Photochemical processing of aqueous atmospheric brown carbon

Zhao, Rongqin; Lee, Alex K. Y.; Huang, Lin; Li, X.; Yang, Fan; Abbatt, Jonathan P. D.

doi:10.5194/acp-15-6087-2015

Cited by 291 publications

(339 citation statements)

References 84 publications

(130 reference statements)

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“…Most of these results are from laboratory experiments and require confirmation from field observations. Forrister et al (2015) use airborne observations of two fire events to show that the absorption associated with BrC decreases following emission, estimating a half-life for biomass burning BrC absorption of 9-15 h. However, this rate is much slower than that suggested by laboratory studies (5 min to 3 h) (Zhong and Jiang, 2011;Lee et al, 2014;Zhao et al, 2015), though none of these has explored how the absorption of primary BrC from biomass burning evolves under oxidizing conditions. Given the above uncertainties, field measurements of BrC are vital not only for constraining models but also for understanding the properties and transformations of this aerosol and its radiative impacts.…”

Section: Introductionmentioning

confidence: 99%

Deriving brown carbon from multiwavelength absorption measurements: method and application to AERONET and Aethalometer observations

et al. 2016

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Abstract. The radiative impact of organic aerosols (OA) is a large source of uncertainty in estimating the global direct radiative effect (DRE) of aerosols. This radiative impact includes not only light scattering but also light absorption from a subclass of OA referred to as brown carbon (BrC). However, the absorption properties of BrC are poorly understood, leading to large uncertainties in modeling studies. To obtain observational constraints from measurements, a simple absorption Ångström exponent (AAE) method is often used to separate the contribution of BrC absorption from that of black carbon (BC). However, this attribution method is based on assumptions regarding the spectral dependence of BC that are often violated in the ambient atmosphere. Here we develop a new AAE method which improves upon previous approaches by using the information from the wavelengthdependent measurements themselves and by allowing for an atmospherically relevant range of BC properties, rather than fixing these at a single assumed value. We note that constraints on BC optical properties and mixing state would help further improve this method. We apply this method to multiwavelength absorption aerosol optical depth (AAOD) measurements at AERONET sites worldwide and surface aerosol absorption measurements at multiple ambient sites. We estimate that BrC globally contributes up to 40 % of the seasonally averaged absorption at 440 nm. We find that the mass absorption coefficient of OA (OA-MAC) is positively correlated with the BC / OA mass ratio. Based on the variability in BC properties and BC / OA emission ratio, we estimate a range of 0.05-1.5 m 2 g −1 for OA-MAC at 440 nm. Using the combination of AERONET and OMI UV absorption observations we estimate that the AAE 388/440 nm for BrC is generally ∼ 4 worldwide, with a smaller value in Europe (< 2). Our analyses of observations at two surface sites (Cape Cod, to the southeast of Boston, and the GoAmazon2014/5 T3 site, to the west of Manaus, Brazil) reveal no significant relationship between BrC absorptivity and photochemical aging in urban-influenced conditions. However, the absorption of BrC measured during the biomass burning season near Manaus is found to decrease with photochemical aging with a lifetime of ∼ 1 day. This lifetime is comparable to previous observations within a biomass burning plume but much slower than estimated from laboratory studies. Given the large uncertainties associated with AERONET retrievals of AAOD, the most challenging aspect of our analysis is that an accurate, globally distributed, multiple-wavelength aerosol absorption measurement dataset is unavailable at present. Thus, achieving a better understanding of the properties, evolution, and impacts of global BrC will rely on the future deployment of accurate multiple-wavelength absorption measurements toPublished by Copernicus Publications on behalf of the European Geosciences Union.

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Section: Introductionmentioning

confidence: 99%

Deriving brown carbon from multiwavelength absorption measurements: method and application to AERONET and Aethalometer observations

et al. 2016

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“…Due to their strong absorption in the near-ultraviolet and visible regions, nitrated phenols are classified as poorly characterized brown carbon (BrC) (Desyaterik et al, 2013;Teich et al, 2017). Though the absorption of BrC is weak compared to that of black carbon (BC), it can enhance the absorption of solar radiation and may have an indirect effect on regional climate (Feng et al, 2013;Mohr et al, 2013;Laskin et al, 2015;Lu et al, 2015;Zhao et al, 2015). Recent studies have shown that several semivolatile nitrated phenols, including nitrophenol, nitrocatechol, and methyl-nitrocatechol (NC), are important photochemical oxidation products of gas-phase precursors, which may play a part in the formation of secondary organic…”

Section: Introductionmentioning

confidence: 99%

Observations of fine particulate nitrated phenols in four sites in northern China: concentrations, source apportionment, and secondary formation

Wang

et al. 2018

Atmos. Chem. Phys.

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Abstract. Filter samples of fine particulate matters were collected at four sites in northern China (urban, rural, and mountain) in summer and winter, and the contents of nine nitrated phenols were quantified in the laboratory with the use of ultra-high-performance liquid chromatography coupled with mass spectrometry. During the sampling periods, the concentrations of particulate nitrated phenols exhibited distinct temporal and spatial variation. On average, the total concentration of particulate nitrated phenols in urban Jinan in the wintertime reached 48.4 ng m −3 , and those in the summertime were 9.8, 5.7, 5.9, and 2.5 ng m −3 in urban Jinan, rural Yucheng and Wangdu, and Mt. Tai, respectively. The elevated concentrations of nitrated phenols in wintertime and in urban areas demonstrate the apparent influences of anthropogenic sources. The positive matrix factorization receptor model was then applied to determine the origins of particulate nitrated phenols in northern China. The five major source factors were traffic, coal combustion, biomass burning, secondary formation, and aged coal combustion plume. Among them, coal combustion played a vital role, especially at the urban site in the wintertime, with a contribution of around 55 %. In the summertime, the observed nitrated phenols were highly influenced by aged coal combustion plumes at all of the sampling sites. Meanwhile, in remote areas, contributions from secondary formation were significant. Further correlation analysis indicates that nitrosalicylic acids were produced mostly from secondary formation that was dominated by NO 2 nitration.

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“…10 Additionally, light absorption properties of OA are influenced by intermolecular interactions resulting in formation of charge−transfer complexes between different OA molecules. 11,12 Numerous studies indicate that the optical properties of BrC evolve significantly as a result of various atmospheric processes such as oxidation, 13,14 solar irradiation, 15,16 changes in temperature 17 and relative humidity. 18−20 These factors make the chemical composition and concentration of BrC chromophores highly variable across sources and locations, 7,8 which in turn results in high uncertainties in predicting and mitigating their climate effects.…”

Section: ■ Introductionmentioning

confidence: 99%

“…Furthermore, the optical properties of BrC may change as BBOA ages in the atmosphere, 29−31 whereas the effect of aging on light absorption strongly depends on the molecular structures of BrC. 15,16,32 It follows that structural characterization of BrC chromophores will facilitate understanding of their photochemical stability and chemical transformations necessary for the accurate prediction of radiative forcing by BrC. 3 The major challenge in the chemical characterization of BrC is distinguishing its light absorbing components (chromophores) from a majority of nonabsorbing aerosol constituents.…”

Section: ■ Introductionmentioning

confidence: 99%

Molecular Characterization of Brown Carbon in Biomass Burning Aerosol Particles

Lin

Aiona

Liu

et al. 2016

Environ. Sci. Technol.

290

372

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Emissions from biomass burning are a significant source of brown carbon (BrC) in the atmosphere. In this study, we investigate the molecular composition of freshly emitted biomass burning organic aerosol (BBOA) samples collected during test burns of sawgrass, peat, ponderosa pine, and black spruce. We demonstrate that both the BrC absorption and the chemical composition of light-absorbing compounds depend significantly on the type of biomass fuels. Common BrC chromophores in the selected BBOA samples include nitro-aromatics, polycyclic aromatic hydrocarbon derivatives, and polyphenols spanning a wide range of molecular weights, structures, and light absorption properties. A number of biofuel-specific BrC chromophores are observed, indicating that some of them may be used as source-specific markers of BrC. On average, ∼50% of the light absorption in the solvent-extractable fraction of BBOA can be attributed to a limited number of strong BrC chromophores. The absorption coefficients of BBOA are affected by solar photolysis. Specifically, under typical atmospheric conditions, the 300 nm absorbance decays with a half-life of ∼16 h. A “molecular corridor” analysis of the BBOA volatility distribution suggests that many BrC compounds in the fresh BBOA have low saturation mass concentration (<1 μg m–3) and will be retained in the particle phase under atmospherically relevant conditions.

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Photochemical processing of aqueous atmospheric brown carbon

Cited by 291 publications

References 84 publications

Deriving brown carbon from multiwavelength absorption measurements: method and application to AERONET and Aethalometer observations

Deriving brown carbon from multiwavelength absorption measurements: method and application to AERONET and Aethalometer observations

Observations of fine particulate nitrated phenols in four sites in northern China: concentrations, source apportionment, and secondary formation

Molecular Characterization of Brown Carbon in Biomass Burning Aerosol Particles

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