TY - JOUR
T1 - Size distributions, mixing state, and morphology of refractory black carbon in an urban atmosphere of northeast Asia during summer
AU - Lim, Saehee
AU - Lee, Meehye
AU - Yoo, Hee Jung
N1 - Funding Information:
This research was supported by the National Research Foundation of Korea (NRF) from the Ministry of Science and ICT ( NRF-2021R1C1C2011543 ) and the Korea Meteorological Administration ( KMA2018-00521 ). ML would like to thank Korea Institute of Science and Technology (KIST) for its support ( 2E31650-22-P019 ). The authors thank the Korea National Institute of Environmental Research (NIER) and Korea Meteorological Administration (KMA) for their ground monitoring data used in the present study.
Funding Information:
This research was supported by the National Research Foundation of Korea (NRF) from the Ministry of Science and ICT (NRF-2021R1C1C2011543) and the Korea Meteorological Administration (KMA2018-00521). ML would like to thank Korea Institute of Science and Technology (KIST) for its support (2E31650-22-P019). The authors thank the Korea National Institute of Environmental Research (NIER) and Korea Meteorological Administration (KMA) for their ground monitoring data used in the present study.
Publisher Copyright:
© 2022
PY - 2023/1/15
Y1 - 2023/1/15
N2 - Black carbon (BC) exerts profound impacts on air quality, human health, and climate. Here, we investigated concentrations and size distributions of refractory BC (rBC) and mixing state and morphology of rBC-containing particles in urban Seoul for 2019 summer. Mass concentrations of rBC ranged from 0.02 μgm−3 to 2.89 μgm−3, and daily maximums of rBC mass, daily minimums of rBC mass median diameter (MMD) (110–130 nm), and shell-to-core ratio (Rshell/core) occurred with NO2 maximums during morning rush hour. As the first report of ground observations on rBC mixing state, these results indicate that vehicle emission is a major local source of rBC in Seoul. MMDs of 127–146 nm and the greatest mass loadings of ≥1 μg m−3 were accompanied by high O3 and PM2.5 concentrations, in contrast to the largest MMDs (135–165 nm) associated with transport from upstream regions. The average Rshell/core was 1.25 for the rBC mass-equivalent diameter (DrBC) of 140–220 nm. Rshell/core increased gradually through the day and was positively correlated with Ox concentration, indicating photochemical aging of rBC particles. Co-emissions of rBC and volatile organic compounds from vehicles facilitated internal mixing during the daytime. However, Rshell/core tended to be low at temperature >∼30 °C, while 58 % of rBC particles with Rshell/core exceeding 1.25 were found at nighttime under relative humidity >75 %. These results demonstrate that the mixing state of freshly-emitted rBC particles was altered through coating by photochemically oxidized vapors during the day and hygroscopic growth at night. Additionally, the delay-time approach revealed rBC morphological characteristics, the most common being the bare type (74 %), and the attached type (6 %) was relatively large in numbers during morning rush hour. Therefore, it is suggested that during summer, rBC particles from traffic emissions should be considered in parallel to winter pollution mitigation strategies in urban atmosphere of northeast Asia.
AB - Black carbon (BC) exerts profound impacts on air quality, human health, and climate. Here, we investigated concentrations and size distributions of refractory BC (rBC) and mixing state and morphology of rBC-containing particles in urban Seoul for 2019 summer. Mass concentrations of rBC ranged from 0.02 μgm−3 to 2.89 μgm−3, and daily maximums of rBC mass, daily minimums of rBC mass median diameter (MMD) (110–130 nm), and shell-to-core ratio (Rshell/core) occurred with NO2 maximums during morning rush hour. As the first report of ground observations on rBC mixing state, these results indicate that vehicle emission is a major local source of rBC in Seoul. MMDs of 127–146 nm and the greatest mass loadings of ≥1 μg m−3 were accompanied by high O3 and PM2.5 concentrations, in contrast to the largest MMDs (135–165 nm) associated with transport from upstream regions. The average Rshell/core was 1.25 for the rBC mass-equivalent diameter (DrBC) of 140–220 nm. Rshell/core increased gradually through the day and was positively correlated with Ox concentration, indicating photochemical aging of rBC particles. Co-emissions of rBC and volatile organic compounds from vehicles facilitated internal mixing during the daytime. However, Rshell/core tended to be low at temperature >∼30 °C, while 58 % of rBC particles with Rshell/core exceeding 1.25 were found at nighttime under relative humidity >75 %. These results demonstrate that the mixing state of freshly-emitted rBC particles was altered through coating by photochemically oxidized vapors during the day and hygroscopic growth at night. Additionally, the delay-time approach revealed rBC morphological characteristics, the most common being the bare type (74 %), and the attached type (6 %) was relatively large in numbers during morning rush hour. Therefore, it is suggested that during summer, rBC particles from traffic emissions should be considered in parallel to winter pollution mitigation strategies in urban atmosphere of northeast Asia.
KW - Coating thickness
KW - Mixing state
KW - Morphology
KW - Photochemical aging
KW - Size distribution
KW - rBC
UR - http://www.scopus.com/inward/record.url?scp=85139356189&partnerID=8YFLogxK
U2 - 10.1016/j.scitotenv.2022.158436
DO - 10.1016/j.scitotenv.2022.158436
M3 - Article
C2 - 36108842
AN - SCOPUS:85139356189
SN - 0048-9697
VL - 856
JO - Science of the Total Environment
JF - Science of the Total Environment
M1 - 158436
ER -
