Language：English   Publishing type：Research paper (scientific journal)   Publisher：Informa UK Limited  

Black carbon is the largest contributor to global aerosol's shortwave absorption in the current atmosphere and is an important positive climate forcer. The complex refractive index, m = m(r) + im(i), the primary determinant of the absorbed and scattered energies of incident radiation per unit volume of particulate material, has not been accurately known for atmospheric black carbon material. An accurate value at visible wavelengths has been difficult to obtain due to the black carbon's wavelength-scale irregularity and variability of aggregate shape, distribution in particle size, and mixing with other aerosol compounds. Here, we present a method to constrain a plausible (m(r), m(i)) domain for black carbon from the observed distribution of the complex forward-scattering amplitude S(0 degrees). This approach suppresses the biases due to the above-mentioned complexities. The S(0 degrees) distribution of black carbon is acquired by performing single particle S(0 degrees) measurements in a water medium after collecting atmospheric aerosols into water. We demonstrate the method operating at lambda = 0.633 mu m for constraining the refractive index of black carbon aerosols in the north-western Pacific boundary layer. From the plausible (m(r), m(i)) domain consistent with the observed S(0 degrees) distributions and the reported range of mass absorption cross-section, we conservatively select 1.95 + 0.96i as a recommendable value of the refractive index for uncoated black carbon at visible wavelengths. The recommendable value is 0.17 larger in m(i) than the widely used value 1.95 + 0.79i in current aerosol-climate models, implying a similar to 16% underestimate of shortwave absorption by black carbon aerosols in current climate simulations.

DOI： 10.1080/02786826.2023.2202243

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Publishing type：Research paper (scientific journal)   Publisher：Copernicus GmbH  

Abstract. In this paper, the Photoacoustic Aerosol Absorption Spectrometer (PAAS-4λ) is introduced. PAAS-4λ was specifically developed for long-term monitoring tasks in (unattended) air quality stations. It uses four wavelengths coupled to a single acoustic resonator in a compact and robust set-up. The instrument has been thoroughly characterized and carefully calibrated in the laboratory using NO2/air mixtures and Nigrosin aerosol. It has an ultimate 1σ detection limit below 0.1 Mm−1, at a measurement precision and accuracy of 3 % and 10 %, respectively. In order to demonstrate the PAAS-4λ suitability for long-term monitoring tasks, the instrument is currently validated at the air quality monitoring station Pallas in Finland, about 140 km north of the Arctic circle. A total of 11 months of PAAS-4λ data from this deployment are presented and discussed in terms of instrument performance. Intercomparisons with the filter-based photometers of a continuous soot monitoring system (COSMOS), the Multi-Angle Absorption Photometer (MAAP), and Aethalometer (AE33) demonstrate the capabilities and value of PAAS-4λ, as well as for the validation of the widely used filter-based instruments.

DOI： 10.5194/amt-16-2753-2023

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Publishing type：Research paper (scientific journal)   Publisher：Informa UK Limited  

DOI： 10.1080/02786826.2022.2144113

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DOI： 10.1175/bams-d-21-0034.1

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Atmospheric Chemistry and Physics  

Black carbon (BC) particles in the Arctic contribute to rapid warming of the Arctic by heating the atmosphere and snow and ice surfaces. Understanding the source contributions to Arctic BC is therefore important, but they are not well understood, especially those for atmospheric and snow radiative effects. Here we estimate simultaneously the source contributions of Arctic BC to near-surface and vertically integrated atmospheric BC mass concentrations (MBC-SRF and MBC-COL), BC deposition flux (MBC-DEP), and BC radiative effects at the top of the atmosphere and snow surface (REBC-TOA and REBC-SNOW) and show that the source contributions to these five variables are highly different. In our estimates, Siberia makes the largest contribution to MBC-SRF, MBC-DEP, and REBC-SNOW in the Arctic (defined as >70° N), accounting for 70 %, 53 %, and 41 %, respectively. In contrast, Asia's contributions to MBC-COL and REBC-TOA are largest, accounting for 37 % and 43 %, respectively. In addition, the contributions of biomass burning sources are larger (29 %-35 %) to MBC-DEP, REBC-TOA, and REBC-SNOW, which are highest from late spring to summer, and smaller (5.9 %-17 %) to MBC-SRF and MBC-COL, whose concentrations are highest from winter to spring. These differences in source contributions to these five variables are due to seasonal variations in BC emission, transport, and removal processes and solar radiation, as well as to differences in radiative effect efficiency (radiative effect per unit BC mass) among sources. Radiative effect efficiency varies by a factor of up to 4 among sources (1471-5326 W g-1) depending on lifetimes, mixing states, and heights of BC and seasonal variations of emissions and solar radiation. As a result, source contributions to radiative effects and mass concentrations (i.e., REBC-TOA and MBC-COL, respectively) are substantially different. The results of this study demonstrate the importance of considering differences in the source contributions of Arctic BC among mass concentrations, deposition, and atmospheric and snow radiative effects for accurate understanding of Arctic BC and its climate impacts.

DOI： 10.5194/acp-22-8989-2022

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Aerosol and Air Quality Research  

Measurement of particulate matter (PM) constituent such as black carbon (BC) over urban sites is critically important owing to its adverse health and climate impacts. However, the impacts associated with BC are poorly understood primarily because of the scarcity and uncertainties of measurements of BC. Here, we present BC measurement at an urban site of Delhi using a characterized continuous soot monitoring system (COSMOS) for a year-long period, i.e., from September, 2019 to August, 2020. This measurement period covers events, i.e., period of crop residue burnings from nearby states, festive events, e.g., Diwali and New Year, and first COVID-19 lockdown period. Effects of these events combining with local emissions and meteorological conditions on BC mass concentration (MBC) are investigated to find the possible cause of severe pollution levels in Delhi. Mean MBC for the complete observation period was found to be 5.02 ± 4.40 µg m–3. MBC showed significant seasonal as well diurnal variations. Winter season (December to February) is observed to be the most polluted season owing to increased local emissions and non-favorable meteorological conditions. Regional emission from crop burning in nearby states during October and November is the main contributing factor for increased pollution in this post-monsoon season. Furthermore, analysis reveals that cracker burning during festivals can also be considered as contributing factor to high MBC for a short period in post-monsoon and winter seasons. Significant decrease in MBC due to COVID-19 lockdown is also observed. MBC in summer and monsoon are lower as compared to other seasons but are still higher than mean MBC levels in several other urban cities of different countries. Also, the BC data obtained from nearby sites and Modern-Era Retrospective analysis for Research and Applications-version 2 (MERRA-2)’s surface black carbon (SBC) are compared against the MBC to evaluate coherency among the different datasets, and discussed in detail.

DOI： 10.4209/aaqr.220128

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Atmospheric Chemistry and Physics  

Filter-based offline analysis of atmospheric aerosol hygroscopicity coupled to composition analysis provides information complementary to that obtained from online analysis. However, its application itself and comparison to online analysis have remained limited to date. In this study, daily submicrometer aerosol particles (PM0.95, 50% cutoff diameter 0.95μm) were collected onto quartz fiber filters on Okinawa Island, a receptor of East Asian outflow, in the autumn of 2015. The chemical composition of water-soluble matter (WSM) in PM0.95, PM0.95 itself, and their respective hygroscopicities were characterized through the offline use of an aerosol mass spectrometer and a hygroscopicity tandem differential mobility analyzer. Thereafter, results were compared with those obtained from online analyses. Sulfate dominated the WSM mass (59%), followed by water-soluble organic matter (WSOM, 20%) and ammonium (13%). WSOM accounted for most (91%) of the mass of extracted organic matter (EOM) and the atomic O-to-C ratios (O:C) of WSOM and EOM were high (mean±standard deviation were 0.84±0.08 and 0.78±0.08, respectively), both of which indicate highly aged characteristics of the observed aerosol. The hygroscopic growth curves showed clear hysteresis for most samples. At 85% relative humidity (RH), the calculated hygroscopicity parameter κ values of the WSM (κWSM), WSOM, EOM, and PM0.95 (κPM0.95) were 0.50±0.03, 0.22±0.12, 0.20±0.11, and 0.47±0.03, respectively. An analysis using the thermodynamic Extended Aerosol Inorganics Model (E-AIM) shows, on average, that inorganic salts and WSOM contributed 88% and 12%, respectively, of the κWSM (or κPM0.95). High similarities were found between offline and online analysis for chemical compositions that are related to particle hygroscopicity (the mass fractions and O:C of organics and the degree of neutralization) and also for aerosol hygroscopicity. As possible factors governing the variation in κWSM, the influences of WSOM abundance and the neutralization of inorganic salts were assessed. At high RH (70%-90%), the hygroscopicity of WSM and PM0.95 was affected considerably by the presence of organic components; at low RH (20%-50%), the degree of neutralization could be important. This study not only characterized aerosol hygroscopicity at the receptor site of East Asian outflow but also shows that offline hygroscopicity analysis is an appropriate method, at least for aerosols of the studied type. The results encourage further applications to other environments and to more in-depth hygroscopicity analysis, in particular for organic fractions.

DOI： 10.5194/acp-22-5515-2022

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Copernicus GmbH  

Abstract. Vertical profiles of the mass concentration of black carbon (BC) weremeasured at altitudes up to 5 km during the PAMARCMiP (Polar Airborne Measurements and Arctic Regional Climate Model simulation Project) aircraft-based fieldexperiment conducted around the northern Greenland Sea (Fram Strait) duringMarch and April 2018 from operation base Station Nord (81.6∘ N,16.7∘ W). Median BC mass concentrations in individual altituderanges were 7–18 ng m−3 at standard temperature and pressure ataltitudes below 4.5 km. These concentrations were systematically lower thanprevious observations in the Arctic in spring, conducted by ARCTAS-A in 2008and NETCARE in 2015, and similar to those observed during HIPPO3 in 2010.Column amounts of BC for altitudes below 5 km in the Arctic (>66.5∘ N; COLBC), observed during the ARCTAS-A and NETCAREexperiments, were higher by factors of 4.2 and 2.7, respectively, than thoseof the PAMARCMiP experiment. These differences could not be explained solelyby the different locations of the experiments. The year-to-year variation ofCOLBC values generally corresponded to that of biomass burning activitiesin northern midlatitudes over western and eastern Eurasia. Furthermore,numerical model simulations estimated the year-to-year variation ofcontributions from anthropogenic sources to be smaller than 30 %–40 %.These results suggest that the year-to-year variation of biomass burningactivities likely affected BC amounts in the Arctic troposphere in spring,at least in the years examined in this study. The year-to-year variations inBC mass concentrations were also observed at the surface at high Arcticsites Ny-Ålesund and Utqiaġvik (formerly known as Barrow, the location ofBarrow Atmospheric Baseline Observatory), although their magnitudes were slightlylower than those in COLBC. Numerical model simulations in general successfully reproduced the observedCOLBC values for PAMARCMiP and HIPPO3 (within a factor of 2), whereas theymarkedly underestimated the values for ARCTAS-A and NETCARE by factors of3.7–5.8 and 3.3–5.0, respectively. Because anthropogenic contributionsaccount for nearly all of the COLBC (82 %–98 %) in PAMARCMiP and HIPPO3,the good agreement between the observations and calculations for these twoexperiments suggests that anthropogenic contributions were generally wellreproduced. However, the significant underestimations of COLBC forARCTAS-A and NETCARE suggest that biomass burning contributions wereunderestimated. In this study, we also investigated plumes with enhanced BCmass concentrations, which were affected by biomass burning emissions,observed at 5 km altitude. Interestingly, the mass-averaged diameter of BC(core) and the shell-to-core diameter ratio of BC-containing particles inthe plumes were generally not very different from those in other airsamples, which were considered to be mostly aged anthropogenic BC. Theseobservations provide a useful basis to evaluate numerical model simulations ofthe BC radiative effect in the Arctic region in spring.

DOI： 10.5194/acp-21-15861-2021

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Copernicus GmbH  

Abstract. Long-term measurements of atmospheric mass concentrationsof black carbon (BC) are needed to investigate changes in its emission,transport, and deposition. However, depending on instrumentation, parametersrelated to BC such as aerosol absorption coefficient (babs) have beenmeasured instead. Most ground-based measurements of babs in the Arctichave been made by filter-based absorption photometers, including particlesoot absorption photometers (PSAPs), continuous light absorption photometers(CLAPs), Aethalometers, and multi-angle absorption photometers (MAAPs). Themeasured babs can be converted to mass concentrations of BC (MBC) byassuming the value of the mass absorption cross section (MAC; MBC= babs/ MAC). However, the accuracy of conversion of babs to MBChas not been adequately assessed. Here, we introduce a systematic method forderiving MAC values from babs measured by these instruments andindependently measured MBC. In this method, MBC was measured with afilter-based absorption photometer with a heated inlet (COSMOS).COSMOS-derived MBC (MBC (COSMOS)) is traceable to a rigorouslycalibrated single particle soot photometer (SP2), and the absolute accuracyof MBC (COSMOS) has been demonstrated previously to be about 15 % inAsia and the Arctic. The necessary conditions for application of this methodare a high correlation of the measured babs with independently measuredMBC and long-term stability of the regression slope, which is denotedas MACcor (MAC derived from the correlation). In general,babs–MBC (COSMOS) correlations were high (r2= 0.76–0.95 forhourly data) at Alert in Canada, Ny-Ålesund in Svalbard, Barrow (NOAA Barrow Observatory) inAlaska, Pallastunturi in Finland, and Fukue in Japan and stable for up to10 years. We successfully estimated MACcor values (10.8–15.1 m2 g−1 at a wavelength of 550 nm for hourly data) for these instruments,and these MACcor values can be used to obtain error-constrainedestimates of MBC from babs measured at these sites even in the past,when COSMOS measurements were not made. Because the absolute values ofMBC at these Arctic sites estimated by this method are consistent witheach other, they are applicable to the study of spatial and temporalvariation in MBC in the Arctic and to evaluation of the performance ofnumerical model calculations.

DOI： 10.5194/amt-14-6723-2021

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Copernicus GmbH  

Abstract. Aerosol light absorption was measured during a 1-month field campaign in June–July 2019 at the Pallas Global Atmospheric Watch (GAW) station in northern Finland. Very low aerosol concentrations prevailed during the campaign, which posed a challenge for the instruments' detection capabilities. The campaign provided a real-world test for different absorption measurement techniques supporting the goals of the European Metrology Programme for Innovation and Research (EMPIR) Black Carbon (BC) project in developing aerosol absorption standard and reference methods. In this study we compare the results from five filter-based absorption techniques – aethalometer models AE31 and AE33, a particle soot absorption photometer (PSAP), a multi-angle absorption photometer (MAAP), and a continuous soot monitoring system (COSMOS) – and from one indirect technique called extinction minus scattering (EMS). The ability of the filter-based techniques was shown to be adequate to measure aerosol light absorption coefficients down to around 0.01 Mm−1 levels when data were averaged to 1–2 h. The hourly averaged atmospheric absorption measured by the reference MAAP was 0.09 Mm−1 (at a wavelength of 637 nm). When data were averaged for >1 h, the filter-based methods agreed to around 40 %. COSMOS systematically measured the lowest absorption coefficient values, which was expected due to the sample pre-treatment in the COSMOS inlet. PSAP showed the best linear correlation with MAAP (slope=0.95, R2=0.78), followed by AE31 (slope=0.93). A scattering correction applied to PSAP data improved the data accuracy despite the added noise. However, at very high scattering values the correction led to an underestimation of the absorption. The AE31 data had the highest noise and the correlation with MAAP was the lowest (R2=0.65). Statistically the best linear correlations with MAAP were obtained for AE33 and COSMOS (R2 close to 1), but the biases at around the zero values led to slopes clearly below 1. The sample pre-treatment in the COSMOS instrument resulted in the lowest fitted slope. In contrast to the filter-based techniques, the indirect EMS method was not adequate to measure the low absorption values found at the Pallas site. The lowest absorption at which the EMS signal could be distinguished from the noise was >0.1 Mm−1 at 1–2 h averaging times. The mass absorption cross section (MAC) value measured at a range 0–0.3 Mm−1 was calculated using the MAAP and a single particle soot photometer (SP2), resulting in a MAC value of 16.0±5.7 m2 g−1. Overall, our results demonstrate the challenges encountered in the aerosol absorption measurements in pristine environments and provide some useful guidelines for instrument selection and measurement practices. We highlight the need for a calibrated transfer standard for better inter-comparability of the absorption results.

DOI： 10.5194/amt-14-5397-2021

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Geophysical Union (AGU)  

Black carbon (BC) aerosol deposited in and onto Arctic snow increases the snow's absorption of solar radiation and accelerates snowmelt. Concentrations of BC in the Arctic atmosphere and snow are controlled by wet deposition; however, details of this process are poorly understood owing to the scarcity of time-resolved measurements of BC in hydrometeors. We measured mass concentrations of BC in hydrometeors (C-MBC) and in air (M-BC) with 16% and 15% accuracies, respectively, at Ny-angstrom lesund, Svalbard during 2012-2019. Median monthly M-BC and C-MBC values showed similar seasonal variations, being high in winter-spring and low in summer. Median monthly BC wet deposition mass flux (F-MBC) was highest in winter and lowest in summer, associated with seasonal patterns of C-MBC and precipitation. Seasonally averaged BC size distributions in hydrometeors were similar except for summer. Measurements of M-BC and C-MBC in spring 2017 showed a size-independent removal efficiency, indicating that BC-containing particles were efficiently activated into cloud droplets. These observations at Ny-angstrom lesund were compared with observations at Barrow, Alaska, during 2013-2017. The near-surface M-BC at Ny-angstrom lesund and Barrow had similar seasonal patterns; however, the two sites differed in C-MBC and F-MBC. In summer, C-MBC was low at Ny-angstrom lesund but moderate at Barrow, likely reflecting differences in M-BC in the lower troposphere. Seasonally averaged BC size distributions in hydrometeors were similar at both sites, suggesting that average BC size distributions are similar in the Arctic lower troposphere. The efficiency of BC removal tends to be size-independent during transport, leading to the observed similarity.

DOI： 10.1029/2020JD034110

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Other Link： https://onlinelibrary.wiley.com/doi/full-xml/10.1029/2020JD034110

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Copernicus GmbH  

Abstract. Aerosol particles were collected at various altitudes in
the Arctic during the Polar Airborne Measurements and Arctic Regional
Climate Model Simulation Project 2018 (PAMARCMiP 2018) conducted in the
early spring of 2018. The composition, size, number fraction, and mixing state of
individual aerosol particles were analyzed using transmission electron
microscopy (TEM), and their sources and transport were evaluated by
numerical model simulations. We found that sulfate, sea-salt, mineral-dust,
K-bearing, and carbonaceous particles were the major aerosol constituents.
Many particles were composed of two or more compositions that had coagulated
and were coated with sulfate, organic materials, or both. The number
fraction of mineral-dust and sea-salt particles decreased with increasing
altitude. The K-bearing particles increased within a biomass burning (BB)
plume at altitudes > 3900 m, which originated from Siberia.
Chlorine in sea-salt particles was replaced with sulfate at high altitudes.
These results suggest that the sources, transport, and aging of Arctic
aerosols largely vary depending on the altitude and air-mass history. We also
provide the occurrences of solid-particle inclusions (soot, fly-ash, and
Fe-aggregate particles), some of which are light-absorbing particles. They
were mainly emitted from anthropogenic and biomass burning sources and were
embedded within other relatively large host particles. Our TEM measurements
revealed the detailed mixing state of individual particles at various
altitudes in the Arctic. This information facilitates the accurate
evaluation of the aerosol influences on Arctic haze, radiation balance,
cloud formation, and snow/ice albedo when deposited.

DOI： 10.5194/acp-21-3607-2021

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.polar.2020.100621

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DOI： 10.1029/2019JD032240

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Geophysical Union (AGU)  

Black carbon (BC), brown carbon, and light-absorbing iron oxides (FeOx) aerosols affect Earth's energy budget through their strong absorption of solar radiation. FeOx aerosols can also affect global biogeochemical cycles through their role as a nutrient for oceanic phytoplankton. However, observational data for these aerosols required for evaluating their effects using global models are scarce, especially for FeOx. Here, we summarize and compare the data sets of BC and FeOx from five ground-based and three aircraft observation campaigns conducted in the East Asian and Arctic regions during the 2009-2018 period acquired using a modified single-particle soot photometer. In these campaigns, >80% of FeOx-containing aerosols in the 170-270 nm FeOx core size range had microphysical features indicating an anthropogenic origin. The particle size distribution for each of the BC and FeOx was similar in all of the data sets except for those dominated by fresh urban pollution or pristine Arctic air. The campaign-averaged mass concentrations of FeOx and BC were similar to 60-360 ng/m(3) and similar to 240-1,300 ng/m(3), respectively, in East Asia, and similar to 6 ng/m(3) and similar to 20-30 ng/m(3), respectively, in the Arctic. The campaign-averaged FeOx/BC mass concentration ratio varied within a narrow range of 0.2-0.6 in both East Asian and Arctic regions. In every campaign, FeOx, BC, and carbon monoxide were tightly correlated with each other with similar slope to the urban campaigns (around Tokyo), implying the spatiotemporal variation of anthropogenic FeOx emission around northern middle-to-high latitudes is similar to those of anthropogenic BC and CO emissions.

DOI： 10.1029/2019JD032301

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Other Link： https://onlinelibrary.wiley.com/doi/full-xml/10.1029/2019JD032301

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.2183/pjab.96.010

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DOI： 10.1029/2019JD030737

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DOI： 10.1029/2019JD030623

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS INC  

Long-term measurements of black carbon (BC) aerosols by filter-based absorption photometers with a heated inlet (COSMOS) in different regions have been useful in elucidating spatial variations and radiative impacts of BC. Evaluations of mass concentrations of BC (M-BC) measured by the COSMOS have been made by our previous studies through comparisons with other measurement techniques. However, how variations in the microphysical properties of BC and the co-existing light scattering aerosols affect the COSMOS measurements should be evaluated in more detail. In this study, we assessed these potential effects under various field environments in the Arctic and in the East Asia. From the slopes of the correlation plots between the M-BC values measured by the COSMOS and a single-particle soot photometer, the average accuracy of the COSMOS was estimated as similar to 10% in the M-BC range 1-3000 ng m(-3). On an hourly basis, the estimated sensitivity of the COSMOS M-BC values to the changes in the BC size distributions was less than 10%, within the typical variabilities of BC size at individual observation sites. The COSMOS measurements depended little on the mixing states of BC and the concentrations of co-existing light scattering aerosols, except in the maritime air masses of East Asia, where the relative abundance of sea salt to BC was very high. The M-BC measured by COSMOS also well agreed with elemental carbon measurements. Our results demonstrate the high reliability of COSMOS measurements under various environments. Copyright (c) 2019 American Association for Aerosol Research

DOI： 10.1080/02786826.2019.1627283

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DOI： doi: 10.1038/s41561-019-0314-x

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DOI： doi: 10.1038/s41612-019-0063-y

Language：English   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：Japanese  

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DOI： 10.1038/s41467-018-03997-0

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：NATURE PUBLISHING GROUP  

Combustion-induced carbonaceous aerosols, particularly black carbon (BC) and brown carbon (BrC), have been largely considered as the only significant anthropogenic contributors to shortwave atmospheric heating. Natural iron oxide (FeOx) has been recognized as an important contributor, but the potential contribution of anthropogenic FeOx is unknown. In this study, we quantify the abundance of FeOx over East Asia through aircraft measurements using a modified single-particle soot photometer. The majority of airborne FeOx particles in the continental outflows are of anthropogenic origin in the form of aggregated magnetite nanoparticles. The shortwave absorbing powers (P-abs) attributable to FeOx and to BC are calculated on the basis of their size-resolved mass concentrations and the mean P-abs(FeOx)/P-abs(BC) ratio in the continental outflows is estimated to be at least 4-7%. We demonstrate that in addition to carbonaceous aerosols the aggregate of magnetite nanoparticles is a significant anthropogenic contributor to shortwave atmospheric heating.

DOI： 10.1038/ncomms15329

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DOI： doi: 10.1038/srep34113

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DOI： doi:10.1002/2014JD022103

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