Untitled Essay, Research Paper

Salt Pollution As awareness for pollution increases, other forms of pollution are

defined. Almost everyone knows about toxic waste and carbon dioxide pollution, but not

many people have heard of salt pollution. Salt pollution has been on the increase since

the evolution of the automobile. With more pressure on government agencies to keep the

highway clear and safe, an increase in the use of salt has developed. It is important to

understand why salt is used and how it work as well as the environmental effects to

understand the salt pollution problem. Salt is a necessary and accepted part of the winter environment. It

provides safety and mobility for motorists, commercial vehicles and emergency vehicles.

Salt is used as the principal deicer because it is the most available and cost-effective

deicer. Rock salt is preferred because it is cheap and effective. It costs 20 dollars a

ton where as an alternative like calcium magnesium cost around 700 dollars a ton. Some 10

million tons of deicing salt is used each year in the U.S. and about 3 million in Canada. Salt is used to keep snow and ice from bonding to the pavement and to

allow snowplows to remove. When salt is applied to ice and snow it creates a brine that

has a lower freezing temperature than the surrounding ice or snow. Salt is the ideal

deicing material because it is: •the least expensive deicer

•easy to spread

•easy to store and handle

•readily available

•non-toxic

•harmless to skin and clothing

Salt pollution is broken into two main groups. Water, which includes

the effects on ground water, surface water and aquatic life and land. Most of the salt applied to the roadways eventually ends up in the

ground water. It is estimated that 30% to 50% of the salt used travels into the ground

water. Salt effect two areas of ground water, chloride concentration and sodium

concentration. Chlorides may be present in the form of sodium chloride crystals or as a

ion in a solution. Normal concentrations in the water are average around 10 mg/litre.

Concentrations found in ground water near major highways have been recorded as high as 250

mg/litre which is around the threshold of taste. The main factor with ground water pollution is the risk to human

health. The raised level in sodium in water can cause high blood pressure and

hypertension. With people who already suffer from these problem it is necessary to keep

their salt intake relatively low, they should not drink water above 20 mg/liter. Although

this is recommended, a study of private well water in Toronto showed that half the wells

exceeded this limit, twenty percent exceeded 100 mg/litre and six percent exceeded 250

mg/litre. This increase in sodium and chlorine can also cause problem with water balance

in the human body. As well as surface water, ground water is also affected by road

salting. Although the effects are not as great as ground water, they still pose problems

to the environment. The problems are based on the salt ions. The salt ions interact with

heavy metal that fall to the bottom of the body of water. An example of this is when

sodium and chlorine ions compete for mercury to bond with. This cause the release of

mercury into the water system. The risk of mercury poisoning is far greater than that of

sodium or chlorine. This increase of sodium and chlorine as well as mercury and other

heavy metal also cause changes in the pH of water. The increase of salt around bodies of water also effect aquatic life in

the area. Two main areas that are effected are osmotic regulation in fish and the death of

micro-biotic life in ponds and lakes. Most fish life can only tolerate a narrow range of

salt content in the water. The increase of salt in the water produced by road de-icing

cause freshwater fish to swell up with water. The increased salt cause a lower

concentration of water in the fishes cells. To compensate, the fishes body takes in water

to restore equilibrium. This can kill fish if the salt concentration becomes to high. Just as important as fish, microorganisms are also effected in a

detrimental way. Microrganisms are tiny organism that sustain aquatic life in all bodies

of water. They are more susceptible to the effect of salt pollution than fish. These

microorganism are at the bottom of the food chain, when they die, it doesn’t take long for

the rest of the food chain to follow. Large increase in salt concentration can cause 75% -

100% death for these microorganisms, The effect of salt is almost immediate. Most of the

organism are only one cell big and blow up in contact with increased amounts of salt. Water insects are also effected by the increase in salt in the

environment. The number of insects lowers because the inability for water insects to

reproduces in the presence of high salt concentrations. With the decreasing numbers in

microorganisms, insects and fish, it is easy to see the effect it would have on the rest

of the food chain even though other animal may be more salt tolerable. Salt pollution also is a major factor to land. It can also be broken up

into the effects on soil, vegetation and animals. The effect of salt on soil may seem relatively less important than the

other topics mentioned so far, but it leads up to more important things. The effect salt

has on soil is that it alters the soil structure. Sodium chloride actually deteriorates

the structure of the soil. This cause a decrease in soil fertility. In most cases calcium

in the soil is replaced by sodium in a anion exchange. The make the soil less usable by

vegetation. This also occurs with magnesium. This depletion of calcium and magnesium also

causes the soil to increase in alkalinity with pH of nearly 10. Normal pH for the soils

tested were between 5.4 and 6.6. High concentrations of sodium in the soil also makes the soil less

permeable. In some case soil may be encrusted in a layer of salt. As a result, moisture

content in the soil may be drastically decreased. High concentrations of salt may also

cause clay to have a decreased concentration of water. This makes the clay harder and

vegetation is less likely to grow. Although salt already effects the soil vegetation grows in, it also can

directly effect vegetation itself. Vegetation can be dehydrate to the point of death when

in contact with high levels of salt. This occurs because the osmotic stress put on the

plant make it react like it was in a drought. A decrease in roots production and burns to

leaf tips cause the plant to go into shock. Salt injury will also occur when plants come into contact with

increased levels of salt. Salt injury is when foliage damage is present by leaf burn,

die-back, defoliation and brooming. It can also cause fruit trees to have reduced quantity

and quality of fruit. This occurs with only a small amount of salt comes in contact with

the plant. It only take 0.5% of the plants tissue dry weight to become salt before the

plant reach toxic levels. Increased chlorine levels can also cause salt injury to a plant

in the same way. Salt injury also effect trees as well as small plant life. Growth of

plants in also effected by the presence of sodium and chlorine. Animal are also greatly effected by roadway de-icing. Although animals

tolerance to salt intake is quite high using salt for de-icing road presents unusual

dangers. Moose and deer become susceptible to salt pollution because of their attraction

to salt. Deer and moose are know to drink the salty water around roads. It becomes an

addiction to them and reduces the level of fear when in contact with cars and people. They

have also been found licking the gravel and the side of the road and even the road itself

in search for salt. Small animals are effected more by the toxicity of high levels of salt.

Increased levels of salt in small wildlife caused kidney hemorrhaging, depression,

excitement, tremors, incoordination, coma and death. Rabbits seem to be the most

susceptible because their inability to stop consuming salt. Household pets are also

effected. once outside, salt collects on their feet. Pets consume a lot salt when cleaning

their feet. This causes cats and dogs to get inflamed stomachs. As one can see, the effect of roadway de-icing on the environment are

tremendous. The use of salt causes a great burden to both land and water. One must weigh

the pro’s and con’s of de-icing when learn about the effects of salt on the environment.