INVESTIGATING THE DIURNAL AND WEEKLY CYCLE OF NO2 BY USING MAX-DOAS OBSERVATIONS

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.