INVESTIGATING THE IMPACTS OF EXTENSIVE USE OF CNG ON NO2 COLUMN DENSITY OVER ISLAMABAD-RAWALPINDI USING SATELLITE AND GROUND BASED OBSERVATIONS

Abstract

Air pollution is a major environmental concern worldwide. In Pakistan, urbanization and traffic is increasing at a faster rate and consequently the air pollution. Compressed Natural Gas (CNG) is an inexpensive, indigenous energy resource which currently accounts for the majority of automobile and domestic energy consumption. This extensive CNG usage, heavily influences the atmospheric composition and hence air quality. This study is designed to monitor the NO2 concentrations over Islamabad-Rawalpindi, Pakistan. Mini MAX-DOAS (Multi Axis – Differential Optical Absorption Spectroscopy) instrument was used to perform ground-based measurements. The spectra were acquired for a period of six months i.e. October 2013-march 2014 at IESE, NUST and field campaigns were conducted in different scenarios when CNG was and was not available. Analysis was performed to retrieve NO2 Differential Slant Column Densities (DSCD). It was observed that CNG availability significantly reduced the NO2 Levels. Satellite observations from Ozone Monitoring Instrument (OMI) were compared with the ground-based observations from Mini MAX-DOAS. Tropospheric NO2 VCDs derived from ground-based mini MAX-DOAS measurement at IESE-NUST monitoring site showed a reasonable agreement with satellite observations over Islamabad-Rawalpindi, Pakistan. The wind data was also used to identify the possible pollution pathways at NUST. High traffic densities on IJP Road, Kashmir Highway and N-5 Highway are the main sources of air pollution being transported to IESE-NUST monitoring site