Mixing State of Black Carbon Particles in Asian Outflow Observed at a Remote Site in Taiwan in the Spring of 2017

Sun, Cuizhi; Adachi, Kouji; Misawa, Kentaro; Cheung, Hing Cho; Chou, Charles C.‐K.; Takegawa, N.

doi:10.1029/2020jd032526

Cited by 4 publications

(1 citation statement)

References 65 publications

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“…Figure 5 (top images) shows a comparison of the mixing states during navigation (a-c) and stop (d-f) from typical BC TEM images. The BC particles collected during navigation are in the embedded (a), external (b), or core-shell (c) mixing states classified with the methods which are based on single particle analysis of island and mountain samples across East China Sea and Japan (Adachi et al, 2014;Sun et al, 2020a). More TEM images for the heavily coated internal and external BC particles from navigation can be found in the SI (section 4, Fig.…”

Section: Single Particle Analysis Of Bc and Tar Ballsmentioning

confidence: 99%

Morphological and optical properties of carbonaceous aerosol particles from ship emissions and biomass burning during a summer cruise measurement in the South China Sea

Sun,

Zhang,

Liang

et al. 2023

Preprint

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Abstract. Carbonaceous aerosols constitute a crucial component of atmospheric marine aerosols, among which black carbon (BC) and brown carbon (BrC) are important contributors to light absorption and hence the positive climatic radiative forcing in the marine atmosphere. We conducted a month-long (May 05–June 09, 2021) onboard sample collections and online measurements of carbonaceous aerosols to characterize their morphological and optical properties during a ship cruise in the South China Sea (SCS), covering a marine region of 11.9–24.5° N and 111.1–118.2° E. Single particles were collected by a single particle sampler and offline analyses were performed to investigate the mixing state and morphology using a transmission electron microscope (TEM). Online measurements of BC in PM2.5 were made by a seven-wavelength aethalometer and organic carbon (OC)/elemental carbon (EC) mass concentrations were measured by a semi-online OC/EC analyzer. Single particle samples were classified into two modes: “stop” when the ship was anchored and “navigation” when the ship sailed at high speed. Feret diameters of the single particles during navigation and stop showed size distributions with the lognormal fitting peaks at 307 and 325 nm, respectively. The fresh (without coating) and aged BC particles (after removal of coating by the electron beams in TEM) showed comparable median fractal dimensions (1.65 vs 1.66), in contrast to their different median lacunarities (0.53 vs 0.59). The aged BC particles showed narrower Feret diameters (298–1980 nm) during navigation than those (304–2982 nm) of freshly-emitted BC from the own ship during stop. Moreover, tar balls, as one important component of single particles from ship emissions and as the tracer of biomass burning, were identified with geometrical diameters of 160–420 nm in the TEM images. The energy dispersive X-ray spectroscopy (EDS) analyses showed those tar balls are mainly mixed with sea salt, organics, BC, and sulfate. We also found a significant fraction of aged BC in various mixing states (core-shell, embedded) with other components of the aerosol particles after long-range transport. The campaign was further divided into several periods (before monsoon period, BMP; transition monsoon period, TMP; after monsoon period, AMP; and ship pollution period, SPP) according to the wind direction during monsoon and the own ship pollution. The median OC/EC ratios were 8.14, 5.20, 6.35, and 2.63 during BMP, TMP, AMP, and SPP, respectively, showing higher OC/EC ratios for biomass burning emissions than for fossil fuel emissions. Additionally, the median absorption Angström exponent (AAE) values derived from all wavelengths were 1.14, 1.02, 1.08, and 1.06 for BMP, TMP, AMP and SPP, respectively. Particularly, a median AAE value of 1.93 was obtained during two significant biomass burning events. These results showed that biomass burning (BB) and fossil fuel (FF) combustion contributed to 18–22 % and 78–82 % of all the BC light absorption without the two intense biomass burning events, during which BB and FF accounted for 42 % and 58 %, respectively. The two BB events originated from the Philippines and Southeast Asia before and after the summer monsoon. Our results demonstrated that BC can serve as the core of aged particles but the fractal dimensions of BC aggerates were subject to little variation; moreover, such BC particles become much more aggerated after aging in the marine atmosphere, which further affects the light absorption of the BC particles in the SCS. This study provides information about the morphology and the optical properties of carbonaceous aerosols which can be used to evaluate their effects on light absorption and hence the climatic radiative forcing in the SCS region.

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Section: Single Particle Analysis Of Bc and Tar Ballsmentioning

confidence: 99%

Morphological and optical properties of carbonaceous aerosol particles from ship emissions and biomass burning during a summer cruise measurement in the South China Sea

Sun,

Zhang,

Liang

et al. 2023

Preprint

View full text Add to dashboard Cite

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Significant contribution of fractal morphology to aerosol light absorption in polluted environments dominated by black carbon (BC)

Romshoo,

Müller,

Ahlawat

et al. 2024

npj Clim Atmos Sci

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In recent years, researchers have emphasized the use of fractal aggregate morphology instead of the core-shell morphology in global climate models for estimating black carbon (BC) forcing. This study confirms that fractal morphology plays an important role in reducing the overestimation of aerosol light absorption calculations in the case of an urban polluted environment. During periods of high anthropogenic BC emissions at Delhi, the particle light absorption is overestimated by 50 to 200% by assumptions of both external mixing and internal core-shell mixing. While incorporating the aggregate morphology model into light absorption simulations is beneficial in such cases, it comes with a high computational burden. To address this, we propose a metric known as morphology index (MI). This index distributes the weightage between the two extreme cases of core-shell and fractal aggregate to obtain accurate particle light absorption. Long-range transported aerosols were estimated to have an MI of 0.78, and fresh local emissions had an MI of 0.48. A BC-based aerosol classification approach was developed to determine the most relevant particle size mode for light absorption. The method is based on patterns found between the correlations of the BC mass concentrations and aerosol number concentrations at the different particles sizes (BC-size correlation spectra). BC-size correlation spectra are introduced as a concept that may be used (i) independently to understand the size-dependent heterogeneous distribution of aerosol light absorption and (ii) in conjunction with MI to accurately model the optical properties of aerosols in different BC regimes.

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Morphological and optical properties of carbonaceous aerosol particles from ship emissions and biomass burning during a summer cruise measurement in the South China Sea

Sun,

Zhang,

Liang

et al. 2024

Atmos. Chem. Phys.

Self Cite

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Abstract. Carbonaceous aerosols constitute a crucial component of atmospheric marine aerosols among which black carbon (BC) and brown carbon (BrC) are important contributors to light absorption and hence the positive climatic radiative forcing in the marine atmosphere. We conducted month-long (5 May–9 June 2021) onboard sample collections and online measurements of carbonaceous aerosols to characterize their morphological and optical properties during a ship cruise in the South China Sea (SCS), covering a marine region of 11.9–24.5° N, 111.1–118.2° E. Single particles were collected by a single-particle sampler, and offline analyses were performed using a transmission electron microscope (TEM) coupled with energy-dispersive X-ray spectroscopy (EDS). Online measurements of BC in PM2.5 were made by a seven-wavelength aethalometer, and organic carbon (OC) and elemental carbon (EC) mass concentrations were measured by a semi-online OC/EC analyzer. Feret diameters of the single particles during navigation and stop showed size distributions with the lognormal fitting peaks at 307 and 325 nm, respectively. The fresh (without coating) and aged BC particles (after removal of coating by the electron beams in the TEM) showed same median fractal dimensions (1.61), in contrast to their different median lacunarities (0.53 vs. 0.59). The aged BC particles showed narrower Feret diameters (229–2557 nm) during navigation than those (78–2926 nm) of freshly emitted BC from the ship's own exhaust during stop. Moreover, tar balls, as one important component of single particles from ship emissions and as the tracer of biomass burning, were identified with geometrical diameters of 160–420 nm in the TEM images. The EDS analyses showed those tar balls are mainly mixed with sea salt, organics, BC, and sulfate. We also found a significant fraction of aged BC in various mixing states (core–shell, embedded) with other components of the aerosol particles after long-range transport. The campaign was further divided into several periods (the before-monsoon period, BMP; transition monsoon period, TMP; after-monsoon period, AMP; and ship pollution period, SPP) according to the wind direction during monsoon and the ship's own pollution. The median absorption Ångström exponent (AAE) values derived from all wavelengths were 1.14, 1.02, 1.08, and 1.06 for BMP, TMP, AMP, and SPP, respectively. Particularly, a median AAE value of 1.93 was obtained during two significant biomass burning events. These results showed that biomass burning (BB) and fossil fuel (FF) combustion contributed to 18 %–22 % and 78 %–82 % of all the BC light absorption without the two intense biomass burning events, during which BB and FF accounted for 42 % and 58 %, respectively. The two BB events originated from the Philippines and Southeast Asia before and after the summer monsoon. Our results demonstrated that BC can serve as the core of aged particles, but the fractal dimensions of BC aggregates were subject to little variation; moreover, such BC particles become much more aggregated after aging in the marine atmosphere, which further affects the light absorption of the BC particles in the SCS.

show abstract

Mixing State of Black Carbon Particles in Asian Outflow Observed at a Remote Site in Taiwan in the Spring of 2017

Cited by 4 publications

References 65 publications

Morphological and optical properties of carbonaceous aerosol particles from ship emissions and biomass burning during a summer cruise measurement in the South China Sea

Morphological and optical properties of carbonaceous aerosol particles from ship emissions and biomass burning during a summer cruise measurement in the South China Sea

Significant contribution of fractal morphology to aerosol light absorption in polluted environments dominated by black carbon (BC)

Morphological and optical properties of carbonaceous aerosol particles from ship emissions and biomass burning during a summer cruise measurement in the South China Sea

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