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For environmentalists of a certain vintage, the words "acid" and "lakes" can stir strangely fond memories. Back in the 1970s and 80s, acid rain from coal-fired power stations was turning lakes across the northern hemisphere into vinegar. Scientists identified the problem, activists campaigned, governments listened. Today, in the West at least, acid rain is largely a thing of the past.
But acid lakes are not. Even while many are still recovering from being deluged with acid rain, they face a resumed assault - this time from carbon dioxide. High concentrations of the gas in the atmosphere means more is dissolving in the world's lakes and rivers. Goodbye sulphuric acid, hello carbonic acid.
The new acid invasion shouldn't come as a surprise. For over a decade, marine biologists have been on alert for the effects of acidifying oceans as rising amounts of atmospheric CO
2 dissolve into them. But until now, the parallel acidification of rivers and lakes has largely escaped attention. That changed in January with the publication of the
first research to pinpoint freshwater lakes accumulating CO
2 from the air, and growing more acidic as a result. "The rate of acidification is really quite fast - three times faster than in the world's oceans," says Linda Weiss of the Ruhr University Bochum in Germany, who led the study (
Current Biology, vol 28, p 327).
That is obviously a cause for concern. Ocean acidification - sometimes known as "
the other CO2 problem" - is expected to have severe effects on marine ecosystems. About a third of all the CO
2 released into the atmosphere dissolves in seawater and turns into carbonic acid. Since the industrial revolution, the pH of the ocean surface has
fallen from 8.16 to 8.05, a 30 per cent increase in the concentration of hydrogen ions. This isn't a concern yet, but if it continues it will eventually cause some corals and shells to dissolve.
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