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Mass concentrations of chemical compounds in both PM 2.5 (particle aerodynamic diameter, Dp < 2.5 μm) and PM 2.5-10 (2.5 < Dp < 10 μm), and acidity of aerosol particles were measured at an urban site in western Japan using a continuous dichotomous Aerosol Chemical Speciation Analyzer (ACSA-12) throughout 2014. Mass concentrations of both PM 2.5 and sulfate had distinct seasonal variabilities with maxima in spring and winter, mostly due to long-range transport with the prevailing westerly wind. Mass concentration of nitrate in PM 2.5 (fNO 3 ) showed an obvious warm-season-low and cold-season-high pattern as a result of both gas-aerosol phase equilibrium processes under high temperature conditions as well as transport. Nitrate in PM 2.5-10 (cNO 3 ) increased during long-range transport of dust, implying the great importance of heterogeneous processes at the surface of coarse mode particles. In this study, Δ[H + ] (derived from the difference in pH of extract liquid with/without sampling) was used to indicate the acidity of particles. We found that acidity of particles in PM 2.5 (fΔH) was mostly positive with a maximum in August because of the large fraction of nitrate and sulfate. Acidity of particles in PM 2.5-10 (cΔH) was negative in winter and spring due to presence of alkaline matter from crustal sources. This study highlights the great importance of anthropogenic pollutants on the acidity of particles in the western Pacific Ocean and further impact on the marine environment and climate., (Copyright © 2017 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Appropriate policies to improve air quality by reducing anthropogenic emissions are urgently needed. This is typified by the particulate matter (PM) problem and it is well known that one type of PM, sulfate aerosol (SO 4 2- ), has a large-scale impact due to long range transport. In this study we evaluate the source-receptor relationships of SO 4 2- over East Asia for 2005, when anthropogenic sulfur dioxide (SO 2 ) emissions from China peaked. SO 2 emissions from China have been declining since 2005-2006, so the possible maximum impact of Chinese contributions of SO 4 2- is evaluated. This kind of information provides a foundation for policy making and the estimation of control effects. The tagged tracer method was applied to estimate the source apportionment of SO 4 2- for 31 Chinese province-scale regions. In addition, overall one-year source apportionments were evaluated to clarify the seasonal dependency. Model performance was confirmed by comparing with ground-based observations over mainland China, Taiwan, Korea, and Japan, and the model results fully satisfied the performance goal for PM. We found the following results. Shandong and Hebei provinces, which were the largest and second largest SO 2 sources in China, had the greatest impact over the whole of East Asia with apportionments of around 10-30% locally and around 5-15% in downwind receptor regions during the year. Despite large SO 2 emissions, the impact of south China (e.g., Guizhou, Guangdong, and Sichuan provinces) was limited to local impact. These results suggest that the reduction policy in south China contributes to improving the local air quality, whereas policies in north and central China are beneficial for both the whole of China and downwind regions. Over Taiwan, Korea, and Japan, the impact of China was dominant; however, local contributions were important during summer., (Copyright © 2016 The Authors. Published by Elsevier Ltd.. All rights reserved.)

We applied the decoupled direct method (DDM), a sensitivity analysis technique for computing sensitivities accurately and efficiently, to determine the source-receptor relationships of anthropogenic SO(2) emissions to sulfate aerosol over East Asia. We assessed source contributions from East Asia being transported to Oki Island downwind from China and Korea during two air pollution episodes that occurred in July 2005. The contribution from China, particularly that from central eastern China (CEC), was found to dominate the sulfate aerosols. To study these contributions in more detail, CEC was divided into three regions, and the contributions from each region were examined. Source contributions exhibited both temporal and vertical variability, largely due to transport patterns imposed by the Asian summer monsoon. Our results are consistent with backward trajectory analyses. We found that anthropogenic SO(2) emissions from China produce significant quantities of summertime sulfate aerosols downwind of source areas. We used a parametric scaling method for estimating anthropogenic SO(2) emissions in China. Using column amounts of SO(2) derived from satellite data, and relationships between the column amounts of SO(2) and anthropogenic emissions, 2009 emissions were diagnosed. The results showed that 2009 emissions of SO(2) from China were equivalent to 2004 levels.

During the spring, the high concentrations of ozone (O3) and aerosols are frequently observed aloft in Japan. Such episodes supposedly are caused by the trans-boundary air pollution from other parts of East Asia. To confirm this hypothesis, an episode during the month of April 1993 is investigated by numerical simulations for East Asia with a regional meteorological model and a chemical transport model; the model can reproduce some of the key features of ozone and sulfate (SO42-) aerosol concentration,s specifically, the time variations in ozone concentrations measured at several remote sites located in Japan and the day-to-day variations and vertical profiles for sulfate aerosol concentrations observed in Osaka. Model simulations show that (1) air pollutants such as sulfate aerosol, nitrate (NO3-) aerosol, and ozone are transported from the Asian continent to the Japanese Islands under synoptic meteorological conditions; (2) the trans-boundary pollutants increase urban air pollution in Japan; and (3) in the future, the air quality in Japan will be greatly impacted by increasing emissions in developing Asia. [ABSTRACT FROM AUTHOR]

Dust aerosol has important climate and environmental effects, which could be changed by internally mixing with anthropogenic aerosol as a result of heterogeneous reactions; however, the importance of these reactions is not fully understood yet. In this study, synergetic observations and an air quality model were used to analyze the transport of a severe dust storm and its impacts on nitrate and sulfate levels over East Asia between 3 and 11 May 2017. The model successfully reproduced the occurrence and transport of the dust storm compared to dust RGB imageries of the Himawari-8 satellite and dust extinction coefficients observed by LIDAR. The model also reasonably simulated the variations of observed nitrate and sulfate concentrations, and the results indicated that the dust heterogeneous reactions were dominant pathways for nitrate formation, but they had limited contribution for sulfate in both fine and coarse mode in Fukuoka, Japan. Dust nitrate formed rapidly after leaving China, and the highest period-averaged concentration of dust nitrate (>5 μg m−3) was shown over the Yellow Sea. Based on model results; we found that the mass ratio of dust nitrate to dust aerosol could reach 10% over the Pacific Ocean. Our results confirmed the importance of heterogeneous reactions on compositions of dust particles. [ABSTRACT FROM AUTHOR]

We verified an algorithm using multi-wavelength Mie-Raman lidar (MMRL) observations to retrieve four aerosol components (black carbon (BC), sea salt (SS), air pollution (AP), and mineral dust (DS)) with in-situ aerosol measurements, and determined the seasonal variation of aerosol components in Fukuoka, in the western region of Japan. PM2.5, PM10, and mass concentrations of BC and SS components are derived from in-situ measurements. MMRL provides the aerosol extinction coefficient (α), particle linear depolarization ratio (δ), backscatter coefficient (β), and lidar ratio (S) at 355 and 532 nm, and the attenuated backscatter coefficient (βatt) at 1064 nm. We retrieved vertical distributions of extinction coefficients at 532 nm for four aerosol components (BC, SS, AP, and DS) using 1α532 + 1β532 + 1βatt,1064 + 1δ532 data of MMRL. The retrieved extinction coefficients of the four aerosol components at 532 nm were converted to mass concentrations using the theoretical computed conversion factor assuming the prescribed size distribution, particle shape, and refractive index for each aerosol component. MMRL and in-situ measurements confirmed that seasonal variation of aerosol optical properties was affected by internal/external mixing of various aerosol components, in addition to hygroscopic growth of water-soluble aerosols. MMRL overestimates BC mass concentration compared to in-situ observation using the pure BC model. This overestimation was reduced drastically by introducing the internal mixture model of BC and water-soluble substances (Core-Gray Shell (CGS) model). This result suggests that considering the internal mixture of BC and water-soluble substances is essential for evaluating BC mass concentration in this area. Systematic overestimation of BC mass concentration was found during summer, even when we applied the CGS model. The observational facts based on in-situ and MMRL measurements suggested that misclassification of AP as CGS particles was due to underestimation of relative humidity (RH) by the numerical model in lidar analysis, as well as mismatching of the optical models of AP and CGS assumed in the retrieval with aerosol properties in the actual atmosphere. The time variation of lidar-derived SS was generally consistent with in-situ measurement; however, we found some overestimation of SS during dust events. The cause of this SS overestimation is mainly due to misclassifying internally mixing DS as SS, implying that to consider internal mixing between DS and water-soluble substances leads to better estimation. The time-variations of PM2.5 and PM10 generally showed good agreement with in-situ measurement although lidar-derived PM2.5 and PM10 overestimated in dust events. [ABSTRACT FROM AUTHOR]

Mixing state of aerosols and optical properties including lidar ratio, particle depolarization ratio, and Ångström exponent were investigated at Fukuoka in western Japan using a multi-wavelength Mie–Raman lidar (MMRL), various aerosol mass-concentration measurements, and a polarization optical particle counter during Winter–Spring 2015. Aerosol extinction coefficient, backscatter coefficient, and depolarization at 355 and 532 nm and attenuated backscatter coefficient at 1064 nm are obtained from the MMRL measurements. Ten aerosol episodes were classified into three categories (air pollution, mineral dust, and marine aerosol) based on aerosol mass-concentration measurements in the fine-mode (particle diameter D p <2.5 μm) and coarse-mode (2.5 μm< D p <10 μm). The mean lidar ratio for air pollution was 57±4 sr at 355 nm and 53±8 sr at 532 nm with Ångström exponent of 1.4±0.5. For mineral dust, a slightly high averaged lidar ratio (50±7 sr at 355 nm and 54±9 sr at 532 nm) was obtained with relatively high Ångström exponent of 0.8±0.3 owing to contributions from fine-mode particles (PM f ). The mean particle depolarization ratios of 13±8% at 355 nm and 16±6% at 532 nm also suggest mixing of mineral dust and anthropogenic fine-mode aerosols. The lowest lidar ratio was obtained for marine case. Classification of aerosol types using the lidar ratio and particle depolarization ratio was conducted based on the results obtained in this study. The classified aerosol types almost corresponded to aerosol category obtained by previous studies. We found no remarkable correlation between the fraction of black carbon and the lidar ratio: this might be due to the complexity of the mixing state among various aerosols. The obtained lidar ratio was rather correlated with the ratio of PM f to PM 10 , representing the mixing state of fine- and coarse-mode particles. [ABSTRACT FROM AUTHOR]

East Asia is suffering from both severe air pollution problem due to intensive anthropogenicemissions and natural mineral dust aerosols. During transport, the aerosol particles undergocomplex mixing processes, resulting in great impacts on regional air quality, human healthand climate. In this study, we conducted a long-term observation using an Optical ParticleCounter equipped with a Polarization detection module (POPC) at an urban sitein Beijing. Mass concentrations of both PM2.5 and PM10 estimated from POPCcompared well with ground-based measurements. The results revealed that theobserved depolarization ratio (DR, termed as the ratio of the intensity of the s-polarizedsignal to the intensity of the 120 degree backward scattering signal [s/(s + p)])for aerosol particles in the fine mode was generally much lower in summer thanthat in spring as a result of predominance of different aerosol types. Mineral dustparticles in the coarse mode normally had a large DR value (0.3 ± 0.05) owing to theirnon-spherical shape; however, particles in the fine mode consisted of large proportionwater-soluble compositions, which lead to apparent decrease of their DR values inparticular high relative humidity (RH) condition. Because the observation site wassubject to frequent impact of dust event in spring, DR value of particle at 1 μm wasalmost twice as high as that (0.07 ± 0.01) in summer. Based on size-resolved DRvalues, anthropogenic pollutants, mineral dust and polluted mineral dust particles,and their contribution to local air quality were well distinguished. About 26.7%of substandard days (daily averaged PM2.5 concentration larger than 75 μg/m3)in Beijing was featured by high atmospheric loading of coarse-mode particles inwinter-spring time. In particular during severe pollution episode in winter, the DRvalues of coarse mode particles decreased by 13%, implies the high possibility ofdust-related heterogeneous processes on pollution formation. During dust event, DRvalues of particle at Dp = 5 μm decreased evidently with increase of PM2.5/PM10ratio as well as RH, indicating of the morphological changes of mineral dust. Thisstudy confirmed that high RH tends to promote water absorption processes on thedust surface as well as coating of soluble compounds, and suggested that complexmixing of dust and anthropogenic particles may lead to underestimate impact ofdust particles in urban area based on remote sensing technique, and interactionbetween dust particle and pollutants should be well considered by the optical model. [ABSTRACT FROM AUTHOR]