to the bottom of the water source accumulating year after year. This accumulation eventually dehydrates microorganisms and small insects disrupting the natural food chain.

Besides its negative effects on the natural environment chloride also impacts or infrastructure. Chloride ions can penetrate and deteriorate concrete, and the reinforcing rods or bridges and parking structures. This eventually leads the structure being compromised at a much faster than originally intended. One study done in Madison Wisconsin estimated that the overall cost of chloride on infrastructure and the automobile industry at over 16 billion dollars a year.

In Minnesota organizations like the Minnesota Pollution-Control Agency have been measuring and analyzing the use of sodium chloride. Their goal is to reduce the harmful effect of chloride while not sacrificing public safety. The goals of the PCA are to educate the general public about the use and effect of sodium chloride. They are also working with the department of transportation trying to reduce and regulate the use of sodium more efficiently. Ultimately the goal is to find a safe displacement material for salt, but for now it seems all we can do is use it wisely.

 

http://www.wsdot.wa.gov/research/reports/fullreports/741.1.pdf

 

http://www.startribune.com/local/118547564.html?page=1&c=y&refer=y

 

http://www.pca.state.mn.us/index.php/water/water-types-and-programs/minnesotas-impaired-waters-and-tmdls/tmdl-projects/special-projects/metro-area-chloride-project/road-salt-and-water-quality.html

 

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