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