1. acids
   1. sulphur dioxide + water
      1. sulphuric acid
   2. nitrogen oxide + water
      1. nitric acid
2. pollutant gases
   1. sulphur dioxide
      1. S(s) + O2(g) ---> SO2(g)
      2. 2SO2(g) + O2(g) + 2H2O(l) ---> 2H2SO4 (aq) [sulphuric acid]
      3. wet deposition (rain) carried many miles away
         1. wind
   2. nitrogen oxides
      1. nitric acid
         1. dry deposition falls close to pollution source
         2. wet deposition (rain) carried many miles away
            1. wind
   3. sources
      1. burning fossil fuels
      2. volcanoes
         1. eruptions
            1. hydrogen sulphide
         2. hot springs
            1. hydrogen sulphide
         3. global ash dust
      3. decomposing plankton
         1. dimethyl sulphide
   4. removal gases
      1. expensive
         1. FGD
            1. flue gas desulpurisation plants
            2. fitted to power plants
         2. catalytic converters
            1. reduce oxides of nitrogen to oxygen and nitrogen
3. consequences
   1. damage to buildings
      1. calcium carbonate
         1. limestone
         2. marble
         3. CaCO3
   2. metal structures
      1. attacked
   3. plants
      1. harms directly
      2. ion depletion
         1. washes ions out
         2. calcium
         3. magnesium
   4. animals
      1. affected rivers & lakes
      2. ion depletion
         1. washes ions out
         2. aluminimu
            1. into rivers and lakes
            2. poisonous to fish