Molecular characterization of organic aerosol in the Himalayas: insight from ultra-high-resolution mass spectrometry

An, Yanqing; Xu, Jianzhong; Feng, Lin; Zhang, Xinghua; Liu, Yanmei; Kang, Shichang; Jiang, Bin; Liao, Yuhong

doi:10.5194/acp-19-1115-2019

Cited by 31 publications

(21 citation statements)

References 71 publications

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“…The fitted MAC values at 370 nm were 2.29, 2.18, and 0.60 m 2 g −1 for BBOA, NOA, and MO-OOA, respectively (Table 2). The relatively higher MAC values for BBOA and NOA were consistent with the findings from previous studies, which showed that nitrogen-containing organics contributed substantially to particle light absorption (An et al, 2019;Chen et al, 2016;Xu et al, 2020). A possible reason for the lower MAC of MO-OOA is that photolysis and/or photochemical oxidation processes might have caused significant photobleaching of BrC chromophores and hence decreased the BrC absorptivity (Chen et al, 2020;Sareen et al, 2013;Wong et al, 2017).…”

Section: Sources Of Brc Based On Light Absorption Apportionmentsupporting

confidence: 90%

Regional Differences in the Light Absorption Properties of Fine Particulate Matter Over the Tibetan Plateau: Insights From HR‐ToF‐AMS and Aethalometer Measurements

Zhang

Kang

et al. 2021

JGR Atmospheres

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The Tibetan Plateau (TP) has received wide scientific concern in recent decades owing to its important impacts on regional climatic and cryospheric changes, hydrological cycles, and environments. However, our understanding of the spatial distribution of the chemical and optical properties of aerosols is still limited based on prior single‐site observations. In this study, aerosol light absorptions from black carbon (BC) and brown carbon (BrC) were explored and compared among three remote TP sites, including Qomolangma Station (QOMS) on the southern TP, Nam Co Station (NamCo) on the central TP, and Waliguan Observatory on the northeastern TP. Although the aerosol mass concentration at QOMS was less than half of that at Waliguan, the light absorption coefficient of aerosols at QOMS was nearly 5 times higher than that at Waliguan, mainly as a result of more light‐absorbing carbonaceous aerosols on the southern TP due to long‐range transported biomass burning emissions. Specifically, BC dominated aerosol light absorption at all wavelengths, whereas BrC contributed ∼30% of the light absorption at 370 nm at QOMS and ∼20% at Waliguan and NamCo. A major contributor to BrC light absorption at QOMS was biomass burning‐related organic aerosols apportioned from aerosol mass spectrometry measurements. Understanding the significant regional differences in aerosol light absorption properties on the TP is useful for evaluating the regional climatic and environmental effects and validating the model results on aerosol radiative forcing.

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Section: Sources Of Brc Based On Light Absorption Apportionmentsupporting

confidence: 90%

Regional Differences in the Light Absorption Properties of Fine Particulate Matter Over the Tibetan Plateau: Insights From HR‐ToF‐AMS and Aethalometer Measurements

Zhang

Kang

et al. 2021

JGR Atmospheres

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“…Our previous studies have reported that there were obvious biomass burning source emissions during the summer observation period (Yan et al, 2015. By contrast, apart from the influence of biomass burning, CHON compounds were also likely to be influenced by coal combustion and formed from atmospheric chemical processes, such as the reactions of VOCs and NO 3 radicals or RO 2 + NO (An et al, 2019;Ng et al, 2017) during the wintertime, when high NO x and ambient anthropogenic VOCs dominated in the winter atmosphere (Zhang et al, 2017) (see Figure S3c). Further studies on CHON compounds from different primary sources and atmospheric reactions among precursors such as VOCs, NO x , as well as atmospheric oxidants like hydroxyl radical (OH), nitrate radical (NO ) and O , should be conducted with more comprehensive gas-, particle-, and aqueous-phase observation data, to further elucidate the formation mechanisms and sources of CHON compounds in the ambient atmosphere in Beijing under different pollution conditions especially during wintertime.…”

Section: Journal Of Geophysical Research: Atmospheresmentioning

confidence: 97%

Molecular Characterization of Water‐Soluble Brown Carbon Chromophores in Beijing, China

et al. 2020

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High abundance and strong light absorption of atmospheric brown carbon (BrC) have been reported in East Asia, especially in northern China. However, the molecular‐level understanding of BrC chromophores in this area is still limited and quite challenging. In this study, elemental composition of individual BrC chromophores was first investigated in the megacity of Beijing, China, using a powerful platform for the characterization of BrC chromophores, with combination of high‐performance liquid chromatography coupled to a UV/Vis absorbance detector and a time‐of‐flight mass spectrometer with an electrospray ionization source. The results from this study showed that S‐containing compounds (e.g., CHOS and CHONS) significantly increased in highly polluted days compared to lightly polluted days, probably due to increased emissions from sources such as coal combustion and favorable conditions for organosulfates formation. It was found that CHON and CHO compounds were the most abundant water‐soluble organic compounds in Beijing especially during the wintertime. Nitroaromatic compounds were the major water‐soluble BrC chromophores, with three major BrC chromophores (e.g., C6H5NO3, C7H7NO4, and C6H5NO4) found under all conditions, while other specific BrC chromophores with CHON‐ and CHO‐containing elemental formulas identified and varied in different seasons and pollution conditions. Overall, the water‐soluble BrC chromophores identified in this study explained about 2%–18% of the bulk BrC absorbance over the wavelength range of 300–400 nm. In‐depth studies on exploring more BrC chromophores as well as their chemical structures, related sources, and formation mechanisms should be conducted in the future.

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“…and RO q 2 + NO → RO q + NO 2 followed by alkoxy H shift (Baldwin and Golden, 1978;Atkinson and Carter, 1991) and peroxidation, RO…”

Section: Characterization Of Homsmentioning

confidence: 99%

On the similarities and differences between the products of oxidation of hydrocarbons under simulated atmospheric conditions and cool flames

et al. 2021

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Abstract. Atmospheric oxidation chemistry and, more specifically, photooxidation show that the long-term oxidation of organic aerosol (OA) progressively erases the initial signature of the chemical compounds and can lead to a relatively uniform character of oxygenated organic aerosol (OOA). This uniformity character observed after a long reaction time seems to contrast with the great diversity of reaction mechanisms observed in the early stages of oxidation. The numerous studies carried out on the oxidation of terpenes, and more particularly on limonene for its diversity of reaction sites (endo- and oxocyclic), allow this evolution to be studied. We have selected, for their diversity of experimental conditions, nine studies of limonene oxidation at room temperature over long reaction times to be compared to the present data set obtained at elevated temperature and short reaction time in order to investigate the similarities in terms of reaction mechanisms and chemical species formed. Here, the oxidation of limonene–oxygen–nitrogen mixtures was studied using a jet-stirred reactor at elevated temperature and atmospheric pressure. Samples of the reacting mixtures were collected and analyzed by high-resolution mass spectrometry (Orbitrap) after direct injection or after separation by reverse-phase ultra-high-pressure liquid chromatography and soft ionization, i.e., (+/-) HESI and (+/-) APCI. Unexpectedly, because of the diversity of experimental conditions in terms of continuous-flow tank reactor, concentration of reactants, temperature, reaction time, mass spectrometry techniques, and analysis conditions, the results indicate that among the 1138 presently detected molecular formulae, many oxygenates found in earlier studies of limonene oxidation by OH and/or ozone are also produced under the present conditions. Among these molecular formulae, highly oxygenated molecules and oligomers were detected in the present work. The results are discussed in terms of reaction pathways involving the initial formation of peroxy radicals (RO2), isomerization reactions yielding keto-hydroperoxides, and other oxygenated intermediates and products up to C25H32O17, products which could derive from RO2 autoxidation via sequential H shift and O2 addition (C10H14O3,5,7,9,11) and products deriving from the oxidation of alkoxy radicals (produced by RO2 self-reaction or reaction with HO2) through multiple H shifts and O2 additions (C10H14O2,4,6,8,10). The oxidation of RO2, with possible occurrence of the Waddington mechanism and of the Korcek mechanism, involving H shifts is also discussed. The present work demonstrates similitude between the oxidation products and oxidation pathways of limonene under simulated atmospheric conditions and in those encountered during the self-ignition of hydrocarbons at elevated temperatures. These results complement those recently reported by Vereecken and Nozière and confirm for limonene the existence of an oxidative chemistry of the alkylperoxy radical beyond 450 K based on the H shift (Nozière and Vereecken, 2019; Vereecken and Nozière, 2020).

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Molecular characterization of organic aerosol in the Himalayas: insight from ultra-high-resolution mass spectrometry

Cited by 31 publications

References 71 publications

Regional Differences in the Light Absorption Properties of Fine Particulate Matter Over the Tibetan Plateau: Insights From HR‐ToF‐AMS and Aethalometer Measurements

Regional Differences in the Light Absorption Properties of Fine Particulate Matter Over the Tibetan Plateau: Insights From HR‐ToF‐AMS and Aethalometer Measurements

Molecular Characterization of Water‐Soluble Brown Carbon Chromophores in Beijing, China

On the similarities and differences between the products of oxidation of hydrocarbons under simulated atmospheric conditions and cool flames

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