Naphthalene‐Derived Secondary Organic Aerosols Interfacial Photosensitizing Properties. Issue 13 (3rd July 2021)

• Record Type: Journal Article
• Authors: Wang, Xinke; Gemayel, Rachel; Baboomian, Vahe J.; Li, Kangwei; Boreave, Antoinette; Dubois, Clement; Tomaz, Sophie; Perrier, Sebastien; Nizkorodov, Sergey A.; George, Christian
• Is Part Of: Geophysical research letters. Volume 48:Issue 13(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-07-03
• Subjects: secondary organic aerosols -- photochemistry -- interface -- sulfate; Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1029/2021GL093465
• Languages: English
• ISSNs: 0094-8276

Abstract

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 (SO2 ). The aerosol particles were observed to grow in size by photosensitized uptake of d‐limonene and β‐pinene. In the presence of SO2, 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. Plain Language Summary: Organic compounds and sulfate anions are important components of atmospheric fine particles, which play an important role in air quality, visibility, climate, as well as human and ecosystem health. Photosensitized chemistry, which is driven by reactions of electronically excited organic molecules, is a proposed pathway for fine particle growth, producing highly oxygenated compounds and sulfate anions from gaseous volatile organics and sulfur dioxide, a key air pollutant. Aromatic hydrocarbons and their oxidation products are important components of fine particles in urban environments. This work shows that fine particles formed by oxidation of naphthalene, a common aromatic hydrocarbon, possess photosensitizing properties making them efficient catalysts for atmospheric oxidation of sulfur dioxide and volatile organics. Key Points: Naphthalene‐derived secondary organic aerosol (SOA) contains oxygenated aromatic compounds with photosensitizing properties Photosensitized oxidation of d‐limonene and β‐pinene by naphthalene‐derived SOA results in particle growth Sulfate is formed through both dark and photosensitized chemical reactions between naphthalene‐derived SOA and SO2