Thursday, March 23, 2017

Ambient air quality monitoring

Ambient air quality refers to the condition or quality of air surrounding us in the outdoors. National Ambient Air Quality Standards are the standards for ambient air quality set by the Central Pollution Control Board (CPCB) and is applicable nationwide.
The CPCB has been conferred this power by the Air (Prevention and Control of Pollution) Act, 1981.

According to the National Ambient Air Quality Monitoring Program:

  • The following factors influence site selection:

  1. The site should be away from source and other interference (Inlet should be at least 15 m away from source or traffic artery)
  2. Height of the inlet should be more than 3 m (preferably between 3 - 10 m) or double the height of nearby wall or obstruction.
  3. The air at site should be free flowing and well mixed
  4. The elevation angle should be less than 30 from inlet to top of building
  5. Collocated samplers should be at least 2 m apart
  • The following factors influence parameter selection
  1. Sensitive location
  2. Health impact stations (All pollutants)
  3. Population and exposure in case of priority pollutants
  4. Criteria pollutants and CO are typically sampled at traffic intersections
  5. Concentration of criteria pollutants and ozone are accumulative and are sampled at 50 m from traffic intersections core commercial areas in the city
In case of manual monitoring, 
  • Gravimetric methods are used to estimate the concentration of PM10 and PM2.5 
  • Wet chemical methods are used to estimate the concentration OF SO2, NO2, NH3 and benzene
  • Gravimetric method of sample processing and chemical analysis is done to estimate the concentration of Benzene, B(a)P, Ni, As and Pb in PM10

In case of automatic monitoring, 
  • Sophisticated analysers are used for instant data generation, online data dissemination, air quality index, early warning system, forecasting, modeling of pollutants such as Sulphur dioxide, Nitrogen dioxide, particulate matter smaller than ten microns, particulate matter smaller than 2.5 microns, Ozone, Carbon monoxide, Ammonia and benzene.

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