Spatio-Temporal Analyses of Formaldehyde over Pakistan by Using SCIAMACHY and GOME-2 Observations

Abstract

This study primarily focuses on monitoring of tropospheric formaldehyde (HCHO) column densities over Pakistan during the time period of year 2003 to 2012. Observations from two satellite instruments SCIAMACHY (Scanning imaging absorption spectrometer for atmospheric chartography, on-board ENVISAT-1) and GOME-2 (Global ozone monitoring experiment, on-board Metop-A) were used. Spatial and temporal distributions of HCHO column densities over Pakistan are analysed. Spatial maps were generated in order to see the distribution of HCHO and to identify major hotspots across the country. Seasonal cycle of HCHO over all provinces of Pakistan showed the summer maximum attributed to increase in biogenic emissions and biomass burning activities. Further emphasis was made on source identification of HCHO emissions. It revealed that agriculture fires and extensive use of compressed natural gas (CNG) as fuel also contribute to tropospheric HCHO in Pakistan. World fire atlas data from along track scanning radiometer (ATSR) was used to identify effect of agriculture waste burning on HCHO concentration in Pakistan. Significant correlation was observed between agricultural fires and increased HCHO column densities.

Diurnal, seasonal and long-term variations of global formaldehyde columns inferred from combined OMI and GOME-2 observations

“…Column inter-annual variabilities are mainly driven by fire events and temperature changes (Millet et al, 2008;Barkley et al, 2009;Stavrakou et al, 2014). However, over industrialised regions, changes in anthropogenic emissions have also been identified as drivers of observed H 2 CO column trends Zhu et al, 2014;Khokhar et al, 2015;Mahajan et al, 2015;Stroud et al, 2015).…”

Temporal Variability and Characterization of Aerosols across the Pakistan Region during the Winter Fog Periods

“…Large numbers of agriculture fires are observed across the Indus plains during crop harvesting seasons. Mainly, fires are intense during the months of April-May for clearing wheat residue and during October-November for rice paddies [54,59], followed by January-February months for the sugarcane crop. Agricultural fires emit aerosol particles, greenhouse gases, and various trace gases into the atmosphere [68].…”

“…Recently, several studies used satellite monitoring of various trace gases such as SO 2 , NO 2 and CO in order to identify the source region of aerosols, as these originate from the same sources as these tiny particles [71][72][73][74]. In order to investigate such a relationship between AOD and aerosol precursor gases, the Indus plains were divided into two different regions: Upper Indus Plains (UIP-light green polygons in Figure 5c [12], SO 2 [75] and formaldehyde [59], mainly caused by vehicular, industrial and biomass burning activities. In contrast, the southern plains host few industries, less population but extensive agriculture activities and fires activities ( Figure 5).…”

“…Major sources of aerosols in Pakistan are seasonal biomass-burning smoke and dust storms in addition to industrial and vehicular activities [34,54,59]. Winds are the carrier of these pollutants as cold winds (western disturbances [60]) that arrive from west Asia, northwest India and then change direction to the eastern part, are considered as a major sources of aerosol movement and spread over Bangladesh and the Ganges-Brahmaputra delta [61][62][63].…”

Formaldehyde total column densities over Mexico City: comparison between MAX-DOAS and solar absorption FTIR measurements

“…It is worth mentioning that these type of strong spatial heterogeneity scenarios have been observed in different areas of the planet and specific studies of atmospheric constituents have been or are currently being performed in other urbanized and densely populated areas such as North America (Boeke et al, 2011;Chance et al, 2000;Millet et al, 2008), China (Cheng et al, 2015;Zhang et al, 2019), particularly in the Beijing-Tianjin-Hebei region (Zhu et al, 2018) and the Yangtze River Delta area (Chan et al, 2019;Hong et al, 2018;Tian et al, 2018;Wang et al, 2016); South Asia (Rana et al, 2019) and more specifically India (Chutia et al, 2019;Surl et al, 2018) and Pakistan (Khan et al, 2018;Khokhar et al, 2015). In addition specific case studies have been conducted globally (Wittrock et al, 2006) or in the Southern Hemisphere (Ahn et al, 2019), the Atlantic Ocean (Behrens et al, 2019) and the East China Sea (Tan et al, 2018).…”