Overview of the environmental impact of salting roads

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Each year between 750,000 and 1.5 million tonnes of salt are dumped on the roads of France to clear snow or melt ice. Around 80 euros per tonne, the annual cost of salting in France exceeds 100 million euros each year (including equipment and personnel). In addition to a very high cost, salting roads has adverse externalities on the environment and public health. Overview of the situation of salting roads.

 

What are the ingredients of the salt that is spread on our roads ?

 Addited with sand and anti-caking agents, the salt used every cold snap can be of two types :

  • Sodium chloride, the most used in France and North America, usable up to -7 ° C ;
  • Magnesium chloride, the worst impacting on environment due to the high quantity needed to be efficient, usable up to -25 ° C ;
  • Calcium chloride, the more efficient and fast-working on de-icing at low temperatures but poses a risk of burns, usable up to -30 ° C.

 

What are the details to know for a good use ?

Salt can be spread preventively or curatively, but in any case it must be ensured that the outside temperature is adequate to the salt used.

In addition, too much salt application is counterproductive because the reaction lowers the temperature of the road causing the formation of ice. It will also be necessary to follow the weather in order to apply the salt only if it is necessary.

 

Despite the Environment Agency estimated that the use of de-icing salt is so rare and episodic it may not have major long-term consequences on ecosystems, studies has found that annual salting of roads is likely to accumulate in nearby lakes and wet areas inducing a continuous increase in chloride concentration in the aquatic environment.

What consequences for neighbouring wildlife are already faced ?

The salinization in North America is progressing to the point that it should – at the current rate – become deadly for many lake species by 2050. Some aquatic species are also sensitive to salinity, such as salmon or toads, according to the WWF.

Another example : If salting in the City of Toronto continues at the same rate, the city’s water table will be unsuitable for consumption in just 20 years.

 

This observation naturally invites us to study alternatives to salting roads, such as sandblasting, peeling gravel, wood chips, the most effective being of course to resort to manual or mechanical snow removal.

While waiting for effective additives to be studied, it will also be necessary to limit our salt intake by observing the meteorology and recommended dosages as well as possible.

Sources :

Is gritting the roads bad for the environment ?, Leo Hickman, The Gardian (published in January 2005 the 14th).

Ken W. F. Howard, Stephen Livingstone ; Transport of urban contaminants into Lake Ontario via sub-surface flow ; Urban Water, Volume 2, Issue 3, Sept. 2000, Pages 183 to 195.

A Sourcebook for Conducting Biological Assessments and Developing Biodiversity Visions for Ecoregion Conservation, Volume II : Freshwater Ecoregions, Robin Abell, Michele Thieme, Eric Dinerstein, and David Olson Conservation Science Program WWF-US.

A propos de Manon BOUREL

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