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Title:Development of novel high-resolution instruments to measure the real-time oxidative potential of ambient particulate matter and their application in source apportionment
Author(s):Puthussery, Joseph Varghese
Director of Research:Verma, Vishal
Doctoral Committee Chair(s):Verma, Vishal
Doctoral Committee Member(s):Riemer, Nicole; Nguyen, Thanh Huong; Koloutsou-Vakakis, Sotiria
Department / Program:Civil & Environmental Eng
Discipline:Environ Engr in Civil Engr
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Oxidative potential
real-time measurement
source apportionment
Biomass burning
Abstract:Exposure to ambient particulate matter (PM) is known to have an adverse effect on human health. One hypothesized mechanism by which PM affects human health is by inducing an oxidative stress, leading to cell damage. Measuring this oxidative stress induced by ambient PM would help find a better association between PM and its health impacts, than the commonly used PM mass concentrations. Conventional oxidative potential (OP) measurement protocols involve measuring the rate of reactive oxygen species (ROS) generation or antioxidant consumption using either cellular or acellular assays. OP measurements are generally performed on PM samples collected using offline filters followed by extraction in a suitable solvent. However, this approach has several shortcomings; for instance, filter-based PM sampling involves long sampling hours and is prone to sampling artifacts, especially when measuring the reactive components in the ambient air. Additionally, due to the long sampling duration, filter-based sampling cannot capture the temporal variations in the PM chemical characteristics and sources, which could significantly alter the OP of the PM. In this study, we designed and developed a new real-time automated instrument that can measure the OP of ambient PM based on multiple acellular assays. The real-time instrument consists of a glass mist chamber (MC) particle into liquid sampler that collects PM2.5 (PM with diameter < 2.5 um) directly into a liquid solution. We used an automated syringe pump system, connected to a spectrophotometer and/or a spectrofluorometer, to measure the OP of the collected PM2.5 sample. The instrument can measure the OP based on the dithiothreitol assay (DTT) and surrogate lung fluid (SLF; a mixture of four antioxidants: ascorbic acid (AA) + glutathione (GSH), uric acid, and citric acid). OP is reported as the rate of consumption of DTT (OPDTT), AA(OPAA), GSH (OPGSH), and rate of hydroxyl radical generation in DTT (OPDTT-OH) and SLF (OPSLF-OH). This instrument can be operated in either single endpoint mode (only OPDTT, time resolution = 1h) or five endpoint mode (time resolution = 3h). This instrument was used in field campaigns in Champaign, Illinois (a small city), and Delhi, India (a highly polluted megacity). For the first time, we report the diurnal OP profile and PM2.5 sources driving the OP in these cities. Source apportionment analysis revealed, secondary aerosols, traffic, industry, and biomass burning were the important PM2.5 sources driving the OP. Using this instrument, we captured the effect of short-duration episodic pollution events like fireworks emissions (Diwali festival and fourth of July) and investigated how it influenced the OP. Finally, we performed an intercomparison of the real-time OP measured based on the five different endpoints and found a poor correlation among the various endpoints. These results suggest that a single OP endpoint probably does not represent the entire OP. Multiple endpoints need to be evaluated together to account for the varying contribution from the diverse redox-active components in PM2.5. The findings from this study demonstrate the usefulness of obtaining highly time resolved PM2.5 OP data to comprehend various emission sources and their relative importance in assessing the risk from PM2.5 exposure.
Issue Date:2021-11-30
Rights Information:Copyright 2021 Joseph Varghese Puthussery
Date Available in IDEALS:2022-04-29
Date Deposited:2021-12

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