Acid Rain

Rain is meant to clean the air, but when we burn fuels that contain sulfur, and run engines hot enough to make the nitrogen in the air react, the rain itself turns sour. Sulfur dioxide and oxides of nitrogen drift up into the clouds, react with oxygen and water vapour, and come back down as weak sulfuric and nitric acids. Carried on the wind, this acid rain can fall hundreds of kilometres from the chimney or exhaust that produced it, which is why it is a problem that crosses borders.

In this lesson you will learn exactly how acid rain forms, from the gases at the source to the acids that fall to Earth. You will study its effects on lakes and the fish in them, on soils, crops and forests, and on the very stone of our buildings. Finally you will examine the strategies used to manage it, from cleaning the gases leaving a power station to fitting catalytic converters to cars, and learn to weigh their benefits against their limitations.