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Stoddard, John L., D.S. Jeffries, A. Lükewille, T.A. Clair, P.J., Dillon, C.T. Driscoll, M. Forsius, M. Johannessen, J.S. Kahl, J.H. Kellogg, A. Kemp, J. Mannio, D. Monteith, P.S. Murdoch, S. Patrick, A. Rebsdorf, B.L. Skjelkvåle, M. Stainton, T. Traaen, H. van Dam, K.E. Webster, J. Wieting, and A. Wilander.1999. Regional trends in aquatic recovery from acidification in North America and Europe. Nature 401:575-578.

Rates of acidic deposition from the atmosphere (‘Acid rain’) have decreased throughout the 1980s and 1990's across large portions of North America and Europe. Many recent studies have attributed observed reversals in surface-water acidification at national and regional scales to the declining deposition. To test whether emissions regulations have led to widespread recovery in surface-water chemistry, we analyzed regional trends between 1980 and 1995 in indicators of acidification (sulphate, nitrate and base-cation concentrations, and measured (Gran) alkalinity for 205 lakes and streams in eight regions of North America and Europe. Dramatic differences in trend direction and strength for the two decades are apparent. In concordance with general concentrations decreased in all regions with the exception of Great Britain; all but one of these regions exhibited stronger downward trends in the 1990s than the 1980's. In contact, regional declines in lake and stream nitrate concentrations were rare and, when detected, very small. Recovery in alkalinity, expected wherever strong regional declines in sulphate concentrations have occurred, was observed in all regions of Europe, especially in the 1990s, but in only one region (of five) in North America. We attribute the lack of recovery in three regions ( south/central Ontario, the Adirondack/Catskill mountains, and midwestern North America) to strong regional declines in base-cation concentrations that exceed the decreases in sulphate concentrations.

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