The normal pH of rain water is about 5.6. This is due to the combination of carbon dioxide in the air with water. The result is a weak solution of carbonic acid.
The increased acidity of rainwater is due to the burning of fossil fuels, like coal and oil, as well as gasoline derived from oil. When fossil fuels are burned, the result is sulfur dioxide and nitrogen oxide. They then combine with water vapour in the atmosphere to form acids. These are the acids that return to the earth contained in rain or snow. This process is called wet deposition, but it is more commonly known as acid rain. If there is dry deposition, this means dry particles of sulphate and nitrate salts descend from the atmosphere.
Acid deposition can also result from factories and power plants burning fossil fuels.
Acid depositions causes adverse effects on lakes, particularly in areas where the soil is thin and lacks limestone which is a buffer to acid deposition. Aluminum is leached from the soil and carried into the lakes, mercury deposits are converted in lake bottom sediments to soluble and toxic methyl mercury. This causes lakes to become more acidic and accumulate toxic substances.
In forest areas, acid deposition causes trees to be weakened because it leaches away nutrients and releases aluminum.
Acid deposition also causes reduction of agricultural yields, damage to marble and limestone monuments and buildings, and even illnesses in humans. Lung and colon cancer have also been linked to acid deposition.
What can we do to prevent acid deposition:
- use alternative energy whenever possible such as solar, wind, hydro power, and geothermal energy.
- we low sulfur coal or remove the sulfur impurities from coal before it is burned
- make a requirement for factories and power plants to use scrubbers, which remove sulfur emissions
- car pool more
- reduce our energy/carbon footprint by implementing energy conservation methods