Photochemical Smog & Acid Deposition

definition of primary pollutants

emitted directly from sources

examples of primary pollutants

• carbon monoxide

• carbon dioxide

• black carbon (soot)

• unburned hydrocarbons (VOCs)

• nitrogen oxides

• sulfur oxides

definition of secondary pollutants

result of chemical reactions in the atmosphere

examples of secondary pollutants

• sunlight catalyses reactions between primary pollutants and chemical endemic to the atmosphere

• tropospheric ozone (O3)

  • O2 + O → O3

  • creates smog

  • causes respiratory issues

• nitrogen oxides

  • nitric acid/nitrates = acid rain & PM pollution

effects of tropospheric ozone

• damge plant tissues, reducing photosynthesis

  • reduced crop yields

  • visible leaf damage

• eye irritation

• reduced lung function

• coughing, throat irritation, asthma

• degrades materials by accelerating photodegradation

  • rubber

  • fabrics

  • plastics

definition of smog

Mix of primary & secondary pollutants

• usually tropospheric ozone & PM

reasons for smog occurence

• areas that slow air movement

  • valleys/basins

• hot/sunny climates

  • more photosynthetic reactions

• thermal inversions

  • cool, dense air trapped under warmer, less dense air

  • inversion conditions prevent the layers from mixing

  • pollutants are trapped & smog builds up

impacts of smog

• healthcare costs

  • cardiovascular diseases

• reduced productivity

  • loss of work days

• damage to vegetation & crops

• decline in property valyes

• increased environmental regulations

4 methods of managing air pollution

• regulation (carbon market)

• altering human activity (public transit)

• technology (catalytic converters)

• clean up measures (reforestation)

causes of acid deposition

• combustion releases sulfur dioxide & fossil fuels

• these can either become nitric/sulphuric acid or dry deposition particles

• transboundary issues

description of dry deposition

• ash/PM + sulphuric/nitric acid

• settle on surfaces, slowly causing damage

description of wet deposition

• acids dissolve in rain/snowflakes; form acidic precipitation

• affects surface water & soils

direct effects of acid deposition

• degradation of limestone & marble

  • calcium carbonate corroded by acid

• lowers pH of water, affecting reproduction

• causes leaf damage

• blocks stomata, preventing gas exchange

  • conifers especially vunerable due to shallow roots & thin bark

indirect effects of acid deposition

• increases solubility of aluminium in water

  • aluminium ions are toxic to fish

• accelerates leaching of essential nutrients

  • lowers productivity

  • increases algal growth = eutrophication

managing acid deposition

• spreading ground limestone/liming lakes

  • neutralises acidity, restoring pH

  • expensive & resource intensive

• planting acid tolerant vegetation

  • Hydrangea

  • Magnolia