Recent Recovery of Lake Water Quality in Southern Québec Following Reductions in Sulfur Emissions |
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Authors: | Daniel Houle Christian Gagnon Suzanne Couture Alain Kemp |
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Institution: | 1. Environnement Canada, Centre Saint-Laurent, 105 rue McGill, Montréal, Québec, Canada, H2Y 2E7 2. Direction de la recherche forestière, Ministère des Ressources Naturelles du Québec, 2700 Einstein St., Sainte-Foy, Québec, Canada, G1P 3W8
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Abstract: | Since 1985, monitoring activities have been conducted in a networkof 43 lakes comprising the Québec portion of the Long-Range Transport of Airborne Pollutants (LRTAP) program. The results to date indicate that Québec lakes generally are responding positively to the generalized decline in precipitation sulfate (SO4 2-), with 40 of the 43 lakes now showing steep declines in SO4 2- concentrations. The drop in SO4 2- was associated with a significant decrease in Ca2+ concentrations in 77% of the lakes (67% for Mg2+ concentrations). Overall, the acid-neutralizing capacity was increasing in 19 lakes and decreasing only in three, while 21 lakes showed no temporal trends. Compared with previous trend studies of the LRTAP-Québec network for the period of 1985–1993, the longer period (1985–1999) shows a clear improvement, with the proportion of lakes that were acidifying changing from 24 to 7% and with the proportion of lakes that were recovering changing from 16 to 35%. These observations suggest that the recent drop in SO4 2- deposition in the northeastern U.S. and eastern Canada was significant enough to allow chemical recovery for a significant proportion of Québec lakes. |
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