Des chercheurs de l'Université de Toronto à Scarborough sont arrivé à la même conclusion que plusieurs autres: le sel que l'on épand sur nos routes contamine nos cours d'eau. La pollution diminue le nombre de poissons, nuit à la diversité aquatique et détruit les milieux humides: ils ont trouvé des niveaux étonnament élevés d'E.coli, de plomb, de chlorure et d'aluminium. Le plus grand coupable de cette destruction? Le sel épandu sur la 401 à quelques kilomètres de là.
L'impact de l'épandage de sel pendant quelques semaines durant l'hiver se fait sentir pendant toute l'année: les 3,600 tonnes de sels de route dissous aboutissent dans l'étang l'hiver à cause du ruissellement de 4 ruisseaux durant les fontes, et des eaux de surfaces qui deviennent saturées de sel avec le temps.
Les autorités de la ville de Pickering sont au courant de cet état de fait depuis des années et c'est pour cela qu'ils ont demandé pour cette étude. Ils avaient demandé une étude semblable en 2003 et avaient eu le même constat. En 2001, Environnement Canada recommandait que les sels de route soient considérés comme une substance toxique à cause de leur impact sur les écosystèmes. Cela ne s'est pas concrétisé. À la place, le gouvernement a adopté un code de pratique volontaire que la plupart des municipalités ont signé volontier.
La plupart des municipalités continuent d'utiliser le sel sur les routes bien qu'ils savent les dommages qu'il cause, mais c'est la solution la moins dispendieuse. Le sel est la solution utilisé à toutes les sauces parce qu'il est efficace dans toutes les conditions météorologiques durant l'hiver, mais la pollution est surtout évidente durant l'été. C'est un polluant qui se fait heureusement diluer dans le lac Ontario, mais il ne fait qu'agraver un problème complexe qui impacte sur la qualité de l'eau puisée pour alimenter le robinet d'une population nombreuse.
Tant que nous continuerons d'épandre du sel sur les routes à tout vent, il y aura toujours des problèmes.
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"Road salt poisoning Pickering waterfront
Highway 401 runoff is main culprit, study says.
The tiny particles of salt that blanket the roads during harsh winter storms bring temporary relief to drivers racing down icy roads, but wreak havoc on vulnerable ecosystems a short drive away. In some cases, road salt is destroying them altogether. An extensive five-year study published this week by researchers at the University of Toronto Scarborough found that Frenchman’s Bay, a coastal inland bay in Pickering considered by many to be the “jewel” of the city’s waterfront, is a stew of harsh contaminants with levels far exceeding provincial water standards.
The pollution has already reduced the number of fish, lowered the aquatic diversity and is destroying the provincially significant wetlands around the north end of the bay. Swimming among the few fishes are “startling” levels of E.coli, lead, chloride and aluminum, said Nick Eyles, professor of geology at UTSC, who led the study. The biggest culprit, he says, is the road salt being sprinkled every winter on Highway 401, just a few kilometres north of the bay.
“There is a year-round impact of putting salt on for just a few weeks in the winter,” said Eyles, who studied the lagoon in the summers and winters of 2002 to 2007. “Just imagine the impact that is having on the fish in the inner northern parts of the bay.” His team determined that 3,600 tonnes of dissolved road salt ends up in the small lagoon in the winter mostly from direct runoff in four creeks during warmer thaws, and from groundwater that has become saturated with the salt water over time.
The highway accounts for more than a quarter of all road salt that ends up in the bay, but covers just over one per cent of the area, he said. “There is a lot of salt put on these roads, and there is almost nothing to prevent it going directly into the creeks,” he said. Metals, oils from the highways and animal waste that is carried along the creeks also contribute to the chemical mix, he said.
Pickering’s city officials say they have been aware of the impending ecological crisis at Frenchman’s Bay for years. They hired Eyles and his team to assess the impact of urban development on the bay in 2003 – and saw similar results. “There is concern that the bay is regressing,” said Richard Holborn, division head of engineering services with the city. Since then, the city began working to create a Frenchman’s Bay storm water management master plan to improve both the water quality, flooding and erosion issues. In the long-term, there may be plans to restore and enhance the wetland in the north end of the bay back to health, he said. The plan is expected to go to council for approval in April.
The study, published in the journal Sedimentary Geology, is the latest in extensive research that points to the hazards of salt on the environment. In 2001, Environment Canada recommended road salt be considered a toxic substance because of its negative impact on ecosystems. That never happened. Instead, the federal government adopted a voluntary “code of practice,” which most municipalities have signed on to. They are expected to release a five-year assessment on the code’s effectiveness on the local environment this year.Almost all municipalities agree that road salt is damaging, yet it continues to be used because it is the cheapest option available. Over the past five years, many municipalities have made an effort to reduce salt use and find cleaner options like beet solution and sand, said Mark Rabbior, a spokesman with the provincial Ministry of Environment
But salt is used as a default option, in part because it can be used regardless of temperature fluctuations and severity of winter weather. The problem is, salt runoff into streams, ponds, and rivers is no longer just a winter problem. Although all salt is dispersed in the winter, the water quality is worse in the summer – when Frenchman’s Bay is busiest, said Eyles.
“In the summer, you get algae blooms, and you get this milky brown water as a result. That cuts off sunlight that reaches the bottom of the lagoon, and so vegetation can’t grow, and fish don’t come into the area,” he said. “If you look at the lake from above, you can see a plume of dirty water coming out of the Bay into Lake Ontario.”The only thing “saving it now” is that it is diluted by water from Lake Ontario. But at the same time, he adds, the polluted bay is adding to the “chemical load” going into the body of water that makes up our main drinking source.
“This is not sustainable,” he said. “We might be fine now, but what about in the next few decades,” he said. “If we can reduce the amount of salt used, we might be able to do something. But if we continue to dumping salt willy-nilly, there will be always be problems.”
Excerpts from article written by Noor Javed in thestar.com here: http://www.thestar.com/news/canada/article/774620--road-salt-poisoning-jewel-of-pickering-waterfront
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