scholarly journals Dynamic shape factor and mixing state of refractory black carbon particles in winter in Beijing using an AAC-DMA-SP2 tandem system

2019 ◽  
Author(s):  
Xiaole Pan ◽  
Hang Liu ◽  
Yu Wu ◽  
Yu Tian ◽  
Yele Sun ◽  
...  
Keyword(s):  
Black Carbon ◽  
Light Absorption ◽  
Shape Factor ◽  
Absorption Enhancement ◽  
Urban Site ◽  
Optical Simulation ◽  
Mixing State ◽  
Dynamic Shape Factor ◽  
Dynamic Shape ◽  
Pollution Episodes

Abstract. Refractory black carbon (rBC) is one of the most important short-lived climate forcers in the atmosphere. Light absorption enhancement capacity largely depends on the morphology of rBC-containing particles and their mixing state. In this study, a tandem measuring system, consisting of an aerodynamic aerosol classifier (AAC), a differential mobility analyzer (DMA) and a single particle soot photometer (SP2), was adopted to investigate dynamic shape factor (𝜒) and its relationship with the mixing state of rBC-containing particles at an urban site of Beijing megacity in winter. The results demonstrated that the aerosol particles with an aerodynamic diameter of 400 ± 1.2 nm normally had a mobility diameter (Dmob) ranging from 250 nm to 320 nm, reflecting a large variation in shape under different pollution conditions. Multiple Gaussian fitting on the number mass-equivalent diameter (Dmev) distribution of the rBC core determined by SP2 had two peaks at Dmev = 106.5 nm and Dmev = 146.3 nm. During pollution episodes, rBC-containing particles tended to have a smaller rBC core than those during clean episodes due to rapid coagulation and condensation processes. The 𝜒 values of the particles were found to be ~ 1.2 during moderate pollution conditions, although the shell-core ratio (S/C) of rBC-containing particles was as high as 2.7 ± 0.3, suggesting that the particles had an irregular structure as a result of the high fraction of nascent rBC aggregates. During heavy pollution episodes, the 𝜒 value of the particles was approximately 1.0, indicating that the majority of particles tended to be spherical, and a shell-core model could be reasonable to estimate the light enhancement effect. Considering the variation in shape of the particles, the light absorption enhancement of the particles differed significantly according to the T-matrix model simulation. This study suggested that accurate description of the morphology of rBC-containing particles was crucially important for optical simulation and better evaluation of their climate effect.

scholarly journals Measuring the morphology and density of internally mixed black carbon with SP2 and VTDMA: new insight into the absorption enhancement of black carbon in the atmosphere

2016 ◽  
Vol 9 (4) ◽  
pp. 1833-1843 ◽  
Author(s):  
Yuxuan Zhang ◽  
Qiang Zhang ◽  
Yafang Cheng ◽  
Hang Su ◽  
Simonas Kecorius ◽  
...  
Keyword(s):  
Black Carbon ◽  
Shape Factor ◽  
Spherical Shape ◽  
Average Density ◽  
Effective Density ◽  
Absorption Enhancement ◽  
Mixing State ◽  
New Approach ◽  
Insight Into ◽  
Dynamic Shape

Abstract. The morphology and density of black carbon (BC) cores in internally mixed BC (In-BC) particles affect their mixing state and absorption enhancement. In this work, we developed a new method to measure the morphology and effective density of the BC cores of ambient In-BC particles using a single-particle soot photometer (SP2) and a volatility tandem differential mobility analyzer (VTDMA) during the CAREBeijing-2013 campaign from 8 to 27 July 2013 at Xianghe Observatory. This new measurement system can select size-resolved ambient In-BC particles and measure the mobility diameter and mass of the In-BC cores. The morphology and effective density of the ambient In-BC cores are then calculated. For the In-BC cores in the atmosphere, changes in their dynamic shape factor (χ) and effective density (ρeff) can be characterized as a function of the aging process (Dp∕Dc) measured by SP2 and VTDMA. During an intensive field study, the ambient In-BC cores had an average shape factor χ of  ∼ 1.2 and an average density of  ∼ 1.2 g cm−3, indicating that ambient In-BC cores have a near-spherical shape with an internal void of  ∼ 30 %. From the measured morphology and density, the average shell ∕ core ratio and absorption enhancement (Eab) of ambient BC were estimated to be 2.1–2.7 and 1.6–1.9, respectively, for In-BC particles with sizes of 200–350 nm. When the In-BC cores were assumed to have a void-free BC sphere with a density of 1.8 g cm−3, the shell ∕ core ratio and Eab were overestimated by  ∼ 13 and  ∼ 17 %, respectively. The new approach developed in this work improves the calculations of the mixing state and optical properties of ambient In-BC particles by quantifying the changes in the morphology and density of ambient In-BC cores during aging.

Mixing state and light absorption enhancement of black carbon aerosols in summertime Nanjing, China

2020 ◽  
Vol 222 ◽  
pp. 117141 ◽  
Author(s):  
Yan Ma ◽  
Congcong Huang ◽  
Halim Jabbour ◽  
Zewen Zheng ◽  
Yibo Wang ◽  
...  
Keyword(s):  
Black Carbon ◽  
Light Absorption ◽  
Absorption Enhancement ◽  
Mixing State ◽  
Carbon Aerosols ◽  
Black Carbon Aerosols

scholarly journals Mixing characteristics of refractory black carbon aerosols determined by a tandem CPMA-SP2 system at an urban site in Beijing

2019 ◽  
Author(s):  
Hang Liu ◽  
Xiaole Pan ◽  
Dantong Liu ◽  
Xiaoyong Liu ◽  
Xueshun Chen ◽  
...  
Keyword(s):  
Black Carbon ◽  
Fractal Structure ◽  
Particle Mass ◽  
Shell Structures ◽  
Absorption Enhancement ◽  
Urban Site ◽  
Core Shell ◽  
Mixing State ◽  
Carbon Aerosols ◽  
Black Carbon Aerosols

Abstract. Black carbon aerosols play an important role in climate change by absorbing solar radiation and degrading visibility. In this study, the mixing state of refractory black carbon (rBC) at an urban site in Beijing was studied with a single particle soot photometer (SP2), as well as a tandem observation system with a centrifugal particle mass analyzer (CPMA) and a differential mobility analyzer (DMA), in early summer of 2018. The results demonstrated that the mass-equivalent size distribution of rBC exhibited an approximately lognormal distribution with a mass median diameter (MMD) of 171.2 nm. When the site experienced prevailing southerly winds, the MMD of rBC increased notably by 19 %. During the observational period, the ratio of the diameter of rBC-containing particles (Dp) to the rBC core (Dc) was 1.20 on average for Dc = 180 nm, indicating that the majority of rBC particles were thinly coated. The Dp / Dc value exhibited a clear diurnal pattern, with a maximum at 1400 LST and an enhancing rate of 0.013/h; higher Ox conditions increased the coating enhancing rate. Bare rBC particles were primarily in a fractal structure with a mass fractal dimension (Dfm) of 2.35, with limited variation during both clean and pollution periods, indicating significant impacts from on-road vehicle emissions. The morphology of rBC-containing particles vairied with aging processes. The mixing state of rBC particles could be indicated by the mass ratio of non-refractory matter to rBC (MR). In the present study, rBC-containing particles were primarily found in an external fractal structure when MR  6, at which the measured scattering cross section of rBC-containing particles was consistent with that based on the Mie-scattering simulation. We found only 9 % of the rBC-containing particles were in core-shell structures on clean days with a particle mass of 10 fg, and the number fraction of core-shell structures increased considerably to 32 % on pollution days. Considering the morphology change, the absorption enhancement (Eabs) was 11.7 % higher based on core-shell structures. This study highlights the combined effects of morphology and coating thickness on the Eabs of rBC-containing particles, which will be helpful for determining the climatic effects of BC.

Mixing State of Black Carbon Aerosol in a Heavily Polluted Urban Area of China: Implications for Light Absorption Enhancement

2014 ◽  
Vol 48 (7) ◽  
pp. 689-697 ◽  
Author(s):  
Qiyuan Wang ◽  
R.-J. Huang ◽  
Junji Cao ◽  
Yongming Han ◽  
Gehui Wang ◽  
...  
Keyword(s):  
Black Carbon ◽  
Urban Area ◽  
Light Absorption ◽  
Absorption Enhancement ◽  
Mixing State ◽  
Black Carbon Aerosol

scholarly journals Implication of Light Absorption Enhancement and Mixing State of Black Carbon (BC) by Coatings in Hong Kong

2018 ◽  
Vol 18 (11) ◽  
pp. 2753-2763 ◽  
Author(s):  
Guo-Liang Li ◽  
Li Sun ◽  
Kin-Fai Ho ◽  
Ka-Chun Wong ◽  
Zhi Ning
Keyword(s):  
Hong Kong ◽  
Black Carbon ◽  
Light Absorption ◽  
Absorption Enhancement ◽  
Mixing State

scholarly journals Strong Light Absorption Induced by Aged Biomass Burning Black Carbon over the Southeastern Tibetan Plateau in Pre-monsoon Season

2020 ◽  
Author(s):  
Tianyi Tan ◽  
Min Hu ◽  
Zhuofei Du ◽  
Gang Zhao ◽  
Dongjie Shang ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Black Carbon ◽  
Biomass Burning ◽  
Climate Warming ◽  
Light Absorption ◽  
Monsoon Season ◽  
Absorption Enhancement ◽  
The Tibetan Plateau ◽  
Mixing State ◽  
Strong Light

Abstract. During the pre-monsoon season, biomass burning (BB) activities are intensive in southern Asia. Facilitated by westerly circulation, those BB plumes can be transported to the Tibetan Plateau (TP). Black carbon (BC), the main aerosol species in BB emissions, is an important climate warming agent, and its absorbing property strongly depends on its size distribution and mixing state. To elucidate the influence of those transported BB plumes on the TP, a field campaign was conducted on the southeast edge of the TP during the pre-monsoon season. It was found that the transported BB plumes substantially increased the number concentration of the atmospheric BC particles by 13 times, and greatly elevated the number fraction of thickly-coated BC from 52 % up to 91 %. Those transported BC particles had slightly larger core size and much thicker coatings than the background BC particles. However, the coating mass was not evenly distributed on BC particles with different sizes. The smaller BC cores were found to have larger shell/core ratios than the larger cores. Besides, the transported BB plumes strongly affected the vertical variation of the BC's abundance and mixing state, resulting in a higher concentration, larger number fraction and higher aging degree of BC particles in the upper atmosphere. Resulted from both increase of BC loading and aging degree, the transported BB plumes eventually enhanced the total light absorption by 15 times, in which 21 % was contributed by the BC aging and 79 % was contributed from the increase of BC mass. Particularly, the light absorption enhancement induced by the aging process during long-range transport has far exceeded the background aerosol light absorption, which implicates a significant influence of BC aging on climate warming over the TP region.

scholarly journals Measuring morphology and density of internally mixed black carbon with SP2 and VTDMA: new insight to absorption enhancement of black carbon in the atmosphere

2015 ◽  
Vol 8 (11) ◽  
pp. 12025-12050 ◽  
Author(s):  
Y. X. Zhang ◽  
Q. Zhang ◽  
Y. F. Cheng ◽  
H. Su ◽  
S. Kecorius ◽  
...  
Keyword(s):  
Black Carbon ◽  
Aging Process ◽  
Spherical Shape ◽  
Average Density ◽  
Effective Density ◽  
Absorption Enhancement ◽  
Mixing State ◽  
Differential Mobility ◽  
New Approach ◽  
Dynamic Shape

Abstract. The morphology and density of black carbon (BC) cores in internally mixed BC (In-BC) particles affects their mixing state and absorption enhancement. In this work, we developed a new method to measure the morphology and effective density of BC cores of ambient In-BC particles using a single particle soot photometer (SP2) and a volatility tandem differential mobility analyzer (VTDMA), during the CAREBeijing-2013 campaign from 8 to 27 July 2013 at Xianghe Observatory. The new measurement system can select size-resolved ambient In-BC particles and measure the mobility size and mass of In-BC cores. The morphology and effective density of ambient In-BC cores are then calculated. For In-BC cores in the atmosphere, changes in the dynamic shape factor (χ) and effective density (ρeff) can be characterized as a function of aging process (Dp ⁄ Dc) measured by SP2 and VTDMA. During an intensive field study, the ambient In-BC cores had an average χ of ∼ 1.2 and an average density of ∼ 1.2 g cm−3, indicating that ambient In-BC cores have a near-spherical shape with an internal void of ∼ 30 %. With the measured morphology and density, the average shell ⁄ core ratio and absorption enhancement (Eab) from ambient black carbon were estimated to be 2.1–2.7 and 1.6–1.9 for different sizes of In-BC particles at 200–350 nm. When assuming the In-BC cores have a void-free BC sphere with a density of 1.8 g cm−3, the shell ⁄ core ratio and Eab could be overestimated by ∼ 13 and ∼ 17 % respectively. The new approach developed in this work will help improve calculations of mixing state and optical properties of ambient In-BC particles by quantification of changes in morphology and density of ambient In-BC cores during aging process.

scholarly journals Measurement report: Strong light absorption induced by aged biomass burning black carbon over the southeastern Tibetan Plateau in pre-monsoon season

2021 ◽  
Vol 21 (11) ◽  
pp. 8499-8510
Author(s):  
Tianyi Tan ◽  
Min Hu ◽  
Zhuofei Du ◽  
Gang Zhao ◽  
Dongjie Shang ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Black Carbon ◽  
Biomass Burning ◽  
Climate Warming ◽  
Light Absorption ◽  
Monsoon Season ◽  
Absorption Enhancement ◽  
The Tibetan Plateau ◽  
Mixing State ◽  
Strong Light

Abstract. During the pre-monsoon season, biomass burning (BB) activities are intensive in southern Asia. Facilitated by westerly circulation, those BB plumes can be transported to the Tibetan Plateau (TP). Black carbon (BC), the main aerosol species in BB emissions, is an important climate warming agent, and its absorbing property strongly depends on its size distribution and mixing state. To elucidate the influence of those transported BB plumes on the TP, a field campaign was conducted on the southeast edge of the TP during the pre-monsoon season. It was found that the transported BB plumes substantially increased the number concentration of the atmospheric BC particles by a factor of 13 and greatly elevated the number fraction of thickly coated BC from 52 % up to 91 %. Those transported BC particles had slightly larger core size and much thicker coatings than the background BC particles. However, the coating mass was not evenly distributed on BC particles with different sizes. The smaller BC cores were found to have larger shell / core ratios than the larger cores. Besides, the transported BB plumes strongly affected the vertical variation in the BC's abundance and mixing state, resulting in a higher concentration, larger number fraction, and higher aging degree of BC particles in the upper atmosphere. Resulting from both increase in BC loading and aging degree, the transported BB plumes eventually enhanced the total light absorption by a factor of 15, of which 21 % was contributed by the BC aging, and 79 % was contributed from the increase in BC mass. Particularly, the light absorption enhancement induced by the aging process during long-range transport has far exceeded the background aerosol light absorption, which implicates a significant influence of BC aging on climate warming over the TP region.

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