After talking about the advantages of nuclear power last week, I decided to do another environmental topic this week, acid rain. To look at the causes of acid rain, you need to know all the steps involved in the formation of acid rain.
Formation of Acid Rain:
- Firstly, the burning of fossil fuels and coal causes sulfur impurities in the fuel to be oxidized to sulfur dioxide. In air, sulfur dioxide is converted to sulfur trioxide. There are very few natural sources of sulfur dioxide. 99% of sulfur dioxide in the air comes from human sources.
- Sulfur trioxide readily reacts with water to form sulfuric acid, which is one of the two main components of acid rain.
- Nitrogen is a very stable element due to the presence of a triple bond (see our article ‘Who Discovered Nitrogen‘). Hence, nitrogen can only break down and react in limited circumstances. In nature, lightning strikes are capable of breaking the triple bond, and the nitrogen reacts with oxygen to produce nitric oxide. The nitric oxide further reacts with oxygen to form nitrogen dioxide. Nitrogen dioxide reacts with water to form both nitric acid (a main component of acid rain) and nitrous acid (only a small component of acid rain as it is a weak acid). Also, the high temperature in car exhausts cause the oxidation of nitrogen to nitric oxide (which then forms nitrogen dioxide and nitric acid).
So the main causes of acid rain are…
- Lightning strikes (cause nitrogen molecules to be oxidized)
- Combustion of hydrogen sulfide (hydrogen sulfide is formed from the breakdown of sulfates in organic matter in the absence of oxygen- anaerobic conditions). This reaction forms sulfur dioxide.
- Combustion engines (car, airplanes etc.)
- Burning of fossil fuels and coal
- Some mineral ores contain sulfur dioxide, and this is released when the minerals are processed.
Other Environmental Topics: