Alkalinity

Alkalinity is measured in mg/l as
calcium carbonate (CaCO3). It
represents a measure of a
solution's ability to buffer or
neutralize acids. Lakes located in
areas of
calcareous glacial till (common
throughout central and southern
Minnesota) will have higher
alkalinity than lakes formed on
non-calcareous bedrock (common in
northeastern Minnesota). Water with
alkalinity less than about 75 mg/L
could be considered soft, 76-150
moderately hard, 151-300 hard, and
greater than 300 very
hard. Alkalinity has also been used
as a basis for estimating
sensitivity to acid precipitation.
For this purpose, lakes with
alkalinity values less than 5 to 10
mg/L could be considered
potentially sensitive to acid
precipitation based on current
levels of deposition across
Minnesota. At this point we have
identified no "culturally
acidified" lakes in Minnesota.