THE SIGNIFICANCE OF IN-LAKE PRODUCTION OF ALKALINITY

Alkalinity production in terrestrial and aquatic ecosystems of Canada, the U. S. A. , Norway and Sweden is calculated from either strong acid titrations or budgets for base cations and strong acid anions, using mass-balance budgets. Where alkalinity budgets for lakes and their catchments are calculated in acid-vulnerable geological settings, in-lake processes often contribute more to lake alkalinity than yield from terrestrial catchments. Nitrate and sulfate removal, and Ca exchange with sediments are the most predominant alkalinity generating mechanisms in lakes. Nitrate and sulfate removal rates increase as the concentrations of NO//3** minus and SO//4**2** minus in lake water increase, so that in-lake acid neutralizing capacity increases as acid deposition increases. Both processes occur in sediments overlain by oxic waters, at rates which seem to be controlled primarily by diffusion.