Abstract:
Air quality is one of the major environmental concerns over worldwide. Air Quality
standards are implemented by regulatory authorities to minimize the air quality that
bases on criteria pollutants; such as nitrogen dioxide. As it has ability to absorb the
light, that’s why it usually results in the yellow brown haze which can occasionally be
seen over major cities. It’s also one of the important contents of photochemical smog.
Nitrogen dioxide is the criteria pollutant that has not been in control since beginning
of air quality regulations (USEPA). This is due to diversity of NO2 sources i.e.,
emissions from automobiles, power-stations, etc.
This study discusses two fixed point MAX-DOAS observations; at IESE, NUST
Islamabad and at LUMS, Lahore. Besides this, it also discusses the observations
collected during the field campaigns which were conducted at Lahore, Faisalabad, and
Sheikhupura periodically. Main objectives of this study were to monitor NO2
concentration and investigation of diurnal and weekly cycle of Nitrogen dioxide.
Results showed that NO2 levels were higher in the Morning and Evening but lower in
daytime due to Photolysis. NO2 levels were higher on busy/congested roads and near
the Industrial area. The level of NO2 concentration in the cities follow this pattern;
Islamabad > Lahore > Faisalabad > Sheikhupura. NO2 pollution levels are exceeding
Pak-NEQS limits at various occasions (Maximum limit: 42.5 ppb).
This study also presents comparison of NO2-VCDs measured by OMI (Ozone
Monitoring Instrument) and MAX-DOAS. The comparison showed similar spatial
distribution of nitrogen dioxide concentrations. However, the Tropospheric NO2
VCDs observed by satellite are approximately an order of magnitude lower than the
ground based observations.
