Unpolluted rain is slightly acidic (pH 5.5) due to the presence of dissolved carbon dioxide. Some rain is far more acidic (pH 4–5). Rainwater with a pH of less than 5.5 is called acid rain.
Acid rain Sulfur dioxide
Learn more about the pH scale in Chemical World 13.2
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Nitrogen oxides
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The burning of fossil fuels, particularly coal, releases sulfur dioxide (SO2). The burning of fuels in cars releases nitrogen oxides (NOx) into the air.
These gases dissolve in the air’s moisture to form sulfuric acid and nitric acid. This falls back to Earth as acid rain.
Effects of Acid Rain
The main effects of acid rain are: zz
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It washes minerals such as aluminium out of soil and into lakes and streams, which kills fish.
It damages buildings and statues, especially those made of limestone. It harms leaves, which means trees and plants cannot photosynthesise.
Reducing the Effects of Global Warming and Acid Rain
The effects of global warming and acid rain can be reduced in the following ways: zz
Use less fossil fuels and use more renewable energy sources, such as solar, wind or hydroelectric energy.
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z z Reduce the sulfur in fuels such as coal, oil and gas.
Drive hybrid electric vehicles and install catalytic converters in cars to decrease the harmful emissions from exhaust fumes.
Plant more trees to return oxygen to the atmosphere and remove carbon dioxide via photosynthesis.
