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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.