MONITORING NITROGEN DIOXIDE CONCENTRATIONS OVER ISLAMABAD AND RAWALPINDI USING CAR MAX-DOAS

Abstract

Air quality is one of the major environmental concerns worldwide. Air quality standards are implemented by regulatory authorities to maintain the air quality based on criteria pollutants; Nitrogen dioxide (NO2) is one of them. It is a reddish-brown gas with a pungent, irritating odour. It absorbs light, precursor for tropospheric ozone formation and leads to the yellow-brown haze sometimes seen over cities - photochemical smog. NO2 is only the criteria pollutant that has not been in control since the advent of air quality standards (US-EPA, 1990). The reason behind is the variety of NO2 sources like vehicles, power plants, lightening, soil emission, solid waste burning, oil refineries etc. Rapid increase in vehicles on roads is the most contributing source of air pollution in Pakistan (Khawaja and Khan, 2005) and worldwide. (Lundy et al. 2011, Han et al. 2006) This thesis presents tropospheric nitrogen dioxide (NO2) measurements made by car Max-DOAS (Multi Axis-Differential Optical Absorption Spectroscopy) instrument. The measurements were performed during various field campaigns within H-12 main Campus NUST and within the cities of Islamabad and Rawalpindi. The device was mounted on the roof top of a van with lens pointing backward. Retrieved NO2 column densities exhibited spatial variances within Islamabad and Rawalpindi with large amount were measured on the road segments of Inter Junction Principle (IJP) road and around the Attock Oil Refinery (ARL) area. These high column densities are attributed mainly to traffic, stack emissions, congestion and solid waste dumping site along IJP road. Correlation of NO2 mixing ratios with population and number of registered vehicles were also made was found significant. Furthermore, the results were validated with OMI satellite observation for respective days. The comparison gave similar NO2 spatial trends, although satellite observations are found to be under estimated.