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PALEOECOLOGICAL ANALYSIS OF LAKE ACIDIFICATION TRENDS IN NORTH AMERICA AND EUROPE USING DIATOMS AND CHRYSOPHYTES
Citation:
Charles, D., R. Battarbee, I. Renberg, H. vanDam, AND J. Smol. PALEOECOLOGICAL ANALYSIS OF LAKE ACIDIFICATION TRENDS IN NORTH AMERICA AND EUROPE USING DIATOMS AND CHRYSOPHYTES. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/D-89/106.
Description:
Analysis of sediment diatom and chrysophyte assemblages is the best technique currently available for inferring past lakewater pH trends, and use of this approach is increasing rapidly. ediment core inferred pH data exist for at least 100 lakes in both North America and Europe. This number will approximately double within the next two years. The pH inference equations are based on at least 15 calibration data sets for North America and 10 for Europe, involving totals of at least 500 and 300 lakes, respectively. Paleoecological studies indicate that recent acidification has been caused by acidic deposition in the Adirondack Mountains (New York), northern New England, Ontario, Quebec, and Canadian Atlantic provinces in North America; England, Scotland, and Wales in the United Kingdom; Norway, Sweden, Finland, The Netherlands, and West Germany in Europe. nferred pH decreases are commonly as much as 0.5-1.5 pH units. o acidification trends were observed in regions currently receiving low deposition of strong acids (eg., Rocky Mountains and Sierra Nevada in the western United States, northwest Norway, and northwest Scotland). light or no trends towards decreasing pH were observed in study lakes receiving moderately acidic deposition (Upper Midwest and northern Florida, United States). The magnitude of pH decline in lakes studies is greater, on the average, in Europe than in North America. he amount of inferred acidification (increase in H+ concentration) correlates with the amount of S and N loading and the ability of watersheds and lakes to neutralize acid inputs, and is generally consistent with current lake acidification models. In most cases, the primary cause of recent acidification trends (post-1850) is atmospheric deposition of acidic material, as opposed to land use changes or natural processes, though these may be contributing factors. Acid loading has decreased in some regions since 1970 (e.g., northeastern United States; United Kingdom). Some lakes have become less acidic in response, but others continue to lose buffering capacity and are becoming more acidic. Many currently acidic lakes were naturally acidic (pH < 5.5) prior to the onset of anthropogenic acidification. These lakes are typically small (< 10 ha), located at moderately high elevations, have thin or peaty soils, or are located in outwash deposits. any of these have acidified further recently.