The Significance of Large pH Fluctuations Observed in Some South African Vleis

Observations by A. D. Harrison and his co-workers (private communication) show that there are very marked pH fluctuations in the soft-water vleis (small fresh-water lakes) in the vicinity of Cape Town, South Africa. These are of two types: (a) Seasonal pH changes, the pH being higher in summer than in winter. (b) Diurnal pH changes in summer, the day pH being much higher than the night pH. In this brief communication, only the diurnal fluctuations in pH will be discussed.