Characterization of atmospheric trace gases and water soluble inorganic chemical ions of PM and PM at Indira Gandhi International Airport, New Delhi during 2017-18 winter.

Water soluble inorganic chemical ions of PM and PM and atmospheric trace gases were monitored simultaneously on hourly resolution at Indira Gandhi International Airport (IGIA), Delhi during 8 December 2017-10 February 2018. Monitoring was made by MARGA (Monitoring AeRosol and Gases in ambient Air) under winter fog experiment (WIFEX) program of the Ministry of Earth Sciences (MoES), Government of India. The result based on the analysis of the data so generated reveals that Cl, NH, NO and SO were dominant ions in order which collectively constituted 96.8 and 97.3% of the of the total measured ionic mass in PM and PM respectively. Their overall average concentrations in PM were 19.5 ± 19.7, 18.4 ± 10.5, 16.6 ± 8.7 and 10.3 ± 5.7 μg/m and in PM were 36.0 ± 33.9, 32.7 ± 17.2, 28.5 ± 13.6 and 19.9 ± 13.9 μg/m. Average concentrations of HCl, HNO, HNO, SO and NH trace gases were 0.7 ± 0.3, 2.7 ± 1.1, 6.6 ± 4.7, 22.0 ± 12.3 and 25.7 ± 9.1 μg/m respectively. Weather parameters along with low mixing height played significant role in the occurrence of high concentration of these chemical species. NH was the prime neutralizer of the acidic components and mostly occurred in (NH)SO/NHHSO, NHNO and NHCl molecular forms. Major sources of these chemical species were fossil fuel combustion in aviation activity and transportation, coal burning in thermal power plants, industrial processes and emissions from biomass burning and agro-based activity. The quality of air with respect to PM always remained deteriorated. It became alarming during low visibility period mainly due to high concentration of Cl, NO, SO and NH. Both meteorological and chemical processes interactively fed each other which occasionally resulted in fog development and visibility degradation. The knowledge gained by this study will help in simulation of atmospheric processes which lead to fog development and dispersal in the Delhi region.