Unit-iv unit-iv environmental Hygiene


Zones of atmosphere cont…



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Atmospheric-pollution

Zones of atmosphere cont….
2. Stratosphere:
  • Height from the earth: 40-50 km
  • Thin layer above troposphere
  • Uniform temperature
  • The zone comprises of ozone layer
  • Protects the earth against the ill-effects of UV irradiation
  • Ozone shield increases the temperature from -560 C to -20 C at 50 km height

3. Mesophere:
  • Height from the earth: 70-80 km
  • Marked reduction in the temperature
  • At an altitude of 70 km,
  • the temperature falls to -92oC (from -20C)

4. Thermosphere:
  • Height from the earth: above 80 km
  • Temperature: very high (upto 12000 C)
  • Thickness of the zone is 500 km
  • It contains O2, nascent oxygen & nitrogen oxide.

The atmospheric pollution is influenced: meteorological conditions present in an area

  • The atmospheric pollution is influenced: meteorological conditions present in an area
  • Meteorological factors influences: magnitude of vertical & horizontal transfer of air pollution
  • Major parameters are:

    Temperature:

    • Direct bearing on the movement of air pollutants
    • Influences the diffusion of pollutants
    • Wind:

    • The direction & speed of wind is an important determinant in the movement of air pollutants
    • Humidity

    • Influences the precipitation of pollutants on earth
    • Many toxic pollutants combine with water vapor precipitate to the surface of earth
    • Atmospheric pressure

    • Influenced the movement of pollutants in an area
    • Important consideration for many pollutional parameter

Influence of metrological conditions

1. Meuse Valley (Belgium), December, 1930

1. Meuse Valley (Belgium), December, 1930

  • The area was covered by a blanket of thick fog for about 5 days
  • More than 60 persons died as a result of toxicity due to oxides of sulphur (and metals) & soot
  • A large section of the population became ill

Air pollution: a historical perspective

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