Friday, May 4, 2012

Acid rain limits global warming

Acid rain restricts global warming by reducing methane emissions from natural wetland areas, suggests a global climate study.

Acid rain is the result of industrial pollution, which causes rainwater to carry small quantities of acidic compounds such as sulphuric and nitric acid. Contaminated rainwater can upset the chemical balance rivers and lakes, killing fish and other organisms and also damage plants, trees and buildings.

But the new study shows that sulphur in acid rain may have benefits, limiting global warming by counteracting the natural production of methane gases by microbes in wetland areas.

Methane is thought to account for 22 percent of the human-enhanced greenhouse effect. And microbes in wetland areas are its biggest producers. They feed off substrates such as hydrogen and acetate in peat and emit methane into the atmosphere.

Global warming itself will only fuel the production of methane as heating up the microbes causes them to produce even more methane. But the new model suggests that sulphur pollution from industry mitigates this.

This is because sulphur-eating bacteria also found in wetland regions outcompete the methane-emitting microbes for substrates. Experiments have shown that sulphur deposits can reduce methane production in small regions by up to 30 per cent by activating the sulphur-eating bacteria.

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