Climate Science

Acid Rain = Alkaline Lake

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Science  07 Mar 2003:
Vol. 299, Issue 5612, pp. 1489
DOI: 10.1126/science.299.5612.1489b

Acid rain has dramatically altered the chemistry of several watersheds and lakes in New England, the western United States, and parts of Europe, particularly in areas where the buffering capacity of soils is low. Many such areas have been studied over the past several decades. But what has the impact been in drainages and lake basins (generally rich in limestone) that are covered in soils with a high pH or buffering capacity? It has been thought that in these areas the impact would be much less or minimal.

Lajewski et al. examined this question by studying sediments in the Finger Lakes region of New York, an area that has received copious amounts of acid rain during the 20th century and that has soils with a high buffering capacity. They found that in several of the lakes, authigenic calcite, which had been absent in the sediments for more than 4000 years, began precipitating during the 1970s. Apparently, acid rain in the region, perhaps augmented by soil disturbances, has increased the weathering of carbonate rocks and thus changed the saturation state of carbonate in the lakes. Paradoxically, acid rain in such regions may make waters more basic. — BH

Geol. Soc. Am. Bull.115, 373 (2003).

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