Recent studies of major ion budgets of lakes have demonstrated the occurence of within-lake alkalinity generation, or acid consumption, that may represent a significant source of buffering against acid precipitation. Consumption of sulfate is associated with a major portion of alkalinity generation. Sources of alkalinity, and the capacities of lakes to neutralize sulfuric acid, corresponding to each of the probable fates of sulfur have not been discussed explicitly in earlier papers. This note was written to clarify these points.