Acid Rain

A  number of oxides can be used to produce acid rain.

Sulphur in coal will combine with oxygen to form sulphur dioxide. 

Sulphur + oxygen   sulphur dioxide

S + O2          SO2

Sulphur dioxide can react with water directly to form sulphurous acid

sulphur dioxide + water    sulphurous acid

SO2  +  H2O H2SO3

Sulphurous acid can react with oxygen and water to form sulphuric acid.

sulphur dioxide + oxygen + water    sulphuric acid

2SO2 + O2 + H2O    2H2SO4

As stated in previous posts, vehicle exhausts produce nitrogen dioxide as follows

nitrogen + oxygen   nitrogen dioxide

N2 + 2O2    2NO2

This in turn reacts with water to form nitric acid and nitrous acid

nitrogen dioxide + water    nitric acid + nitrous acid

2NO2 + H2O    HNO3  + HNO2

Acid rain forms in the atmosphere as these gases react with the water that is already in the atmosphere has a number of consequences.  When it reaches the ground, it can have a number of consequences:

1. Damaging the foliage of plants
2. Rapid leaching of essential nutrients from the soils
3. Releasing heavier metals from the soil (e.g. copper, zinc) so that they have toxic effects on plants.
4. Acidifying waterways causing fish kills.
5. Damaging statues or parts of buildings made of limestone and marble (some types of sandstone are also candidates for damage)

As the cartoon implies, the acid emissions of one country can affect neighbouring areas.  This was the case in Canada where northern USA emission damaged the environment.  In Scandinavia acid forming pollution from western Europe again caused damage.

In 1983 an international treaty, The  Convention on the Long-Range Transport Air Pollutants (LRTAP) came into force with 50 signatories to try and reduce the emissions that produce acid rain.  More on this later.