Tuesday, March 10, 2015

Salt Contamination - Causes and Effects


Salt contamination is when an area of land becomes over salinized, causing a negative impact on soil fertility. In order to get their required hydration, plants use the process of osmosis where ground water is taken in from the typically lower salt concentrated soil to the higher salt concentrated plant cells. When this balance is thrown off it can have bad consequences like water uptake being drastically slowed down, and plants becoming so concentrated with toxic levels of salt that they show signs of dying like dry patchy leaves and defoliation. This is a phenomenon that can either occur naturally or through human activity, known as primary or secondary salinity respectively. Primary salinity happens through means like salt marshes, salt lakes, and through natural disasters like tsunamis that suddenly introduce heavy amounts of salt water into the ecosystem. Of greater concern is secondary salinity which can be caused by poor irrigation practices and through using mass amounts of salt as a means of deicing roads in cold climates.

Visual identifiers of salt contamination include the formation white patches and land cracking.
Salt contamination is commonly present in in places that are suffering from low rainfall and irrigation must be used to supply crops with the necessary amount of water. Poor drainage of irrigated land, use of water that is already heavy in salt, and over irrigating that causes roots to be waterlogged and inhibits their ability to exclude sodium intake are all farming practices that can lead to salt contamination.

Dousing roads with heavy amounts of salt in cold climate areas is an effective way of keeping them free of ice and snow because the salt lowers the freezing point of the water, thus making driving conditions much safer. The EPA estimates that 15 million tons of sodium chloride are used on U.S. roads every year and suggests using alternatives methods when possible. Calcium chloride, magnesium chloride, and potassium chloride are all effective at even lower temperatures but their higher price point makes them a less desirable option.  Once the soil along roads and freeways becomes contaminated, plants become overly saturated and lose their ability to take in water and other nutrients and the balance of the soil can be thrown off to a degree that can lead to erosion, posing a threat of pollution in nearby bodies of water. Preventive measures to these problems range from properly maintaining salt piles on the sides of roads to the use of acetate based deicers, although these deicers are more expensive and don’t tend to work in temperatures lower than 23 degrees Fahrenheit. 

It is easy to pass off salt as a commonly occurring substance that can’t cause harm to our planet and its ecosystems but it is definitely a cause for concern. Preventive measures may be more expensive from a money point of view but, in the long run, not implementing them could prove more costly in other ways.

Added by Will Baker

Sources:




http://www.dpi.nsw.gov.au/__data/assets/pdf_file/0018/310365/Irrigation-salinity-causes-and-impacts.pdf

Images:

http://a01019949a-wongwingsang.blogspot.com/2015/02/soil-acidification-and-heavy-metal.html

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