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Long term response of acid-sensitive Vermont Lakes to sulfate deposition
Citation:
OELSNER, G. P. AND J. L. STODDARD. Long term response of acid-sensitive Vermont Lakes to sulfate deposition. Presented at ASLO/NABS Joint Meeting, Santa Fe, NM, June 06 - 11, 2010.
Impact/Purpose:
Atmospheric deposition of sulfur can negatively affect the health of lakes and streams, particularly in poorly buffered catchments.
Description:
Atmospheric deposition of sulfur can negatively affect the health of lakes and streams, particularly in poorly buffered catchments. In response to the Clean Air Act Amendments, wet deposition of sulfate decreased more than 35% in Vermont between 1990 and 2008. However, most of the sulfate deposition decrease occurred in the early 1990s. While sulfate concentrations in precipitation have continuously decreased, recent increases in precipitation have resulted in relatively consistent sulfate deposition loads in the past decade. Lake chemistry data collected as part of the U.S. EPA’s Long Term Monitoring Program indicate that in 11 acid-sensitive Vermont lakes sulfate concentrations have decreased continuously since the mid-1980s, despite the relatively minor changes in sulfate deposition in the last decade. Due to synchronous decreases in base cation concentrations, ANC has not increased significantly in many of the lakes. Precipitation variability can explain 20 to 40% of the sulfate concentration variability in most of the lakes. Additionally, lake sulfate concentrations are likely mediated by sulfate retention in the soil. These results suggest that climate and hydrology variability can affect atmospheric deposition and lake chemistry.