Molecular Analysis of Secondary Brown Carbon Produced from the Photooxidation of Naphthalene
We investigate the chemical composition of organic light-absorbing components, also known as brown carbon (BrC) chromophores, formed in a proxy of anthropogenic secondary organic aerosol generated from the photooxidation of naphthalene (naph-SOA) in the absence and presence of NO x . High-performanc...
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Published in | Environmental science & technology Vol. 56; no. 6; pp. 3340 - 3353 |
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Main Authors | , , , , , , |
Format | Journal Article |
Language | English |
Published |
United States
American Chemical Society
15.03.2022
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Subjects | |
Online Access | Get full text |
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Summary: | We investigate the chemical composition of organic light-absorbing components, also known as brown carbon (BrC) chromophores, formed in a proxy of anthropogenic secondary organic aerosol generated from the photooxidation of naphthalene (naph-SOA) in the absence and presence of NO x . High-performance liquid chromatography equipped with a photodiode array detector and electrospray ionization high-resolution mass spectrometer is employed to characterize naph-SOA and its BrC components. We provide molecular-level insights into the chemical composition and optical properties of individual naph-SOA components and investigate their BrC relevance. This work reveals the formation of strongly absorbing nitro-aromatic chromophores under high-NO x conditions and describes their degradation during atmospheric aging. NO x addition enhanced the light absorption of naph-SOA while reducing wavelength-dependence, as seen by the mass absorption coefficient (MAC) and absorption Ångström exponent (AAE). Optical parameters of naph-SOA generated under low- and high-NO x conditions showed a range of values from MACOM 405nm ∼ 0.12 m2 g–1 and AAE300–450nm ∼ 8.87 (low-NO x ) to MACOM 405nm ∼ 0.19 m2 g–1 and AAE300–450nm ∼ 7.59 (high-NO x ), consistent with “very weak” and “weak” BrC optical classes, respectively. The weak-BrC class is commonly attributed to biomass smoldering emissions, which appear to have optical properties comparable with the naph-SOA. Molecular chromophores contributing to naphthalene BrC absorption were identified with substantial nitro-aromatics, indicating that these species may be used as source-specific markers of BrC related to the anthropogenic emissions. |
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Bibliography: | ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 |
ISSN: | 0013-936X 1520-5851 |
DOI: | 10.1021/acs.est.1c03135 |