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pH
(Adapted from The Streamwatch Manual – 3rd Edition)
Definition
pH is a measure of the relative acidity or alkalinity of a substance. pH is expressed on a log scale of 0 (acid) to 14 (alkaline), with the neutral point at 7.
Why test pH?
The pH test gives an indication of the type of biological activity occurring in the water. Changes in pH affect different chemical reactions in the water.
The optimal pH for most organisms in Australian freshwaters is 6.5 – 8.2. Changes in pH outside this normal range will cause a reduction in species diversity, as the more sensitive species disappear. Extremely high or low pH levels will lead to the death of aquatic life.
pH can be influenced by geology, characteristics of the catchment, runoff from urban areas, acid sulphate soils and the amount of photosynthesis occurring in the water.
Equipment
- Small beaker
- Liquid waste container
- Sample bottle
- pH strips including container
- Distilled water
- Recording sheets
Method
- Rinse a small beaker with sample water over the liquid waste container.
- Fill the beaker with sample water
- Take one pH strip out of the pH container.
- Immerse the coloured squares on the pH strip into the sample water for 5 minutes.
- Match the colours on the pH strip to the colours on the chart provided on the container.
- Record the result on the recording sheets.
Updated: 04 Jan 2012