Review of Brown Carbon Aerosols in China: Pollution Level, Optical Properties, and Emissions

Zhou, Yuyi; Ma, Nan; Zhu, Yong; Zhao, Xiaocong; Zhu, Shijie; Tao, Jiangchuan; Hong, Juan; Wu, Wenjie; Cheng, Yafang; Su, Hang

doi:10.1029/2021jd035473

Cited by 23 publications

(13 citation statements)

References 162 publications

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“…While this study reports the first measurements of the quantum yields and steady-state concentrations of values reported in our study serve as lower limits since they were measured using extracts comprised of only the water-soluble fraction of PM 2.5 . Water-insoluble BrC, which reportedly dominates the total BrC absorption in some parts of China (Bai et al, 2020;Huang et al, 2020;Wang et al, 2022), will likely produce 1 O 2 and 3 C * as well. Second, due to limited extract volumes for photochemical experiments and chemical analysis, only one 3 C * chemical probe was used in our study to quantify 3 C * quantum yields, formation rates, and steady-state concentrations.…”

Section: Discussionmentioning

confidence: 99%

Efficient production of singlet oxygen and organic triplet excited states in aqueous PM_2.5 in Hong Kong, South China

LYU

Hau

et al. 2023

Preprint

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Abstract. Photooxidants drive many atmospheric chemical processes. The photoexcitation of light-absorbing organic compounds (i.e., brown carbon (BrC)) in atmospheric waters can lead to the generation of reactive organic triplet excited states (3C∗), which can undergo further reactions to produce other photooxidants such as singlet oxygen (1O2). To determine the importance of these aqueous photooxidants in SOA formation and transformation, we must know their steady-state concentrations and quantum yields. However, there has been limited measurements of aqueous 3C∗ and 1O2 in atmospheric samples outside of North America and Europe. In this work, we report the first measurements of the steady-state concentrations and quantum yields of 3C∗ and 1O2 produced in aerosols in South China. We quantified the production of 3C∗ and 1O2 in illuminated aqueous extracts of PM2.5 collected in different seasons at two urban sites and one coastal semi-rural site during a year-round study conducted in Hong Kong, South China. The mass absorption coefficients at 300 nm for BrC in the aqueous PM2.5 extracts ranged from 0.49 × 104 to 2.01 × 104 cm2 g-C−1 for the three sites. Both 1O2 and 3C∗ were produced year-round. The steady-state concentrations of 1O2 ([1O2]ss) in the illuminated aqueous extracts spanned two orders of magnitude, ranging from 1.56 × 10−14 to 1.35 × 10−12 M, with a study average of (4.02 ± 3.52) × 10−13 M. The steady-state concentrations of 3C∗ ([3C∗]ss) in the illuminated aqueous extracts spanned two orders of magnitude, ranging from 2.93 × 10−16 to 8.08 × 10−14 M, with a study average of (1.09 ± 1.39) × 10−14 M. The [1O2]ss and [3C∗]ss correlated with the concentration and absorbance of BrC, thus implying that the amount of BrC drives the steady-state concentrations of these photooxidants. The locations (urban vs. semi-rural) did not have a significant effect on [3C∗]ss and [1O2]ss, which indicated that BrC from local sources did not have a significant influence on the year-round 3C∗ and 1O2 production. 3C∗ and 1O2 production were found to be the highest in winter and the lowest in summer for all three sites. The observed seasonal trends of 1O2 and 3C∗ production could be attributed to the seasonal variations in long-range air mass transport. Our analysis highlighted the key role that regional sources play in influencing the composition and concentrations of water-soluble BrC in winter PM2.5 in Hong Kong, which contributed to their highest 3C∗ and 1O2 production. The current results will be useful for modeling seasonal aqueous organic aerosol photochemistry in the South China region.

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Section: Discussionmentioning

confidence: 99%

Efficient production of singlet oxygen and organic triplet excited states in aqueous PM_2.5 in Hong Kong, South China

LYU

Hau

et al. 2023

Preprint

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“…Due to the molecular diversity of BrC compounds and the complexity of atmospheric conditions, BrC undergoes dynamic changes in the atmosphere, leading to regional variations in its impact on climate. , Given the potentially higher BrC emission in China (BrC columnar mass concentration: 4.4–92 mg m –2 ) − than in Europe and North America (BrC columnar content: around 5 mg m –2 ), more comprehensive studies are required to fully elucidate the chemical composition and light absorption properties of BrC in different Chinese cities. , Moreover, research on the seasonal variation of BrC remains limited. In this study, aerosol samples were collected in six Chinese megacities, including Beijing, Harbin, Xi’an, Chengdu, Guangzhou, and Wuhan, in winter and summer, to investigate the light absorption properties, chemical species, and molecular composition of BrC.…”

Section: Introductionmentioning

confidence: 99%

Insight into the Role of NH₃/NH₄⁺ and NO_x/NO₃^– in the Formation of Nitrogen-Containing Brown Carbon in Chinese Megacities

Wang,

Shen,

Yang

et al. 2024

Environ. Sci. Technol.

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Particulate brown carbon (BrC) plays a crucial role in the global radiative balance due to its ability to absorb light. However, the effect of molecular formation on the light absorption properties of BrC remains poorly understood. In this study, atmospheric BrC samples collected from six Chinese megacities in winter and summer were characterized through ultrahigh-performance liquid chromatography coupled with Orbitrap mass spectrometry (UHPLC-Orbitrap MS) and light absorption measurements. The average values of BrC light absorption coefficient at a wavelength of 365 nm (b abs365 ) in winter were approximately 4.0 times higher than those in summer. Nitrogen-containing organic molecules (CHNO) were identified as critical components of light-absorbing substances in both seasons, underscoring the importance of N-addition in BrC. These nitrogencontaining BrC chromophores were more closely related to nitro-containing compounds originating from biomass burning and nitrogen oxides (NO x )/nitrate (NO 3 − ) reactions in winter. In summer, they were related to reduced N-containing compounds formed in ammonia (NH 3 )/ammonium (NH 4 + ) reactions. The NH 3 /NH 4 + -mediated reactions contributed more to secondary BrC in summer than winter, particularly in southern cities. Compared with winter, the higher O/Cw, lower molecule conjugation indicator (double bond equivalent, DBE), and reduced BrC b abs365 in summer suggest a possible bleaching mechanism during the oxidation process. These findings strengthen the connection between molecular composition and the light-absorbing properties of BrC, providing insights into the formation mechanisms of BrC chromophores across northern and southern Chinese cities in different seasons.

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“…To elucidate the formation mechanism of BrC in the troposphere, synchronous observations on atmospheric BrC were conducted on the mountainside and the mountain foot of Mt. Hua, which is located closely to Guanzhong Basin, one of the areas with heaviest PM2.5 pollution in China owing to intensive activities of fossil fuel combustion and the unfavorable topography (Wang et al, 2022b;Wu et al, 2020;Wang et al, 2011;Wang et al, 2016). Our previous study has shown that inorganic aerosol chemistry in the atmosphere over Mt.…”

Section: Introductionmentioning

confidence: 99%

Measurement report: Formation of tropospheric brown carbon in a lifting air mass

Wu,

Liu,

Zhang

et al. 2024

Preprint

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Abstract. An enhanced formation of brown carbon (BrC) with a non-negligible warming effect at the tropopause has recently been found. However, its formation mechanism is unclear. Here we report a BrC formation process that happens during air mass upward transport by conducting simultaneously a 4-hour time resolution of measurement on atmospheric BrC at the mountain foot (MF, 400 m a.s.l.) and mountainside (MS, 1120 m a.s.l.) of Mt. Hua, China in 2016 summer. Our results showed that the daytime light-absorption (Abs365nm) of BrC at MS is approximately 60 % lower than that at MF due to a dilution effect caused by the planetary boundary layer expansion, but the daytime light-absorption of BrC relative to black carbon at MS is about 30 % higher than that at MF, suggesting a significant formation of secondary BrC in the lifting process of air mass from MF to MS. Such a secondary formation accounted for >50 % of BrC at MS but only 27 % of BrC at MF. Moreover, N:C elemental ratio of the daytime BrC was 15 % higher at MS than that at MF, mainly due to an aerosol aqueous phase formation of water-soluble organic nitrogen (WSON) compounds. Stable nitrogen isotope composition further indicated that such light-absorbing WSON compounds were produced from the aerosol aqueous-phase reaction of carbonyls with NH4+. Our work for the first time revealed that ammonia -induced aerosol aqueous reactions can significantly promote BrC formation during the air mass lifting process, which is probably responsible for an enhanced light absorption of BrC in the upper troposphere.

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Review of Brown Carbon Aerosols in China: Pollution Level, Optical Properties, and Emissions

Cited by 23 publications

References 162 publications

Efficient production of singlet oxygen and organic triplet excited states in aqueous PM_2.5 in Hong Kong, South China

Efficient production of singlet oxygen and organic triplet excited states in aqueous PM_2.5 in Hong Kong, South China

Insight into the Role of NH₃/NH₄⁺ and NO_x/NO₃^– in the Formation of Nitrogen-Containing Brown Carbon in Chinese Megacities

Measurement report: Formation of tropospheric brown carbon in a lifting air mass

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Review of Brown Carbon Aerosols in China: Pollution Level, Optical Properties, and Emissions

Cited by 23 publications

References 162 publications

Efficient production of singlet oxygen and organic triplet excited states in aqueous PM2.5 in Hong Kong, South China

Efficient production of singlet oxygen and organic triplet excited states in aqueous PM2.5 in Hong Kong, South China

Insight into the Role of NH3/NH4+ and NOx/NO3– in the Formation of Nitrogen-Containing Brown Carbon in Chinese Megacities

Measurement report: Formation of tropospheric brown carbon in a lifting air mass

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Resources

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Efficient production of singlet oxygen and organic triplet excited states in aqueous PM_2.5 in Hong Kong, South China

Efficient production of singlet oxygen and organic triplet excited states in aqueous PM_2.5 in Hong Kong, South China

Insight into the Role of NH₃/NH₄⁺ and NO_x/NO₃^– in the Formation of Nitrogen-Containing Brown Carbon in Chinese Megacities