5.1.2 Air Quality Monitoring Network

Number and Distributiion of Air Quality Monitoring Stations:
The National Air Quality Monitoring Programme (NAMP) Network was established during 1985-85 at national level with 7 air quality monitoring stations. Air quality monitoring network had been progessively expanded steadily to comprise 290 stations covering90 cities/town in 24 states and five union territiries in the country by the end of March 1992 and consistently being monitored (Table 5.2). The year-wise groeth of number of stations in air quality monitoring network is presented in Fig. 5.1, while state-wise distribution of Air Quality Monitoring Stations is presented in Fig 5.2.

Parameters monitored: The air quality measurement/monitoring being undertaken at various monitoring stations in Indian cities, respective monitoring agencies and parameters monitored are depicted in Table 5.1.

Table 5.1 Air Quality Parameters monitored in Air Quality Monitoring Programme in India

The coordination among these agencies are undertaken by Pollution Assessment Monitoring and Survey (PAMS) Division of Central Pollution Control Board, Delhi to ensure uniformity, consistency of air quality data and provides technical and financial support for operation of the Air Quality Monitoring Network in the country.

Classification of monitoring stations, frequency, averaging period and number of observations :         The monitoring location had been selected in various cities based on area land use and the monitoring sites are deemed to be representative of industrial and residential locations. The air quality parameters regularly monitored nationwide in NAMP network are Suspended Particulate Matter (SPM), Sulphur dioxide (SO₂), and Nitrogen dioxide (NO₂). In addition, some metro cities like Delhi/New Delhi, additional parameters viz. Carbon monoxide, PAH, Ozone, RSPM, Benzene, Trace metals (Lead, cadmium and zinc) are additionally monitored under air quality monitoring network.

Table 5.2 : State-wise locations of Air Quality Monitoring Stations under NAMP Programme in India

Sulphur dioxide, Nitrogen dioxide and Suspended particulate matter (SPM) samples are collected for 24 hrs with 4 hrs averaging of gaseous parameters and 8 hrs averaging of suspended particulate matter for twice a week. The annual target frequency as prescribed is 104 days in a year.

The National ambient air quality standards were based on 8 hrs averaging time upto the year 1994. During air quality standard revision, the standards were revised for 24 hrs and annual averaging time during 1994. To determine 24 hrs average for gaseous parameters, six 4 hourly observation of gaseous parameters are averaged to determine 24 hrs average or daily average while three 8 hourly values are averaged to get 24 hrs average value for SPM. The target frequency of air quality monitoring are twice a week i.e. about 104 nos. of observation are expected during operation of each monitoring stations, but practically due to various problems like power failure, instrumental failure, trained manpower availability etc. the target frequency of number of observations could not be achieved at all the locations, and at some places these are reduced substantially.