Hypolimnetic alkalinity

If we omit the ions contributing little or no net gain (i.e., Fe2+, NH4+, and probably Mn2+) to the alkalinity generated in the hypolimnion during August 1990, the decrease in sulfate between the epilimnion and hypolimnion was responsible for about 50% of the increase in alkalinity the increase in Ca2+ was responsible for 30%. Increases in Mg2 and K+ contributed 7 and 6%, respectively. The increase in Al3+ contributed about 5%, but this cannot be considered to be mitigative because of the toxicity of aluminum to aquatic biota. The relative contributions of each ion to the hypolimnetic alkalinity are similar to the relative contributions to whole-basin alkalinity as determined by ion budgets. 

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