Stoddard, J. J.. U.S. Environmental Protection Agency, stoddard@mail.cor.epa.gov
Jeffries, D. J.. Environment Canada, Dean.Jeffries@CCIW.ca
Lukeville, A. Norwegian Institute for Forest, Anke.Lukewille@nilu.no
Skjelkvaale, B. L.. Norwegian Institute of Water Research, brit.skjelkvaale.niva.no

 
RECOVERY OF LAKES AND STREAMS FROM ACIDIFICATION: REGIONAL TRENDS IN NORTH AMERICA AND EUROPE IN THE 1980s AND 1990s
 
We use a Seasonal Kendall test for trend and meta-analysis to examine regional trends in indicators of acidification (alkalinity, and sulfate, nitrate, and base cation concentrations) for 205 lakes and streams in North America and Europe for the periods 1980-89 and 1990-95. Many sites exhibited dramatically different trends in the 1980s vs. the 1990s, prompting us to examine trends separately for the two decades. Regional groupings were based on the sites' geographic proximity, their chemical similarity, and the likelihood that they would have experienced similar changes in atmospheric deposition during the 1980s and 1990s. Decreases in sulfate were universal, with most regions exhibiting stronger downward trends in the 1990s than in the 1980s. Regional nitrate trends were rare. Only the Adirondack/Catskill Mountains and Northern Europe exhibited ecologically significant nitrate trends; in both cases the trends were upward in the 1980s and strongly downward in the 1990s. Regional recovery in alkalinity, to be expected from strong regional declines in sulfate, was observed in all regions of Europe, and most regions of North America, especially in the 1990s. In the Adirondack/Catskill Mountain and the Upper Midwest/Northwest Ontario regions, where recovery was not observed, strong regional declines in base cations (of a magnitude greater than sulfate declines) seem to be responsible.
 
Day: Wednesday, Feb. 3
Time: Poster
Location: Sweeney Center
 
Code: SS50WE1530S