Why test for electrical conductivity, acidity and alkalinity?
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Why test for electrical conductivity?
Electrical conductivity is used as an indirect measure of salinity. The greater the concentration of salt in water, the better it conducts electricity. By measuring electrical conductivity, we can infer the salinity of the water.
Salts occur naturally in the environment and are released through geological processes such as weathering of rocks. Salts are highly soluble. When salts are dissolved in water they are able to move and concentrate in the environment. Generally speaking, salinity increases as water evaporates or moves down through a catchment.
Salinity can be a major factor in determining the plant and animal species occurring in an aquatic environment. Changes in salinity can adversely affect the composition of freshwater communities.
Large and rapid changes in salinity are usually the result of human activities. Increases in the salinity of fresh water can result from:
- land clearing or chopping down trees
- excess watering of farm crops
- industrial discharge
- mining activities
- sewage discharge.
Why test for acidity and alkalinity?
Acidity is measured on the pH scale. This scale ranges from 0 to 14, where values less than 7 are acidic, 7 is neutral, and values greater than 7 are basic.
Most aquatic organisms are adapted to living within narrow pH ranges around neutral. The optimal pH range for most Australian freshwater organisms is from 6.5 to 8.0.
Shifts in pH can damage aquatic animals’ gills, skin and eyes, which then makes them more susceptible to disease. If the pH remains outside the optimal range, aquatic organisms will become stressed and it can cause a decrease in the number of species living in a waterway. Changes in pH can result in the toxicity of pollutants increasing.
Factors that affect the pH of freshwater include:
- geology
- aquatic plant photosynthesis - raises pH
- aquatic plant respiration - lowers pH
- decomposing organic matter - lowers pH
- temperature - affects water chemistry and photosynthesis
- mining leachate, cleaning products and chemicals discharged into waterways.
