Helena Joyce
Road salt is a common deicing agent used to prevent the formation of ice on roads and other paved surfaces. While it helps to improve safety for vehicles and pedestrians, its usage has been associated with various environmental concerns, particularly water pollution. The accumulation of salt in the environment, including in freshwater lakes, rivers, wetlands, and groundwater, has led to concerns about its potential impact on ecosystems and human health. This raises the question of whether road salt can be considered a non-point source of pollution, which refers to any source of water pollution that does not meet the legal definition of point source as outlined in the Clean Water Act.
| Characteristics | Values |
|---|---|
| Definition | Any source of water pollution that does not meet the legal definition of "point source" in the Clean Water Act |
| Impact | Threat to freshwater ecosystems, human health, and wildlife |
| Examples | Salt used for de-icing roads, chloride de-icers |
| Negative Effects | Osmoregulatory stress, changes to food webs, water contamination, toxic to aquatic wildlife, corrosion of drinking water infrastructure |
| Alternatives | Beet wastewater, cheese brine, pickle juice, potato juice |
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What You'll Learn
Road salt is a pollutant of freshwaters
Salt is a common mineral that has played a significant role in notable historic events, such as Gandhi's Salt March, an act of civil protest against colonial oppression. Today, salt is still widely used, particularly in the chemical industry and as a road deicer. While it helps create safer conditions for vehicles and pedestrians by lowering the freezing point of water, it also poses a significant threat to freshwater ecosystems.
Road salt is a leading cause of freshwater salinization in regions with heavy road salt use. When roads are salted, the salt moves directly through storm sewers or gradually percolates through soils, eventually making its way into freshwater lakes, rivers, wetlands, and groundwater. This process is particularly prevalent in colder, humid regions of North America, where road salt usage is high and winters are harsh.
The sodium and chloride ions in road salt interfere with water molecules' ability to bond together and form ice. As a result, salt increases the salinity of freshwater bodies and can have detrimental effects on aquatic life. At high concentrations, salt can be fatal to some aquatic animals, and even at lower concentrations, it can have toxic effects on aquatic wildlife, including plankton and fish.
The ecological changes caused by road salt affect water quality and can lead to the formation of salty pockets near the bottom of lakes, creating biological dead zones. These changes can also impact food sources and disrupt amphibian osmoregulation. Additionally, high chloride levels can cause oxygen depletion in water bodies, creating an oxygen-deficient layer that is harmful to fish and other aquatic life.
The impact of road salt pollution extends beyond freshwater ecosystems. Groundwater sources can also be contaminated, posing risks to human health. In East Fishkill, New York, for example, a multi-year study found that over half of the private drinking water wells sampled exceeded EPA health standards for sodium. Furthermore, road salt spray can damage vegetation near roadways, and it can impair roadside soils by displacing minerals or absorbing water, leading to physiological drought.
Given the environmental and health risks associated with road salt pollution, it is essential to explore alternative deicing methods and practices that are more environmentally friendly. Some communities are already seeking environmentally safe alternatives, such as beet wastewater, cheese brine, pickle juice, and potato juice, which have shown promising results in lowering the melting point of ice without the same ecological impacts as road salt.
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Salt impacts the health of aquatic life
Salt has a significant impact on the health and survival of aquatic life. Firstly, it is important to note that salt concentrations in water bodies can be affected by both natural and anthropogenic (human-induced) factors. Natural salinity fluctuations occur in estuaries, where seawater mixes with freshwater from river systems. Certain species, such as salmon and sea trout, have adapted to these variations as part of their life cycle, migrating between seawater and freshwater environments.
However, human activities, such as road salting, have become a significant source of salt pollution in freshwater ecosystems. The salt used to de-ice roads is released into the environment, percolating through soils or entering storm sewers, eventually reaching freshwater lakes, rivers, wetlands, and groundwater. This has led to the widespread salinization of these freshwater habitats, which are particularly vulnerable to salt pollution due to their susceptibility to changes in salinity.
The increase in salt concentration has direct and indirect effects on aquatic organisms. Directly, it causes osmoregulatory stress, impacting the ability of organisms to regulate their internal salt and water balance. This is particularly harmful to freshwater fish, as elevated salt levels can disrupt their osmoregulation and lead to health issues. Additionally, salt pollution can alter the flow of energy and materials through food webs, affecting the entire aquatic community.
Moreover, salt concentration has been linked to the reproductive behaviors of certain aquatic species, such as eels, crabs, and shrimps. Changes in salinity can influence the timing and success of their reproductive cycles, potentially impacting population dynamics. While some aquatic organisms can tolerate a range of salinity levels, others are highly sensitive to even slight decreases in salinity, such as cnidarians and cephalopods, which may perish under such conditions.
In conclusion, salt pollution, particularly from road salt, has significant impacts on the health and survival of freshwater aquatic life. It disrupts osmoregulation, alters energy flows in food webs, and influences reproductive behaviors. With freshwater ecosystems being particularly susceptible to salinization, it is important to address this form of non-point source pollution and explore alternative de-icing methods or improved practices to protect the health of aquatic organisms and maintain the ecological balance of freshwater environments.
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Salt can cause corrosion of drinking water infrastructure
Salt is a well-known cause of corrosion in drinking water infrastructure. The use of road salt has been identified as the primary contributor to chloride and sodium contamination in groundwater. This is due to the fact that salt, specifically sodium chloride (NaCl), is applied to roads and paved surfaces to prevent the buildup of ice, creating safer conditions for vehicles and pedestrians.
The process by which salt contributes to corrosion is as follows: when salt comes into contact with water, it binds to the water molecules, forming a mixture known as brine. This brine then seeps into the ground and makes its way into groundwater, including wells and other sources of drinking water. The presence of chloride in the brine increases the corrosiveness of water by lowering its pH level. This heightened corrosiveness affects the thousands of miles of pipes that supply drinking water, causing galvanic corrosion, dezincification of plumbing materials, and other premature plumbing failures.
The impact of road salt on drinking water infrastructure was studied in New York, where chloride levels were found to vary based on proximity to sources of road salt. Private wells located near road salt storage facilities or within 30 meters of a major roadway exhibited the highest chloride levels. Consequently, 70% of well users surveyed in the affected areas stopped drinking their well water due to aesthetic and safety concerns.
The study also revealed that increasing chloride concentrations in water led to increased galvanic corrosion and dezincification, resulting in heightened metal leaching and thinning of pipe walls. These issues can have severe implications for water infrastructure, leading to plumbing failures and potential health risks for those relying on contaminated water sources.
The findings underscore the necessity of including the potential damage to public and private drinking water infrastructure in future discussions and planning related to road salt management.
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Salt is a threat to freshwater ecosystems
Salt pollution is a growing concern for freshwater lakes, rivers, wetlands, and groundwater, particularly in regions with heavy road salt use. As salt accumulates in the environment, it poses a threat to both ecosystems and human health. Research has shown that road salt is the dominant source of increased salinity in colder, humid regions of the northeastern United States. This salinization of freshwater can strip it of its "fresh" designation, as it is the only pollutant capable of doing so.
The ecological implications of road salt pollution are far-reaching. Elevated salt concentrations directly impact species through osmoregulatory stress and community-level changes in energy and material flow through food webs. Salt can be fatal to some aquatic animals, and even at lower concentrations, it can have sub-lethal effects, such as weakening individuals and increasing egg mortality rates. High chloride levels can also inhibit the growth and reproduction of aquatic species, impact food sources, and disrupt amphibian osmoregulation. For example, young fish that feed on plankton may not thrive if their food source is affected by high chloride levels.
In addition to its ecological impacts, salt pollution also affects water quality and water-related infrastructure. Excessive chloride levels can accelerate the corrosion of drinking water infrastructure, compromising groundwater sources and private water supplies. This has led to an increased interest in environmentally friendly alternatives to road salt, such as beet wastewater, cheese brine, pickle juice, and potato juice, which have been shown to be more effective at lower temperatures while reducing the amount of chloride applied to roads.
The threat of salt pollution to freshwater ecosystems is a complex issue that requires further research and education to reform practices and protect both freshwater and human health. With the exponential increase in road salt usage over the past decades, it is crucial to address this emerging threat and explore alternative solutions to maintain safe road conditions during winter.
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Salt can damage vegetation near roadways
Secondly, salt-laden water from runoff can also harm plants. When salt is applied to roads, it dissolves in water to form a brine, which helps melt ice and prevent further ice formation. This brine can run off the pavement and reach the roots and foliage of adjacent vegetation, causing injury. High-salt concentrations in the water can also change the flow of energy and materials through food webs, impacting aquatic organisms and ecosystems.
The type and amount of salt applied play a role in the damage caused. Sodium chloride (rock salt) is commonly used for de-icing due to its low cost and effectiveness, but it can be very harmful to plants. De-icing compounds without chloride, such as urea, are safer alternatives. The volume of freshwater applied also matters; while salts are easily leached by water in well-drained soils, they accumulate in poorly drained soils, increasing the potential for vegetation damage.
The distance of plants from treated pavements is another factor. Plants within the "`spray zone'" of moving vehicles, about 15 feet and more if downwind, are more susceptible to salt injury. Additionally, the direction of surface-water flow should be considered, as it affects the dispersion of salt-laden runoff.
To mitigate salt damage to vegetation, several strategies can be employed. Physical barriers, such as burlap, plastic, or wood, can be used to protect plants. Salt-tolerant plants can be chosen for areas near roads, driveways, and sidewalks, although it is important to note that salt tolerance does not mean injury-free. Combining salt with other materials like sand, sawdust, or cinders can provide traction while reducing salt use. Using de-icing materials with salts other than sodium chloride, such as calcium chloride or magnesium chloride, can also reduce plant injury, although they are more expensive. Proper application and targeting of salt away from landscape beds or lawns can help minimize the impact on vegetation.
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Frequently asked questions
Road salt is a substance used to prevent or eliminate ice on roads and other surfaces. It is usually sodium chloride, the same as table salt but coarser.
Salt works by lowering the freezing point of water, creating safer conditions for vehicles and pedestrians.
Yes, road salt is a non-point source of pollution. Non-point source pollution is defined as any source of water pollution that does not meet the legal definition of "point source" in the Clean Water Act. Salt pollution is a threat to freshwater ecosystems, and road salt is the leading cause of widespread salinization of freshwater lakes, rivers, wetlands, and groundwater in regions with heavy road salt use.
The environmental impacts of road salt include water contamination, harm to aquatic life, vegetation damage, and soil impairment. High chloride levels caused by road salt can be toxic to aquatic wildlife, inhibit the growth and reproduction of aquatic species, impact food sources, and cause oxygen depletion.
Yes, some communities are exploring environmentally safe alternatives to road salt, such as beet wastewater, cheese brine, pickle juice, and potato juice. These alternatives have been shown to be more effective at lower temperatures and reduce the amount of chloride applied to the road.
