*pH & Alkalinity information pages are currently in draft form.
What is it?
When we consider the acidity of lake water, we talk about two conditions which are tied together: pH and alkalinity. pH tells us how acidic or basic water is. Alkalinity is the ability of the water to buffer or resist acidity.
pH
More specifically, pH actually refers to the concentration of hydrogen ions in water. The measure of pH is on a scale of 0 -14, a pH of 7 is neutral (neither acidic or basic). pH below 7 are acidic and waters above 7 are basic, also called alkaline. pH of lakes vary in Maine from 4.45 to 9.35, the average is 6.7. A one unit change in pH represents a 10 fold change in acidity or alkalinity.
Below you can see where household items fall on the pH scale.
Alkalinity
The alkalinity of lake water is mostly determined by the geology of the soils and rocks surrounding the lake. Rocks the contain carbonate, bicarbonate and hydroxide compounds contribute to alkalinity. Also, borates, silicates and phosphates may add to the buffering capacity of water. Limestone is an example of a rock that is rich in carbonates, and has contributes to alkalinity in lake water. Granite is the opposite in that it does not contain any minerals that contribute to alkalinity, so lakes with a granite geology have low alkalinity, and poor buffering capacity.
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