Jun 10, 2012

Acid rain and ozone depletion


Combustion of fossil fuels (in power stations, domestic & industrial boilers)
Releases sulphur dioxide & oxides of nitrogen (NO & NO2)
Both the gases combine with water vapour formed sulphuric acid & nitric acid
They fall to earth as acid rain (with pH less than 5)

The soil becomes very acidic
Thus, unsuitable for cultivation of crops
Causes leaching of minerals (such as potassium, calcium, magnesium)
Affects growth of crops
Photosynthetic tissues are destroyed.
Reduce the producers.
Germination of seed & growth of young seedling is inhibited.
Insoluble aluminium ions accumulate in lakes & rivers (due to leaching)
This can kill aquatic organisms (excessive secretion of mucus by fish gills)
Kill phytoplanktons (that affects the food chain)
Acidic soil releases ions of certain heavy metals (Eg. mercury, lead, cadmium)
This can contaminate supply of drinking water.
Metal railings, steel, cars, bridges, underground pipes corrode
Corrosion of sandstone & limestone.                                                   
Ways to overcome
Use scrubbers that clean up emissions from power stations & industrial plants
Use catalytic converters that clean up emissions from vehicle exhaust

Increase level of CFCs (chlorofluorocarbons
CFCs used in coolants in air conditioners / refrigerators // propellants is aerosol cans // foaming agents making styrofoam / polystyrene 
(Once in the atmosphere) CFCs are broken down by UV rays into chlorine radicalsChlorine radicals break down ozone molecules (O3)

Ozone depletion causes direct exposure to UV radiation.
Prolong exposure causes skin cancer, cataracts & sunburns
UV rays also weaken immune system / decreases body resistant against infectious disease
UV rays reduces nutrient contents & crop yields
Leaf cells & chlorophyll are easily damaged
UV rays also kill microbes & phytoplankton
Leads to increase in the earth temperature / global warming
Ways to overcome
Reduce / Stop uses of CFCs
Replace CFCs with HCFCs or HFCs.