Chemistry of Bulk Precipitation in Halifax and its Effects on Chain and Chocolate Lakes

Abstract

Fifty-nine weekly bulk deposition samples and about 1100 lake water samples from the study area were analyzed for water quality parameters to document the bulk deposition chemistry and its effects on Chain and Chocolate Lakes. The composition of bulk deposition in Halifax (on chemical equivalent basis) was: chloride, 28 % of total ions; sodium, 25% sulfate, 15%; hydrogen, 14%; calcium, 6%; total nitrogen, 6%; magnesium, 4%; nitrate(N), 2%; ammonia(N), 1%; total phosphorus, 0.06%; and orthophosphorus, 0.03%. Marine sources contributed almost all of chloride and magnesium, 97% of sodium, 17% of sulfate, and 13% of calcium. Bulk deposition was not the major source of sodium, chloride, sulfate, calcium, magnesium, hydrogen, nitrogen, and phosphorus to the study lakes. However, it was the principal source of hydrogen, nitrogen, and total phosphorus to the forested watersheds of Chain Lakes, and of hydrogen, orthophosphorus and total phosphorus to the urbanized watershed of Chocolate Lake. The effects of these ions were not reflected in the lakes' water quality, probably because of the excess alkalinity produced in the watersheds of Chain Lakes, and also because of high flushing rates of the lakes.