ORCID Profile
0000-0003-4848-0616
Current Organisation
University of Toronto
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Publisher: American Geophysical Union (AGU)
Date: 03-07-2021
DOI: 10.1029/2021GL093465
Abstract: We investigated the photosensitizing properties of secondary organic aerosol (SOA) formed during the hydroxyl radical (OH) initiated oxidation of naphthalene. This SOA was injected into an aerosol flow tube and exposed to UV radiation and gaseous volatile organic compounds or sulfur dioxide (SO 2 ). The aerosol particles were observed to grow in size by photosensitized uptake of d‐limonene and β‐pinene. In the presence of SO 2 , a photosensitized production (0.2–0.3 µg m −3 h −1 ) of sulfate was observed at all relative humidity (RH) levels. Some sulfate also formed on particles in the dark, probably due to the presence of organic peroxides. The dark and photochemical pathways exhibited different trends with RH, unraveling different contributions from bulk and surface chemistry. As naphthalene and other polycyclic aromatics are important SOA precursors in the urban and suburban areas, these dark and photosensitized reactions are likely to play an important role in sulfate and SOA formation.
Publisher: American Geophysical Union (AGU)
Date: 16-09-2022
DOI: 10.1029/2022GL098035
Abstract: 28 snowpack s les were collected across northern Xinjiang, northwestern China in January 2018. 16 of these liquid snowmelt s les, 15 with pH 6.8 and one with the highest nitrate anion (NO 3 − ) concentration, were selected to investigate the photochemical gaseous nitrous acid (HONO) production rate (P(HONO) (g) ), which was observed to range from 4.0 to 180.9 ppt min −1 at room temperature. Surprisingly, the ratio of HONO production rate and NO 3 − concentration (P(HONO) (g) /[NO 3 ˉ]) was significantly higher than those obtained from the photolysis of aqueous NO 3 − solutions with similar pH, due to the complex organic compounds present in the snowmelt s les, enhancing HONO formation or the coexistence of other photochemical HONO sources. We also found that P(HONO) (g) was highly correlated with the pH of snowmelt s les, which were significantly lower in rural/remote areas than those from urban/industrial sites, suggesting a significant influence of anthropogenic activities on pH and P(HONO) (g) of snowmelt.
Publisher: Proceedings of the National Academy of Sciences
Date: 03-04-2023
Abstract: Hydroxyl radical (OH) is a key oxidant that triggers atmospheric oxidation chemistry in both gas and aqueous phases. The current understanding of its aqueous sources is mainly based on known bulk (photo)chemical processes, uptake from gaseous OH, or related to interfacial O 3 and NO 3 radical-driven chemistry. Here, we present experimental evidence that OH radicals are spontaneously produced at the air–water interface of aqueous droplets in the dark and the absence of known precursors, possibly due to the strong electric field that forms at such interfaces. The measured OH production rates in atmospherically relevant droplets are comparable to or significantly higher than those from known aqueous bulk sources, especially in the dark. As aqueous droplets are ubiquitous in the troposphere, this interfacial source of OH radicals should significantly impact atmospheric multiphase oxidation chemistry, with substantial implications on air quality, climate, and health.
No related grants have been discovered for Xinke WANG.