The sight of snowplows and salt trucks is a common sight in Canada">

Road Salt It's use and impact on the Spanish River The sight of snowplows and salt trucks is a common sight in Canada, especially so for the more northern regions such as Espanola and area. Large amounts of salt are spread onto the frozen, snow-covered highways and streets to keep drivers safe from sliding off the road. While many citizens have concerns regarding the effects of salt on their vehicles, there is a growing number of people questioning the impact on our rivers and lakes. The focus of this newsletter is to touch on the chemistry of road-salt, explore the potential impact of road-salt on the Spanish River, and compare the concentrations measured in our river to other rivers. While there are several types of road salt used on Canadian roads (calcium chloride, magnesium chloride, and potassium chloride), the most common form of road salt is sodium chloride, simply a coarser form of common table salt. When dissolved in water, sodium chloride breaks down into sodium ions and chloride ions. Elevated levels of sodium are generally considered more of an aesthetic issue (due to taste if used for drinking water), however there is currently debate on this issue due to the ion's link to the development of hypertension and hypernatraemia. A guideline of 200-mg/L sodium is generally accepted, however the European Economic Community has set their guideline at 20 mg/L. According to the Great Lakes Information Network (GLIN), high chloride levels can lead to the release of heavy metals into the water column from the sediments. Furthermore, GLIN states that up to 10% of aquatic organisms are 'harmed' by prolonged exposure to chloride concentrations greater than 222 mg/L Simply knowing what concentrations are harmful is only half of the equation; the other half is relating that information to actual concentrations in the Spanish River. The chart below summarizes three years data collected by Domtar during their river surveys, and compares that to both the average lake/river concentrations, and those levels which are considered harmful. Substance Concern Limit Major Rivers Range* Spanish River Sodium (Na) 200 mg/L 1.3-25 mg/L 14.9 mg/L Chloride (Cl) 222 mg/L 0.6-25 mg/L <10 mg/L * Soil and Water Conservation Society of Metro Halifax While there does not appear to be a persistent problem with salt in the Spanish River, it would be very difficult to determine the impact during the spring melt. However, even it one assumes the worst (much higher levels during the freshet), there does not appear to be any sustained impact.