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Author

Kei Sato

Bio: Kei Sato is an academic researcher from National Institute for Environmental Studies. The author has contributed to research in topics: Aerosol & Isoprene. The author has an hindex of 26, co-authored 95 publications receiving 2199 citations. Previous affiliations of Kei Sato include Community emergency response team & Japan Atomic Energy Research Institute.
Topics: Aerosol, Isoprene, Particulates, Ab initio, Ozone


Papers
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Journal ArticleDOI
TL;DR: The role of distinct PM components in health impacts and mortality needs to be clarified by integrated research on various spatiotemporal scales for better evaluation and mitigation of aerosol effects on public health in the Anthropocene.
Abstract: Poor air quality is globally the largest environmental health risk. Epidemiological studies have uncovered clear relationships of gaseous pollutants and particulate matter (PM) with adverse health outcomes, including mortality by cardiovascular and respiratory diseases. Studies of health impacts by aerosols are highly multidisciplinary with a broad range of scales in space and time. We assess recent advances and future challenges regarding aerosol effects on health from molecular to global scales through epidemiological studies, field measurements, health-related properties of PM, and multiphase interactions of oxidants and PM upon respiratory deposition. Global modeling combined with epidemiological exposure-response functions indicates that ambient air pollution causes more than four million premature deaths per year. Epidemiological studies usually refer to PM mass concentrations, but some health effects may relate to specific constituents such as bioaerosols, polycyclic aromatic compounds, and transition metals. Various analytical techniques and cellular and molecular assays are applied to assess the redox activity of PM and the formation of reactive oxygen species. Multiphase chemical interactions of lung antioxidants with atmospheric pollutants are crucial to the mechanistic and molecular understanding of oxidative stress upon respiratory deposition. The role of distinct PM components in health impacts and mortality needs to be clarified by integrated research on various spatiotemporal scales for better evaluation and mitigation of aerosol effects on public health in the Anthropocene.

344 citations

Journal ArticleDOI
TL;DR: The chemical compositions of SOA produced by photoirradiation of the toluene/NOx/air system in laboratory chamber experiments are analyzed by a combination of liquid chromatography-mass spectrometry, hybrid high-performance liquid Chromatography- mass spectromaetry, and iodometry-spectrophotometry to conclude that the major chemical components of the aerosol are hemiacetal and peroxy hemiacETal oligomers and low-molecular-weight dicar
Abstract: The photooxidation of toluene is a potential source of secondary organic aerosol (SOA) in urban air, but only a small portion of the compounds present in SOA have been identified. In this study, we...

159 citations

Journal ArticleDOI
TL;DR: In this paper, the optical properties of secondary organic aerosols (SOAs) generated during photooxidation of toluene in the presence of NOx and the ozonolysis of α-pinene were investigated.
Abstract: [1] It has recently been suggested that some organic aerosols can absorb solar radiation, especially at the shorter visible and UV wavelengths. Although quantitative characterization of the optical properties of secondary organic aerosols (SOAs) is required in order to confirm the effect of SOAs on the atmospheric radiation balance, the light absorption of SOAs has not yet been thoroughly investigated. In this study, we conducted laboratory experiments to measure the optical properties of SOAs generated during the photooxidation of toluene in the presence of NOx and the ozonolysis of α-pinene. Extinction and scattering coefficients of the SOAs were measured by a cavity ring-down aerosol extinction spectrometer and an integrating nephelometer, respectively. Refractive indices of the SOAs were determined so that the measured particle size dependence of the extinction and scattering efficiencies could be reproduced by calculations using Mie scattering theory. As a result, significant light absorption was found at 355 nm for the toluene SOAs. In contrast, no significant absorption was found either at 355 or 532 nm for the α-pinene SOAs. Using the obtained refractive index, mass absorption cross-section values of the toluene SOAs were calculated to be 0.3–3 m2 g−1 at 355 nm. The results indicate that light absorption by the SOAs formed from the photooxidation of aromatic hydrocarbons have a potential to influence the total aerosol light absorption, especially at UV wavelengths.

130 citations

Journal ArticleDOI
TL;DR: In this article, the complex refractive index (RI, m = n-ki values at 405, 532, and 781 nm of the secondary organic aerosols generated during the photooxidation of toluene (toluene-SOAs) under a variety of initial nitrogen oxide (NOx = NO + NO2) conditions were examined by photoacoustic spectroscopy (PAS) and cavity ring-down spectrography (CRDS).
Abstract: . Recently, secondary organic aerosols (SOAs) generated from anthropogenic volatile organic compounds have been proposed as a possible source of light-absorbing organic compounds, "brown carbon," in the urban atmosphere. However, the atmospheric importance of these SOAs remains unclear due to limited information about their optical properties. In this study, the complex refractive index (RI, m = n-ki values at 405, 532, and 781 nm of the SOAs generated during the photooxidation of toluene (toluene-SOAs) under a variety of initial nitrogen oxide (NOx = NO + NO2) conditions were examined by photoacoustic spectroscopy (PAS) and cavity ring-down spectroscopy (CRDS). The complex RI-values obtained in the present study and reported in the literature indicate that the k-value, which represents the light absorption of the toluene-SOAs, increased to shorter wavelengths at

129 citations

Journal ArticleDOI
TL;DR: In this paper, the authors measured the mass spectra of secondary organic aerosol (SOA) formed from the photooxidation of aromatic hydrocarbons using an Aerodyne aerosol mass spectrometer (AMS) and reported that SOA aging is slowed with increasing number of alkyl groups in the precursor molecule.
Abstract: Oxygenated organic aerosol (OOA) observed in remote areas is believed to comprise aged secondary organic aerosol (SOA); however, the reaction processes relevant to SOA chemical aging have hitherto been unclear We recently measured the mass spectra of SOA formed from the photooxidation of aromatic hydrocarbons using an Aerodyne aerosol mass spectrometer (AMS) and reported that SOA aging is slowed with increasing number of alkyl groups in the precursor molecule In this study, we selected benzene and 1,3,5-trimethylbenzene (TMB) as precursors to analyze SOA formed from the photooxidation of aromatic hydrocarbons in the presence of NOx using high-resolution time-of-flight AMS (H-ToF-AMS) and liquid chromatography/time-of-flight mass spectrometry (LC/TOF-MS) A van Krevelen diagram was studied using the O/C and H/C ratios obtained by H-ToF-AMS for organics present in SOA The results showed these organics to be rich in carboxylic acids or hydroxycarbonyls and the O/C ratio of SOA formed by the reaction of 1,3,5-TMB to be lower than that for benzene Analytical results from LC/TOF-MS showed the particulate products formed by the reaction of 1,3,5-TMB to be richer in ketocarboxylic acids than for benzene These results indicate that SOA aging proceeds mainly by formation of carboxylic acids and that the rate of SOA aging in laboratory chambers is limited by the oxidation of ketone groups SOA formed in laboratory chamber experiments is less oxidized than for ambient OOA, not only because the experimental duration is insufficient or the SOA mass loading in the chamber is higher than that of the atmosphere The laboratory chamber experiments under dry conditions are not able to simulate ketocarboxylic acid photochemical oxidation in the aqueous phase The fractions of organic peroxides to the total SOA mass were determined by iodometric spectrophotometry to be 12 ± 8% (1,3,5-TMB) and

103 citations


Cited by
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01 Jan 1989
TL;DR: In this article, a two-dimensional version of the Pennsylvania State University mesoscale model has been applied to Winter Monsoon Experiment data in order to simulate the diurnally occurring convection observed over the South China Sea.
Abstract: Abstract A two-dimensional version of the Pennsylvania State University mesoscale model has been applied to Winter Monsoon Experiment data in order to simulate the diurnally occurring convection observed over the South China Sea. The domain includes a representation of part of Borneo as well as the sea so that the model can simulate the initiation of convection. Also included in the model are parameterizations of mesoscale ice phase and moisture processes and longwave and shortwave radiation with a diurnal cycle. This allows use of the model to test the relative importance of various heating mechanisms to the stratiform cloud deck, which typically occupies several hundred kilometers of the domain. Frank and Cohen's cumulus parameterization scheme is employed to represent vital unresolved vertical transports in the convective area. The major conclusions are: Ice phase processes are important in determining the level of maximum large-scale heating and vertical motion because there is a strong anvil componen...

3,813 citations

Journal ArticleDOI
TL;DR: In this article, an overview of the atmospheric degradation mechanisms for SOA precursors, gas-particle partitioning theory and analytical techniques used to determine the chemical composition of SOA is presented.
Abstract: Secondary organic aerosol (SOA) accounts for a significant fraction of ambient tropospheric aerosol and a detailed knowledge of the formation, properties and transformation of SOA is therefore required to evaluate its impact on atmospheric processes, climate and human health. The chemical and physical processes associated with SOA formation are complex and varied, and, despite considerable progress in recent years, a quantitative and predictive understanding of SOA formation does not exist and therefore represents a major research challenge in atmospheric science. This review begins with an update on the current state of knowledge on the global SOA budget and is followed by an overview of the atmospheric degradation mechanisms for SOA precursors, gas-particle partitioning theory and the analytical techniques used to determine the chemical composition of SOA. A survey of recent laboratory, field and modeling studies is also presented. The following topical and emerging issues are highlighted and discussed in detail: molecular characterization of biogenic SOA constituents, condensed phase reactions and oligomerization, the interaction of atmospheric organic components with sulfuric acid, the chemical and photochemical processing of organics in the atmospheric aqueous phase, aerosol formation from real plant emissions, interaction of atmospheric organic components with water, thermodynamics and mixtures in atmospheric models. Finally, the major challenges ahead in laboratory, field and modeling studies of SOA are discussed and recommendations for future research directions are proposed.

3,324 citations

Journal ArticleDOI
TL;DR: A review of the chemistry of the formation and continuing transformation of low-volatility species in the atmosphere can be found in this article, where the primary focus is chemical processes that can change the volatility of organic compounds: oxidation reactions in the gas phase, reaction in the particle phase, and reaction in either phase over several generations.

1,411 citations

Journal ArticleDOI
TL;DR: In this paper, a review summarizes the current knowledge on aqueous phase organic reactions and combines evidence that points to a significant role of aqSOA formation in the atmosphere.
Abstract: . Progress has been made over the past decade in predicting secondary organic aerosol (SOA) mass in the atmosphere using vapor pressure-driven partitioning, which implies that SOA compounds are formed in the gas phase and then partition to an organic phase (gasSOA). However, discrepancies in predicting organic aerosol oxidation state, size and product (molecular mass) distribution, relative humidity (RH) dependence, color, and vertical profile suggest that additional SOA sources and aging processes may be important. The formation of SOA in cloud and aerosol water (aqSOA) is not considered in these models even though water is an abundant medium for atmospheric chemistry and such chemistry can form dicarboxylic acids and "humic-like substances" (oligomers, high-molecular-weight compounds), i.e. compounds that do not have any gas phase sources but comprise a significant fraction of the total SOA mass. There is direct evidence from field observations and laboratory studies that organic aerosol is formed in cloud and aerosol water, contributing substantial mass to the droplet mode. This review summarizes the current knowledge on aqueous phase organic reactions and combines evidence that points to a significant role of aqSOA formation in the atmosphere. Model studies are discussed that explore the importance of aqSOA formation and suggestions for model improvements are made based on the comprehensive set of laboratory data presented here. A first comparison is made between aqSOA and gasSOA yields and mass predictions for selected conditions. These simulations suggest that aqSOA might contribute almost as much mass as gasSOA to the SOA budget, with highest contributions from biogenic emissions of volatile organic compounds (VOC) in the presence of anthropogenic pollutants (i.e. NOx) at high relative humidity and cloudiness. Gaps in the current understanding of aqSOA processes are discussed and further studies (laboratory, field, model) are outlined to complement current data sets.

1,032 citations

Journal ArticleDOI
TL;DR: Understanding of the climate-related properties of atmospheric OC is still incomplete and the specific ways in which OC impacts atmospheric environment and climate forcing are just beginning to be understood.
Abstract: Organic carbon (OC) accounts for a large fraction of atmospheric aerosol and has profound effects on air quality, atmospheric chemistry and climate forcing. Molecular composition of the OC and its evolution during common processes of atmospheric aging have been a subject of extensive research over the last decade (see reviews of Ervens et al.,1 Hallquist et al.,2 Herckes et al.,3 Carlton et al.,4 Kroll and Seinfeld,5 Rudich et al.,6 and Kanakidou et al.7). Even though many fundamental advances have been reported in these studies, our understanding of the climate-related properties of atmospheric OC is still incomplete and the specific ways in which OC impacts atmospheric environment and climate forcing are just beginning to be understood. This review covers one topic of particular interest in this area –environmental chemistry of light-absorbing aerosol OC and its impact on radiative forcing.

1,026 citations