American Association for Aerosol Research - Abstract Submission

AAAR 39th Annual Conference
October 18 - October 22, 2021

Virtual Conference

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Influence of Extreme Air Pollution Episodes on the Oxidative Potential of Ambient Particulate Matter in Delhi, India

JOSEPH V PUTHUSSERY, Ashutosh Shukla, Jay Dave, Sreenivas Gaddamidi, Atinderpal Singh, Dilip Ganguly, Neeraj Rastogi, Sachchida N. Tripathi, Vishal Verma, University of Illinois Urbana-Champaign

     Abstract Number: 264
     Working Group: Health-Related Aerosols

Abstract
The oxidative potential (OP) of ambient particulate matter (PM) is a health metric used to estimate PM toxicity. In this study, we measured the real-time OP of ambient fine PM (or PM2.5) in Delhi, India. PM2.5 mass concentrations in Delhi peak during the months of October - January, because of various extreme air pollution episodes (such as biomass burning, Diwali fireworks, and the winter haze events), occurring during that period. Here, we investigated the effect of these pollution episodes on the PM2.5 OP and identified the emission sources contributing to PM2.5 OP. We measured the hourly averaged real-time OP of ambient PM2.5 based on a dithiothreitol assay using a custom-built automated OP measurement instrument which was designed in our lab. The chemical composition of PM2.5 was also measured using various collocated online instruments such as a high-resolution time-of-flight aerosol mass spectrometer, aethalometer, and Xact®625i. We sampled ambient PM2.5 at Delhi intermittently from October 11, 2019, to January 8, 2020 (~50 days).

Both PM2.5 mass concentration and OPv peaked during the winter/haze period [327 (±163) µg/m3, 5.3 (±4) nmol/min/m3, respectively]. However, the mass normalized OP was highest (43±30 pmol/min/µg) during Diwali. Positive matrix factorization analysis results showed that sulfate-rich aerosols and biomass burning aerosols together contributed to more than 50% of the total OPv during the fall period, followed by dust (19%). However, fireworks became a significant source during Diwali, driving more than 20% of OPv. Biomass burning (~40%) and sulfate-rich aerosols (~40%) dominated the OPv during the winter/haze period. These findings reveal substantial temporal heterogeneity in the redox properties of PM and highlight the importance of determining the PM chemical composition along with its mass concentrations for predicting the overall health impacts associated with aerosol exposure.