Impacts of black carbon mixing state on black carbon nucleation scavenging: Insights from a particle-resolved model

Abstract. In the present study, a ground-based counterflow virtual impactor (GCVI) was used to sample cloud droplet residual (cloud RES) particles, while a parallel PM2.5 inlet was used to sample cloud-free or cloud interstitial (cloud INT) particles. The mixing state of black carbon (BC)-containing particles in a size range of 0.1–1.6 µm and the mass concentrations of BC in the cloud-free, RES and INT particles were investigated using a single particle aerosol mass spectrometer (SPAMS) and two aethalometers, respectively, at a mountain site (1690 m a.s.l.) in southern China. The measured BC-containing particles were internally mixed extensively with sulfate, and were activated into cloud droplets to the same extent as all the measured particles. The results indicate the preferential activation of larger particles and/or that the production of secondary compositions shifts the BC-containing particles towards larger sizes. BC-containing particles with an abundance of both sulfate and organics were activated less than those with sulfate but limited organics, implying the importance of the mixing state on the incorporation of BC-containing particles into cloud droplets. The mass scavenging efficiency of BC with an average of 33 % was similar for different cloud events independent of the air mass. This is the first time that both the mixing state and cloud scavenging of BC in China have been reported. Since limited information on BC-containing particles in the free troposphere is available, the results also provide an important reference for the representation of BC concentrations, properties, and climate impacts in modeling studies.

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Seasonal size distribution and mixing state of black carbon aerosols in a polluted urban environment of the Yangtze River Delta region, China

The Science of The Total Environment ◽

10.1016/j.scitotenv.2018.11.087 ◽

2019 ◽

Vol 654 ◽

pp. 300-310 ◽

Cited By ~ 6

Author(s):

Yifan Yang ◽

Xiaofeng Xu ◽

Yunjiang Zhang ◽

Shanshan Zheng ◽

Lingrui Wang ◽

...

Keyword(s):

Urban Environment ◽

Size Distribution ◽

Black Carbon ◽

Yangtze River ◽

Yangtze River Delta ◽

The Yangtze River ◽

Mixing State ◽

Yangtze River Delta Region ◽

Carbon Aerosols ◽

The Yangtze River Delta

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Size distribution and coating thickness of black carbon from the Canadian oil sands operations

10.5194/acp-2017-1015 ◽

2017 ◽

Author(s):

Yuan Cheng ◽

Shao-Meng Li ◽

Mark Gordon ◽

Peter Liu

Keyword(s):

Size Distribution ◽

Black Carbon ◽

Coating Thickness ◽

Oil Sands ◽

Radiative Forcing ◽

Climate Models ◽

Source Area ◽

Size Distributions ◽

Mixing State ◽

Earth’S Climate

Abstract. Black carbon (BC) plays an important role in the Earth’s climate system. However, parameterization of BC size and mixing state have not been well addressed in aerosol-climate models, introducing substantial uncertainties into the estimation of radiative forcing by BC. In this study, we focused on BC emissions from the massive oil sands (OS) industry in northern Alberta, based on an aircraft campaign conducted over the Athabasca OS region in 2013. A total of 14 flights were made over the OS source area, in which the aircraft was typically flown in a 4- or 5-sided polygon pattern along flight tracks encircling an OS facility. Another 3 flights were performed downwind of the OS source area, each of which involved at least three intercepting locations where the well-mixed OS plume was measured along flight tracks perpendicular to the wind direction. Comparable size distributions were observed for refractory black carbon (rBC) over and downwind of the OS facilities, with rBC mass median diameters (MMD) between ~ 135 and 145 nm that were characteristic of fresh urban emissions. This MMD range corresponded to rBC number median diameters (NMD) of ~ 60–70 nm, approximately 100 % higher than the NMD settings in some aerosol-climate models. The typical in- and out-of-plume segments of a flight, which had different rBC concentrations and photochemical ages, showed consistent rBC size distributions. Moreover, rBC size distributions remained unchanged at different downwind distances from the source area, suggesting that atmospheric aging would not necessarily change rBC size distribution. However, aging indeed influenced rBC mixing state. Coating thickness for rBC cores in the diameter range of 130–160 nm was nearly doubled within three hours when the OS plume was transported over a distance of 90 km from the source area.

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Mixing state of refractory black carbon aerosol in the South Asian outflow over the northern Indian Ocean during winter

10.5194/acp-2020-836 ◽

2020 ◽

Author(s):

Sobhan Kumar Kompalli ◽

Surendran Nair Suresh Babu ◽

Krishnaswamy Krishnamoorthy ◽

Sreedharan Krishnakumari Satheesh ◽

Mukunda M. Gogoi ◽

...

Keyword(s):

Indian Ocean ◽

Black Carbon ◽

South Asian ◽

Arabian Sea ◽

Equatorial Indian Ocean ◽

Mixing State ◽

Air Masses ◽

Continental Outflow ◽

Mass Concentrations

Abstract. Regional climatic implications of aerosol black carbon (BC) are well recognized over South Asia, which has a wide variety of anthropogenic sources in a large abundance. Significant uncertainties remain in its quantification due to lack of sufficient information on the microphysical properties (its concentration, size, and mixing state with other aerosol components), which determine the absorption potential of BC. Especially the information on mixing state of BC is extremely sparse over this region. In this study, first-ever observations of the size distribution and mixing state of individual refractory black carbon (rBC) particles in the south Asian outflow to Southeastern Arabian Sea, northern and equatorial Indian Ocean regions are presented based on measurements using a single particle soot photometer (SP2) aboard the ship cruise of the Integrated Campaign for Aerosols, gases, and Radiation Budget (ICARB-2018) during winter-2018 (16 January to 13 February). The results revealed significant spatial heterogeneity of BC characteristics. Highest rBC mass concentrations (~ 938 ± 293 ng m−3) with the highest relative coating thickness (RCT; the ratio of BC core to its coating diameters) of ~ 2.16 ± 0.19 are found over the Southeast Arabian Sea (SEAS) region, which is in the proximity of the continental outflow. As we move to farther oceanic regions, though the mass concentrations decreased by nearly half (~ 546 ± 80 ng m−3), BC still remained thickly coated (RCT ~ 2.05 ± 0.07). The air over the remote equatorial Indian Ocean, which received considerable marine air masses compared to the other regions, showed the lowest rBC mass concentrations (~ 206 ± 114 ng m−3), with a moderately thick coating (RCT ~ 1.73 ± 0.16). Even over oceanic regions far from the landmass, regions which received the outflow from more industrialized east coast/the Bay of Bengal had thicker coating (~ 104 nm) compared to regions that received outflow from the west coast/peninsular India (~ 86 nm). Although different regions of the ocean depicted contrasting concentrations and mixing state parameters due to varying extent and nature of the continental outflow as well as the atmospheric lifetime of air masses, the modal parameters of rBC mass-size distributions were similar over all the regions. The observed mono-modal distribution with mean mass median diameters (MMD) in the range of 0.19–0.20 μm suggested mixed sources of BC. The mean fraction of BC containing particles (FBC) varied in the range 0.20–0.28 (suggesting significant amounts of non-BC particles), whereas the bulk mixing ratio of coating mass to rBC mass was highest (8.77 ± 2.77) over the outflow regions compared to the remote ocean (4.29 ± 1.54) highlighting the role of outflow in providing condensable material for coating on rBC. These parameters, along with the information on size-resolved mixing state of BC cores, throw light on the role of sources and secondary processing of their complex mixtures for coating on BC under highly polluted conditions. Examination of the non-refractory sub-micrometre aerosol chemical composition obtained using the aerosol chemical speciation monitor (ACSM) suggested that the overall aerosol system was sulfate dominated over the far-oceanic regions. In contrast, organics were equally prominent adjacent to the coastal landmass. Association between the BC mixing state and aerosol chemical composition suggested that sulfate was the probable dominant coating material on rBC cores.

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