Hygroscopicity of materials internally mixed with black carbon measured in Tokyo

Ohata, Sho; Schwarz, J. P.; Moteki, Nobuhiro; Koike, M.; Takami, Akinori; Kondo, Yutaka

doi:10.1002/2015jd024153

Cited by 27 publications

(33 citation statements)

References 57 publications

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“…The number fractions of dust‐like FeO x particles to all of the FeO x particles with D m = 170–270 nm reached 25% during this period (Figure S6a), whereas, in other periods, they were generally 5% in Tokyo (Figure ). The median log( C s‐be / C s‐oi ) value for BC with D m = 200 nm reached 0.7 (Figure S6b), which corresponds to a coating thickness of ~100 nm under an assumed core‐shell structure for BC‐containing particles (Ohata et al, ). This coating thickness for BC is much larger than the typical coating thickness (~10 nm) observed during the other periods in Tokyo.…”

Section: Resultsmentioning

confidence: 96%

“…The observation periods in Tokyo spanned 20 days in July and August 2014 and 16 days in February 2014; for simplicity, we refer to these periods as “summer” and “winter,” respectively. The observations in the summer were conducted as a Black Carbon/Carbonaceous Aerosol Removal Experiment in Tokyo (BC‐CARE Tokyo) field campaign, which was discussed in our previous study (Ohata et al, ). The observation period in Chiba spanned 21 days in September 2016.…”

Section: Methodsmentioning

confidence: 99%

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Abundance of Light‐Absorbing Anthropogenic Iron Oxide Aerosols in the Urban Atmosphere and Their Emission Sources

et al. 2018

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Light-absorbing iron oxide (FeO x ) aerosols such as magnetite contribute to shortwave atmospheric heating and possibly affect the biogeochemical cycle. However, their atmospheric abundance and emission sources are poorly understood. In this study, we quantified the abundance and mixing states of FeO x at two urban sites in Tokyo and Chiba, Japan, using a modified single-particle soot photometer and filter-based instruments. At both sites, the majority of the FeO x were of anthropogenic origin in the form of aggregated magnetite nanoparticles, and their concentrations generally correlated with those of black carbon (BC) and carbon monoxide. In Chiba, where the observatory was located near an integrated steel plant, we observed distinctly high FeO x concentrations and high FeO x /BC concentration ratios when the air mass passed through the plant. From the observed FeO x plumes with the mass equivalent diameter range of 170-2,100 nm, we made an estimate of their emission flux to be approximately 0.012% of the crude steel production, assuming that a Gaussian plume approximation was applicable to our data analysis. Meanwhile, in Tokyo, where the observatory was 20-40 km northwest of steel plants, the FeO x concentrations and FeO x /BC ratios showed clear diurnal variations and depended little on wind direction. This indicates that other human activities also locally produce FeO x aerosols in Tokyo. Our data imply that although steel plant activities emit a large amount of FeO x , emissions from other anthropogenic sources, for example, motor vehicles, have a major contribution to the abundance of FeO x aerosols at the regional and global scales.

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Section: Resultsmentioning

confidence: 96%

Section: Methodsmentioning

confidence: 99%

Abundance of Light‐Absorbing Anthropogenic Iron Oxide Aerosols in the Urban Atmosphere and Their Emission Sources

et al. 2018

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“…Coating thickness is calculated from the measured optical size using Mie theory, assuming a spherical core-shell morphology. Ohata et al [2016] recently evaluated the accuracy of this method using mass-selected internal mixtures of laboratory aerosol. They found that the SP2 Journal of Geophysical Research: Atmospheres 10.1002/2016JD025688 scattering estimate of coating thickness agreed with that calculated from the difference between the total particle mass and the BC core mass to within 10% for particles with a total diameter at least 1.5 times the diameter of the core (i.e., thickly coated particles).…”

Section: Bc Aerosol Methodsmentioning

confidence: 99%

In situ measurements of water uptake by black carbon‐containing aerosol in wildfire plumes

et al. 2017

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Water uptake by black carbon (BC)‐containing aerosol was quantified in North American wildfire plumes of varying age (1 to ~40 h old) sampled during the SEAC4RS mission (2013). A Humidified Dual SP2 (HD‐SP2) is used to optically size BC‐containing particles under dry and humid conditions from which we extract the hygroscopicity parameter, κ, of materials internally mixed with BC. Instrumental variability and the uncertainty of the technique are briefly discussed. An ensemble average κ of 0.04 is found for the set of plumes sampled, consistent with previous estimates of bulk aerosol hygroscopicity from biomass burning sources. The temporal evolution of κ in the Yosemite Rim Fire plume is explored to constrain the rate of conversion of BC‐containing aerosol from hydrophobic to more hydrophilic modes in these emissions. A BC‐specific κ increase of ~0.06 over 40 h is found, fit well with an exponential curve corresponding to a transition from a κ of 0 to a κ of ~0.09 with an e‐folding time of 29 h. Although only a few percent of wildfire particles contain BC, a similar κ increase is estimated for bulk aerosol and the measured aerosol composition is used to infer that the observed κ change is driven by a combination of incorporation of ammonium sulfate and oxidation of existing organic materials. Finally, a substantial fraction of wildfire‐generated BC‐containing aerosol is calculated to be active as cloud condensation nuclei shortly after emission likely indicating efficient wet removal. These results can constrain model treatment of BC from wildfire sources.

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“…At the remote site of Hedo (26.9°N, 128.3°E) on Okinawa Island, Japan, the contribution was about 8% in spring 2016 (section A4, Figure a). BC particles become more active as cloud condensation nuclei as their diameters increase, and larger BC particles have been observed to be removed more efficiently by wet deposition than BC particles with smaller diameters [ Ohata et al , ; Moteki et al ., ; Kondo et al , ]. BC particles larger than 1 µm should be scavenged more efficiently during long‐range transport to the Arctic from lower latitudes.…”

Section: Comparisons Of Mbc (Cosmos) With Mec Measurements At Barrow mentioning

confidence: 99%

Evaluation of ground‐based black carbon measurements by filter‐based photometers at two Arctic sites

et al. 2017

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Long‐term measurements of the light absorption coefficient (babs) obtained with a particle soot absorption photometer (PSAP), babs (PSAP), have been previously reported for Barrow, Alaska, and Ny‐Ålesund, Spitsbergen, in the Arctic. However, the effects on babs of other aerosol chemical species coexisting with black carbon (BC) have not been critically evaluated. Furthermore, different mass absorption cross section (MAC) values have been used to convert babs to BC mass concentration (MBC = babs/MAC). We used a continuous soot monitoring system (COSMOS), which uses a heated inlet to remove volatile aerosol compounds, to measure babs (babs (COSMOS)) at these sites during 2012–2015. Field measurements and laboratory experiments have suggested that babs (COSMOS) is affected by about 9% on average by sea‐salt aerosols. MBC values derived by COSMOS (MBC (COSMOS)) using a MAC value obtained by our previous studies agreed to within 9% with elemental carbon concentrations at Barrow measured over 11 months. babs (PSAP) was higher than babs (COSMOS), by 22% at Barrow (PM1) and by 43% at Ny‐Ålesund (PM10), presumably due to the contribution of volatile aerosol species to babs (PSAP). Using babs (COSMOS) as a reference, we derived MBC (PSAP) from babs (PSAP) measured since 1998. We also established the seasonal variations of MBC at these sites. Seasonally averaged MBC (PSAP) decreased at a rate of about 0.55 ± 0.30 ng m−3 yr−1. We also compared MBC (COSMOS) and scaled MBC (PSAP) values with previously reported data and evaluated the degree of inconsistency in the previous data.

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Hygroscopicity of materials internally mixed with black carbon measured in Tokyo

Cited by 27 publications

References 57 publications

Abundance of Light‐Absorbing Anthropogenic Iron Oxide Aerosols in the Urban Atmosphere and Their Emission Sources

Abundance of Light‐Absorbing Anthropogenic Iron Oxide Aerosols in the Urban Atmosphere and Their Emission Sources

In situ measurements of water uptake by black carbon‐containing aerosol in wildfire plumes

Evaluation of ground‐based black carbon measurements by filter‐based photometers at two Arctic sites

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