Temporal Record of Tropospheric Formaldehyde Column Densities Over Pakistan By Using Satellite Observations

Abstract

Air pollution is one of the most rapidly growing environmental problems in Pakistan. Addition of various trace gases like Nitrogen dioxide (NO2), Sulphur dioxide (SO2), Ozone (O3) and organic compounds including Formaldehyde (HCHO) has degraded air quality of developing countries including Pakistan. HCHO in troposphere is altering the chemical composition of earth’s atmosphere. This study primarily focuses on the preparation of a database of HCHO column densities during last decade (2003-2012) by using data from two satellite instruments SCIAMACHY (Scanning Imaging Absorption spectroMeter for Atmospheric CartograpHY) and GOME- 2 (Global Ozone Monitoring Experiment). Spatial and Temporal distribution of HCHO column densities all over Pakistan are analyzed. Spatial maps were generated in order to see the distribution of HCHO major hotspots (areas with higher concentration of HCHO) all over Pakistan. Seasonal cycle of HCHO in all provinces of Pakistan was also investigated which showed the highest concentration of HCHO in summers attributed to increase in biogenic emissions and biomass burning. Further emphasis was placed on source identification that revealed that vegetation fires also contribute to tropospheric HCHO in Pakistan. Results indicated that in Punjab and Sindh provinces, vegetation and agricultural fires contributed to increase in HCHO Columns. No temporal evolution in HCHO columns over Pakistan is observed. Furthermore, trend analysis for different seasons did not show any statistically significant increase or decrease in HCHO data over Pakistan.