Salt is a natural substance that is safe in small portions. Just ask your doctor. But in great concentrations, it can be hazardous to your health. Similarly, salt in big piles on streets and sidewalks can be hazardous to the health of birds, trees and other plants, aquatic life and the groundwater.
This photo, taken at the corner of the Boulevard of the Allies near Commonwealth Place Downtown, is what you might call a great concentration. It is a speed bump of salt right up against a drainage grate just waiting to be washed into the slurry of water that will end up at Alcosan for treatment.
The piles of salt on the sidewalk are likely to drain off in the next rain into a strip of young trees that are already tightly girded by Christmas lights.
As we approach February with hope for mercy from another bout of painful cold, we know we will continue to see those guys with wheelbarrows out there tossing and dumping mountains of salt on sidewalks and roadways for at least another month or so.
There’s a way to use de-icing road salts and there’s an obnoxious way.
The Journal for Surface Water Quality Professionals reports on the ramifications of excessive salt run-off based on several studies that conclude that excessive road salt causes all manner of ecological imbalance and disruption.
“Road salts applied to roadways can enter air, soil, groundwater, and surface water from direct or snowmelt runoff, release from surface soils, and/or wind-borne spray. These salts remain in solution in surface waters and are not subject to any significant natural removal mechanisms. Their accumulation and persistence in watersheds pose risks to aquatic ecosystems and to water quality. Approximately 55% of road-salt chlorides are transported in surface runoff with the remaining 45% infiltrating through soils and into groundwater aquifers.
“Exposure to NaCl inhibits some soil bacteria at concentrations as low as 90 mg/l, which ultimately compromises soil structure and thereby inhibits erosion control.
“Elevated sodium and chloride levels in soils create osmotic imbalances in plants, which inhibit water absorption and reduce root growth. Salt also disrupts the uptake of plant nutrients and inhibits long-term growth.
“Numerous studies attribute tree injury and decline to road-salt application, concluding that NaCl can cause severe injury to the flowering, seed germination, roots, and stems of roadside plant species. Damage to vegetation can occur up to 200m from roadways that are treated with deicing salts. Up to 50.8% of woody plant species are sensitive to NaCl.
“Damage to vegetation degrades wildlife habitat by destroying food resources, habitat corridors, shelter, and breeding or nesting sites. Behavioral and toxicological impacts to wildlife also are associated with road salts.
“Seed-eating birds may not be able to distinguish between road-salt crystals and the mineral grit their diets require. Laboratory studies of sparrows consuming salt particles at the upper limits of their known preference range reveal that ingestion of 0.25 NaCl particles (266 mg/kg) results in a breach of homeostasis; ingestion of 1.4 particles (1,500 mg/kg) may result in death (median lethal dose = 2.8 at 3,000 mg/kg). This means behavioral abnormalities can occur in small bird species with ingestion of a single salt particle and death can occur with ingestion of two particles.”
“Reports of chloride concentrations in highway runoff run as high as 19,135 mg/l. Salt tolerance of fishes ranges from 400 to 30,000 mg/l, greater than the salt concentration of seawater. A seven-day exposure of 1,000 mg/l is lethal to rainbow trout (NRC, 1991).”
“Evergreen plants near roadways are especially vulnerable to salt spray damage. Melt water containing salts can leach into nearby soil where plants can take up the sodium and chloride ions as they resume growth in the spring. This uptake may cause stunted growth, desiccation and dieback. The accumulation of salt in soil over successive years may result in progressive plant decline and eventual death.
“Sodium chloride that leaches into the soil may contaminate nearby wells or groundwater supplies. Runoff may enter surface waters. Also, sodium chloride is highly corrosive to cars, buildings and some paved surfaces.”
Reminder News reports on two organically-based de-icing alternatives — calcium magnesium acetate (CMA) and potassium acetate. They are biodegradable and pose little harm to vegetation but only if used as directed. Too much of these substances can run into surface water and reduce oxygen levels.
Remember that a little goes a long way. And we have a long way to go before the trees start to bud.