Sources, composition, and mixing state of submicron particulates over the central indo-gangetic plain

• Main Authors: Singh, Nandita, Banerjee, Tirthankar, Deboudt, Karine, Chakraborty, Abhishek, Khan, Md Firoz, Latif, Mohd Talib
• Format: Article
• Published: Amer Chemical Soc 2021
• Subjects: Q Science (General); QD Chemistry
• Online Access: http://eprints.um.edu.my/28484/

Submicron particulates, collected between 2015 and 2018 in an urban environment over the central Indo-Gangetic Plain, South Asia, were analyzed. Particulate concentration was typically high during winter (DJF, 115 50 tig m-3) and post -monsoon seasons (ON, 79 52 pg m-3). Submicron particulates constituted a major fraction (69%) of fine particulates (PM).,) without much seasonal discrepancies. Particulates were metal-enriched (17 6%) with signature of crustal and road dust resuspensions. Metal enrichment was evident specifically for Zn, Co, and Cr. Sulfate was the most robust ion contributing 10% ( 4%) of particulate mass followed by nitrate (6 3%) and ammonium (4 2%). Overall, water-soluble ions accounted for one-third of particulate mass mainly comprised secondary ones. The n-alkane homologues (C17 C35) showed prevalence of lowmolecular-weight (LMW) alkanes (<C25) with the carbon preference index (CPI) close to one (1.3 0.3) referring predominant contribution of burning of fossil fuels. Similarly, prevalence of LMVV fatty acids (<C20) with a high CPI (9.9) indicates emissions from residential cooking. The presence of dicarboxylic acids and phthalates with a vital signature of anthropogenic emissions was also traced. Strong enrichment of levoglucosan (600 388 ng m-3) was noted especially during peak biomass -burning episodes. Single -particle analysis indicates high abundance of carbonaceous particles (CPs) having both chain-like soot spherules and amorphous tar balls. These CPs were mostly pure, externally mixed against secondary particles for which the mixing state varied among the seasons. Source apportionment by an advanced receptor model indicates secondary aerosols and biomass -burning emissions as the major sources of submicron aerosols (43%), followed by resuspensions of mineral dusts (18%) and emissions from refuse/waste combustion (18%).