Reactive oxygen species generation from winter water-soluble organic aerosols in Delhi's PM2.5

• Published in: Atmospheric Environment: X Vol. 22; p. 100262
• Main Authors: Bhowmik, Himadri S., Tripathi, Sachchida N., Puthussery, Joseph V., Verma, Vishal, Dave, Jay, Rastogi, Neeraj
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.04.2024; Elsevier
• Subjects: Dithiothreitol (DTT) activity; Multi-linear Regression (MLR); Oxidative Potential (OP); Positive Matrix Factorization (PMF); Reactive Oxygen Species (ROS); Water Soluble Organic Aerosol (WSOA); Water Soluble Organic Aerosol (WSOA); Dithiothreitol (DTT) activity; Oxidative Potential (OP); Reactive Oxygen Species (ROS); Positive Matrix Factorization (PMF); Multi-linear Regression (MLR)
• ISSN: 2590-1621; 2590-1621
• DOI: 10.1016/j.aeaoa.2024.100262

In this study, we evaluate the relative redox activity of various water-soluble organic aerosol (WSOA) sources in Delhi's winter PM2.5, focusing on their capacity to generate reactive oxygen species (ROS). Using offline-aerosol mass spectrometry (AMS) and positive matrix factorization (PMF), we identified two oxidized factors—more oxidized oxygenated organic aerosol (MO-OOA) and less oxidized oxygenated organic aerosol (LO-OOA)—and three primary factors, namely nitrogen-enriched hydrocarbon-like organic aerosol (NHOA), biomass-burning organic aerosol (BBOA), and solid-fuel combustion organic aerosol (SFC-OA). The ROS-generating capability of PM2.5 was assessed using a real-time oxidative potential (OP) measurement system based on the dithiothreitol (DTT) assay. We employed multivariate linear regression technique (MLR) to explore the association between the DTT activity of water-soluble PM2.5 and these identified factors. We found BBOA, SFCOA, and MO-OOA significantly contributed to volume-normalized OP, with intrinsic water-soluble activities of 39 ± 11, 106 ± 31 and 160 ± 43 pmol/min/μg, respectively. MO-OOA, primarily from non-fossil precursors, serves as a proxy for aged biomass burning, which intensifies during winter and significantly influences the DTT activity. Additionally, OP is significantly influenced by WSOA derived from local incomplete solid fuel combustion sources, including coal and wood burning for household cooking and heating, burning of leaves, biodegradable waste, and garbage along the roadside. Interestingly, water-soluble metals (Mn, Cu, and Fe) showed no discernible contribution to the OP. These findings highlight the need for targeted mitigation strategies addressing local combustion processes and unregulated biomass burning to effectively reduce PM health exposure in Delhi. [Display omitted] •Delhi's winter OP surpasses American and European cities by more than 5 times.•MO-OOA from aged biomass burning boosts OP, albeit less than BBOA in WSOA loading.•Unregulated solid fuel combustion and biomass burning strongly impact Delhi's winter OP.•Water-soluble metals (Mn, Cu, Fe) lack OP impact, highlighting organic aerosol dominance.