Light-absorption enhancement of black carbon in the Asian outflow inferred from airborne SP2 and in-situ measurements during KORUS-AQ

Chaeyoon Cho; Joshua P. Schwarz; Anne E. Perring; Kara D. Lamb; Yutaka Kondo; Jong Uk Park; Do Hyeon Park; Kyuseok Shim; Jin Soo Park; Rokjin J. Park; Meehye Lee; Chang Keun Song; Sang Woo Kim

doi:10.1016/j.scitotenv.2021.145531

Light-absorption enhancement of black carbon in the Asian outflow inferred from airborne SP2 and in-situ measurements during KORUS-AQ

Chaeyoon Cho, Joshua P. Schwarz, Anne E. Perring, Kara D. Lamb, Yutaka Kondo, Jong Uk Park, Do Hyeon Park, Kyuseok Shim, Jin Soo Park, Rokjin J. Park, Meehye Lee, Chang Keun Song, Sang Woo Kim

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Abstract

We investigated the changes in the size distribution, coating thickness, and mass absorption cross-section (MAC) of black carbon (BC) with aging and estimated the light absorption enhancement (E_abs) in the Asian outflow from airborne in-situ measurements during 2016 KORUS-AQ campaign. The BC number concentration decreased, but mass mean diameter increased with increasing altitude in the West Coast (WC) and Seoul Metropolitan Area (SMA), reflecting the contrast between freshly emitted BC-containing particles at the surface and more aged aerosol associated with aggregation during vertical mixing and transport. Contradistinctively, BC number and mass size distributions were relatively invariant with altitude over the Yellow Sea (YS) because sufficiently aged BC from eastern China were horizontally transported to all altitudes over the YS, and there are no significant sources at the surface. The averaged inferred MAC of refractory BC in three regions reflecting differences in their size distributions increased to 9.8 ± 1.0 m² g⁻¹ (YS), 9.3 ± 0.9 m² g⁻¹ (WC), and 8.2 ± 0.9 m² g⁻¹ (SMA) as BC coating thickness increased from 20 nm to 120 nm. The absorption coefficient of BC calculated from the coating thickness and MAC were highly correlated with the filter-based absorption measurements with the slope of 1.16 and R² of 0.96 at 550 nm, revealing that the thickly coated BC had a large MAC and absorption coefficient. The E_abs due to the inferred coatings was estimated as 1.0–1.6, which was about 30% lower than those from climate models and laboratory experiments, suggesting that the increase in the BC absorption by the coatings in the Asian outflow is not as large as calculated in the previous studies. Organics contributed to the largest E_abs accounting for 69% (YS), 61% (WC), and 64% (SMA). This implies that organics are largely responsible for the lensing effect of BC rather than sulfates in the Asian outflow.

Original language	English
Article number	145531
Journal	Science of the Total Environment
Volume	773
DOIs	https://doi.org/10.1016/j.scitotenv.2021.145531
Publication status	Published - 2021 Jun 15

Bibliographical note

Publisher Copyright:
© 2021 Elsevier B.V.

Keywords

Absorption enhancement
Aging process
Black carbon
KORUS-AQ
SP2

ASJC Scopus subject areas

Environmental Engineering
Environmental Chemistry
Waste Management and Disposal
Pollution

UN SDGs

This output contributes to the following UN Sustainable Development Goals (SDGs)

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10.1016/j.scitotenv.2021.145531

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Cho, C., Schwarz, J. P., Perring, A. E., Lamb, K. D., Kondo, Y., Park, J. U., Park, D. H., Shim, K., Park, J. S., Park, R. J., Lee, M., Song, C. K., & Kim, S. W. (2021). Light-absorption enhancement of black carbon in the Asian outflow inferred from airborne SP2 and in-situ measurements during KORUS-AQ. Science of the Total Environment, 773, Article 145531. https://doi.org/10.1016/j.scitotenv.2021.145531

Cho, C, Schwarz, JP, Perring, AE, Lamb, KD, Kondo, Y, Park, JU, Park, DH, Shim, K, Park, JS, Park, RJ, Lee, M, Song, CK & Kim, SW 2021, 'Light-absorption enhancement of black carbon in the Asian outflow inferred from airborne SP2 and in-situ measurements during KORUS-AQ', Science of the Total Environment, vol. 773, 145531. https://doi.org/10.1016/j.scitotenv.2021.145531

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abstract = "We investigated the changes in the size distribution, coating thickness, and mass absorption cross-section (MAC) of black carbon (BC) with aging and estimated the light absorption enhancement (Eabs) in the Asian outflow from airborne in-situ measurements during 2016 KORUS-AQ campaign. The BC number concentration decreased, but mass mean diameter increased with increasing altitude in the West Coast (WC) and Seoul Metropolitan Area (SMA), reflecting the contrast between freshly emitted BC-containing particles at the surface and more aged aerosol associated with aggregation during vertical mixing and transport. Contradistinctively, BC number and mass size distributions were relatively invariant with altitude over the Yellow Sea (YS) because sufficiently aged BC from eastern China were horizontally transported to all altitudes over the YS, and there are no significant sources at the surface. The averaged inferred MAC of refractory BC in three regions reflecting differences in their size distributions increased to 9.8 ± 1.0 m2 g−1 (YS), 9.3 ± 0.9 m2 g−1 (WC), and 8.2 ± 0.9 m2 g−1 (SMA) as BC coating thickness increased from 20 nm to 120 nm. The absorption coefficient of BC calculated from the coating thickness and MAC were highly correlated with the filter-based absorption measurements with the slope of 1.16 and R2 of 0.96 at 550 nm, revealing that the thickly coated BC had a large MAC and absorption coefficient. The Eabs due to the inferred coatings was estimated as 1.0–1.6, which was about 30% lower than those from climate models and laboratory experiments, suggesting that the increase in the BC absorption by the coatings in the Asian outflow is not as large as calculated in the previous studies. Organics contributed to the largest Eabs accounting for 69% (YS), 61% (WC), and 64% (SMA). This implies that organics are largely responsible for the lensing effect of BC rather than sulfates in the Asian outflow.",

keywords = "Absorption enhancement, Aging process, Black carbon, KORUS-AQ, SP2",

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AU - Cho, Chaeyoon

AU - Schwarz, Joshua P.

AU - Perring, Anne E.

AU - Lamb, Kara D.

AU - Kondo, Yutaka

AU - Park, Jong Uk

AU - Park, Do Hyeon

AU - Shim, Kyuseok

AU - Park, Jin Soo

AU - Park, Rokjin J.

AU - Lee, Meehye

AU - Song, Chang Keun

AU - Kim, Sang Woo

PY - 2021/6/15

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AB - We investigated the changes in the size distribution, coating thickness, and mass absorption cross-section (MAC) of black carbon (BC) with aging and estimated the light absorption enhancement (Eabs) in the Asian outflow from airborne in-situ measurements during 2016 KORUS-AQ campaign. The BC number concentration decreased, but mass mean diameter increased with increasing altitude in the West Coast (WC) and Seoul Metropolitan Area (SMA), reflecting the contrast between freshly emitted BC-containing particles at the surface and more aged aerosol associated with aggregation during vertical mixing and transport. Contradistinctively, BC number and mass size distributions were relatively invariant with altitude over the Yellow Sea (YS) because sufficiently aged BC from eastern China were horizontally transported to all altitudes over the YS, and there are no significant sources at the surface. The averaged inferred MAC of refractory BC in three regions reflecting differences in their size distributions increased to 9.8 ± 1.0 m2 g−1 (YS), 9.3 ± 0.9 m2 g−1 (WC), and 8.2 ± 0.9 m2 g−1 (SMA) as BC coating thickness increased from 20 nm to 120 nm. The absorption coefficient of BC calculated from the coating thickness and MAC were highly correlated with the filter-based absorption measurements with the slope of 1.16 and R2 of 0.96 at 550 nm, revealing that the thickly coated BC had a large MAC and absorption coefficient. The Eabs due to the inferred coatings was estimated as 1.0–1.6, which was about 30% lower than those from climate models and laboratory experiments, suggesting that the increase in the BC absorption by the coatings in the Asian outflow is not as large as calculated in the previous studies. Organics contributed to the largest Eabs accounting for 69% (YS), 61% (WC), and 64% (SMA). This implies that organics are largely responsible for the lensing effect of BC rather than sulfates in the Asian outflow.

KW - Absorption enhancement

KW - Aging process

KW - Black carbon

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KW - SP2

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AN - SCOPUS:85100638529

SN - 0048-9697

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JO - Science of the Total Environment

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ER -

Light-absorption enhancement of black carbon in the Asian outflow inferred from airborne SP2 and in-situ measurements during KORUS-AQ

Abstract

Bibliographical note

Keywords

ASJC Scopus subject areas

UN SDGs

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