The Atmosphere and Environment

The Atmosphere and Environment

1. Composition of air

   • Atmosphere
     • layer of air surrounding Earth that protects it
       • from excessive radiation
       • maintain Earth's Temperature
   • air
     • mixture of gases
       • elements
       • compunds
     • nitrogen - 78%
     • oxygen - 21%
       • used for
         • make steel
         • oxygen tanks in hospitals
         • oxy-actylene
         • oxygen gas cylinders for drivers
     • noble gases - 0.97%
     • carbon dioxide - 0.03%
     • separated via fractional distillation

2. Air Pollution

   • condition in which air contains a high concentration of chemicals that may harm living things or damage non-living things
   • air pollutants
     • carbon monoxide, sulfur dioxide, methane, ozone, unburnt hydrocarbons, oxides of nitrogens
     • solid particles and poisonous gases in the atmosphere
     • Acid rain
       • It is formed when acidic air pollutants such as sulfur dioxide and nitrogen dioxide react with water in the atmosphere.
         • formations
           • sulfur dioxide dissolves in water to form sulfurous acid
             • presence of oxygen cause it to oxide to sulfuric acid
           • oxides of nitrogen with presence of oxygen and water forms nitric acid
           • carbon dioxide dissolves in rainwater to form carbonic acid
       • Effects
         • pH below 4 streams result in dying of fishes and other aquatic life
         • react with metals and carbonate damaging infrastructure
         • react with aluminium hydroxide in the soil to produce aluminium oxide that are toxic to plants

3. Reducing Air Pollution

   • NEA monitors and controls problems of air and water pollutions in SG
   • Liming which calcium carbonate is used to neutralisewater bodies
   • catalytic converters
     • reduce air pollution by exhaust systems
     • Process
       • hot exhaust gass containing CO, oxides of nitrogen, unburnt hydrocarbons are passed over to platinium and rhodium catalysts
         • Conversion to harmless substances via redox reaction
           • CO oxides into CO2
             • 2NO +2CO into N2 + 2CO2
               • 2C8H18+25O2 into 16CO2 + 18H20
   • flue gas desulfurisation
     • Process
       • Sulfur dioxide react with aqueous suspension of calcium carbontae to form calcium sulfite and carbon dioxide gas
         • calcium sulfite oxidises to calcium sulfate
       • calcium oxide react with sulfur dioxide into calcium sulfite

4. Depletion of Ozone Layer

   • Ozone is an allotrope of oxygen. It is pale blue gas with pungent odour. (O3)
     • in the stratosphere it helps to filter out some of the harmful ultraviotlet raditations
     • act as a giant sunscreen
   • Causes: Chlorofluorocarbons known as CFCs, are compound containing carbon, fluorine and chlorine
     • propellants in aerosols and coolants in refrigerators, air conditioners release CFCs
       • CFCs decompose into chlorine atoms due to UV radiations
         • chlorine atoms react with ozone molecules in stratosphere to form chlorine oxide and oxygen thus destroyig the ozone layer
           • UV radiation enters through the holes

5. Global Warming

   • Greenhouse Effects
     • gases
       • carbon dioxide, methane, nitrous oxide and more
     • solar radiation pass through atmosphere
       • some radiation reflected back into space
         • It warms the Earth's surface but some infrared radiation rise from surface to escape
           • Greenhouse gases trap some of the heat
   • Carbon Cycle
     • mechanism that maintains the level of carbon dioxide in the atmosphere
       • added
         • Decay and bacteria decomposition
         • combustion of fuels
         • Respiration
       • removed
         • Ocean uptake
         • Photosynthesis
   • It is the increase in Earth's average temp. due to build up of greenhouse gases in atmosphere
     • Effects
       • more occurrences of unusual weather
       • decrease of crops yield
       • melting of the Poles increases ocean levels and flooding low lying countries
       • Rapid evaporation of waters