Connecting Brown Carbon Composition and Physicochemical Properties of Aqueous Urban PM2.5 to their Photosensitized Production of Singlet Oxygen and Organic Triplet Excited States
Yuting Lyu, Yitao Li, Ruihan Ma, Tianye Zhou, Nadine Borduas-Dedekind, Theodora Nah
TL;DR
This study connects the composition of brown carbon in urban PM2.5 to its ability to produce reactive oxygen species through photosensitization.
Contribution
A new framework is introduced to predict and apportion photosensitizers in brown carbon using optical measurements and statistical modeling.
Findings
Highly oxygenated organic aerosols mainly contribute to singlet oxygen production.
Less oxygenated organic aerosols mainly contribute to organic triplet excited states production.
Statistical models successfully predict reactive species concentrations and quantum yields from optical data.
Abstract
Oxidants, including singlet oxygen (1O2*) and organic triplet excited states (3C*) formed from the photoexcitation of brown carbon (BrC), drive many chemical processes in atmospheric waters. However, due to the chemical complexity of atmospheric BrC, many questions remain about the specific BrC chromophores and physicochemical properties that primarily control 1O2* and 3C* production. In this study, we present a framework for apportioning photosensitizers and predicting the production of 1O2* and 3C* based on measurable physicochemical properties of BrC. This is achieved by combining photochemical experiments with absorbance and fluorescence measurements and statistical modeling of a year-long data set of PM2.5 extracts from Hong Kong SAR, China. Parallel Factor and Non-negative Matrix Factorization analyses of the fluorescence data revealed that highly oxygenated organic aerosols were…
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Taxonomy
TopicsAtmospheric chemistry and aerosols · Atmospheric Ozone and Climate · Air Quality and Health Impacts