Precipitation Loading of Acid and Heavy Metals to a Small Acid Lake near Sudbury, Ontario

Abstract

The pH of Lumsden Lake was closely related to the measured amount of acid entering the lake from bulk precipitation. In 1972 it was estimated that an excess of 2135 kg of H2SO4 was added to the lake from the atmosphere. The predicted annual change in lake pH was from 5.2 to 4.8 and the actual measured change was from 5.2 to 4.7. In 1973 an estimated excess of 1271 kg of H2SO4 was added to the lake from the atmosphere. The predicted annual pH change was from 4.8 to 4.7 and there was no net change in the lake pH in 1973.Lumsden Lake also had high concentrations of sulfate, manganese, zinc, and nickel in comparison with remote or "unpolluted" lakes. High concentrations of manganese and possibly some zinc in the lake appeared to result from increased mobilization from the lake sediments or watershed or both as the pH decreased. Atmospheric fallout also contributed substantial quantities of nickel and copper to the watershed, some of which appeared to be retained in the lake water. The high concentrations of lead in the precipitation were not retained in the lake.