EXPLORING THE POTENTIAL OF MAX-DOAS INSTRUMENT FOR ATMOSPHERIC MONITORING OF NO2 CONCENTRATION DURING THE TIME PERIOD OF 2014-2018

Abstract

Air pollution is one of the emerging issues in most of the urban centers of Pakistan. Increasing traffic load, power generation, industrial, and construction activities are contributing to air pollution. Air quality standards are regulated by monitoring criteria air pollutants such as NO2. It’s a major contributor in the formation of acid rain, tropospheric ozone and several other secondary pollutants. This study was designed to monitor the tropospheric NO2 in Islamabad, Pakistan during the time period of September 2014 to September 2018 by using MAX-DOAS. Besides continuous monitoring, field campaigns by using MAX-DOAS were conducted in different forest types in Pakistan were also incorporated in the present study. NO2 diurnal, weekly, and annual cycles were observed. Results show that NO2 concentration was higher in morning and evening but lower during the noon time due to higher photolysis rate of NO2. It was also observed that NO2 was lowest on Friday (business holiday), while annual cycle shows highest average concentrations in winters and lowest in summers. During field campaigns conducted in different forest areas, the NO2 concentrations were found within permissible limit (42.5ppb). NO2 MAX-DOAS measurements were also compared with the OMI instrument observations and a similar spatial distribution of NO2 was identified by the both data sets. A good correlation was observed when MAX-DOAS data was averaged for 01-02 pm (PST) and compared with OMI observations, as the satellite passes over Pakistan between 01-02 pm (PST). However, the OMI instrument tends to underestimate the NO2 concentration as compared to ground based MAX-DOAS observations.