What is Salinity?
Salinity is the presence of soluble salts in soils or waters. It is a general term used to describe the presence of elevated levels of different salts such as sodium chloride, magnesium and calcium sulfates and bicarbonates, in soil and water. It usually results from water tables rising to, or close to, the ground surface.
To most people, the word salinity refers to the situation when the quantity or availability of salts in the landscape causes problems with soil and water quality, agriculture, the built and natural environment, and biodiversity. The salt is mainly sodium chloride (NaCl) or common table salt. There are two kinds of soil salinity: irrigated land salinity and dryland salinity. Dryland salinity is the movement of salt to the land surface with groundwater, occurring on land that is not used for irrigation, and it causes the most widespread damage. The amount of salt in Australia is not increasing but is being brought towards the surface: before European settlement and extensive farming this salt was stored safely in the earth below the depth of plant roots.
Salinity was originally defined as the amount of dissolved salts present in seawater. Early measures typically involved weighing the solids left when seawater was dried. Unfortunately, drying is not only tedious but it is relatively inaccurate because some of the solids are driven off as gases before all of the water is removed. Consequently, scientists have developed a wide array of techniques for measuring salinity, including conductivity, refractive index and density. While all of these are suitable for hobbyists, conductivity is recognized by scientists as being the most precise, and this article will provide an understanding of the how’s and why’s of this technique. It is beyond the scope of this article to describe why one is interested in controlling salinity in a marine aquarium. Suffice it to say that all organisms have a range of salinities that they can exist in, and a smaller range in which they thrive. Once that range is established, one need only keep them within it. If a
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 salinity is sometimes expressed as a percentage as well. A number of devices are designed to be used in the assessment of salinity, as the salinity of a substance is a very important characteristic. Many people think of salinity 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 in
Salinity is the accumulation of salt in land and water to a level that impacts on both the natural and built environments. The impacts of salinity can affect native plants and animals, aquatic and terrestrial ecosystems, agricultural crops and pastures, water supplies and infrastructure such as roads and buildings. Salinity occurs naturally in many parts of Australia because of a combination of biophysical conditions. In particular: • a geological and climatic history that has generated and stored high levels of salt; • its present day arid climate and relatively flat landscape which promote salt accumulation and concentration in specific areas; and • long-term climate trends driving changes in groundwater levels and salt mobilisation. Salinity is a process inherent in the Australian landscape; however, human activities have accelerated the process of salt mobilisation and accumulation. Salinity is often classified into several different types based on the broad cause as described belo
