Identification of Carbonaceous Species and FTIR Profiling of PM(2.5) Aerosols for Source Estimation in Old Delhi Region of India

In this study, PM(2.5) samples from a traffic-influenced site in old Delhi were collected from January 2021 to June 2021 (January–March, 2021: months with regular activities; April–June, 2021: partially restricted months due to second wave of pandemic) and analysed to assess noteworthy effect on their infrared (IR) spectral features and carbonaceous content viz., organic carbon (OC) and elemental carbon (EC) and their sub-fractions with their link to major sources in the vicinity of the sampling site of Delhi. Absorbance peaks for the structural and functional groups for previously identified compounds associated with vehicular/combustion/biogenic emissions at the site were notable. Intensive peaks for C=C, C–H, O–H and NH(4)NO(3) were observed on certain days pointing towards enhanced emission of the related compounds. Lower spectral peaks were observed for March and first half of April probably due to transitioning meteorological variables and imposed restrictions. Monthly variation in ratios, such as OC/EC, EC/TC and OM/OC, revealed about the probable emission sources. Comparatively higher peaks/values were observed during January, February and June. The overall results followed a general pattern of variation for regular days.