Ambient Air quality Monitoring Guidlines. - Maharashtra Pollution ...

e based on compromise between available resources and site specific parameters such as nearby
sources, concentration gradients of the pollutants, topographical features etc.
Table 4.4: A minimum distance of the sampler from road for measurement of
Ozone and NOx (Source: ETC, Canada, 1995).
Average Traffic
(vehicle per day)
Minimum
distance of
sampler from
road (meters)
≤ 10,000
≥ 10
15,000
20
81
20,000
40,000
70,000
In general the following requirement may be met for siting the monitoring station.
30
50
100
≥ 110,000
≥ 250
(vi) Height of the inlet must be 3 – 10 m above the ground level.
(vii) The sampler must be more than 20 m from trees.
(viii) Distance of the sampler to any air flow obstacle i.e. buildings, must be more than
two times the height of the obstacle above the sampler.
(ix) There should be unrestricted airflow in three of four quadrants
(x) There should be no nearby furnace or incinerator fumes.
Once a area has been selected for locating a monitoring stations, the site can be
selected by finding maximum concentration using air quality modeling. Modeling refers
to the mathematical expression for the fate of pollutants when they are released into the
atmosphere taking into consideration the various aspects of atmospheric effects such
as dispersion, advection etc. Air quality models are capable of predicting the temporal
and spatial distribution of pollutants for a given domain of interest. Air quality modeling
can be applied to ground level sources, elevated points sources, line sources, areas
sources, flying sources under unlimited mixing, limited mixing, inversion, fumigation,
trapping and also on complex terrain, flat terrain and coastal areas. The methodology is
different in each case. Maximum ground level concentrations can be calculated where
the air quality monitoring station can be located.
4.2.3 Selection of Pollutants
Prior to selection of pollutants, an emission inventory study or modeling results can be
carried out or used if available. The pollutants expected from the sources present
should be monitored. For monitoring in metropolitan cities and urban areas, the
common urban air pollutants such as carbon monoxide, SO2, NO2, SPM and RSPM
should be measured on a regular basis. Resource availability can play a very important
role in determining the pollutants to be measured in an area. If enough resources are
available then monitoring of specific parameters such as Polycyclic Aromatic
Hydrocarbons (PAHs), ozone etc. can also be carried out.
The pollutant selection criteria is as follows: