MARTYN F. CHILLMAID / SCIENCE PHOTO LIBRARY MARTYN F. CHILLMAID / SCIENCE PHOTO LIBRARY
Measuring acidity of rainwater samples. Test tubes of normal rain (left) and acid rain (right) with universal indicator added to show acidity. The normal rainwater has a pH (a measure of acidity) of around 5, with the acid rain at 4. Acid rain is caused by pollutants in the air, such as sulphur dioxide, dissolving in atmospheric water, where they form acids, such as sulphurous acid. When this falls it can damage plants, lakes and rivers and even buildings. Reduction in emissions of such pollutants can help to reduce the problem.
Model release not required. Property release not required.