Light absorption of brown carbon aerosol in the PRD region of China

Abstract. The strong spectral dependence of light absorption of brown carbon (BrC) aerosol is regarded to influence aerosol's radiative forcing significantly. The Absorption Angstrom Exponent (AAE) method has been widely used in previous studies to attribute light absorption of BrC at shorter wavelengths for ambient aerosols, with a theoretical assumption that the AAE of "pure" black carbon (BC) aerosol equals to 1.0. In this study, the AAE method was applied to both urban and rural environments in the Pearl River Delta (PRD) region of China, with an improvement of constraining the realistic AAE of "pure" BC through statistical analysis of on-line measurement data. A three-wavelength photo-acoustic soot spectrometer (PASS-3) and aerosol mass spectrometers (AMS) were used to explore the relationship between the measured AAE and the relative abundance of organic aerosol to BC. The regression and extrapolation analysis revealed that more realistic AAE values for "pure" BC aerosol (AAEBC) were 0.86, 0.82, and 1.02 between 405 and 781 nm, and 0.70, 0.71, and 0.86 between 532 and 781 nm, in the campaigns of urbanwinter, urbanfall, and ruralfall, respectively. Roadway tunnel experiments were conducted and the results further confirmed the representativeness of the obtained AAEBC values for the urban environment. Finally, the average light absorption contributions of BrC (&pm; relative uncertainties) at 405 nm were quantified to be 11.7 % (&pm;5 %), 6.3 % (&pm;4 %), and 12.1 % (&pm;7 %) in the campaigns of urbanwinter, urbanfall, and ruralfall, respectively, and those at 532 nm were 10.0 % (&pm;2 %), 4.1 % (&pm;3 %), and 5.5 % (&pm;5 %), respectively. The relatively higher BrC absorption contribution at 405 nm in the ruralfall campaign could be reasonably attributed to the biomass burning events nearby, which was then directly supported by the biomass burning simulation experiments performed in this study. This paper indicates that the BrC contribution to total aerosol light absorption at shorter wavelengths is not negligible in the highly urbanized and industrialized PRD region.

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Light absorption of brown carbon aerosol in the PRD region of China

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-15-28453-2015 ◽

2015 ◽

Vol 15 (20) ◽

pp. 28453-28482 ◽

Cited By ~ 3

Author(s):

J.-F. Yuan ◽

X.-F. Huang ◽

L.-M. Cao ◽

J. Cui ◽

Q. Zhu ◽

...

Keyword(s):

Biomass Burning ◽

Light Absorption ◽

Radiative Forcing ◽

Urban Environments ◽

Theoretical Assumption ◽

Brown Carbon ◽

Mass Spectrometers ◽

Rural Environments ◽

The Pearl River ◽

532 Nm

Abstract. The strong spectral dependence of light absorption of brown carbon (BrC) aerosol is regarded to influence aerosol's radiative forcing significantly. The Absorption Angstrom Exponent (AAE) method was widely used in previous studies to attribute light absorption of BrC at shorter wavelengths for ambient aerosol, with a theoretical assumption that the AAE of "pure" black carbon (BC) aerosol equals to 1.0. In this study, the previous AAE method was improved by statistical analysis and applied in both urban and rural environments in the Pearl River Delta (PRD) region of China. A three-wavelength photo-acoustic soot spectrometer (PASS-3) and aerosol mass spectrometers (AMS) were used to explore the relationship between the measured AAE and the relative abundance of organic aerosol to BC. The regression and extrapolation analysis revealed that the more realistic AAE values for "pure" BC aerosol were 0.86, 0.82, and 1.02 at 405 nm, and 0.70, 0.71, and 0.86 at 532 nm, in the campaigns of urban_winter, urban_fall, and rural_fall, respectively. Roadway tunnel experiments were also conducted, and the results further supported the representativeness of the obtained AAE values for "pure" BC aerosol in the urban environments. Finally, the average aerosol light absorption contribution of BrC was quantified to be 11.7, 6.3, and 12.1 % (with relative uncertainties of 4, 4, and 7 %) at 405 nm, and 10.0, 4.1, and 5.5 % (with relative uncertainties of 2, 2, and 5 %) at 532 nm, in the campaigns of urban_winter, urban_fall, and rural_fall, respectively. The relatively higher BrC absorption contribution at 405 nm in the rural_fall campaign was likely a result of the biomass burning events nearby, which was supported by the biomass burning simulation experiments performed in this study. The results of this paper indicate that the brown carbon contribution to aerosol light absorption at shorter wavelengths is not negligible in the highly urbanized and industrialized PRD region.

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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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Absorptivity of brown carbon in fresh and photo-chemically aged biomass-burning emissions

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-13-11509-2013 ◽

2013 ◽

Vol 13 (5) ◽

pp. 11509-11536 ◽

Cited By ~ 2

Author(s):

R. Saleh ◽

C. J. Hennigan ◽

G. R. McMeeking ◽

W. K. Chuang ◽

E. S. Robinson ◽

...

Keyword(s):

Biomass Burning ◽

Light Absorption ◽

Radiative Forcing ◽

Uv Light ◽

Wavelength Dependence ◽

Organic Aerosol ◽

The United States ◽

Prescribed Fires ◽

Brown Carbon ◽

Chemical Aging

Abstract. Experiments were conducted to investigate light absorption of organic aerosol (OA) in fresh and photo-chemically aged biomass-burning emissions. The experiments considered residential hardwood fuel (oak) and fuels commonly consumed in wild-land and prescribed fires in the United States (pocosin pine and gallberry). Photo-chemical aging was performed in an environmental chamber. We constrained the light-absorption properties of the OA using conservative limiting assumptions, and found that both primary organic aerosol (POA) in the fresh emissions and secondary organic aerosol (SOA) produced by photo-chemical aging absorb light to a significant extent, and are categorized as brown carbon. This work presents the first direct evidence that SOA produced in aged biomass-burning emissions is absorptive. For the investigated fuels, SOA is less absorptive than POA in the long visible, but exhibits steeper wavelength-dependence (larger Absorption Ångström Exponent) and is more absorptive in the short visible and near-UV. Light absorption by SOA in biomass-burning emissions might be an important contributor to the global radiative forcing budget.

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Absorptivity of brown carbon in fresh and photo-chemically aged biomass-burning emissions

Atmospheric Chemistry and Physics ◽

10.5194/acp-13-7683-2013 ◽

2013 ◽

Vol 13 (15) ◽

pp. 7683-7693 ◽

Cited By ~ 162

Author(s):

R. Saleh ◽

C. J. Hennigan ◽

G. R. McMeeking ◽

W. K. Chuang ◽

E. S. Robinson ◽

...

Keyword(s):

Biomass Burning ◽

Light Absorption ◽

Radiative Forcing ◽

Uv Light ◽

Wavelength Dependence ◽

Organic Aerosol ◽

The United States ◽

Prescribed Fires ◽

Brown Carbon ◽

Chemical Aging

Abstract. Experiments were conducted to investigate light absorption of organic aerosol (OA) in fresh and photo-chemically aged biomass-burning emissions. The experiments considered residential hardwood fuel (oak) and fuels commonly consumed in wild-land and prescribed fires in the United States (pocosin pine and gallberry). Photo-chemical aging was performed in an environmental chamber. We constrained the effective light-absorption properties of the OA using conservative limiting assumptions, and found that both primary organic aerosol (POA) in the fresh emissions and secondary organic aerosol (SOA) produced by photo-chemical aging contain brown carbon, and absorb light to a significant extent. This work presents the first direct evidence that SOA produced in aged biomass-burning emissions is absorptive. For the investigated fuels, SOA is less absorptive than POA in the long visible, but exhibits stronger wavelength-dependence and is more absorptive in the short visible and near-UV. Light absorption by SOA in biomass-burning emissions might be an important contributor to the global radiative forcing budget.

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Light absorption properties and potential sources of particulate brown carbon in the Pearl River Delta region of China

Atmospheric Chemistry and Physics ◽

10.5194/acp-19-11669-2019 ◽

2019 ◽

Vol 19 (18) ◽

pp. 11669-11685 ◽

Cited By ~ 7

Author(s):

Zhujie Li ◽

Haobo Tan ◽

Jun Zheng ◽

Li Liu ◽

Yiming Qin ◽

...

Keyword(s):

Optical Properties ◽

Light Absorption ◽

Radiative Forcing ◽

Pearl River Delta ◽

Organic Aerosols ◽

Pearl River ◽

Brown Carbon ◽

The Real ◽

The Pearl River Delta ◽

The Pearl River

Abstract. Brown carbon (BrC) is a special type of organic aerosol (OA), capable of absorbing solar radiation from near-ultraviolet (UV) to visible wavelengths, which may lead to an increased aerosol radiative effect in the atmosphere. While high concentrations of OAs have been observed in the Pearl River Delta (PRD) region of China, the optical properties and corresponding radiative forcing of BrC in the PRD are still not well understood. In this work, we conducted a set of comprehensive measurements of atmospheric particulate matter from 29 November 2014 to 2 January 2015 to investigate aerosol compositions, optical properties, source origins, and radiative forcing effects at a suburban station in Guangzhou. The particle absorption Ångström exponent (AAE) was deduced and utilized to distinguish light absorption by BrC from that by black carbon (BC). The results showed that the average absorption contributions of BrC were 34.1±8.0 % at 370 nm, 23.7±7.3 % at 470 nm, 16.0±6.7 % at 520 nm, 13.0±5.4 % at 590 nm, and 8.7±4.3 % at 660 nm. A sensitivity analysis of the evaluation of the absorption Ångström exponent of BC (AAEBC) was conducted based on the Mie theory calculation assuming that the BC-containing aerosol was mixed with the core–shell and external configurations. The corresponding uncertainty in AAEBC was acquired. We found that variations in the imaginary refractive index (RI) of the BC core can significantly affect the estimation of AAEBC. However, AAEBC was relatively less sensitive to the real part of the RI of the BC core and was least sensitive to the real part of the RI of the non-light-absorbing shell. BrC absorption was closely related to aerosol potassium cation content (K+), a common tracer of biomass burning emissions, which was most likely associated with straw burning in the rural area of the western PRD. Diurnal variation in BrC absorption revealed that primary organic aerosols had a larger BrC absorption capacity than secondary organic aerosols (SOAs). Radiative transfer simulations showed that BrC absorption may cause 2.3±1.8 W m−2 radiative forcing at the top of the atmosphere (TOA) and contribute to 15.8±4.4 % of the aerosol warming effect. A chart was constructed to conveniently assess the BrC radiative forcing efficiency in the studied area with reference to certain aerosol single-scattering albedo (SSA) and BrC absorption contributions at various wavelengths. Evidently, the BrC radiative forcing efficiency was higher at shorter wavelengths.

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Light absorption property and potential source of particulate brown carbon in the Pearl River Delta region of China

10.5194/acp-2018-1331 ◽

2019 ◽

Author(s):

Zhujie Li ◽

Haobo Tan ◽

Jun Zheng ◽

Li Liu ◽

Yiming Qin ◽

...

Keyword(s):

Optical Properties ◽

Light Absorption ◽

Radiative Forcing ◽

Pearl River Delta ◽

Organic Aerosol ◽

Pearl River ◽

Brown Carbon ◽

The Real ◽

The Pearl River Delta ◽

The Pearl River

Abstract. Brown carbon (BrC) is a type of light-absorbing component of organic aerosol (OA), covering from near-ultraviolet (UV) to visible wavelength ranges, and thus may cause additional aerosol radiative effect in the atmosphere. While high concentrations of OA have been observed in the Pearl River Delta (PRD) region of China, optical properties and the corresponding radiative forcing of BrC in PRD are still not well understood. In this work, we conducted a set of comprehensive measurements of atmospheric particulate matters from 29 November 2014 to 5 January 2015 to investigate aerosol composition, optical properties, source origins and radiative forcing effects at a suburban station of Guangzhou. Particle absorption Ångström exponent (AAE) was deduced and utilized to differentiate light absorption by BrC from black carbon (BC). The results showed that the average absorption contributions of BrC were 25.9 ± 9.0 % at 370 nm, 19.7 ± 7.9 % at 470 nm, 14.1 ± 6.9 % at 520 nm, 11.6 ± 5.6 % at 590 nm and 7.7 ± 4.4 % at 660 nm, respectively. A sensitivity analysis of the evaluation of absorption Ångström exponent of BC (AAEBC) was conducted based on the Mie theory calculation, assuming that the BC-containing aerosol was internally mixed, with a core-shell configuration. The corresponding uncertainty of BrC absorption contribution was acquired. We found that variations in the imaginary refractive index (RI) of BC core can significantly affect the estimation of BrC absorption contribution. However, BrC absorption contribution was relatively less sensitive to the real part of RI of BC core and was least sensitive to the real part of RI of non-light absorbing shell. BrC absorption was closely related to aerosol potassium cation content (K+), a common tracer of biomass burning emission, which was most likely associated with straw burning in the rural area of western PRD. Diurnal variation of BrC absorption revealed that primary organic aerosol had a larger BrC absorption capacity than secondary organic aerosol (SOA) had. Radiative transfer simulations showed that BrC absorption may cause 2.2 ± 2.3 W m−2 radiative forcing at the top of atmosphere (TOA) and contribute 14.2 ± 6.2 % of the aerosol warming effect. A chart was constructed to conveniently assess the BrC radiative forcing efficiency in the studied area with reference to a certain aerosol single-scattering albedo (SSA) and BrC absorption contribution at various wavelengths. Evidently, BrC radiative forcing efficiency was higher in shorter wavelength.

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Light absorption properties of brown carbon over the western Pacific region

10.5194/egusphere-egu2020-15121 ◽

2020 ◽

Author(s):

Shantanu Kumar Pani ◽

Neng-Huei Lin ◽

Chung-Te Lee ◽

Sheng-Hsiang Wang

Keyword(s):

Biomass Burning ◽

Light Absorption ◽

Radiative Forcing ◽

Western Pacific ◽

Pacific Region ◽

Western Pacific Region ◽

Brown Carbon ◽

Near Ultraviolet ◽

The Impact ◽

The Western Pacific

Brown carbon (BrC) is generally emitted during coal combustion, biomass burning, and the formation of secondary organic aerosols. BrC is an exceptional type of organic compound that absorbs the incoming solar radiation efficiently at near-ultraviolet wavelengths and can influence the direct radiative forcing estimates. Lulin Atmospheric Background Station (LABS, 23.47&#176;N, 120.87&#176;E; 2862 m above sea level) on the summit of Lulin Mountain in central Taiwan is the only high-altitude background station in the western Pacific region to study the impact of various long-range transported air pollutants. LABS usually receives the westerly winds coupled with biomass-burning emissions from peninsular Southeast Asia during the springtime. Aerosol measurements are carried out at LABS as a part of the Seven South East Asian Studies/Biomass-burning Aerosols & Stratocumulus Environment: Lifecycles & Interactions Experiment (7-SEAS/BASELInE) 2013 spring campaign. Light absorption coefficients are measured by the Aethalometer (AE 31, Magee Scientific, USA). Assuming a negligible contribution from dust, absorption solely due to BrC is estimated by subtracting the absorption of black carbon (BC) from total absorption. The relationships between BrC light absorption and carbonaceous fractions are investigated during the sampling period. The atmospheric radiative forcing due to BrC over the western Pacific region accounts for approximately 30% of that from BC. The detailed results will be presented.

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Chemical characteristics of brown carbon in atmospheric particles at a suburban site near Guangzhou, China

Atmospheric Chemistry and Physics ◽

10.5194/acp-18-16409-2018 ◽

2018 ◽

Vol 18 (22) ◽

pp. 16409-16418 ◽

Cited By ~ 20

Author(s):

Yi Ming Qin ◽

Hao Bo Tan ◽

Yong Jie Li ◽

Zhu Jie Li ◽

Misha I. Schurman ◽

...

Keyword(s):

Chemical Composition ◽

Absorption Coefficient ◽

Light Absorption ◽

Radiative Forcing ◽

Chemical Characterization ◽

Organic Aerosol ◽

Atmospheric Particles ◽

Chemical Characteristics ◽

Brown Carbon ◽

Suburban Site

Abstract. Light-absorbing organic carbon (or brown carbon, BrC) in atmospheric particles has received much attention for its potential role in global radiative forcing. While a number of field measurement campaigns have differentiated light absorption by black carbon (BC) and BrC, the chemical characteristics of BrC are not well understood. In this study, we present co-located real-time light absorption and chemical composition measurements of atmospheric particles to explore the relationship between the chemical and optical characteristics of BrC at a suburban site downwind of Guangzhou, China, from November to December 2014. BrC and BC contributions to light absorption were estimated using measurements from a seven-wavelength aethalometer, while the chemical composition of non-refractory PM1 was measured with a high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS). Using the absorption Ångström exponent (AAE) method, we estimated that BrC contributed 23.6 % to the total aerosol absorption at 370 nm, 18.1 % at 470 nm, 10.7 % at 520 nm, 10.7 % at 590 nm, and 10.5 % at 660 nm. Biomass burning organic aerosol (BBOA) has the highest mass absorption coefficient among sources of organic aerosols. Its contribution to total brown carbon absorption coefficient decreased but that of low-volatility oxygenated organic aerosol (LVOOA) increased with increasing wavelength, suggesting the need for wavelength-dependent light absorption analysis for BrC in association with its chemical makeup. Clear correlations of N-containing ion fragments with absorption coefficient were observed. These correlations also depended on their degrees of unsaturation/cyclization and oxygenation. While the current study relates light absorption by BrC to ion fragments, more detailed chemical characterization is warranted to constrain this relationship.

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Brown carbon aerosol in urban Beijing: Significant contributions from biomass burning and secondary formation

10.5194/egusphere-egu2020-7241 ◽

2020 ◽

Author(s):

Ting Wang ◽

Rujin Huang ◽

Lu Yang ◽

Wei Yuan ◽

Yuquan Gong

Keyword(s):

Biomass Burning ◽

Light Absorption ◽

Coal Combustion ◽

Absorption Efficiency ◽

Traffic Emission ◽

Brown Carbon ◽

Factorization Model ◽

Secondary Formation ◽

Vis Spectroscopy ◽

The Impact

Atmospheric brown carbon (BrC) has significant impact on Earth&#8217;s radiative budget. However, due to our very limited knowledge about the relationship between BrC light absorption and the associated sources, the estimation for radiative effects of BrC is still largely constrained. In this study, we combine ultraviolet&#8722;visible (UV&#8722;vis) spectroscopy measurements and chemical analyses of BrC samples collected from January to December 2015 in urban Beijing, to investigated the sources of atmospheric BrC. The multiple liner regression model was applied to apportion the contributions of individual primary and secondary organic aerosol (OA) source components to light absorption of BrC. Our results indicated that biomass burning emission and secondary formation are highly absorbing up to 500 nm, and their contributions increased with the wavelengths. In contrast, the contribution of traffic emission and coal combustion to total absorption decreased with the wavelength and the large contributions were mostly found at shorter wavelengths. Then the mass absorption efficiency (MAE) of major light-absorbing components were estimated, which can provide a support to estimate the impact of BrC from these sources on the climate. The positive matrix factorization model were also used to verify the contributions of different source components of BrC absorption at 365 nm. The results consistently demonstrate that the biomass burning and secondary formation contributes significantly to the overall absorption, followed by coal combustion and traffic emission.

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Light absorption properties, chromophore composition and sources of brown carbon aerosol in Xi’an, Northwest China

10.5194/egusphere-egu2020-6702 ◽

2020 ◽

Author(s):

Ru-Jin Huang ◽

Wei Yuan ◽

Lu Yang ◽

Jie Guo ◽

Jing Duan ◽

...

Keyword(s):

Light Absorption ◽

Coal Combustion ◽

Radiative Forcing ◽

Northwest China ◽

Absorption Efficiency ◽

Vehicular Emissions ◽

Absorption Properties ◽

Seasonal Differences ◽

Brown Carbon ◽

The Impact

The impact of brown carbon aerosol (BrC) on the Earth&#8217;s radiative forcing balance has been widely recognized but remains uncertain, mainly because the relationships among BrC sources, chromophores, and optical properties of aerosol are poorly understood (Feng et al., 2013; Laskin et al., 2015). In this work, the light absorption properties and chromophore composition of BrC were investigated for samples collected in Xi&#8217;an, Northwest China from 2015 to 2016. Both absorption &#197;ngstro&#776;m exponent and mass absorption efficiency show distinct seasonal differences, which could be attributed to the differences in sources and chromophore composition of BrC. Three groups of light-absorbing organics were found to be important BrC chromophores, including those show multiple absorption peaks at wavelength > 350 nm (12 polycyclic aromatic hydrocarbons and their derivatives) and those show single absorption peak at wavelength < 350 nm (10 nitrophenols and nitrosalicylic acids and 3 methoxyphenols). These measured BrC chromophores show distinct seasonal differences and contribute on average about 1.1% and 3.3% of light absorption of methanol-soluble BrC at 365 nm in summer and winter, respectively, about 7 and 5 times higher than the corresponding mass fractions in total organic carbon. The sources of BrC were resolved by positive matrix factorization (PMF) using these chromophores instead of commonly used non-light absorbing organic markers as model inputs. Our results show that in spring vehicular emissions and secondary formation are major sources of BrC (~70%), in fall coal combustion and vehicular emissions are major sources (~70%), in winter biomass burning and coal combustion become major sources (~80%), while in summer secondary BrC dominates (~60%).&#160;References:Feng, Y., V. Ramanathan, and V. R. Kotamarthi: Brown carbon: A significant atmospheric absorber of solar radiation?, Atmos. Chem. Phys., 13, 8607-8621, doi:10.5194/acp-13-8607-2013, 2013.Laskin, A., J. Laskin, and S. A. Nizkorodov: Chemistry of atmospheric brown carbon, Chem. Rev., 115, 4335-4382, doi:10.1021/cr5006167, 2015.

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