Hygroscopic Properties of Water-Soluble Counterpart of Ultrafine Particles from Agriculture Crop-Residue Burning in Patiala, Northwestern India

• Published in: Atmosphere Vol. 15; no. 7; p. 835
• Main Authors: Alang, Ashmeet Kaur, Aggarwal, Shankar G., Singh, Khem, Johri, Prabha, Agarwal, Ravinder, Kawamura, Kimitaka
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 01.07.2024
• Subjects: Abundance; Aerosol content; Aerosol particles; aerosol size-resolved hygroscopicity; aerosol water content; Aerosols; Analog computers; Biomass; Biomass burning; Burning; Carbon; Chemical analysis; Chemical composition; Constituents; Crop residues; crop-residue burning aerosols; Crops; Dehumidification; Growth factors; Humidity; hygroscopic tandem differential mobility analyzer; Hygroscopicity; Inorganic salts; Moisture content; Organic carbon; Relative humidity; Residues; Rice; Rural areas; Salts; Shrinkage; Straw; Ultrafines; Water; Water chemistry; Water content; Water uptake; Wheat; Patiala India; India
• ISSN: 2073-4433; 2073-4433
• DOI: 10.3390/atmos15070835

To determine the link between hygroscopicity and the constituent chemical composition of real biomass-burning atmospheric particles, we collected and analyzed aerosols during wheat-straw (April–May), rice-straw (October–November), and no-burning periods (August–September) in 2008 and 2009 in Patiala, Punjab. A hygroscopicity tandem differential mobility analyzer (HTDMA) system was used to measure hygroscopicity at ~5 to ~95% relative humidity (RH) of aerosolized 100 nm particles generated from the water extracts of PM0.4 burning and no-burning aerosol samples. The chemical analyses of the extracts show that organic carbon and water-soluble inorganic-ion concentrations are 2 to 3 times higher in crop-residue burning aerosol samples compared to no-burning aerosols, suggesting the substantial contribution of biomass burning to the carbonaceous aerosols at the sampling site. We observed that aerosolized 100 nm particles collected during the crop-residue burning period show higher and more variable hygroscopic growth factor (g(RH)) ranging from 1.21 to 1.68 at 85% RH, compared to no-burning samples (1.27 to 1.33). Interestingly, crop-residue burning particles also show considerable shrinkage in their size (i.e., g(RH) < 1) at lower RH (<50%) in the dehumidification mode. The increased level of major inorganic ions in biomass-burning period aerosols is a possible reason for higher g(RH) as well as the observed particle shrinkage. Overall, the measured g(RH), together with the correlation observed between aerosol water content and ionic-species volume fraction, and the study of the abundance of individual constituent ionic species suggests that inorganic salts and their proportion in aerosol particles primarily governed the aerosol hygroscopicity.