Links between the Optical Properties and Chemical Compositions of Brown Carbon Chromophores in Different Environments: Contributions and Formation of Functionalized Aromatic Compounds

Abstract. To investigate the characteristics of atmospheric brown carbon (BrC) in the semiarid region of East Asia, PM2.5 and size-resolved particles in the urban atmosphere of Xi'an, inland China, during the winter and summer of 2017 were collected and analyzed for optical properties and chemical compositions. Methanol extracts (MeOH extracts) were more light-absorbing than water extracts (H2O extracts) in the optical wavelength of 300–600 nm and well correlated with nitrophenols, polycyclic aromatic hydrocarbons (PAHs) and oxygenated PAHs (r > 0.78). The light absorptions (absλ=365 nm) of H2O extracts and MeOH extracts in winter were 28±16 and 49±32 M m−1, respectively, which are about 10 times higher than those in summer, mainly due to the enhanced emissions from biomass burning for house heating. Water-extracted BrC predominately occurred in the fine mode (< 2.1 µm) during winter and summer, accounting for 81 % and 65 % of the total absorption of BrC, respectively. The light absorption and stable carbon isotope composition measurements showed an increasing ratio of absλ=365 nm-MeOH to absλ=550 nm-EC along with an enrichment of 13C in PM2.5 during the haze development, indicating an accumulation of secondarily formed BrC (e.g., nitrophenols) in the aerosol aging process. Positive matrix factorization (PMF) analysis showed that biomass burning, fossil fuel combustion, secondary formation, and fugitive dust are the major sources of BrC in the city, accounting for 55 %, 19 %, 16 %, and 10 % of the total BrC of PM2.5, respectively.

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Measurement Report: Optical properties and sources of water-soluble brown carbon in Tianjin, North China: insights from organic molecular compositions

10.5194/acp-2021-1045 ◽

2022 ◽

Author(s):

Junjun Deng ◽

Hao Ma ◽

Xinfeng Wang ◽

Shujun Zhong ◽

Zhimin Zhang ◽

...

Keyword(s):

Optical Properties ◽

Biomass Burning ◽

Light Absorption ◽

Radiative Forcing ◽

North China ◽

Water Soluble ◽

Formation Mechanisms ◽

Chemical Compositions ◽

Brown Carbon ◽

Near Ultraviolet

Abstract. Brown carbon (BrC) aerosols exert vital impacts on climate change and atmospheric photochemistry due to their light absorption in the wavelength range from near-ultraviolet (UV) to visible light. However, the optical properties and formation mechanisms of ambient BrC remain poorly understood, limiting the estimation of their radiative forcing. In the present study, fine aerosols (PM2.5) were collected during 2016–2017 on a day/night basis over urban Tianjin, a megacity in North China, to obtain seasonal and diurnal patterns of atmospheric water-soluble BrC. There were obvious seasonal but no evident diurnal variations in light absorption properties of BrC. In winter, BrC showed much stronger light absorbing ability since mass absorption efficiency at 365 nm (MAE365) (1.54 ± 0.33 m2 g−1), which was 1.8 times larger than that (0.84 ± 0.22 m2 g−1) in summer. Direct radiative effects by BrC absorption relative to black carbon in the UV range were 54.3 ± 16.9 % and 44.6 ± 13.9 %, respectively. In addition, five fluorescent components in BrC, including three humic-like fluorophores and two protein-like fluorophores were identified with excitation-emission matrix fluorescence spectrometry and parallel factor (PARAFAC) analysis. The lowly-oxygenated components contributed more to winter and nighttime samples, while more-oxygenated components increased in summer and daytime samples. The higher humification index (HIX) together with lower biological index (BIX) and fluorescence index (FI) suggest that the chemical compositions of BrC were associated with a high aromaticity degree in summer and daytime due to photobleaching. Fluorescent properties indicate that wintertime BrC were predominantly affected by primary emissions and fresh secondary organic aerosol (SOA), while summer ones were more influenced by aging processes. Results of source apportionments using organic molecular compositions of the same set of aerosols reveal that fossil fuel combustion and aging processes, primary bioaerosol emission, biomass burning, and biogenic and anthropogenic SOA formation were the main sources of BrC. Biomass burning contributed much larger to BrC in winter and at nighttime, while biogenic SOA contributed more in summer and at daytime. Especially, our study highlights that primary bioaerosol emission is an important source of BrC in urban Tianjin in summer.

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Water-soluble brown carbon in atmospheric aerosols along the transport pathway of Asian dust: optical properties, chemical compositions, and potential sources

The Science of The Total Environment ◽

10.1016/j.scitotenv.2021.147971 ◽

2021 ◽

pp. 147971

Author(s):

Hui Wen ◽

Yue Zhou ◽

Xuanye Xu ◽

Tianshuang Wang ◽

Quanliang Chen ◽

...

Keyword(s):

Optical Properties ◽

Atmospheric Aerosols ◽

Asian Dust ◽

Water Soluble ◽

Chemical Compositions ◽

Transport Pathway ◽

Brown Carbon ◽

Potential Sources

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Supplementary material to "Measurement report: PM<sub>2.5</sub>-bound nitrated aromatic compounds in Xi'an, Northwest China: Seasonal variations and contributions to optical properties of brown carbon"

10.5194/acp-2020-703-supplement ◽

2020 ◽

Author(s):

Wei Yuan ◽

Ru-Jin Huang ◽

Lu Yang ◽

Ting Wang ◽

Jing Duan ◽

...

Keyword(s):

Optical Properties ◽

Seasonal Variations ◽

Aromatic Compounds ◽

Northwest China ◽

Brown Carbon ◽

Supplementary Material

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The characteristics of atmospheric brown carbon in Xi'an, inland China: sources, size distributions and optical properties

10.5194/acp-2019-640 ◽

2019 ◽

Author(s):

Can Wu ◽

Gehui Wang ◽

Jin Li ◽

Jianjun Li ◽

Cong Cao ◽

...

Keyword(s):

Optical Properties ◽

Urban Atmosphere ◽

Chemical Compositions ◽

Size Distributions ◽

Brown Carbon ◽

Optical Wavelength ◽

Polycyclic Aromatic ◽

Fine Mode ◽

Semi Arid Region ◽

Oxygenated Pahs

Abstract. To investigate the characteristic of atmospheric brown carbon (BrC) in the semi-arid region of East Asia, PM2.5 and size-resolved particles in the urban atmosphere of Xi'an, inland China during the winter and summer of 2017 were collected and analyzed for optical properties and chemical compositions. Methanol extracts (MeOH-extracts) were more light-absorbing than water extracts (H2O- extracts) in the optical wavelength of 300–600 nm, and well correlated with nitrophenols, polycyclic aromatic hydrocarbons (PAHs) and oxygenated PAHs (R2 > 0.6). The light absorptions (absλ=365nm) of H2O- extracts and MeOH-extracts in winter were 28 ± 16 M/m and 49 ± 32 M/m, respectively, which are about 10 times higher than those in summer, mainly due to the enhanced emissions from biomass burning for house heating. Water extracted BrC predominately occurred in the fine mode (

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Relationship between the Optical Properties and Chemical Composition of Urban Aerosol Particles in Lithuania

Advances in Meteorology ◽

10.1155/2018/8674173 ◽

2018 ◽

Vol 2018 ◽

pp. 1-10 ◽

Cited By ~ 1

Author(s):

Julija Pauraite ◽

Kristina Plauškaitė ◽

Vadimas Dudoitis ◽

Vidmantas Ulevicius

Keyword(s):

Optical Properties ◽

Chemical Composition ◽

Organic Aerosol ◽

Single Scattering ◽

Chemical Compositions ◽

Spectra Analysis ◽

Average Value ◽

Aerosol Mass ◽

In Situ Investigation

In situ investigation results of aerosol optical properties (absorption and scattering) and chemical composition at an urban background site in Lithuania (Vilnius) are presented. Investigation was performed in May-June 2017 using an aerosol chemical speciation monitor (ACSM), a 7-wavelength Aethalometer and a 3-wavelength integrating Nephelometer. A positive matrix factorisation (PMF) was used for the organic aerosol mass spectra analysis to characterise the sources of ambient organic aerosol (OA). Five OA factors were identified: hydrocarbon-like OA (HOA), biomass-burning OA (BBOA), more and less oxygenated OA (LVOOA and SVOOA, respectively), and local hydrocarbon-like OA (LOA). The average absorption (at 470 nm) and scattering (at 450 nm) coefficients during the entire measurement campaign were 16.59 Mm−1 (standard deviation (SD) = 17.23 Mm−1) and 29.83 Mm−1 (SD = 20.45 Mm−1), respectively. Furthermore, the absorption and scattering Angström exponents (AAE and SAE, respectively) and single-scattering albedo (SSA) were calculated. The average AAE value at 470/660 nm was 0.97 (SD = 0.16) indicating traffic-related black carbon (BCtr) dominance. The average value of SAE (at 450/700 nm) was 1.93 (SD = 0.32) and could be determined by the submicron particle (PM1) dominance versus the supermicron ones (PM > 1 µm). The average value of SSA was 0.62 (SD = 0.13). Several aerosol types showed specific segregation in the SAE versus SSA plot, which underlines different optical properties due to various chemical compositions.

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