气候变化领域集成服务门户(CCPortal): Molecular composition and photochemical lifetimes of brown carbon chromophores in biomass burning organic aerosol

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DOI	10.5194/acp-20-1105-2020
	Molecular composition and photochemical lifetimes of brown carbon chromophores in biomass burning organic aerosol
	Fleming L.T.; Lin P.; Roberts J.M.; Selimovic V.; Yokelson R.; Laskin J.; Laskin A.; Nizkorodov S.A.
发表日期	2020
ISSN	1680-7316
起始页码	1105
结束页码	1129
卷号	20 期号:2
英文摘要	To better understand the effects of wildfires on air quality and climate, it is important to assess the occurrence of chromophoric compounds in smoke and characterize their optical properties. This study explores the molecular composition of light-absorbing organic aerosol, or brown carbon (BrC), sampled at the Missoula Fire Sciences laboratory as a part of the FIREX Fall 2016 lab intensive. A total of 12 biomass fuels from different plant types were tested, including gymnosperm (coniferous) and angiosperm (flowering) plants and different ecosystem components such as duff, litter, and canopy. Emitted biomass burning organic aerosol (BBOA) particles were collected onto Teflon filters and analyzed offline using high-performance liquid chromatography coupled to a photodiode array spectrophotometer and a high-resolution mass spectrometer (HPLC-PDA-HRMS). Separated BrC chromophores were classified by their retention times, absorption spectra, integrated absorbance in the near-UV and visible spectral range (300-700 nm), and chemical formulas from the accurate m/z measurements. BrC chromophores were grouped into the following classes and subclasses: lignin-derived products, which include lignin pyrolysis products; distillation products, which include coumarins and flavonoids; nitroaromatics; and polycyclic aromatic hydrocarbons (PAHs). The observed classes and subclasses were common across most fuel types, although specific BrC chromophores varied based on plant type (gymnosperm or angiosperm) and ecosystem component(s) burned. To study the stability of the observed BrC compounds with respect to photodegradation, BBOA particle samples were irradiated directly on filters with near UV (300-400 nm) radiation, followed by extraction and HPLC-PDA-HRMS analysis. Lifetimes of individual BrC chromophores depended on the fuel type and the corresponding combustion condition. Lignin-derived and flavonoid classes of BrC generally had the longest lifetimes with respect to UV photodegradation. Moreover, lifetimes for the same type of BrC chromophores varied depending on biomass fuel and combustion conditions. While individual BrC chromophores disappeared on a timescale of several days, the overall light absorption by the sample persisted longer, presumably because the condensed-phase photochemical processes converted one set of chromophores into another without complete photobleaching or from undetected BrC chromophores that photobleached more slowly. To model the effect of BrC on climate, it is important to understand the change in the overall absorption coefficient with time. We measured the equivalent atmospheric lifetimes of the overall BrC absorption coefficient, which ranged from 10 to 41 d, with subalpine fir having the shortest lifetime and conifer canopies, i.e., juniper, having the longest lifetime. BrC emitted from biomass fuel loads encompassing multiple ecosystem components (litter, shrub, canopy) had absorption lifetimes on the lower end of the range. These results indicate that photobleaching of BBOA by condensed-phase photochemistry is relatively slow. Competing chemical aging mechanisms, such as heterogeneous oxidation by OH, may be more important for controlling the rate of BrC photobleaching in BBOA. © 2020 Author(s).
语种	英语
scopus关键词	absorbance; aerosol composition; aerosol formation; air quality; biomass burning; carbon; lignin; molecular analysis; PAH; photodegradation; Abies lasiocarpa; Coniferophyta; Gymnospermae; Juniperus; Magnoliophyta
来源期刊	Atmospheric Chemistry and Physics
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/141581
作者单位	Department of Chemistry, University of California, Irvine, Irvine, CA 92697, United States; Department of Chemistry, Purdue University, West Lafayette, IN 47907, United States; Chemical Sciences Division, Earth System Research Laboratory, National Oceanic and Atmospheric Administration, Boulder, CO 80305, United States; Department of Chemistry, University of Montana, Missoula, MT 59812, United States; California Air Resources Board, El Monte, CA 91731, United States
推荐引用方式 GB/T 7714	Fleming L.T.,Lin P.,Roberts J.M.,et al. Molecular composition and photochemical lifetimes of brown carbon chromophores in biomass burning organic aerosol[J],2020,20(2).
APA	Fleming L.T..,Lin P..,Roberts J.M..,Selimovic V..,Yokelson R..,...&Nizkorodov S.A..(2020).Molecular composition and photochemical lifetimes of brown carbon chromophores in biomass burning organic aerosol.Atmospheric Chemistry and Physics,20(2).
MLA	Fleming L.T.,et al."Molecular composition and photochemical lifetimes of brown carbon chromophores in biomass burning organic aerosol".Atmospheric Chemistry and Physics 20.2(2020).