What is Salinity?
Salinity refers to the dissolved salt content of a substance like soil or water. It may be measured in a number of ways; parts per thousand and parts per million are the two most common measurements, and it is sometimes expressed as a percentage as well. A number of devices are designed to be used in the assessment, as the salinity of a substance is a very important characteristic. Many people think of it in terms of salty water, but high salinity in soils is also a major issue.
In ocean water, salinity is more properly termed halinity, since a group of salts known as halides are dissolved in the ocean. Some people are surprised to learn that ocean halinity varies around the world, and that deeper water as a general rule tends to be saltier. The movement of water around the world's oceans is known as thermohaline circulation, a reference to the factors of temperature and halinity which lead to differing densities. Some scientists have expressed concerns about interruption of the thermohaline circulation system.
In other types of water, salinity is a perfectly accurate measure. Generally, when the level is less than 500 parts per million, the water is considered to the fresh water. Brackish water is somewhat saltier, with levels of up to 30,000 parts per million. Saline water has a salinity of between 30-50,000 parts per million, while even saltier water is considered brine. The dissolved salt content of water can be measured with a variety of tools, most of which can be used in the field by scientists.
Since salts have a profound impact on many living organisms, water salinity is an important concern for biologists. In an estuary, for example, a zone where salt and fresh water mix, the levels vary widely, supporting a wide range of flora and fauna. If this balance is disturbed by something like a storm surge or a flood of freshwater, it can have unpleasant results for some of the animals that call the estuary home.
In soils, salt can prevent crops from growing, a major concern in several countries where soil salinity is on the rise. Levels in soil are generally increased through poor land management, such as overfarming and excessive use of chemical fertilizers, compounded with extremely dry conditions. If the rise in salinity is not checked, the land can become useless for farming, and it may take decades to recover.
Besides salinity, there are much more toxic levels of minerals to measure in the ocean water and other areas where salt can affect the quality of life. One thing to remember is that the salinity levels will actually effect the way that other toxins in the soil or water actually can harm people and plants. Because salt is a significant chemical that many take for granted it is imperative that we at least consider the interaction with sodium chloride and other toxins present.
Hopefully the over saliniation of water by humans will actually counteract the harmful toxins that we also corrupted our land with.
I will be honest, I find it incredibly hilarious when people freak out about the amount of salt that we are adding to our oceans. Does it not occur to these people that the reason the sea is salty is because it has salt in it to begin with. marine salinity has yet to be proven that it is effected by man's actions and I highly doubt that we as humans even have the means to control such a monstrous body of salt water as the great oceans of the world.
Hopefully someday, scientists will be able to effectively determine the direct effects of our actions on our world's waterways and oceans. Until then all we can do is try and not mess things up.
@vogueknit17, I think you are completely right about your assessment in people's knowledge of the salinity in the oceans. This is a major risk to the marine life that people do not take seriously. Salinity tests have recently shown that salt is a major factor to the contamination of bay water and other areas where our fresh water systems are meeting the ocean.
This unnatural increase in salt levels perhaps could be explained by the fact that we use heavy fertilizers and other soil amendments to our agricultural fields that when irrigated will eventually make their runoff to the ocean through underground rivers and other man made means of water transport.
This means that the nutrients that we are spreading onto our ground does have an effect on the overall environment and it is something that we need to seriously discuss if we actually care about our Earth.
I have heard salinity is on the rise due to the increased attempt at irrigation in the southwest and other areas where there are frankly too many people in areas without enough naturally occurring water. At the same time, salinity control is one of many environmental issues that most people know very little about, if anything.
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