Acid Deposition

• Acid rain has a pH of less than 5.6
• Acid deposition - the process by which acidic particles, gases and precipitation leave the atmosphere
• Wet deposition, due to the dissolution of acidic oxides, is known as acid rain but can include snow, fog, dew and other forms of precipitation
• Dry deposition includes acidic gases and particles.
• Where do Oxides of Sulfur (SOx) come from?

  • occurs naturally from volcanoes
  • man made through the combustion of sulfur containing fossil fuels and the smelting of sulphide ores
• Effect on vegetation:

  • increased acidity leeches nutrients in the soil (Ca2+, Mg2+, K+)
  • stunts plant growth, makes trees yellow, loss of leaves
  • Al+ stops roots from absorbing water and nutrients
• Effect of lakes and rivers:

  • Increased levels of Al ions can kill fish
  • Fish (salmon and algae) populations decline at pH 6
  • lakes dead at pH 4
  • oxides of nitrogen cause eutrophication
• Effects of buildings:

  • marble contains calcium carbonate (CaCO3) which is eroded by acid rain
  • Rain exposes more stone, making it worse
  • Salts can cause stone to crack and disintegrate
  • CaCO3(s) + H2SO4(aq) ->CaSO4(aq) + CO2(g) + H2O(l)
• Effect on Human Health:

  • oxides of sulphur and oxides of nitrogen irritate mucous membranes and increase risk of respiratory illnesses (asthma, bronchitis)
  • Pb2+ and Cu2+ leached from pipes and high levels of Al might increase risk of Alzheimer's.
• Three methods to stop acid deposition:

  • Remove sulphur from sulphur containing fossil fuels, during and after combustion.
  • use catalytic converters to lower amounts of nitrates oxides and sulphides released into air.
  • use renewable sources of energy, use public transport
  • adding lime (calcium oxide or calcium hydroxide) to lakes to neutralize pH and precipitate aluminum
• Oxides of nitrogen:

  • produced naturally from electrical storms and bacterial action
  • nitrogen monoxide is man made in internal combustion engines and jet engines