Prehistoric pH Trends in Kejimkujik Lake, Nova Scotia

Abstract

Kejimkujik Lake in Nova Scotia has an average pH of 4.8 and receives wet precipitation with a weighted mean pH of 4.62. The lake is situated in a drainage basin where organic rich soils and bogs rest upon poorly buffered igneous and metamorphic rocks. Fossil diatoms from a sediment core reveal that since 21.7cm the pH trend has been to a lower pH. The flora of the lake between 13.0 and 10.7cm indicate a climatic change to a dryer period followed by a return to a more moist and humid climate. Colonization by European settlers, around 1850 A.D. drastically altered the pH of Kejimkujik Lake through deforestation and burning of lumbering refuse. The effect of potassium hydroxide, by leaching potassium from wood ash, on the lake continued to 2.2cm (about 1950) when the acidity began to drop to lower more normal levels. The overriding effect on the lake appears to have been the presence of organic soils and bogs which have contributed organic acids to the system since at least 21.7cm.