A range of pH 6.5 to pH 8.2 is optimal for most organisms. Most organisms have adapted to life in water of a specific pH and may die if it changes even slightly. The toxicity level of ammonia to fish, for example, varies tremendously within a small range of pH values. Acid rain containing nitric and sulferic acids can sharply lower the pH of a stream as the rain runs quickly off streets and roofs into creeks.
Acidic water can cause heavy metals such as copper and aluminum to be released into the water.
Copper from worn automobile brake pads is often present in runoff. Rapids growing algae remove carbon dioxide from the water during photosynthesis, which can result in a significant increase in pH levels. It may be more convenient to perform the calibration indoors just before heading to the test site. Rinse the electrode off with demineralized water and pour the used water and used buffer solution into the waste container. Replace the cap.