Environment free essay sample

â€Å"Road salt† is a common term used for some chloride salts, including sodium chloride (NaCl), which are used as de-icing agents on roads. The application of these de-icers on roads and other impervious surfaces in North America during winter months was in practice since the 1960s. The amount of snow fall is so high in these areas that snow and ice management becomes very essential to prevent road accidents, to maintain a continuous flow of traffic and to ensure safe pedestrian travel during winter months. Sodium chloride is the most commonly used de-icing agent (Road salting). Sometimes, it can be used along with some anti-caking agents like sodium hexacyanoferrate (II) or sand and grits. These elements like sodium, chloride, ferrocyanide and other impurities seep into our environment when the snow or ice melts, and poses a threat to water bodies, soil, vegetation and large number of species sustaining on them (Environmental, Health and Economic Impacts of Road Salt). De-icing of the roads is, beyond a doubt, very essential, as it saves lives by preventing accidents, but there are more alternatives other than the use of road salt which I will also explain. This research paper explains how road salt acts as a de-icing agent and what factors promote its widespread use. The primary aim of this paper is to give an elaborate idea about how road salt damages our environment. It also provides a list of some safer alternatives which can be used for de-icing. Road salt does not allow the ice or snow to adhere to the pavement and form a hard pack. Sodium chloride can readily depress the freezing point of ice, so that the ice starts melting. Salt crystals can pull water molecules from ice crystals to form brine. The formation of brine facilitates the process of meting of ice. However, the rate of melting depends upon the temperature at that time. At temperatures below 15 ° F, sodium chloride cannot form solution efficiently; hence its efficiency is reduced. In fact, even if sodium chloride is applied at high rates at these temperatures, it cannot melt snow or ice effectively. Hence, people involved in road management should acquire knowledge about the current and expected temperatures (Road Salt and Water Quality, 1). Sodium chloride also prevents the formation of ice on roads. Depending upon the conditions, road salt is applied as either liquid or solid medium. When compared with other salts, sodium chloride is less expensive with an average cost of $50 $60 per ton. Some other characteristics like easy availability and ease in handling and storage make it a more commonly used de-icing agent. Salt as such is non-hazardous to the environment and does not degrade to produce harmful substances. Problem of bio-accumulation is also not associated with sodium chloride. Addition of an anti-caking agent like sodium hexacyanoferrate (II) in low levels (below 100mg/kg), prevents the salt from caking, and makes it readily usable during the winter months (Road Salt and Water Quality, 1) (De-Icing the Environment). When dissolved in melting ice or snow, road salt gets dissociated into 40 percent sodium ions (Na+) and 60 percent chloride ions (Cl-). Chloride settles down in the bottom of the water bodies because of its density and increased mobility. Chloride is completely soluble and mobile. At a concentration of 230 mg/l and above, chloride is toxic to aquatic life and affects vegetation and wild life. Chloride gets accumulated in the long run as no natural process can break it down or metabolize it. Chloride cannot be absorbed by the vegetation. Gradual accumulation of chloride has damaged many water bodies, by changing the taste of the water. On the other hand, sodium (Na+) ions are subjected to ion exchange. These ions can either bind to the negatively charged soil particles, hence altering the soil chemistry, or be taken up in biological processes. They promote the release of nutrients into the groundwater and surface water, hence affecting the aquatic environment. Anti-caking agents like ferrocyanide can also impact the human life and environment, when used in large quantities. Exposure to sunlight and action of certain types of bacteria stimulates the release of cyanide ions from these additives. This compound has been added to the list of toxic pollutants by USEPA in 2003. Soil gets impacted at every stage of de-icing. Improper maintenance of salt piles by road management people may contaminate the soil and vegetation growing on the road side, as they become saturated with road salt. In fact, wherever soil comes in contact with road salt for a long time, the soil chemistry gets altered by the exchange of sodium ions with other positively charged ions like, calcium, magnesium, and potassium. These exchanged ions are released into the ground water. This ion exchange also increases the mobilization of metals. The soil permeability is altered as the soil becomes impervious and water infiltration is blocked. The overall fertility of the soil gets reduced and the soil pH and stability are also affected. Excess of salt damages the soil biota, especially some bacteria, which participate in the structuring of the soil. As a result, the soil is subjected to erosion and increases the sediment in runoff (Environmental, Health and Economic Impacts of Road Salt). The primary impact of salt on plants is by the creation of the osmotic imbalances, due to which water absorption is inhibited and root growth is reduced. The uptake of nutrients by the plants is also affected, hence affecting the long term growth of the plants. Accumulation of chloride for a long time in plants leads to osmotic stress and the plant tissues get dehydrated similar to a drought-like condition. The germination of grass and wildflower seeds on the road side is also affected by the high salinity. As the penetration of air and water is hampered, the growth of the new plant shoots is also affected (Wegner and Yaggi). Deposition of salt on plants may add to the weight and promote tissue damage by local dehydration. The plants may physically break at these damaged points. Splashing and spraying of salt on the foliage of the plants leads to scorching of leaves, defoliation and dying of twigs. Degradation of vegetation indirectly affects the wild life, by damaging their habitat, food resources, breeding or nesting sites and shelter places. Mammals like deer and moose consume the salt crystals on the roadway, to remove their sodium deficiency. Strange behavioral abnormality like loss of fear of humans and vehicles is noticed in these animals when they drink salt-rich water. As a result, these animals succumb to vehicular accidents. Over consumption of salt by these animals increases the salt toxicity in their blood and tissues (Environmental, Health and Economic Impacts of Road Salt). Birds often consume the salt crystals as they are similar to seeds. Even small quantities of salt are toxic to birds, leading to their death. Studies have shown that even a single salt crystal can lead to behavioral abnormalities and these birds are more vulnerable to car strike (Wegner and Yaggi). Surface waters, rich in sodium chloride, could also be toxic to many aquatic species like fish, amphibians, insects, and macro invertebrates. An elevated level of chloride affects the growth, survival and reproduction of many species. Some toxic metals get released from the sediments in the presence of salt in water. As a result the oxygen gets reduced, which harms the growth of aquatic species. The distribution and cycling of oxygen and nutrients gets affected. The fresh water fish are mainly affected by the increase in the salt concentration and a drastic change in the species diversity is noticed (Environmental, Health and Economic Impacts of Road Salt) (Wegner and Yaggi). The salt on the highway seeps into the ground water in a number of ways like during runoff from the highways, migration of dissolved salt along with water to water table, during the melting of ice, etc. The presence of high salt content not only changes the taste but is also harmful to people suffering from hypertension, as they are advised to take low quantities of sodium. A concentration of sodium above 20 mg per liter of water is considered to be harmful by US Environmental Protection Agency (EPA). Presence of chloride at high levels is not injurious to health, but the taste and odor of the water gets affected. Due to increase in salt concentrations, many water bodies and wells have been abandoned (Environmental, Health and Economic Impacts of Road Salt) (Wegner and Yaggi). Conductivity of water is enhanced by the presence of chloride ions and this increases the corrosion of bridges, buildings, etc. Many parts of the vehicles like brake linings, bumpers and the body get corroded. Huge cost is involved in the protection of the corrosion and repair of the damaged parts. Even though the use of road salt is hazardous, the use of better management practices can minimize the loss to the environment. Some other non-hazardous ways of treating snow and ice on roadways are: †¢ Salt or other de-icing chemicals should not be used to burn snow, rather snow or ice should be removed with mechanical devices like shovel, plow, etc. †¢ A thin layer of snow can be easily melted with the help of deicing agents. Hence, during the snow storm, a shovel should be used to remove as much of snow as possible. Later, the area should be properly swept, so that the remaining snow does not form ice making the area slippery. Ice on the surface can be scraped with the help of a flat hoe. These practices would minimize the use of de-icing agents. †¢ The equipment used for spreading should be calibrated so that optimum quantities of salt is released, minimizing the environmental impacts. †¢ Knowledge about the temperatures at which different materials used for de-icing are most effective is advantageous. †¢ Pre-wetting the salt with brine reduces the application rates by 20 percent. †¢ Proactive application of de-icing chemicals before the accumulation of snow or ice minimizes the quantity of chemicals required for de-icing. A mixture of salt and sand should not be applied as they work against each other. †¢ Sensitive areas like public water sources should be identified and safer alternatives to road salt should be used in these areas. †¢ Identification of salt sensitive vegetation and minimization of the use of de-icing agents containing chlorides can prevent the damage to the vegetation. †¢ During the storage of sand and salt, care should be taken to store them on impervious surfaced area, which is covered and has adequate drainage facility. This will prevent the run-off of these substances and accumulation in the water bodies. During loading, care should be taken to prevent the spilling of salt or sand. By better management one can minimize the loss to the environment and the search of safer alternatives might decrease the environmental impacts completely. Some chemicals have been used as road salt alternatives, but they were either used for a short duration or in limited quantities. The long term impact of these chemicals is yet to be studied. Some of these chemicals are: Calcium chloride – It is the second most commonly used de-icing agent and it can perform well at lower temperatures. It can be directly applied in liquid form and prevent the bonding of snow or ice to the pavement. However, some disadvantages like, difficulty in storing and handling, higher cost, environmental impact of chloride, tendency to corrode metals, have limited its use. Potassium chloride – It is a naturally occurring material but can damage concrete, damage the vegetation by burning leaves and inhibit plant growth It can prove to be hazardous to environment due to the presence of chloride. These disadvantages have limited the use of this material for de-icing (Road Salt and Water Quality, 4). Magnesium chloride – It shows faster action in comparison to sodium chloride and is effective in very cold conditions (at a temperature of 5 °F). However, incorrect application might lead to slippery condition and also shows corrosive action on metals. . Urea – It is a fertilizer and when used in huge quantities for de-icing, it can increase the nutrient content of the water systems, which might lead to eutrophication in future. It gets rapidly broken down into ammonia which gets released into the environment. It also shows corrosive action (Road Salt and Water Quality, 4). Potassium acetate – This material is biodegradable and has shown less environmental impact. It shows high performance and is less corrosive in nature. Except mild irritation after inhalation, no other health hazards have been recorded. This material depletes the oxygen from the aquatic ecosystems temporarily and might stimulate the growth of the plants. However, further research is required to ascertain the efficacy of the potassium acetate as road salt. Calcium Magnesium Acetate – This material is prepared by mixing limestone with acetic acid. It shows less negative effects on aquatic biota, soil and vegetation. The impact of this material on ground water has been noted to be less, when compared with sodium chloride. The main limiting factor associated with the use of potassium acetate and calcium magnesium acetate, is their huge cost. As they are costly and less accessible, they are presently being used on bridges as they show less corrosive action and in environmental sensitive areas. Research promoting the huge production of these materials can reduce the cost and prevent environmental hazards. Simultaneously, the long term impacts of these materials should also be analyzed (Wegner and Yaggi). Some natural substances show the capacity of de-icing, but generally they cannot be used commercially on a widespread manner. But initiatives taken from each home, depending upon the availability of these substances, can lessen the environmental impacts to some extent. These substances include: Sand –Many properties like inexpensive nature, no harmful impacts on the environment, easy sweeping capacity and tendency to provide traction, make it a better alternative to salt. Brick sand can better serve the purpose as it is granular and coarser than the regular sand. It is easily available at building supply stores. Sand can absorb sunlight and warm the ice or snow lying beneath. This will facilitate the faster melting of ice (Road Salts Alternatives). Ashes – People having a wood burning fireplace can use ashes as it is economical and convenient to use. Ashes also absorb sunlight and provide traction, hence increasing the rate at which ice melts. Cat litters – It is one of the expensive options but if it is available at home, it can be used (Road Salts Alternatives). Agricultural byproducts – Some agricultural byproducts obtained from corn have lower freezing point due to which they delay the process of the formation of ice crystals. However, they are not efficient in melting the snow or ice. These products can be used to prevent the formation of ice (Road Salt and Water Quality). De-icing is very essential to treat many roadways so everyday life can carry on, but it should not be at the cost of environment. We should be taking measures to preserve our environment, not damage it. Which is why we need to look for and use safer and environmental friendly alternatives for de-icing. C/R B. B