Regional Differences of Chemical Composition and Optical Properties of Aerosols in the Tibetan Plateau

Xu, Jianzhong; Hettiyadura, Anusha P. S.; Liu, Yanmei; Zhang, Xinghua; Kang, Shichang; Laskin, Alexander

doi:10.1029/2019jd031226

Cited by 23 publications

(44 citation statements)

References 51 publications

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“…Waliguan, Gongga, Lhasa, and Mt. Yulong (Cong et al., 2015; Kang et al., 2016; Wan et al., 2016; Xu et al., 2020; Zhang et al., 2001, 2012; Zhao et al., 2013). Chemical characterization of submicron aerosols has also been carried out by using aerosol mass spectrometer at a few sites such as Menyuan (Du et al., 2015), Mt.…”

Section: Introductionmentioning

confidence: 99%

Unexpected High Absorption of Atmospheric Aerosols Over a Western Tibetan Plateau Site in Summer

et al. 2021

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The assessment of atmospheric aerosol radiative effects in the Tibetan Plateau (TP) suffers from large uncertainties due to limited understanding of aerosol physicochemical properties. To quantify aerosol optical properties, size distributions, and chemical compositions in the western TP, an intensive field campaign was carried out at Shiquanhe National Reference Climatological Station from July 8 to August 2, 2019. Unexpected low single scattering albedo (SSA) at 870 nm was found for the fine aerosols with an average value of 0.73 ± 0.18. SSA was even lower than 0.60 in the morning when fine aerosols peaked, indicating high absorption of the fine aerosols induced by anthropogenic activities. Coarse mode aerosols accounted for 70.58% ± 14.98% of the total volume concentration and mineral dust was the most abundant species in total suspended particles with a mass fraction of 48.7%. Fine mode aerosol concentrations showed little dependence on wind speed while coarse mode aerosols and metallic element concentrations exhibited strong positive correlations with wind speed, indicating the importance of wind‐blown dust particles. The present study for the first time quantified key aerosol parameters in the western TP and unexpected high absorption of atmospheric aerosols were found over the site in summer. Our results suggest the need to carefully consider the radiative effects caused by aerosol absorption in the TP region.

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Section: Introductionmentioning

confidence: 99%

Unexpected High Absorption of Atmospheric Aerosols Over a Western Tibetan Plateau Site in Summer

et al. 2021

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“…2018; Yan et al, 2015a). For example, a model study showed that BrC contributes up to +0.25 W m −2 of radiative forcing on a planetary scale, which is approximately 19 % of the absorption by anthropogenic aerosols (Feng et al, 2013).…”

Section: Introductionmentioning

confidence: 99%

Optical properties and molecular compositions of water-soluble and water-insoluble brown carbon (BrC) aerosols in northwest China

Zhang

Wang

et al. 2020

Atmos. Chem. Phys.

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Abstract. Brown carbon (BrC) contributes significantly to aerosol light absorption and thus can affect the Earth's radiation balance and atmospheric photochemical processes. In this study, we examined the light absorption properties and molecular compositions of water-soluble (WS-BrC) and water-insoluble (WI-BrC) BrC in PM2.5 collected from a rural site in the Guanzhong Basin – a highly polluted region in northwest China. Both WS-BrC and WI-BrC showed elevated light absorption coefficients (Abs) in winter (4–7 times those in summer) mainly attributed to enhanced emissions from residential biomass burning (BB) for heating of homes. While the average mass absorption coefficients (MACs) at 365 nm (MAC365) of WS-BrC were similar between daytime and nighttime in summer (0.99±0.17 and 1.01±0.18 m2 g−1, respectively), the average MAC365 of WI-BrC was more than a factor of 2 higher during daytime (2.45±1.14 m2 g−1) than at night (1.18±0.36 m2 g−1). This difference was partly attributed to enhanced photochemical formation of WI-BrC species, such as oxygenated polycyclic aromatic hydrocarbons (OPAHs). In contrast, the MACs of WS-BrC and WI-BrC were generally similar in winter and both showed few diel differences. The Abs of wintertime WS-BrC correlated strongly with relative humidity, sulfate and NO2, suggesting that aqueous-phase reaction is an important pathway for secondary BrC formation during the winter season in northwest China. Nitrophenols on average contributed 2.44±1.78 % of the Abs of WS-BrC in winter but only 0.12±0.03 % in summer due to faster photodegradation reactions. WS-BrC and WI-BrC were estimated to account for 0.83±0.23 % and 0.53±0.33 %, respectively, of the total down-welling solar radiation in the ultraviolet (UV) range in summer, and 1.67±0.72 % and 2.07±1.24 %, respectively, in winter. The total absorption by BrC in the UV region was about 55 %–79 % relative to the elemental carbon (EC) absorption.

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“…Xu et al. (2020) also found a distinctly higher light absorption efficiency of BrC at QOMS than at Waliguan through water extraction of filter samples collected during these two studies. The B abs,370 at QOMS was comparable with that (15.0 Mm −1 ) measured at Lulang, one remote site located on the southeastern TP, but much lower than that (53.0 Mm −1 , Table 1) measured at an urban site in Lhasa (Zhu et al., 2017).…”

Section: Resultsmentioning

confidence: 71%

“…The campaign‐averaged B abs,BrC at 370 nm (B abs,BrC,370 ) was 4.4, 0.6, and 0.7 Mm −1 for QOMS, Waliguan, and NamCo, which contributed 33.1%, 22.4%, and 21.3% of the total light absorption at 370 nm, respectively. Similar to the total light absorption, the B abs,BrC,370 at NamCo and Waliguan was extremely low, which might be caused by the low aerosol mass loading at NamCo or the limited abundance of light‐absorbing matter at Waliguan (Xu et al., 2020). In contrast, the relatively higher B abs,BrC,370 and the higher BrC contribution at QOMS might be attributed to the important contribution of light‐absorbing matter from the transported biomass burning emissions (An et al., 2019; Xu et al., 2020).…”

Section: Resultsmentioning

confidence: 99%

“…Insightful investigations on the sources, chemical composition, and light absorption properties of carbonaceous aerosols, especially for the highly complex BrC on the TP, are needed. To date, numerous studies have reported the absorption properties of BrC on the TP; however, most of them focused on the extracted water‐soluble BrC or methanol‐soluble BrC from off‐line analysis of filter samples collected with relatively low time resolution (Kirillova et al., 2016; Li, Yan, et al., 2016; Wu et al., 2020; Xu et al., 2020; Zhang et al., 2017; Zhu et al., 2018). Only a few real‐time measurements of particle light absorption using online optical instruments have been conducted in recent years, mostly at southern TP locations (Chen, Kang, et al., 2018; Wang, Han, et al., 2019; Zhao et al., 2019; Zhu et al., 2017).…”

Section: Introductionmentioning

confidence: 99%

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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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Regional Differences of Chemical Composition and Optical Properties of Aerosols in the Tibetan Plateau

Cited by 23 publications

References 51 publications

Unexpected High Absorption of Atmospheric Aerosols Over a Western Tibetan Plateau Site in Summer

Unexpected High Absorption of Atmospheric Aerosols Over a Western Tibetan Plateau Site in Summer

Optical properties and molecular compositions of water-soluble and water-insoluble brown carbon (BrC) aerosols in northwest China

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

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