scholarly journals Sources and light absorption of water-soluble brown carbon aerosols in the outflow from northern China

2013 ◽  
Vol 13 (7) ◽  
pp. 19625-19648 ◽  
Author(s):  
E. N. Kirillova ◽  
A. Andersson ◽  
J. Han ◽  
M. Lee ◽  
Ö. Gustafsson
Keyword(s):  
Light Absorption ◽  
Radiative Forcing ◽  
Climate Models ◽  
Large Fraction ◽  
Regional Climate ◽  
Northern China ◽  
Water Soluble ◽  
Cloud Formation ◽  
Carbonaceous Aerosols ◽  
Brown Carbon

Abstract. High loadings of anthropogenic carbonaceous aerosols in Chinese air influence the air quality for over 1 billion people and impact the regional climate. A large fraction (17–80%) of this aerosol carbon is water soluble, promoting cloud formation and thus climate cooling. Recent findings, however, suggest that water-soluble carbonaceous aerosols also absorb sunlight, bringing additional direct and indirect climate warming effects, yet the extent and nature of light absorption by this water-soluble brown carbon (WS-BrC) and its relation to sources is poorly understood. Here, we combine source estimates constrained by dual-carbon-isotope with light absorption measurements of WS-BrC for a March 2011 campaign at the Korea Climate Observatory at Gosan (KCOG), a receptor station in SE Yellow Sea for the outflow from N. China. The mass absorption cross-section (MAC) of WS-BrC for air masses from N. China were in general higher (0.8–1.1 m2 g−1), than from other source regions (0.3–0.8 m2 g−1). We estimate that this effect corresponds to 13–49% of the radiative forcing caused by light absorption by black carbon. Radiocarbon constraints show that the WS-BrC in Chinese outflow had significantly higher amounts of fossil sources (30–50%) compared to previous findings in S. Asia, N. America and Europe. Stable carbon (δ13C) measurements indicated influence of aging during air mass transport. These results indicate the importance of incorporating WS-BrC in climate models and the need to constrain climate effects by emission source sector.

scholarly journals Sources and light absorption of water-soluble organic carbon aerosols in the outflow from northern China

2014 ◽  
Vol 14 (3) ◽  
pp. 1413-1422 ◽  
Author(s):  
E. N. Kirillova ◽  
A. Andersson ◽  
J. Han ◽  
M. Lee ◽  
Ö. Gustafsson
Keyword(s):  
Organic Carbon ◽  
Light Absorption ◽  
Radiative Forcing ◽  
Large Fraction ◽  
Northern China ◽  
Water Soluble ◽  
Cloud Formation ◽  
Carbonaceous Aerosols ◽  
Water Soluble Organic Carbon ◽  
Soluble Organic Carbon

Abstract. High loadings of anthropogenic carbonaceous aerosols in Chinese air influence the air quality for over one billion people and impact the regional climate. A large fraction (17–80%) of this aerosol carbon is water-soluble, promoting cloud formation and thus climate cooling. Recent findings, however, suggest that water-soluble carbonaceous aerosols also absorb sunlight, bringing additional direct and indirect climate warming effects, yet the extent and nature of light absorption by this water-soluble "brown carbon" and its relation to sources is poorly understood. Here, we combine source estimates constrained by dual carbon isotopes with light-absorption measurements of water-soluble organic carbon (WSOC) for a March 2011 campaign at the Korea Climate Observatory at Gosan (KCOG), a receptor station in SE Yellow Sea for the outflow from northern China. The mass absorption cross section at 365 nm (MAC365) of WSOC for air masses from N. China were in general higher (0.8–1.1 m2 g−1), than from other source regions (0.3–0.8 m2 g−1). However, this effect corresponds to only 2–10% of the radiative forcing caused by light absorption by elemental carbon. Radiocarbon constraints show that the WSOC in Chinese outflow had significantly higher fraction fossil sources (30–50%) compared to previous findings in S. Asia, N. America and Europe. Stable carbon (δ13C) measurements were consistent with aging during long-range air mass transport for this large fraction of carbonaceous aerosols.

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

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.

scholarly journals Enhancement of snow albedo reduction and radiative forcing due to coated black carbon in snow

2021 ◽  
Vol 15 (5) ◽  
pp. 2255-2272
Author(s):  
Wei Pu ◽  
Tenglong Shi ◽  
Jiecan Cui ◽  
Yang Chen ◽  
Yue Zhou ◽  
...  
Keyword(s):  
Black Carbon ◽  
Light Absorption ◽  
Radiative Forcing ◽  
Climate Models ◽  
Northern China ◽  
Climate Impact ◽  
Arctic Sea Ice ◽  
The Arctic ◽  
Core Shell ◽  
Snow Albedo

Abstract. When black carbon (BC) is mixed internally with other atmospheric particles, the BC light absorption effect is enhanced. This study explicitly resolved the optical properties of coated BC in snow based on the core / shell Mie theory and the Snow, Ice, and Aerosol Radiative (SNICAR) model. Our results indicated that the BC coating effect enhances the reduction in snow albedo by a factor ranging from 1.1–1.8 for a nonabsorbing shell and 1.1–1.3 for an absorbing shell, depending on the BC concentration, snow grain radius, and core / shell ratio. We developed parameterizations of the BC coating effect for application to climate models, which provides a convenient way to accurately estimate the climate impact of BC in snow. Finally, based on a comprehensive set of in situ measurements across the Northern Hemisphere, we determined that the contribution of the BC coating effect to snow light absorption exceeds that of dust over northern China. Notably, high enhancements of snow albedo reduction due to the BC coating effect were found in the Arctic and Tibetan Plateau, suggesting a greater contribution of BC to the retreat of Arctic sea ice and Tibetan glaciers.

scholarly journals Photochemical degradation affects the light absorption of water-soluble brown carbon in the South Asian outflow

2019 ◽  
Vol 5 (1) ◽  
pp. eaau8066 ◽  
Author(s):  
Sanjeev Dasari ◽  
August Andersson ◽  
Srinivas Bikkina ◽  
Henry Holmstrand ◽  
Krishnakant Budhavant ◽  
...  
Keyword(s):  
South Asia ◽  
Light Absorption ◽  
Climate Models ◽  
Temporal Dynamics ◽  
Regional Scale ◽  
Water Soluble ◽  
Photochemical Oxidation ◽  
Photochemical Degradation ◽  
Gangetic Plain ◽  
Brown Carbon

Light-absorbing organic aerosols, known as brown carbon (BrC), counteract the overall cooling effect of aerosols on Earth’s climate. The spatial and temporal dynamics of their light-absorbing properties are poorly constrained and unaccounted for in climate models, because of limited ambient observations. We combine carbon isotope forensics (δ13C) with measurements of light absorption in a conceptual aging model to constrain the loss of light absorptivity (i.e., bleaching) of water-soluble BrC (WS-BrC) aerosols in one of the world’s largest BrC emission regions—South Asia. On this regional scale, we find that atmospheric photochemical oxidation reduces the light absorption of WS-BrC by ~84% during transport over 6000 km in the Indo-Gangetic Plain, with an ambient first-order bleaching rate of 0.20 ± 0.05 day−1 during over-ocean transit across Bay of Bengal to an Indian Ocean receptor site. This study facilitates dynamic parameterization of WS-BrC absorption properties, thereby constraining BrC climate impact over South Asia.

scholarly journals Light absorption by organic carbon from wood combustion

2009 ◽  
Vol 9 (5) ◽  
pp. 20471-20513 ◽  
Author(s):  
Y. Chen ◽  
T. C. Bond
Keyword(s):  
Organic Carbon ◽  
Light Absorption ◽  
Radiative Forcing ◽  
Water Soluble ◽  
Carbonaceous Aerosols ◽  
Radiative Balance ◽  
Near Ultraviolet ◽  
Water Soluble Organic Carbon ◽  
Soluble Organic Carbon ◽  
Visible Wavelengths

Abstract. Carbonaceous aerosols affect the radiative balance of the Earth by absorbing and scattering light. While BC is highly absorbing, some organic compounds also have significant absorption, which is greater at near-ultraviolet and blue wavelengths. To the extent that OC absorbs visible light, it may be a non-negligible contributor to direct aerosol radiative forcing. In this work, we examine absorption by primary OC emitted from solid fuel pyrolysis. We provide absorption spectra of this material, which can be related to the imaginary refractive index. This material has polar character but is not fully water-soluble: more than 92% was extractable by methanol or acetone, compared with 73% for water and 52% for hexane. Water-soluble organic carbon contributed to light absorption at both ultraviolet and visible wavelengths. However, a larger portion came from organic carbon that is extractable only by methanol. The spectra of water-soluble organic carbon are similar to others in the literature. We compared spectra for material generated with different wood type, wood size and pyrolysis temperature. Higher wood temperature is the main factor creating organic aerosol with higher absorption, causing about a factor of four increase in mass-normalized absorption at visible wavelengths. A simple model suggests that, despite the absorption, both high-temperature and low-temperature carbon have negative climate forcing over a surface with average albedo.

scholarly journals Enhancement of snow albedo reduction and radiative forcing due to coated black carbon in snow

2020 ◽  
Author(s):  
Wei Pu ◽  
Tenglong Shi ◽  
Jiecan Cui ◽  
Yang Chen ◽  
Yue Zhou ◽  
...  
Keyword(s):  
Black Carbon ◽  
Light Absorption ◽  
Radiative Forcing ◽  
Climate Models ◽  
Northern China ◽  
Climate Impact ◽  
Arctic Sea Ice ◽  
The Arctic ◽  
Core Shell ◽  
Snow Albedo

Abstract. When black carbon (BC) is internally mixed with other atmospheric particles, BC light absorption is effectively enhanced. This study is the first to explicitly resolve the optical properties of coated BC in snow, based on core/shell Mie theory and a snow, ice, and aerosol radiative model (SNICAR). Our results indicate that a "BC coating effect" enhances the reduction of snow albedo by a factor of 1.1–1.8 for a non-absorbing shell and 1.1–1.3 for an absorbing shell, depending on BC concentration, snow grain radius, and core/shell ratio. We develop parameterizations of the BC coating effect for application to climate models, which provides a convenient way to accurately estimate the climate impact of BC in snow. Finally, based on a comprehensive set of in situ measurements across the Northern Hemisphere, we find that the contribution of the BC coating effect to snow light absorption has exceeded that of dust over northern China. Notably, the high enhancements of snow albedo reductions by BC coating effect were found in the Arctic and Tibetan Plateau, suggesting a greater contribution of BC to the retreat of Arctic sea ice and Tibetan glaciers.

scholarly journals Atmospheric circulation and hydroclimate impacts of alternative warming scenarios for the Eocene

2017 ◽  
Vol 13 (8) ◽  
pp. 1037-1048 ◽  
Author(s):  
Henrik Carlson ◽  
Rodrigo Caballero
Keyword(s):  
Surface Temperature ◽  
Radiative Forcing ◽  
Climate Models ◽  
Climate Model ◽  
Regional Climate ◽  
Warm Season ◽  
Cloud Albedo ◽  
Cloud Properties ◽  
Atmospheric Co2 Concentrations ◽  
Global Mean

Abstract. Recent work in modelling the warm climates of the early Eocene shows that it is possible to obtain a reasonable global match between model surface temperature and proxy reconstructions, but only by using extremely high atmospheric CO2 concentrations or more modest CO2 levels complemented by a reduction in global cloud albedo. Understanding the mix of radiative forcing that gave rise to Eocene warmth has important implications for constraining Earth's climate sensitivity, but progress in this direction is hampered by the lack of direct proxy constraints on cloud properties. Here, we explore the potential for distinguishing among different radiative forcing scenarios via their impact on regional climate changes. We do this by comparing climate model simulations of two end-member scenarios: one in which the climate is warmed entirely by CO2 (which we refer to as the greenhouse gas (GHG) scenario) and another in which it is warmed entirely by reduced cloud albedo (which we refer to as the low CO2–thin clouds or LCTC scenario) . The two simulations have an almost identical global-mean surface temperature and equator-to-pole temperature difference, but the LCTC scenario has  ∼  11 % greater global-mean precipitation than the GHG scenario. The LCTC scenario also has cooler midlatitude continents and warmer oceans than the GHG scenario and a tropical climate which is significantly more El Niño-like. Extremely high warm-season temperatures in the subtropics are mitigated in the LCTC scenario, while cool-season temperatures are lower at all latitudes. These changes appear large enough to motivate further, more detailed study using other climate models and a more realistic set of modelling assumptions.

Light absorption properties of elemental carbon (EC) and water-soluble brown carbon (WS–BrC) in the Kathmandu Valley, Nepal: A 5-year study

2020 ◽  
Vol 261 ◽  
pp. 114239 ◽  
Author(s):  
Pengfei Chen ◽  
Shichang Kang ◽  
Lekhendra Tripathee ◽  
Kirpa Ram ◽  
Maheswar Rupakheti ◽  
...  
Keyword(s):  
Light Absorption ◽  
Elemental Carbon ◽  
Water Soluble ◽  
Kathmandu Valley ◽  
Absorption Properties ◽  
Brown Carbon

scholarly journals Attribution of aerosol light absorption to black carbon, brown carbon, and dust in China – interpretations of atmospheric measurements during EAST-AIRE

2009 ◽  
Vol 9 (6) ◽  
pp. 2035-2050 ◽  
Author(s):  
M. Yang ◽  
S. G. Howell ◽  
J. Zhuang ◽  
B. J. Huebert
Keyword(s):  
Optical Properties ◽  
Black Carbon ◽  
Light Absorption ◽  
Northern China ◽  
Wavelength Dependence ◽  
Atmospheric Measurements ◽  
Brown Carbon ◽  
Mass Distributions ◽  
Limit Value ◽  
Light Absorbers

Abstract. Black carbon, brown carbon, and mineral dust are three of the most important light absorbing aerosols. Their optical properties differ greatly and are distinctive functions of the wavelength of light. Most optical instruments that quantify light absorption, however, are unable to distinguish one type of absorbing aerosol from another. It is thus instructive to separate total absorption from these different light absorbers to gain a better understanding of the optical characteristics of each aerosol type. During the EAST-AIRE (East Asian Study of Tropospheric Aerosols: an International Regional Experiment) campaign near Beijing, we measured light scattering using a nephelometer, and light absorption using an aethalometer and a particulate soot absorption photometer. We also measured the total mass concentrations of carbonaceous (elemental and organic carbon) and inorganic particulates, as well as aerosol number and mass distributions. We were able to identify periods during the campaign that were dominated by dust, biomass burning, fresh (industrial) chimney plumes, other coal burning pollution, and relatively clean (background) air for Northern China. Each of these air masses possessed distinct intensive optical properties, including the single scatter albedo and Ångstrom exponents. Based on the wavelength-dependence and particle size distribution, we apportioned total light absorption to black carbon, brown carbon, and dust; their mass absorption efficiencies at 550 nm were estimated to be 9.5, 0.5 (a lower limit value), and 0.03 m2/g, respectively. While agreeing with the common consensus that black carbon is the most important light absorber in the mid-visible, we demonstrated that brown carbon and dust could also cause significant absorption, especially at shorter wavelengths.

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

2018 ◽  
Vol 18 (22) ◽  
pp. 16409-16418 ◽  
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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