The ROx cycle plays a central role in tropospheric oxidation. In this study, we propose and evaluate a peroxy radical chemical amplification (PERCA)-based method for investigating the atmospheric ROx radical budget. By combining the measurements of total OH reactivity (OHR) with total ROx concentrations, we estimated the ROx loss rate, D(ROx), within a photochemical steady-state (PSS) framework without requiring the individual measurements of OH, HO2, and RO2 radicals.The theoretical consistency of the method was first evaluated using WRF–CMAQ simulations, where PSS-derived D(ROx) accurately reproduced the model-derived values (slope = 0.95). The framework was then applied to field observations conducted in suburban Tsukuba, Japan, in August 2022. Although P(ROx) and D(ROx) were generally consistent under low-NO conditions, a substantial imbalance emerged at elevated NO concentrations (>1 ppb), with D(ROx) exceeding P(ROx) by up to an order of magnitude. The magnitude of the discrepancy increased in the case of the transport of air masses from the Tokyo metropolitan area and could not be fully explained by the XO2NO2 interference alone.Although measurement interference in the PERCA technique cannot be completely excluded, the PERCA–OHR method is a useful diagnostic tool for identifying inconsistencies in the ROx budget. The observed discrepancy may also be related to the widely reported ozone production gap under high-NOx conditions. By reducing the technical barrier to implementation, this approach enables the broader deployment of radical budget analyses.

The ozone production regime (OPR) is an important parameter to establish suitable ozone reduction strategies and has been extensively studied. However, most publications only reported indirect OPR evaluations combining observed steady-state concentrations of atmospheric trace constituents and numerical simulations. For direct assessment, we had previously developed an OPR evaluation system. Here, we applied this instrument to direct in situ atmospheric OPR evaluation from 23 July to 3 August 2019 at Yokohama in the Keihin Industrial Zone, the largest industrial area in Japan. Simultaneously, we measured the atmospheric concentrations of ozone and its precursors. During most of the observation period, the main OPR controlling factor was the atmospheric variation of volatile organic compound (VOC) concentrations, indicating a “VOC-limited” regime in which reducing VOC emissions could effectively cause a decrease in ozone concentrations. Measured values of the concentration ratios of HCHO to NO2 and the OH reactivity ratios of VOCs to NOx were consistent with the direct observation results of the OPR. The ozone formation potential, calculated for the 127 distinct VOCs considered in this study, was consistently highest for aldehydes over the entire observation period, demonstrating that aldehydes were the main contributors to photochemical ozone production at the observation site.

Introduction: We previously reported that acute exposure to fine particulate matter (PM 2.5 ) within one day before the onset (lag days 0-1) is linked to ischemic stroke events. This study aimed to examine the association between specific components of PM 2.5 and the occurrence of ischemic stroke. Methods: Toral of 5,872 patients with acute ischemic stroke enrolled in a multicenter, hospital-based stroke registry in Fukuoka, Japan. All patients were previously independent and were hospitalized within 24 hours of stroke onset between November 2013 and September 2019. We collected data on daily mean concentrations of PM 2.5 and its specific chemical components that were measured aerosol speciation analyzers (ACSA, Kimoto Electric Co., Ltd) within Fukuoka city —including optical black carbon, water-soluble organic compounds, nitrate ion, and sulfate ion. The time of symptom onset was confirmed, and the association between these specific PM 2.5 components and ischemic stroke occurrence was analyzed using a time-stratified case-crossover design and a conditional logistic regression model. Results and Conclusions: Ambient PM 2.5 at lag days 0 to 1 was not associated with the subsequent occurrence of ischemic stroke (percent increase for ischemic stroke per 10 μg/m 3 PM 2.5 [95% confidence interval]: 2.7 [-2.7 to 8.3]), after adjusting for ambient temperature, humidity, influenza epidemics, and PM 2.5 at lag days 2 to 3 and lag days 4 to 6. No significant association was found between the specific chemical components of PM 2.5 and ischemic stroke occurrence, either in a single-component model (percent increase for ischemic stroke [95% confidence interval]: optical black carbon, -7.3 [-24.7 to 14.2]; water-soluble organic carbon, -2.6 [-13.6 to 9.8]; nitrate ion, -3.6 [-9.5 to 2.7]; sulfate ion, -0.3 [-3.0 to 2.5]) or in a multicomponent model (percent increase for ischemic stroke [95% confidence interval]: optical black carbon, 0.6 [-23.7 to 32.6]; water-soluble organic carbon, 5.1 [-14.8 to 29.7]; nitrate ion, -6.5 [-16.3 to 4.4]; sulfate ion, 5.1 [-3.1 to 4.0]). These results were consistent across different age groups, sexes, and ischemic stroke etiologies. In conclusions, these findings suggest that short-term exposure to specific chemical components of PM 2.5 within 1 day before onset is not associated with the subsequent occurrence of ischemic stroke. Further studies are warranted to clarify the effects of PM 2.5 on ischemic stroke occurrence.

Particulate matter with an aerodynamic diameter of ≤2.5 µm (PM2.5) is a heterogeneous mixture, and specific substances that affect cardiovascular events remain unknown. We aimed to examine the association of short-term exposure to PM2.5 and its components with hospital admissions for acute myocardial infarction (AMI). The concentrations of total PM2.5 and its individual components were continuously measured using Aerosol Chemical Speciation Analysers. From a national-scale administrative database collected from 828 facilities in 47 prefectures across Japan from April 2017 to December 2019, we extracted AMI data for seven prefectures where these aerosol analysers were installed. The primary outcome was the relationship of PM2.5 and its components with AMI hospitalisation. A time-stratified case-crossover analysis was conducted, and the approximate risk of AMI by pollutant concentrations was estimated using a conditional logistic regression model. In total, 44,232 patients with AMI aged 40–104 years (74.9

ABSTRACTWe observed the size distributions of mass concentration, ionic composition, and trace metal concentration in aerosols collected at an urban site in Kumamoto Prefecture (KM) and a rural site at Cape Hedo in Okinawa Prefecture (HD) between 2012 and 2015. To evaluate the contribution of transboundary nitrate and locally emitted nitrate in the aerosols at Kumamoto, we distinguished between days of transboundary air pollution from East Asia and days of local air pollution on the basis of a threshold for Pb concentration and the ratio Pb (in 0.5 < projected area diameter (Dp) < 1.0 µm)/Cu (in 2.5 < Dp < 10 µm). Fine nitrate (particulate NH4NO3) did not arrive at HD from the Asian continent even under long-range transport conditions. Fine nitrate emitted in Kumamoto and its vicinity also was not transported to HD, even in an air mass that passed over KM and reached HD within one day. Almost all fine nitrate was converted to coarse nitrate during transport by dissociation of fine nitrate and adsorption of HNO3 on larger aerosol particles. Transboundary nitrate existed largely in the particle size range of 0.5 < Dp < 10 µm, and the contribution of transboundary nitrate in the particle size range of 0.1 < Dp < 0.5 µm was about 20% even under long-range transport conditions. The contribution of transboundary nitrate in particles with Dp < 2.5 µm at KM was approximately 50%, 50%, and 80% in spring, autumn, and winter, respectively.

New particle formation (NPF) in the East Asian region is strongly influenced by photochemical processes during the long-range transport of air pollutants. Our previous measurements (Seto et al., 2013; Chandra et al., 2016) relating to the incomplete and weak NPF (onset diameter > 10 nm) on Fukue Island in Japan (downstream from the Asian continent) suggested nucleation in the upstream region. The vertical structure of atmospheric nanoparticle concentrations (particle size > 6 nm and altitude < 1.2 km) during NPF was observed using a Kite-Plane at Fukue Island. Three different event types were identified through aerial observations (different vertical profiles of nanoparticles), ground-based measurements (the initial detected diameter of nanoparticles, NPF starting time, and dominant chemical component in PM1), and air mass backward trajectory analysis. A stronger NPF event (Event I: > 35,000 particles cm−3) than in our previous measurements (from 2012 to 2016, 20,000 particles cm−3) with a particle size as small as 5 nm, affected by the long-range transport of air pollutants under a high-pressure system, was detected. A sudden increase in particle number and SO2 concentrations with weak NPF caused by a change in the air mass origin (Event II: < 10,000 particles cm−3) as well as no NPF with aged sulfate particles during conditions with low particle number and SO2 concentrations (< 0.15 ppb) (Event III: < 2,000 particles cm−3) were also observed.

Quantitative estimation of particulate matter (PM) pollution from coal combustion, which is one of the major anthropogenic emission sources in China, is urgently needed to better understand transboundary pollution in the East Asian region. As a first step, we conducted laboratory experiments for the mass spectrometric characterization of fly ash from coal combustion using a fluidized bed reactor. Here, we report detection of notable signals at m/z 85, 87, and 133 in mass spectra for organic species obtained by an Aerodyne quadrupole aerosol mass spectrometer (AMS). Nine different coals, six of which were mined in north-east Asian region, were tested with three different combustion temperatures. The results showed that signals at m/z 85, 87, and 133 were significantly larger than those at the adjacent m/z, with similar observations having been made in different field studies carried out in western Japan. The m/z 85 to m/z 87 ratios were reproducible over the coals tested, suggesting the potential usefulness of these for fingerprinting coal combustion PM. The average ratio with the standard error of the mean was 2.8 ± 0.1. While the m/z 133 to m/z 87 ratios varied more, the mean ratio with the standard error of the mean was 1.5 ± 0.2, and the results were still reproducible. A comparison of the m/z 85 and 133 to m/z 87 ratios from other studies that also used AMS suggests that the ratios obtained in the current work are distinctive from those for vehicular emissions, plastic burning, and cooking emissions, but close to those for biomass burning. Despite this similarity, the results here still offer useful information for source identification of PM with the use of AMS measurements.

This study aimed to characterize the wintertime surface aerosol chemistry over islands and mountains sites (i.e., Cape Fuguei, Mt. Bamboo, Mt. Lulin, Cape Hedo, and Kumamoto) in East Asia. Aerosols were sampled over a 24-h period as part of an intensive observational period (IOP) in winter 2015. Aerosol samples were analyzed for water-soluble inorganic ions (WSIIs), organic carbon (OC), and elemental carbon (EC). PM2.5 mean concentration (in µg m−3) was found the highest over Kumamoto (22 ± 7), followed by Cape Fuguei (20 ± 9), Cape Hedo (11 ± 5), Mt. Bamboo (10 ± 13), and Mt. Lulin (4 ± 3). Strong correlations (r > 0.91) in ion charge balance suggested the good quality of data-sets and the ions share common source origins. Larger variations in (non-sea-salt-sulfate) nss-SO42− and NH4+ over all the sites indicated the significant contribution of anthropogenic emissions from continental Asian outflow. OC was found the most abundant resolved component in PM2.5 over Mt. Lulin (37.58 ± 25.90

To investigate long-range transport and oxidation states of nitrogen compounds from the Asian continent, especially of total odd nitrogen species (NOy), we carried out continuous observations of NOy, total nitrate (T.NO3; the sum of gaseous nitric acid and particulate nitrate) and NOx (= NO + NO2) at Fukue Island, located in westernmost Japan. NOy and T.NO3 exhibited similar seasonal cycles, with maximum concentrations observed during winter-spring seasons, and minimum concentrations during summer. NOx had a seasonal cycle, with maximum and minimum concentrations in winter and summer, respectively; NOx concentrations also decreased markedly from winter to spring. High-concentration event analyses to assess transboundary pollution of NOy were performed. Transboundary pollution events for NOy were extracted, and classified as either “Case 1” or “Case 2”. Case 1 involved transport of NOy, T.NO3, and NOx from the Asian continent to Fukue Island, while Case 2 involved transport of NOy and T.NO3, but not NOx. Case 1 and Case 2 occurred predominantly in winter and spring, respectively. Air mass trajectories indicated that in Case 1, 52% of air masses passed through Korea, while only 5% passed through Korea in Case 2. These results indicate that some NOx emitted from the Asian continent is transported to Fukue Island as NOx, without it undergoing oxidation, reflecting low photochemical activity and/or short transport times.

An intensive observation campaign at Cape Hedo, Okinawa, Japan was conducted from late October to early November 2015 to investigate the behavior of long-range transported atmospheric pollutants. During this period, sulfate (SO42−) was the dominant aerosol component. The sources of SO42− were estimated by using the air quality model with the tagged tracer method. The main source of high SO42− concentration varied day-to-day. When the westerly wind was dominant (October 27), the main source was anthropogenic SO2 emissions in China. When the northerly wind prevailed (November 1), the impact of volcanoes in western Japan was significant and the conversion ratio from SO2 to SO42− was lowest, at less than 70

The extensive emissions of black carbon (BC) from the Indo-Gangetic Plain (IGP) region of India have been well recognized. Particularly, biomass emissions from month-specific crop-residue burning (April, May, October, November) and heating activities (December-February) are considered substantial contributors to BC emissions in the IGP. However, their precise contribution to ambient BC aerosol has not been quantified yet and remains an issue of debate. Therefore, this study aims to fill this gap by quantifying the contribution of these month-specific biomass emissions to ambient BC at an urban site in IGP. This study presents the analysis of BC mass concentrations (M-BC) measured for 3 years (2020-2022) in Delhi using an optical photometer i.e., continuous soot monitoring system (COSMOS). A statistical analysis of monthly mean M-BC and factors affecting the M-BC (ventilation coefficients, air mass back trajectories, fire counts) is performed to derive month-wise contribution due to background concentration, conventional emission, regional transport, crop-residue burning, and heating activities. The yearly mean M-BC (5.3 +/- 4.7, 5.6 +/- 5.0, and 5.3 +/- 3.5 mu g m(-3) during 2020, 2021, and 2022, respectively) remained relatively consistent with repetitive monthly patterns in each year. The peak concentrations were observed from November to January and low concentrations from June to September. Anthropogenic activities contributed significantly to M-BC over Delhi with background concentration contributing only 30 % of observed M-BC. The percentage contribution of emissions from crop-residue burning varied from 15 % (May) to 37 % (November), while the contribution from heating activities ranged from 25 % (December) to 39 % (January). This source quantification study highlights the significant impact of month-specific biomass emissions in the IGP and can play a vital role in better management and control of these emissions in the region.

This study collected samples of particulate matter that are 2.5 μm or less in diameter (PM2.5) in Kanazawa, Japan, and Noto Peninsula located 100 km north on the windward side of the westerlies from the Asian continent and characterized the extent of polycyclic aromatic hydrocarbons (PAHs) and nitro-PAHs (NPAHs) pollution in Kanazawa. Emission areas and specific sources of PM2.5 and of PAHs and NPAHs were clarified via back-trajectory analysis and the NP-method, respectively. The results indicate that during 2020 and 2021, most PAHs (93%) in Kanazawa were transported from the Asian continent by westerlies and that the main source was coal and biomass combustion. The presence of NPAHs in Kanazawa was caused by a mixture of transport from the Asian continent (53%) and local emissions (47%), with the main source of the latter being from vehicles. Although the content of combustion-derived particulates (Pc) was <2.4% of PM2.5 in Kanazawa, this showed a similar seasonal variation (winter > summer) to that of PAHs. The contribution of Pc transported from the Asian continent exceeded that of locally emitted Pc. The current situation of Kanazawa is considerably different from that of 1997, when local vehicles were the main source of pollution.

Trace metals in aerosols were observed at an urban site (Kumamoto, Kyushu, Japan) and a rural site (Cape Hedo, Okinawa, Japan) to investigate the relative contributions of transboundary air pollutants from mainland Asia and local air pollutants in western Japan. We used a cascade impactor to collect aerosols in five size classes. We apportioned the sources of the air masses on the basis of elemental components. Transboundary and local air pollutants were distinguished by use of the Pb/Cu and V/As ratios in selected size fractions of aerosols. The contribution of Pb (primarily from coal combustion in China) to total anthropogenic elements was greatest in spring, autumn, and winter in the 0.5–1 µm size fraction at both collection sites. The atmospheric environment at both sites was affected by this transboundary air pollutant. The contribution of Cu (primarily from local vehicle traffic) to total anthropogenic elements was greatest in all seasons in the 2.5–10 µm fraction at Kumamoto. Local air pollutants such as road dust, automobile brake abrasion, and waste incineration affected ambient air quality in Kumamoto. Because these pollutants resided mainly in the coarse aerosol fraction (> 2.5 µm), most of them were not transported to Cape Hedo in air bodies that we were able to trace to Kumamoto by backward projection. Based on our data the ambient air quality at Cape Hedo was little affected by local air pollutants emitted in the Kumamoto area.

We developed an index to investigate the effect of transboundary air pollution (TAP) on the air quality of Kumamoto City, Japan. We estimated the effect of TAP by using the index and positive matrix factorization (PMF). Polycyclic aromatic hydrocarbons (PAHs) and trace metals were analyzed from the daily samples of the Total Suspended Particles (TSPs) collected seasonally from Oct. 2014 to Aug. 2015. These chemical components exhibited high concentrations in spring and winter, which is consistent with the data in the literature. Pb was identified as the TAP tracer owing to its high concentrations in winter and spring. Indeno(1, 2, 3-cd)pyrene (IcdP) was used as the local emission tracer in Kumamoto on the basis of previous studies. We applied the IcdP/Pb ratio as the index. The index enables the detection of TAP in daily data sets. PMF identified six factors: soil and road dust, biomass and waste burning, heavy oil combustion, fishing boats, vehicle emission, and coal combustion. The average contribution of TAP on the days when transboundary pollution was high was evaluated as being 46%.

Due to economic growth in China, emissions of gaseous components from factories and automobiles have been increasing, which has resulted in severe air pollution. During the winter and spring seasons, Japan, which is on the leeward side of the Asian continent, is on the receiving end of this increasingly problematic transboundary air pollution. In this study, the mass concentration and chemical components of the particulate PM2.5 were continuously observed using an automatic analyzer at Kumamoto on the west coast of Japan from October 2014 to March 2015. A greater number of high PM2.5 days were observed in winter than in autumn. This seasonal change in concentrations was believed to be due to transboundary air pollution traveling from the Asian continent due to seasonal monsoons. The analysis of the chemical composition of PM2.5 supported this idea. The factors leading to high PM2.5 concentrations were investigated and categorized into transboundary air pollution, local air pollution, and volcanic activity based on the analysis of sulfate (SO42−) and sulfur dioxide (SO2) concentrations and model simulations. The average concentration of chemical components showed that local air pollution also influenced air quality in Kumamoto.

Particulate matter with an aerodynamic diameter of ≤ 2.5 µm (PM2.5) is a heterogeneous mixture, but specific substances that affect cardiovascular events remain unknown. We aimed to examine the association of short-term exposure to PM2.5 and its components with hospital admissions for acute myocardial infarction (AMI). The concentrations of total PM2.5 and its individual components were continuously measured using aerosol speciation analyzers. From a national-scale administrative database collected from 828 facilities in 47 prefectures across Japan from April 2017 to December 2019, we extracted AMI data for seven prefectures where these aerosol analyzers were installed. The primary outcome was the relationship of PM2.5 and its components with AMI hospitalization. A time-stratified case-crossover analysis was conducted, and the approximate risk of AMI by pollutant concentrations was estimated using a conditional logistic regression model. A total of 44,232 patients with AMI were examined. The estimated effects of an increase in the interquartile range of total PM2.5 on AMI-associated hospitalization were significant and comparable to those of optically measured black carbon concentrations. Short-term exposure to PM2.5 was associated with an increased AMI incidence. Reduction in black carbon concentration may decrease the risk of future air quality-related AMI.

In order to understand transported and local pollution in an urban area that are strongly affected by long-range transport of air pollution, daily concentrations of 15 polycyclic aromatic hydrocarbons (PAHs) and 20 n-alkanes in the total suspended particles were simultaneously measured at sites in Western Japan on Fukue Island (FI), located downwind of mainland East Asia, and Fukuoka City (FC), a megacity close (< 200 km) to the FI site, in spring and winter 2010 and summer 2011. The average total PAH concentration observed at the FC site (2.93 ± 2.17 ng/m3) was higher than that at the FI site (1.78 ± 1.70 ng/m3). The average total n-alkane concentration at the FC site (34.7 ± 21.8 ng/m3) was also higher than that at the FI site (12.2 ± 9.2 ng/m3). However, the total PAH and n-alkane concentrations measured at the FI site were considerably high, despite its remote location. The seasonal changes in the specific PAH ratios, used to determine the source of pollutants, were similar between the FC and FI sites. The average fluoranthene/(fluoranthene + pyrene) ratio was 0.57–0.65 in winter and spring and 0.48–0.51 in summer. PAHs observed at both sites mainly originated from coal or biomass combustion in spring or winter, whereas those were affected by petroleum combustion as well as coal and biomass combustion in summer. These field results show that pollutants transported from mainland East Asia make a significant contribution to the total PAHs and n-alkanes at the FC site in the winter and spring seasons.

This study investigated the source categories and emission areas of carbonaceous aerosols transported from East Asia to the East China Sea. Mass concentrations of heavy metals, ionic components, organic carbon, and elemental carbon (EC) were measured at the Cape Hedo Atmosphere and Aerosol Monitoring Station in Okinawa, Japan, throughout 2010. The relative influences of different categories of aerosols were determined by positive matrix factorization, and the source regions of each emissions category were evaluated by using the total potential source contribution function. Five source categories were identified: dust, sea salt and nitrate, secondary species, coal combustion, and oil combustion. The results showed that the major source of aerosols in North China is coal combustion, whereas the major source in South China, Japan, and Korea is oil combustion. The relative contributions of the five sources to EC concentrations at Cape Hedo were dust 7.0%, sea salt and nitrate 19.1%, secondary species 28.5%, oil combustion 12.8%, and coal combustion 32.6%. In particular, wintertime coal combustion in residential areas of North China contributed significantly to EC in 2010. The results also indicate that the contribution of coal combustion in source areas was higher in winter (52%), whereas the contribution of oil combustion was higher in spring (33%).

(1) Background: To date, little research has epidemiologically examined whether the concentration of particulate matter (PM) 2.5 and its ionic components is related to the prevalence of skin symptom exacerbations. Therefore, this study aimed to clarify this association in patients with allergic diseases. (2) Methods: From 1 February to 31 May 2020, we evaluated the daily prevalence of skin symptoms in outpatients with allergic diseases being treated at Fukuoka National Hospital, Fukuoka, Japan, and measured the concentration of PM2.5 and its ionic components. (3) Results: Univariate analysis showed a statistically significant association between skin symptoms and the concentration of PM2.5 and the ionic components SO42−, NH4+, K+, and Mg2+; multivariate analysis showed a statistically significant association between the daily prevalence of skin symptom and the concentration of the ionic components SO42− or Mg2+. (4) Conclusions: Our findings indicate that the concentration of some PM2.5 ionic components may affect skin symptom in patients with allergic diseases.