Zinc Cycling in an Acidic Adirondack Lake

Acidification of surface waters by acidic deposition has reportedly caused increased concentrations of Zn. Elevated concentrations of Zn are of interest due to potential toxicity to aquatic organisms. Researchers have also examined the chronology of Zn deposition to lake sediments as an indicator of changes in atmospheric deposition. However, there have been few studies that focus on Zn chemistry and transport in acidic lakes. Elevated concentrations of Zn (0.15-1.2 µmol L^–1; mean = 0.39 µmol L^–1) were observed in acidic Darts Lake. Although peak concentrations of 1.2 µmol of Zn L^–1 were observed during snowmelt, spatial and temporal variations in Zn concentration were minor and limited to melt water in streams and at the lake surface. On the basis of mass balance calculations and sediment trap observations, Zn did not appear to be significantly retained in Darts Lake. Long- and short-term variations in in-lake retention of Zn, caused by surface water acidification, may complicate quantitative interpretation of Zn deposition in sediments.