|Zhe WANG||Last modified date：2020.07.21|
Assistant Professor / Division of Earth Environment Dynamics / Research Institute for Applied Mechanics
|Zhe WANG||Last modified date：2020.07.21|
|1.||Xueshun Chen, Wenyi Yang, Zifa Wang, Jie Li, Min Hu, Junling An, Qizhong Wu, Zhe Wang, Huansheng Chen, Ying Wei, Huiyun Du, Dawei Wang, Improving new particle formation simulation by coupling a volatility-basis set (VBS) organic aerosol module in NAQPMS+APM, Atmospheric Environment, 10.1016/j.atmosenv.2019.01.053, 204, 1-11, 2019.05, We developed a new modeling framework to simulate aerosol microphysics by incorporating a volatility basis-set (VBS) organic aerosol (OA) module into a three-dimensional (3-D) atmospheric transport model, namely, Nested Air Quality Prediction Modeling System with an Advanced Particle Microphysics (NAQPMS + APM). The new model calculates not only the condensation of sulfuric acid, nitrate, and ammonium and the coagulation of five types of particles (namely secondary, sea salt, dust, black carbon and organic carbon particles) but also the condensation of low-volatility organic vapors and the equilibrium partitioning of semi-volatile organic compounds. The new model was applied to simulate new particle formation (NPF) in summer in Beijing. The new model could noticeably improve the NPF simulation. On comparing the simulation with observation, the ion-mediated nucleation scheme was found to underestimate nucleation rates in summer in Beijing. By incorporating a nucleation formula involving the participation of organic compounds, NPF events could be reproduced satisfactorily. Reasonably calculating nucleation rates is essential for successfully simulating NPF. Accounting for the condensation of anthropogenic low-volatility organic vapors and the volatility of primary OA (POA) can improve the temporal variation of the number concentrations of particles in Aitken and accumulation modes. On a regional scale, anthropogenic low-volatility secondary organic gases (LV-SOGs) and the volatility of POA have large impacts on the aerosol number concentration and cloud condensation nuclei (CCN) concentration. Both anthropogenic LV-SOGs and volatility of POA must be considered to quantify the contribution of NPF to the aerosol number concentration and CCN concentration..|
|2.||Yu Tian, Xiaole Pan, Jinpei Yan, Qi Lin, Yele Sun, Mei Li, Conghui Xie, Itsushi Uno, Hang Liu, Zhe Wang, Pingqing Fu, Zifa Wang, Size distribution and depolarization properties of aerosol particles over the northwest pacific and arctic ocean from shipborne measurements during an R/V xuelong cruise, Environmental Science and Technology, 10.1021/acs.est.9b00245, 53, 14, 7984-7995, 2019.07, Atmospheric aerosols over polar regions have attracted considerable attention for their pivotal effects on climate change. In this study, temporospatial variations in single-particle-based depolarization ratios (?: s-polarized component divided by the total backward scattering intensity) were studied over the Northwest Pacific and the Arctic Ocean using an optical particle counter with a depolarization module. The δvalue of aerosols was 0.06 ± 0.01 for the entire observation period, 61 ± 10% lower than the observations for coastal Japan (0.12 ± 0.02) (Pan et al. Atmos. Chem. Phys. 2016, 16, 9863-9873) and inland China (0.19 ± 0.02) (Tian et al. Atmos. Chem. Phys. 2018, 18, 18203-18217) in summer. The volume concentration showed two dominant size modes at 0.9 and 2 μm. The supermicrometer particles were mostly related to sea-salt aerosols with a δvalue of 0.09 over marine polar areas, ?22% larger than in the low-latitude region because of differences in chemical composition and dry air conditions. The δvalues for fine particles (<1 μm) were 0.05 ± 0.1, 50% lower than inland anthropogenic pollutants, mainly because of the complex mixtures of submicrometer sea salts. High particle concentrations in the Arctic Ocean could mostly be attributed to the strong marine emission of sea salt associated with deep oceanic cyclones, whereas long-range transport pollutants from the continent were among the primary causes of high particle concentrations in the Northwest Pacific region..|
|3.||Dongsheng Ji, Wenkang Gao, Willy Maenhaut, Jun He, Zhe Wang, Jiwei Li, Wupeng Du, Lili Wang, Yang Sun, Jinyuan Xin, Bo Hu, Yuesi Wang, Impact of air pollution control measures and regional transport on carbonaceous aerosols in fine particulate matter in urban Beijing, China
Insights gained from long-term measurement, Atmospheric Chemistry and Physics, 10.5194/acp-19-8569-2019, 19, 13, 8569-8590, 2019.07, As major chemical components of airborne fine particulate matter (PM2:5), organic carbon (OC) and elemental carbon (EC) have vital impacts on air quality, climate change, and human health. Because OC and EC are closely associated with fuel combustion, it is helpful for the scientific community and policymakers assessing the efficacy of air pollution control measures to study the impact of control measures and regional transport on OC and EC levels. In this study, hourly mass concentrations of OC and EC associated with PM2:5 were semi-continuously measured from March 2013 to February 2018. The results showed that annual mean OC and EC concentrations declined from 14.0 to 7.7 μgm-3 and from 4.0 to 2.6 μgm-3, respectively, from March 2013 to February 2018. In combination with the data of OC and EC in previous studies, an obvious decreasing trend in OC and EC concentrations was found, which was caused by clean energy policies and effective air pollution control measures. However, no obvious change in the ratios of OC and EC to the PM2:5 mass (on average, 0.164 and 0.049, respectively) was recorded, suggesting that inorganic ions still contributed a lot to PM2:5. Based on the seasonal variations in OC and EC, it appeared that higher OC and EC concentrations were still observed in the winter months, with the exception of winter of 20172018. Traffic policies executed in Beijing resulted in nighttime peaks of OC and EC, caused by heavy-duty vehicles and heavy-duty diesel vehicles being permitted to operate from 00:00 to 06:00 (China standard time, UTCC8, for all times throughout the paper). In addition, the fact that there was no traffic restriction in weekends led to higher concentrations on weekends compared to weekdays. Significant correlations between OC and EC were observed throughout the study period, suggesting that OC and EC originated from common emission sources, such as exhaust of vehicles and fuel combustion. OC and EC levels increased with enhanced SO2, CO, and NOx concentrations while the O3 and OC levels were enhanced simultaneously when O3 concentrations were higher than 50 μgm-3. Non-parametric wind regression analysis was performed to examine the sources of OC and EC in the Beijing area. It was found that there were distinct hot spots in the northeast wind sector at wind speeds of approximately 06 km h-1, as well as diffuse signals in the southwestern wind sectors. Source areas further away from Beijing were assessed by potential source contribution function (PSCF) analysis. A highpotential source area was precisely pinpointed, which was located in the northwestern and southern areas of Beijing in 2017 instead of solely in the southern areas of Beijing in 2013. This work shows that improvement of the air quality in Beijing benefits from strict control measures; however, joint prevention and control of regional air pollution in the regions is needed for further improving the air quality. The results provide a reference for controlling air pollution caused by rapid economic development in developing countries..
|4.||Baozhu Ge, Xiaobin Xu, Zhiqiang Ma, Xiaole Pan, Zhe Wang, Weili Lin, Bin Ouyang, Danhui Xu, James Lee, Mei Zheng, Dongsheng Ji, Yele Sun, Huabin Dong, Freya Anne Squires, Pingqing Fu, Zifa Wang, Role of Ammonia on the Feedback Between AWC and Inorganic Aerosol Formation During Heavy Pollution in the North China Plain, Earth and Space Science, 10.1029/2019EA000799, 6, 9, 1675-1693, 2019.09, Atmospheric NH3 plays a vital role not only in the environmental ecosystem but also in atmosphere chemistry. To further understand the effects of NH3 on the formation of haze pollution in Beijing, ambient NH3 and related species were measured and simulated at high resolutions during the wintertime Air Pollution and Human Health-Beijing (APHH-Beijing) campaign in 2016. We found that the total NHx (gaseous NH3+particle NH4 +) was mostly in excess of the SO4 2−-NO3 −-NH4 +-water equilibrium system during our campaign. This NHx excess made medium aerosol acidity, with the median pH value being 3.6 and 4.5 for polluted and nonpolluted conditions, respectively, and enhanced the formation of particle phase nitrate. Our analysis suggests that NH4NO3 is the most important factor driving the increasing of aerosol water content with NO3 − controlling the prior pollution stage and NH4 + the most polluted stage. Increased formation of NH4NO3 under excess NHx, especially during the nighttime, may trigger the decreasing of aerosol deliquescence relative humidity even down to less than 50% and hence lead to hygroscopic growth even under RH conditions lower than 50% and the wet aerosol particles become better medium for rapid heterogeneous reactions. A further increase of RH promotes the positive feedback “aerosol water content-heterogeneous reactions” and ultimately leads to the formation of severe haze. Modeling results by Nested Air Quality Prediction Monitor System (NAQPMS) show the control of 20% NH3 emission may affect 5–11% of particulate matter PM2.5 formation under current emissions conditions in the North China Plain..|
|5.||Jie Li, Tatsuya Nagashima, Lei Kong, Baozhu Ge, Kazuyo Yamaji, Joshua S. Fu, Xuemei Wang, Qi Fan, Syuichi Itahashi, Hyo Jung Lee, Cheol Hee Kim, Chuan Yao Lin, Meigen Zhang, Zhining Tao, Mizuo Kajino, Hong Liao, Meng Li, Jung Hun Woo, Jun Ichi Kurokawa, Zhe Wang, Qizhong Wu, Hajime Akimoto, Gregory R. Carmichael, Zifa Wang, Model evaluation and intercomparison of surface-level ozone and relevant species in East Asia in the context of MICS-Asia Phase III - Part 1
Overview, Atmospheric Chemistry and Physics, 10.5194/acp-19-12993-2019, 19, 20, 12993-13015, 2019.10, Spatiotemporal variations of ozone (O3) and nitrogen oxide (NOx) mixing ratios from 14 state-of-the-art chemical transport models (CTMs) are intercompared and evaluated with O3 observations in East Asia, within the framework of the Model Inter-Comparison Study for Asia Phase III (MICS-Asia III). This study was designed to evaluate the capabilities and uncertainties of current CTMs simulations for Asia and to provide multi-model estimates of pollutant distributions. These models were run by 14 independent groups working in China, Japan, South Korea, the United States and other countries/regions. Compared with the previous phase of MICS-Asia (MICS-Asia II), the evaluation with observations was extended from 4 months to 1 full year across China and the western Pacific Rim. In general, model performance levels for O3 varied widely by region and season. Most models captured the key patterns of monthly and diurnal variation of surface O3 and its precursors in the North China Plain and western Pacific Rim but failed to do so for the Pearl River Delta. A significant overestimation of surface O3 was evident from May to September/October and from January to May over the North China Plain, the western Pacific Rim and the Pearl River Delta. Comparisons drawn from observations show that the considerable diversity in O3 photochemical production partly contributed to this overestimation and to high levels of inter-model variability in O3 for North China. In terms of O3 soundings, the ensemble average of models reproduced the vertical structure for the western Pacific, but overestimated O3 levels to below 800 hPa in the summer. In the industrialized Pearl River Delta, the ensemble average presented an overestimation for the lower troposphere and an underestimation for the middle troposphere. The ensemble average of 13 models for O3 did not always exhibit superior performance compared with certain individual models in contrast with its superior value for Europe. This finding suggests that the spread of ensemble-model values does not represent all of the uncertainties of O3 or that most MICS-Asia III models missed key processes. This study improved the performance of modeling O3 in March at Japanese sites compared with MICS-Asia II. However, it overpredicted surface O3 concentrations for western Japan in July, which was not found by MICS-Asia II. Major challenges still remain with regard to identifying the sources of bias in surface O3 over East Asia in CTMs..
|6.||Zhe Wang, Itsushi Uno, Keiya Yumimoto, Xiaole Pan, Xueshun Chen, Jie Li, Zifa Wang, Atsushi Shimizu, Nobuo Sugimoto, Dust Heterogeneous Reactions during Long-Range Transport of a Severe Dust Storm in May 2017 over East Asia, Atmosphere, 10.3390/atmos10110680, 10, 11, 2019.11, 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..|
|7.||Lei Kong, Xiao Tang, Jiang Zhu, Zifa Wang, Joshua S. Fu, Xuemei Wang, Syuichi Itahashi, Kazuyo Yamaji, Tatsuya Nagashima, Hyo Jung Lee, Cheol Hee Kim, Chuan Yao Lin, Lei Chen, Meigen Zhang, Zhining Tao, Jie Li, Mizuo Kajino, Hong Liao, Zhe Wang, Kengo Sudo, Yuesi Wang, Yuepeng Pan, Guiqian Tang, Meng Li, Qizhong Wu, Baozhu Ge, Gregory R. Carmichael, Evaluation and uncertainty investigation of the NO2, CO and NH3 modeling over China under the framework of MICS-Asia III, Atmospheric Chemistry and Physics, 10.5194/acp-20-181-2020, 20, 1, 181-202, 2020.01, Despite the significant progress in improving chemical transport models (CTMs), applications of these modeling endeavors are still subject to large and complex model uncertainty. The Model Inter-Comparison Study for Asia III (MICS-Asia III) has provided the opportunity to assess the capability and uncertainty of current CTMs in East Asian applications. In this study, we have evaluated the multi-model simulations of nitrogen dioxide (NO2), carbon monoxide (CO) and ammonia (NH3) over China under the framework of MICS-Asia III. A total of 13 modeling results, provided by several independent groups from different countries and regions, were used in this study. Most of these models used the same modeling domain with a horizontal resolution of 45 km and were driven by common emission inventories and meteorological inputs. New observations over the North China Plain (NCP) and Pearl River Delta (PRD) regions were also available in MICS-Asia III, allowing the model evaluations over highly industrialized regions. The evaluation results show that most models captured the monthly and spatial patterns of NO2 concentrations in the NCP region well, though NO2 levels were slightly underestimated. Relatively poor performance in NO2 simulations was found in the PRD region, with larger root-mean-square error and lower spatial correlation coefficients, which may be related to the coarse resolution or inappropriate spatial allocations of the emission inventories in the PRD region. All models significantly underpredicted CO concentrations in both the NCP and PRD regions, with annual mean concentrations that were 65.4 % and 61.4 % underestimated by the ensemble mean. Such large underestimations suggest that CO emissions might be underestimated in the current emission inventory. In contrast to the good skills for simulating the monthly variations in NO2 and CO concentrations, all models failed to reproduce the observed monthly variations in NH3 concentrations in the NCP region. Most models mismatched the observed peak in July and showed negative correlation coefficients with the observations, which may be closely related to the uncertainty in the monthly variations in NH3 emissions and the NH3 gas-aerosol partitioning. Finally, model intercomparisons have been conducted to quantify the impacts of model uncertainty on the simulations of these gases, which are shown to increase with the reactivity of species. Models contained more uncertainty in the NH3 simulations. This suggests that for some highly active and/or short-lived primary pollutants, like NH3, model uncertainty can also take a great part in the forecast uncertainty in addition to the emission uncertainty. Based on these results, some recommendations are made for future studies..|
|8.||Syuichi Itahashi, Baozhu Ge, Keiichi Sato, Joshua S. Fu, Xuemei Wang, Kazuyo Yamaji, Tatsuya Nagashima, Jie Li, Mizuo Kajino, Hong Liao, Meigen Zhang, Zhe Wang, Meng Li, Junichi Kurokawa, Gregory R. Carmichael, Zifa Wang, MICS-Asia III
Overview of model intercomparison and evaluation of acid deposition over Asia, Atmospheric Chemistry and Physics, 10.5194/acp-20-2667-2020, 20, 5, 2667-2693, 2020.03, The Model Inter-Comparison Study for Asia (MICS-Asia) phase III was conducted to promote understanding of regional air quality and climate change in Asia, which have received growing attention due to the huge amount of anthropogenic emissions worldwide. This study provides an overview of acid deposition. Specifically, dry and wet deposition of the following species was analyzed: S (sulfate aerosol, sulfur dioxide (SO2), and sulfuric acid (H2SO4)), N (nitrate aerosol, nitrogen monoxide (NO), nitrogen dioxide (NO2), and nitric acid (HNO3)), and A (ammonium aerosol and ammonia (NH3)). The wet deposition simulated by a total of nine models was analyzed and evaluated using ground observation data from the Acid Deposition Monitoring Network in East Asia (EANET). In the phase III study, the number of observation sites was increased from 37 in the phase II study to 54, and southeast Asian countries were newly added. Additionally, whereas the analysis period was limited to representative months of each season in MICS-Asia phase II, the phase III study analyzed the full year of 2010. The scope of this overview mainly focuses on the annual accumulated deposition. In general, models can capture the observed wet deposition over Asia but underestimate the wet deposition of S and A, and show large differences in the wet deposition of N. Furthermore, the ratio of wet deposition to the total deposition (the sum of dry and wet deposition) was investigated in order to understand the role of important processes in the total deposition. The general dominance of wet deposition over Asia and attributions from dry deposition over land were consistently found in all models. Then, total deposition maps over 13 countries participating in EANET were produced, and the balance between deposition and anthropogenic emissions was calculated. Excesses of deposition, rather than of anthropogenic emissions, were found over Japan, northern Asia, and southeast Asia, indicating the possibility of long-range transport within and outside of Asia, as well as other emission sources. To improve the ability of models to capture the observed wet deposition, two approaches were attempted, namely, ensemble and precipitation adjustment. The ensemble approach was effective at modulating the differences in performance among models, and the precipitation-adjusted approach demonstrated that the model performance for precipitation played a key role in better simulating wet deposition. Finally, the lessons learned from the phase III study and future perspectives for phase IV are summarized..
|9.||Itsushi Uno, Zhe Wang, Syuichi Itahashi, Keiya Yumimoto, Yuki Yamamura, Ayako Yoshino, Akinori Takami, Masamitsu Hayasaki, Byung Gon Kim, Paradigm shift in aerosol chemical composition over regions downwind of China, Scientific reports, 10.1038/s41598-020-63592-6, 10, 1, 2020.12, A rapid decrease in PM2.5 concentrations in China has been observed in response to the enactment of strong emission control policies. From 2012 to 2017, total emissions of SO2 and NOx from China decreased by approximately 63% and 24%, respectively. Simultaneously, decreases in the PM2.5 concentration in Japan have been observed since 2014, and the proportion of stations that satisfy the PM2.5 environmental standard (daily, 35 µg/m3; annual average, 15 µg/m3) increased from 37.8% in fiscal year (FY) 2014 (April 2014 to March 2015) to 89.9% in FY 2017. However, the quantitative relationship between the PM2.5 improvement in China and the PM2.5 concentration in downwind regions is not well understood. Here, we (1) quantitatively evaluate the impacts of Chinese environmental improvements on downwind areas using source/receptor analysis with a chemical transport model, and (2) show that these rapid emissions reductions improved PM2.5 concentrations both in China and its downwind regions, but the difference between SO2 and NOx reduction rates led to greater production of nitrates (e.g., NH4NO3) due to a chemical imbalance in the ammonia–nitric acid–sulfuric acid–water system. Observations from a clean remote island in western Japan and numerical modeling confirmed this paradigm shift..|
|10.||Itsushi Uno, Keiya Yumimoto, Xiaole Pan, Zhe Wang, Kazuo Osada, Syuichi Itahashi, Shigekazu Yamamoto, Simultaneous dust and pollutant transport over East Asia
The Tripartite Environment Ministers Meeting March 2014 case study, Scientific Online Letters on the Atmosphere, 10.2151/sola.2017-009, 13, 47-52, 2017.01, Heavy dust storms that occurred between 13 and 23 March 2014 were selected for analysis as a case study of dust and sand storm events by the Tripartite Environment Ministers Meeting. During this period, two dust and anthropogenic aerosol events were observed and analyzed. The GEOS-Chem chemical transport model, which includes dust-acid uptake processes, successfully reproduced the aerosol variations and explained the Asian-scale dust-pollutant transport processes. Our results confirmed the importance of coarse-mode dust-nitrate as evidence of 'polluted dust' pollution. The model analysis showed that the formation of dust-nitrate occurred over the Yellow Sea and East China Sea before arriving in Japan. We showed that more than 40% of nitrate exists in dust-nitrate when air mass arrived in Japan..
|11.||Itsushi Uno, Keiya Yumimoto, Kazuo Osada, Zhe Wang, Xiaole Pan, Syuichi Itahashi, Shigekazu Yamamoto, Dust acid uptake analysis during long-lasting dust and pollution episodes over East Asia based on synergetic observation and chemical transport model, Scientific Online Letters on the Atmosphere, 10.2151/sola.2017-020, 13, 109-113, 2017.01, Two heavy dust storms that occurred between 24-26 May 2014 in Mongolia and Inner Mongolia, China were responsible for long-lasting dust episodes observed from 26 May to 2 June 2014 in Fukuoka, Japan. During this period, dust and anthropogenic pollutants were transported simultaneously to Fukuoka and Korea and remained there for almost 8 days. We successfully observed fine and coarse aerosol time variations (1-hour intervals) in Fukuoka. The GEOS-Chem chemical transport model, which includes dust-acid uptake processes, successfully reproduced the aerosol variations and explained the Asian-scale dust-pollutant transport and transformation processes. Model sensitivity analyses with and without dust-acid uptake processes showed that the formation of dust-nitrate occurred over the Yellow Sea and East China Sea before arriving in Japan. The model sensitivity analysis showed that less than 5% of the coarse dust-nitrate originated from NOx emissions from Japan, and large amounts of dustnitrate originated outside of Japan..|
|12.||Xueshun Chen, Zifa Wang, Jie Li, Wenyi Yang, Huansheng Chen, Zhe Wang, Jianqi Hao, Baozhu Ge, Dawei Wang, Huili Huang, Simulation on different response characteristics of aerosol particle number concentration and mass concentration to emission changes over mainland China, Science of the Total Environment, 10.1016/j.scitotenv.2018.06.181, 643, 692-703, 2018.12, In this study, Nested Air Quality Prediction Modeling System with Advance Particle Microphysics module (NAQPMS+APM) is applied to simulate the response characteristics of aerosol particle number concentration and mass concentration to emission changes over mainland China. It is the first attempt to investigate the response of both aerosol mass concentration and number concentration to emission changes using a chemical transport model with detailed aerosol microphysics over mainland China. Results indicate that the response characteristics are obviously different between aerosol particle number concentration and mass concentration. Generally, the response of number concentration shows a more heterogeneous spatial distribution than that of mass concentration. Furthermore, number concentration has a higher sensitivity not only to primary particles emission but also to precursor gases than that of mass concentration. Aerosol particle mass concentration exhibits a consistent trend with the emission change and yet aerosol number concentration does not. Due to the nonlinearity of aerosol microphysical processes, reduction of primary particles emission does not necessarily lead to an obvious decrease of aerosol number concentration and it even increases the aerosol number concentration. Over Central-Eastern China (CEC), the most polluted regions in China, reducing primary particles emission rather than precursor gas emissions is more effective in reducing particles number concentration. By contrast, the opposite is true over the northwestern China. The features of fine particles pollution revealed in this study are associated with the spatial differences in China's population, geography, climate and economy. Considering the more adverse effects of ultrafine particles on human health and the spatial distribution of population, making different measures in controlling particles number concentration from that controlling mass concentration in different regions over mainland China is indicated. Main findings: FPN concentration responds more heterogeneously to emission than FPM. Spatial difference of response of FPN to emission is distinguished by a boundary line..|
|13.||Xiaole Pan, Baozhu Ge, Zhe Wang, Yu Tian, Hang Liu, Lianfang Wei, Siyao Yue, Itsushi Uno, Hiroshi Kobayashi, Tomoaki Nishizawa, Atsushi Shimizu, Pingqing Fu, Zifa Wang, Synergistic effect of water-soluble species and relative humidity on morphological changes in aerosol particles in the Beijing megacity during severe pollution episodes, Atmospheric Chemistry and Physics, 10.5194/acp-19-219-2019, 19, 1, 219-232, 2019.01, Depolarization ratio (δ) of backscattered light is an applicable parameter for distinguishing the sphericity of particles in real time, which has been widely adopted by groundbased lidar observation systems. In this study, δ values of particles and chemical compositions in both PM2:5 (aerodynamic diameter less than 2.5 μm) and PM10 (aerodynamic diameter less than 10 μm) were concurrently measured on the basis of a bench-top optical particle counter with a polarization detection module (POPC) and a continuous dichotomous aerosol chemical speciation analyzer (ACSA-14) from November 2016 to February 2017 at an urban site in Beijing megacity. In general, measured δ values depended on both size and sphericity of the particles. During the observation period, mass concentrations of NO-3 in PM
) were about an order of magnitude higher than that in PM
) with a mean fNO
ratio of 14±10. A relatively low fNO
ratio (∼ 5) was also observed under higher relative humidity conditions, mostly due to heterogeneous processes and particles in the coarse mode. We found that δ values of ambient particles in both PM
obviously decreased as mass concentration of water-soluble species increased at unfavorable meteorological conditions. This indicated that the morphology of particles was changed as a result of water-absorbing processes. The particles with optical size (Dp) of DpD5 μm were used to represent mineral dust particles, and its δ values (δDpD5) decreased by 50% as the mass fraction of cNO
increased from 2% to 8% and ambient relative humidity increased up to 80 %, suggesting that mineral dust particles were likely to be spherical during humid pollution episodes. During the observation, relative humidity inside the POPC measuring chamber was stable at 34±2 %, lower than the ambient condition. Its influence on the morphology was estimated to be limited and did not change our major conclusion. This study highlights the evident alteration of non-sphericity of mineral dust particles during their transport owing to a synergistic effect of both pollutant coatings and hygroscopic processes, which plays an important role in the evaluation of its environmental effect..
|14.||Chen, X., Z. Wang, J. Li, W. Yang, H. Chen, Z. Wang,, J. Hao, B. Ge, D. Wang, H. Huang, Simulation on different response characteristics of aerosol particle number concentration and mass concentration to emission changes over mainland China, Science of the Total Environment, 643, 692–703, 2018.06.|
|15.||Xiaole Pan, Itsushi Uno, Zhe Wang, Shigekazu Yamamoto, Yukari Hara, Zifa Wang, Seasonal variabilities in chemical compounds and acidity of aerosol particles at urban site in the west Pacific, Environmental Pollution, 10.1016/j.envpol.2017.11.089, 237, 868-877, 2018.03, Mass concentrations of chemical compounds in both PM2.5 (particle aerodynamic diameter, Dp < 2.5 μm) and PM2.5-10 (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 PM2.5 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 PM2.5 (fNO3) 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 PM2.5-10 (cNO3) 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 PM2.5 (fΔH) was mostly positive with a maximum in August because of the large fraction of nitrate and sulfate. Acidity of particles in PM2.5-10 (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. Meteorology and transport played a key role in the allocation of aerosol phase nitrate in PM2.5, PM2.5-10. Seasonal variability of acidity of PM2.5 was mainly attributed to fraction of water-soluble secondary inorganics and source regions..|
|16.||Zhe Wang, Xiaole Pan, Itsushi Uno, Xueshun Chen, Shigekazu Yamamoto, Haitao Zheng, Jie Li, Zifa Wang, Importance of mineral dust and anthropogenic pollutants mixing during a long-lasting high PM event over East Asia, Environmental Pollution, 10.1016/j.envpol.2017.11.068, 234, 368-378, 2018.03, A long-lasting high particulate matter (PM) concentration episode persisted over East Asia from May 24 to June 3, 2014. The Nested Air Quality Prediction Model System (NAQPMS) was used to investigate the mixing of dust and anthropogenic pollutants during this episode. Comparison of observations revealed that the NAQPMS successfully reproduced the time series PM2.5 and PM10 concentrations, as well as the nitrate and sulfate concentrations in fine (aerodynamic diameter ≤ 2.5 μm) and coarse mode (2.5 μm < aerodynamic diameter ≤ 10 μm). This episode originated from two dust events that occurred in the inland desert areas of Mongolia and China, and then the long-range transported dust and anthropogenic pollutants were trapped over the downwind region of East Asia for more than one week due to the blocked north Pacific subtropical high-pressure system over the east of Japan. The model results showed that mineral dust accounted for 53–83% of PM10, and 39–67% of PM2.5 over five cities in East Asia during this episode. Sensitivity analysis indicated that the Qingdao and Seoul regions experienced dust and pollution twice, by direct transport from the dust source region and from dust detoured over the Shanghai area. The results of the NAQPMS model confirmed the importance of dust heterogeneous reactions (HRs) over East Asia. Simulated dust NO3 − concentrations accounted for 75% and 84% of total NO3 − in fine and coarse mode, respectively, in Fukuoka, Japan. The horizontal distribution of model results revealed that the ratio of dust NO3 −/dust concentration increased from about 1% over the Chinese land mass to a maximum of 8% and 6% respectively in fine and coarse mode over the ocean to the southeast of Japan, indicating that dust NO3 − was mainly formed over the Yellow Sea and the East China Sea before reaching Japan. Capsule abstract: Mineral dust and related heterogeneous reactions had dominant impacts on the concentration of PM as well as nitrate and sulfate over East Asia during a long-lasting high PM episode..|
|17.||Qingqing Wang, Yele Sun, Weiqi Xu, Wei Du, Libo Zhou, Guiqian Tang, Chen Chen, Xueling Cheng, Xiujuan Zhao, Dongsheng Ji, Tingting Han, Zhe Wang, Jie Li, Zifa Wang, Vertically resolved characteristics of air pollution during two severe winter haze episodes in urban Beijing, China, Atmospheric Chemistry and Physics, 10.5194/acp-18-2495-2018, 18, 4, 2495-2509, 2018.02, We conducted the first real-Time continuous vertical measurements of particle extinction (bext/, gaseous NO2, and black carbon (BC) from ground level to 260m during two severe winter haze episodes at an urban site in Beijing, China. Our results illustrated four distinct types of vertical profiles: (1) uniform vertical distributions (37% of the time) with vertical differences less than 5 %, (2) higher values at lower altitudes (29 %), (3) higher values at higher altitudes (16 %), and (4) significant decreases at the heights of ∼100-150m (14 %). Further analysis demonstrated that vertical convection as indicated by mixing layer height, temperature inversion, and local emissions are three major factors affecting the changes in vertical profiles. Particularly, the formation of type 4 was strongly associated with the stratified layer that was formed due to the interactions of different air masses and temperature inversions. Aerosol composition was substantially different below and above the transition heights with ∼20-30% higher contributions of local sources (e.g., biomass burning and cooking) at lower altitudes. A more detailed evolution of vertical profiles and their relationship with the changes in source emissions, mixing layer height, and aerosol chemistry was illustrated by a case study. BC showed overall similar vertical profiles as those of bext (R2 D 0.92 and 0.69 in November and January, respectively). While NO2 was correlated with bext for most of the time, the vertical profiles of bext =NO2 varied differently for different profiles, indicating the impact of chemical transformation on vertical profiles. Our results also showed that more comprehensive vertical measurements (e.g., more aerosol and gaseous species) at higher altitudes in the megacities are needed for a better understanding of the formation mechanisms and evolution of severe haze episodes in China..|
|18.||Xueshun Chen, Zifa Wang, Jie Li, Huansheng Chen, Min Hu, Wenyi Yang, Zhe Wang, Baozhu Ge, Dawei Wang, Explaining the spatiotemporal variation of fine particle number concentrations over Beijing and surrounding areas in an air quality model with aerosol microphysics, Environmental Pollution, 10.1016/j.envpol.2017.08.103, 231, 1302-1313, 2017.12, In this study, a three-dimensional air quality model with detailed aerosol microphysics (NAQPMS + APM) was applied to simulate the fine particle number size distribution and to explain the spatiotemporal variation of fine particle number concentrations in different size ranges over Beijing and surrounding areas in the haze season (Jan 15 to Feb 13 in 2006). Comparison between observations and the simulation indicates that the model is able to reproduce the main features of the particle number size distribution. The high number concentration of total particles, up to 26600 cm−3 in observations and 39800 cm−3 in the simulation, indicates the severity of pollution in Beijing. We find that primary particles with secondary species coating and secondary particles together control the particle number size distribution. Secondary particles dominate particle number concentration in the nucleation mode. Primary and secondary particles together determine the temporal evolution and spatial pattern of particle number concentration in the Aitken mode. Primary particles dominate particle number concentration in the accumulation mode. Over Beijing and surrounding areas, secondary particles contribute at least 80% of particle number concentration in the nucleation mode but only 10–20% in the accumulation mode. Nucleation mode particles and accumulation mode particles are anti-phased with each other. Nucleation or primary emissions alone could not explain the formation of the particle number size distribution in Beijing. Nucleation has larger effects on ultrafine particles while primary particles emissions are efficient in producing large particles in the accumulation mode. Reduction in primary particle emissions does not always lead to a decrease in the number concentration of ultrafine particles. Measures to reduce fine particle pollution in terms of particle number concentration may be different from those addressing particle mass concentration. Nucleation is more important in forming ultrafine particles while primary particle emissions are more efficient in producing particles in accumulation mode in Beijing..|
|19.||Itsushi Uno, Kazuo Osada, Keiya Yumimoto, Zhe Wang, Syuichi Itahashi, Xiaole Pan, Yukari Hara, Shigekazu Yamamoto, Tomoaki Nishizawa, Importance of long-range nitrate transport based on long-term observation and modeling of dust and pollutants over East Asia, Aerosol and Air Quality Research, 10.4209/aaqr.2016.11.0494, 17, 12, 3052-3064, 2017.12, Long-term synergetic fine and coarse mode aerosol observations were analyzed at 1-h intervals at Fukuoka, Japan, from January to June 2015. The GEOS-Chem chemical transport model, including dust and sea-salt acid uptake processes, was used for detailed analysis of observation data. Several Asian dust events and long-range anthropogenic aerosol transport events were observed during our analysis period, and the numerical model generally explained the observed time variation for both fine and coarse mode aerosols. We found that (i) the majority of fine mode NO3 – can be considered as long-range transport (LRT) outside of Japan during the cold season, and (ii) the peak timing of fine mode NO3 – coincided with that of SO4 –, indicating that both aerosols are controlled by LRT. Also, an observed mass concentration ratio of NO3 –/SO4 2– > 0.9 occurred during the cold season, indicating the importance of NO3 – as a major contributor to the PM2.5 mass fraction. Finally, we clearly showed that large-scale dust-nitrate outflow from China to Fukuoka was confirmed in all cases of dust events, indicating that the anthropogenic NOx is converted to dust-nitrate and transported to Japan with dust. These results demonstrate the importance of anthropogenic NO3 – LRT during the cold season and dust-nitrate LRT for all dust events (even in June)..|
|20.||Zhe Wang, Syuichi Itahashi, Itsushi Uno, Xiaole Pan, Kazuo Osada, Shigekazu Yamamoto, Tomoaki Nishizawa, Kei Tamura, Zifa Wang, Modeling the long-range transport of particulate matters for january in East Asia using NAQPMS and CMAQ, Aerosol and Air Quality Research, 10.4209/aaqr.2016.12.0534, 17, 12, 3065-3078, 2017.12, Two regional chemical transport models were applied to simulate high concentrations of particulate matters (PM) observed in East Asia in January 2015; the first model is the Nested Air Quality Prediction Modeling System (NAQPMS) and the second is the Community Multi-scale Air Quality Model (CMAQ). The variation of PM2.5 in both models showed well agreement with measurements over both eastern China and western Japan. Based on the model results and the aerosol compositions observed in Fukuoka in western Japan, three types of PM long-range transport (LRT) were identified: N-, S-, and D-type. The N episode showed higher fine-mode nitrate (fNO3–) concentrations than fine-mode sulfate (fSO42–), indicating the importance of NO3– LRT. The S episode showed the highest fSO42– concentrations (28.9 µg m–3), which were 3.4-fold higher than fNO3–, due to high relative humidity. During the D episode, dust stagnated in Fukuoka for three days, due to the influence of low- and high-pressure systems; thus, dust LRT is also important in winter besides spring. Both models reasonable explained variations in aerosol components during both N and S episodes; however, both underestimated fSO42– especially during D episode, suggesting that they may miss certain emissions or chemical mechanisms. High coarse-mode NO3– (cNO3–) concentrations (maximum: 6.3 µg m–3), and high cNO3–/fNO3– ratios (maximum: 1.2) were observed during D episode. NAQPMS successfully captured this cNO3– peak after including heterogeneous reactions on dust. Our results emphasize the importance of such heterogeneous processes for understanding the LRT of dust and anthropogenic pollutants over East Asia..|
|21.||Xiaole Pan, Itsushi Uno, Zhe Wang, Tomoaki Nishizawa, Nobuo Sugimoto, Shigekazu Yamamoto, Hiroshi Kobayashi, Yele Sun, Pingqing Fu, Xiao Tang, Zifa Wang, Real-time observational evidence of changing Asian dust morphology with the mixing of heavy anthropogenic pollution, Scientific Reports, 10.1038/s41598-017-00444-w, 7, 1, 2017.12, Natural mineral dust and heavy anthropogenic pollution and its complex interactions cause significant environmental problems in East Asia. Due to restrictions of observing technique, real-time morphological change in Asian dust particles owing to coating process of anthropogenic pollutants is still statistically unclear. Here, we first used a newly developed, single-particle polarization detector and quantitatively investigate the evolution of the polarization property of backscattering light reflected from dust particle as they were mixing with anthropogenic pollutants in North China. The decrease in observed depolarization ratio is mainly attributed to the decrease of aspect ratio of the dust particles as a result of continuous coating processes. Hygroscopic growth of Calcium nitrate (Ca(NO3)2) on the surface of the dust particles played a vital role, particularly when they are stagnant in the polluted region with high RH conditions. Reliable statistics highlight the significant importance of internally mixed, 'quasi-spherical' Asian dust particles, which markedly act as cloud condensation nuclei and exert regional climate change..|
|22.||Xiaole Pan, Yugo Kanaya, Fumikazu Taketani, Takuma Miyakawa, Satoshi Inomata, Yuichi Komazaki, Hiroshi Tanimoto, Zhe Wang, Itsushi Uno, Zifa Wang, Emission characteristics of refractory black carbon aerosols from fresh biomass burning
A perspective from laboratory experiments, Atmospheric Chemistry and Physics, 10.5194/acp-17-13001-2017, 17, 21, 13001-13016, 2017.11, The emission characteristics of refractory black carbon (rBC) from biomass burning are essential information for numerical simulations of regional pollution and climate effects.We conducted combustion experiments in the laboratory to investigate the emission ratio and mixing state of rBC from the burning of wheat straw and rapeseed plants, which are the main crops cultivated in the Yangtze River Delta region of China. A single particle soot photometer (SP2) was used to measure rBC-containing particles at high temporal resolution and with high accuracy. The combustion state of each burning case was indicated by the modified combustion efficiency (MCE), which is calculated using the integrated enhancement of carbon dioxide and carbon monoxide concentrations relative to their background values. The mass size distribution of the rBC particles showed a lognormal shape with a mode mass equivalent diameter (MED) of 189 nm (ranging from 152 to 215 nm), assuming an rBC density of 1.8 g cm-3. rBC particles less than 80 nm in size (the lower detection limit of the SP2) accounted for ∼5% of the total rBC mass, on average. The emission ratios, which are expressed as ΔrBC =ΔCO (Δ indicates the difference between the observed and background values), displayed a significant positive correlation with the MCE values and varied between 1.8 and 34 ngm-3 ppbv-1. Multi-peak fitting analysis of the delay time (Δt, or the time of occurrence of the scattering peak minus that of the incandescence peak) distribution showed that rBC-containing particles with rBC MED = 200±10 nm displayed two peaks at Δt = 1.7 μs and Δt = 3.2 μs, which could be attributed to the contributions from both flaming and smoldering combustion in each burning case. Both the Δt values and the shell / core ratios of the rBC-containing particles clearly increased as the MCE decreased from 0.98 (smoldering-dominant combustion) to 0.86 (flaming-dominant combustion), implying the great importance of the rapid condensation of semi-volatile organics. This laboratory study found that the mixing state of rBC particles from biomass burning strongly depends on its combustion processes, and overall MCE should be taken carefully into consideration while the climate effect of rBC particles from open biomass burning is simulated..
|23.||Itsushi Uno, Kazuo Osada, Keiya Yumimoto, Zhe Wang, Syuichi Itahashi, Xiaole Pan, Yukari Hara, Yugo Kanaya, Shigekazu Yamamoto, Thomas Duncan Fairlie, Seasonal variation of fine- and coarse-mode nitrates and related aerosols over East Asia
Synergetic observations and chemical transport model analysis, Atmospheric Chemistry and Physics, 10.5194/acp-17-14181-2017, 17, 23, 14181-14197, 2017.11, We analyzed long-term fine- and coarse-mode synergetic observations of nitrate and related aerosols (SO2 4 , NO3 , NHC4 , NaC, Ca2C) at Fukuoka (33.52 N, 130.47 E) from August 2014 to October 2015. A Goddard Earth Observing System chemical transport model (GEOS-Chem) including dust and sea salt acid uptake processes was used to assess the observed seasonal variation and the impact of long-range transport (LRT) from the Asian continent. For fine aerosols (fSO2 4 , fNO3 , and fNHC4 ), numerical results explained the seasonal changes, and a sensitivity analysis excluding Japanese domestic emissions clarified the LRT fraction at Fukuoka (85% for fSO2 4 , 47% for fNO3 , 73% for fNHC4 ). Observational data confirmed that coarse NO3 (cNO3 ) made up the largest proportion (i.e., 40-55 %) of the total nitrate (defined as the sum of fNO3 , cNO3 , and HNO3) during the winter, while HNO3 gas constituted approximately 40% of the total nitrate in summer and fNO3 peaked during the winter. Large-scale dust-nitrate (mainly cNO3 ) outflow from China to Fukuoka was confirmed during all dust events that occurred between January and June. The modeled cNO3 was in good agreement with observations between July and November (mainly coming from sea salt NO3 ). During the winter, however, the model underestimated cNO3 levels compared to the observed levels. The reason for this underestimation was examined statistically using multiple regression analysis (MRA).We used cNaC, nsscCa2 C, and cNHC4 as independent variables to describe the observed cNO3 levels; these variables were considered representative of sea salt cNO3 , dust cNO3 , and cNO3 accompanied by cNHC4 ), respectively. The MRA results explained the observed seasonal changes in dust cNO3 and indicated that the dust-acid uptake scheme reproduced the observed dust-nitrate levels even in winter. The annual average contributions of each component were 43% (sea salt cNO3 ), 19% (dust cNO3 ), and 38% (cNHC4 term). The MRA dust-cNO3 component had a high value during the dust season, and the sea salt component made a large contribution throughout the year. During the winter, cNHC4 term made a large contribution. The model did not include aerosol microphysical processes (such as condensation and coagulation between the fine anthropogenic aerosols NO3 and SO2 4 and coarse particles), and our results suggest that inclusion of aerosol microphysical processes is critical when studying observed cNO3 formation, especially in winter..
|24.||Yuanlin Wang, Zhe Wang, Xueshun Chen, Zifa Wang, Shaojia Fan, Duohong Chen, Qizhong Wu, Impact of typical meteorological conditions on air pollution over Pearl River Delta in autumn, Huanjing Kexue Xuebao / Acta Scientiae Circumstantiae, 10.13671/j.hjkxxb.2017.0096, 37, 9, 3229-3239, 2017.09, Through analyzing the observed air quality index (AQI), pollutant concentrations, meteorological observations, synoptic charts and the WRF mesoscale numerical weather prediction results together, the impacts of weather conditions and meteorological characteristics on air pollution over the Pearl River Delta in October 2014 were investigated. Comparison with observations showed that WRF was able to reproduce temporal and spatial variations of ground-level and upper meteorological elements, with the correlation coefficient between simulated and observed average surface temperature, relative humidity and wind speed at nine cities of 0.90, 0.87 and 0.78, respectively. Analysis of all three pollution episodes in October showed that the bottom of the high-pressure control type and uniform pressure control type are the main meteorological factors of air pollution in the PRD. Low wind speed (<2 m·s-1) and pollutant transport along with the northerly wind led to the increase of the pollutant concentrations in the PRD. In addition, O3 was the primary pollutant when the relative humidity (RH) was lower than 65%, while PM2.5 became the primary pollutant when the RH was higher than 70%. The photochemical reaction during high temperature conditions also caused the increase of air pollution in the PRD..|
|25.||Jianqi Hao, Baozhu Ge, Zifa Wang, Zhe Wang, Si Huang, Xuefeng Yao, Characteristics and meteorological conditions analysis of severe haze events over Beijing-Tianjin-Hebei area, Huanjing Kexue Xuebao / Acta Scientiae Circumstantiae, 10.13671/j.hjkxxb.2017.0087, 37, 8, 3032-3043, 2017.08, Eastern China has suffered severe and continual haze pollution. The meteorological condition which is very important to influence the formation and depletion of the air pollution has been investigated based on the data from European Centre form Medium-Range Weather Forecasts (ECMWF), Meteorological Information Comprehensive Analysis and Process System (MICAPS) and Chinese Network of Environmental Monitor Center (CNEMC) in this study. Besides, the Nested Air Quality Prediction Model System (NAQPMS) was used to simulate the severe haze events occurred in January 2013. The results showed a significant seasonal change of diurnal concentration of PM2.5 in summer and autumn. The maximum and minimum monthly averaged concentrations were observed in January and July, respectively. Westerly flow in 500 hPa and weakly warm advection stabilized the atmospheric stratification and impaired the diffusivity of pollutants on the surface, especially when Beijing-Tianjin-Hebei Area was in the back or bottom of weak anticyclone on the surface. Furthermore, NAQPMS quantified this effect that when temperature increased by 0~5℃, relative humidity increased by 30%~50% and wind decreased by 2~3 m·s-1, PM2.5 concentration increased by 300 μg·m-3..|
|26.||Uno, I., Yumimoto, K., Osada, K., Wang, Z., Pan, X., Itahashi, S. and Yamamoto, S, Dust Acid Uptake Analysis during Long-Lasting Dust and Pollution Episodes over East Asia Based on Synergetic Observation and Chemical Transport Model, SOLA, 13, 109–113, 2017.05.|
|27.||Syuichi Itahashi, Itsushi Uno, Kazuo Osada, Yusuke Kamiguchi, Shigekazu Yamamoto, Kei Tamura, Zhe Wang, Yasunori Kurosaki, Yugo Kanaya, Nitrate transboundary heavy pollution over East Asia in winter, Atmospheric Chemistry and Physics, 10.5194/acp-17-3823-2017, 17, 6, 3823-3843, 2017.03, High PM2. 5 concentrations of around 100μgm-3 were observed twice during an intensive observation campaign in January 2015 at Fukuoka (33.52°N, 130.47°E) in western Japan. These events were analyzed comprehensively with a regional chemical transport model and synergetic ground-based observations with state-of-the-art measurement systems, which can capture the behavior of secondary inorganic aerosols (SO4 2-, NO3-, and NH4-). The first episode of high PM2. 5 concentration was dominated by NO3- (type N) and the second episode by SO4 2- (type S). The concentration of NH4- (the counterion for SO4 2- and NO3-) was high for both types. A sensitivity simulation in the chemical transport model showed that the dominant contribution was from transboundary air pollution for both types. To investigate the differences between these types further, the chemical transport model results were examined, and a backward trajectory analysis was used to provide additional information. During both types of episodes, high concentrations of NO3- were found above China, and an air mass that originated from northeast China reached Fukuoka. The travel time from the coastline of China to Fukuoka differed between types: It was 18h for type N and 24h for type S. The conversion ratio of SO2 to SO4 2- (Fs) was less than 0.1 for type N, but reached 0.3 for type S as the air mass approached Fukuoka. The higher Fs for type S was related to the higher relative humidity and the concentration of HO2, which produces H2O2, the most effective oxidant for the aqueous-phase production of SO4 2-. Analyzing the gas ratio as an indicator of the sensitivity of NO3- to changes in SO4 2- and NH4- showed that the air mass over China was NH3-rich for type N, but almost NH3-neutral for type S. Thus, although the high concentration of NO3- above China gradually decreased during transport from China to Fukuoka, higher NO3- concentrations were maintained during transport owing to the lower SO4 2- for type N. In contrast, for type S, the production of SO4 2- led to the decomposition of NH4NO3, and more SO4 2- was transported. Notably, the type N transport pattern was limited to western Japan, especially the island of Kyushu. Transboundary air pollution dominated by SO4 2- (type S) has been recognized as a major pattern of pollution over East Asia. However, our study confirms the importance of transboundary air pollution dominated by NO3-, which will help refine our understanding of transboundary heavy PM2. 5 pollution in winter over East Asia..|
|28.||Uno, I., Yumimoto, K., Pan, X.L., Wang, Z., Osada, K., Itahashi, S., and Yamamoto, S, Simultaneous Dust and Pollutant Transport over East Asia: the Tripartite Environment Ministers Meeting March 2014 Case Study, SOLA, 13, 47-52, 2017.02.|
|29.||Xueshun Chen, Zifa Wang, Fangqun Yu, Xiaole Pan, Jie Li, Baozhu Ge, Zhe Wang, Min Hu, Wenyi Yang, Huansheng Chen, Estimation of atmospheric aging time of black carbon particles in the polluted atmosphere over central-eastern China using microphysical process analysis in regional chemical transport model, Atmospheric Environment, 10.1016/j.atmosenv.2017.05.016, 163, 44-56, 2017.01, Mixing state of black carbon (BC) particles has significant impacts on their radiative forcing, visibility impairment and the ability in modifying cloud formation. In this study, an aging scheme of BC particles using prognostic variables based on aerosol microphysics was incorporated into a regional atmospheric chemistry model, Nested Air Quality Prediction Modeling System with Advanced Particle Microphysics (NAQPMS + APM), to investigate the temporal and spatial variations in aging time scale of BC particles in polluted atmosphere over central-eastern China. The model results show that the aging time scale has a clear diurnal variation with a lower value in the daytime and a higher value in the nighttime. The shorter aging time scale in the daytime is due to condensation aging associated with intense photochemical reaction while the longer aging time scale in the nighttime is due to coagulation aging, which is much slower than that due to condensation. In Beijing, the aging time scale is 2 h or less in the surface layer in daytime, which is far below the fixed 1.2 days used in many models. As a result, the fraction of hydrophilic BC particles by the new scheme is larger than that by the scheme with fixed aging time scale though the mean aging time scale by the new scheme is much larger than 1.2 days. Hydrophilic fraction of BC particles increases with the increase of height. Over central-eastern China, the averaged aging time scale calculated by the new scheme is in the range from 12 h to 7 days, with higher values in regions far from the source areas. Hydrophilic fraction of BC particles is more than 90% at the higher levels in polluted atmosphere. Difference of simulated BC concentration with internal mixing and microphysical aging is within 5%, indicating that the assumption of internal mixing for BC particles to respond to in-cloud scavenging is more appropriate than the external mixing assumption in polluted atmosphere over central-eastern China..|
|30.||Zhe Wang, Xiaole Pan, Itsushi Uno, Jie Li, Zifa Wang, Xueshun Chen, Pingqing Fu, Ting Yang, Hiroshi Kobayashi, Atsushi Shimizu, Nobuo Sugimoto, Shigekazu Yamamoto, Significant impacts of heterogeneous reactions on the chemical composition and mixing state of dust particles
A case study during dust events over northern China, Atmospheric Environment, 10.1016/j.atmosenv.2017.03.044, 159, 83-91, 2017.01, The impact of heterogeneous reactions on the chemical components and mixing state of dust particles are investigated by observations and an air quality model over northern China between March 27, 2015 and April 2, 2015. Synergetic observations were conducted using a polarization optical particle counter (POPC), a depolarized two-wavelength Lidar and filter samples in Beijing. During this period, dust plume passed through Beijing on March 28, and flew back on March 29 because of synoptic weather changes. Mineral dust mixed with anthropogenic pollutants was simulated using the Nested Air Quality Prediction Modeling System (NAQPMS) to examine the role of heterogeneous processes on the dust. A comparison of observations shows that the NAQPMS successfully reproduces the time series of the vertical profile, particulate matter concentration, and chemical components of fine mode (diameterï¿½≤ï¿½2.5ï¿½μm) and coarse mode (2.5ï¿½μmï¿½<ï¿½diameterï¿½≤ï¿½10ï¿½μm) particles. After considering the heterogeneous reactions, the simulated nitrate, ammonium, and sulfate are in better agreement with the observed values during this period. The modeling results with observations show that heterogeneous reactions are the major mechanisms producing nitrate reaching 19ï¿½μg/m3, and sulfate reaching 7ï¿½μg/m3, on coarse mode dust particles, which were almost 100% of the coarse mode nitrate and sulfate. The heterogeneous reactions are also important for fine mode secondary aerosols, for producing 17% of nitrate and 11% of sulfate on fine mode dust particles, with maximum mass concentrations of 6ï¿½μg/m3 and 4ï¿½μg/m3. In contrast, due to uptake of acid gases (e.g. HNO3 and SO2) by dust particles, the fine mode anthropogenic ammonium nitrate and ammonium sulfate decreased. As a result, the total fine mode nitrate decreased with a maximum of 14ï¿½μg/m3, while the total fine mode sulfate increased with a maximum of 2ï¿½μg/m3. Because of heterogeneous reactions, 15% of fine mode secondary inorganic aerosols and the entire coarse mode nitrate and sulfate were internally mixed with dust particles. The significant alterations of the chemical composition and mixing state of particles due to heterogeneous reactions are important for the direct and indirect climate effects of dust and anthropogenic aerosols..
|31.||Xiaole Pan, Itsushi Uno, Yukari Hara, Kazuo Osada, Shigekazu Yamamoto, Zhe Wang, Nobuo Sugimoto, Hiroshi Kobayashi, Zifa Wang, Polarization properties of aerosol particles over western Japan
Classification, seasonal variation, and implications for air quality, Atmospheric Chemistry and Physics, 10.5194/acp-16-9863-2016, 16, 15, 9863-9873, 2016.08, Ground-based observation of the polarization properties of aerosol particles using a polarization optical particle counter (POPC) was made from 27 October 2013, to 31 December 2015, at a suburban site in the Kyushu area of Japan. We found that the depolarization ratio (DR, the fraction of s-polarized signal in the total backward light scattering signal) of aerosol particles showed prominent seasonal variability, with peaks in spring (0.21-0.23) and winter (0.19-0.23), and a minimum value (0.09-0.14) in summer. The aerosol compositions in both fine mode (aerodynamic diameter of particle, Dp < 2.5 μm) and coarse mode (2.5 μm < Dp < 10 μm), and the size-dependent polarization characteristics were analyzed for long-range transport dust particles, sea salt, and anthropogenic pollution-dominant aerosols. The DR value increased with increasing particle size, and DR= 0.1 was a reliable threshold value to identify the sphericity of supermicron (Dp > 1 μm) particles. Occurrence of substandard air quality days in Kyushu was closely related with mixed type (coexistence of anthropogenic pollutants and dust particles in the atmosphere), especially in winter and spring, indicating that dust events in the Asian continent played a key role in the cross-boundary transport of continental pollution. Backward trajectory analysis demonstrated that air masses originating from the western Pacific contained large amounts of spherical particles due to the influence of sea salt, especially in summer; however, for air masses from the Asian continent, the dependence of number fraction of spherical particles on air relative humidity was insignificant, indicating the predominance of less-hygroscopic substances (e.g., mineral dust), although the mass concentrations of anthropogenic pollutants were elevated..
|32.||Ruizhu Huang, Huansheng Chen, Baozhu Ge, Shiquan Yao, Zhe Wang, Wenyi Yang, Xueshun Chen, Lili Zhu, Si Huang, Zifa Wang, Numerical study on source contributions to PM2.5 over Beijing-Tianjin-Hebei area during a severe haze event, Huanjing Kexue Xuebao / Acta Scientiae Circumstantiae, 10.13671/j.hjkxxb.2015.0046, 35, 9, 2670-2680, 2015.09, Identification of the source regions of PM2.5 and quantification of theircontributions are critical for efficient haze pollution control. In this study, the Nested Air Quality Prediction Model System (NAQPMS) coupled with an online source-tagging module was employed to simulate an extreme severe haze episode over Beijing-Tianjin-Hebei (BTH) area in January 2013. A detailed quantification of the source contributions from different regions was provided. The simulation was validated through comparisonwith surface observations, which suggested that the model could reasonably reproduce the temporal and spatial variations of PM2.5 concentrations during this episode. The results of the source-tagging calculation suggested that local emissions were the dominated sources of the surface PM2.5, accounting for 29.8% to 63.7% contributions of the surface PM2.5 concentrations. On the other hand, PM2.5 at 800 m layer was mainly contributed by the sources of the surrounding areas with the contributed ratio from 69.3% to 86.3%. For the most polluted southeast BTH area (including Xingtai, Handan, Cangzhou and Hengshui), emissions from Shandong and Henan provinces had significant contribution to the PM2.5 pollution with the largest contributions 25.2% and 31.5% at surface and 800 m layer, respectively. Therefore, the control of haze pollution over BHT areas should not only focus on the collaborative emission control within BHT areas but also take into account the joint emission control for BHT regions, Shandong and Henan Provinces..|
|33.||Si Huang, Xiao Tang, Wenshuai Xu, Zhe Wang, Huansheng Chen, Jie Li, Qizhong Wu, Zifa Wang, Application of ensemble forecast and linear regression method in improving PM10 forecast over Beijing areas, Huanjing Kexue Xuebao / Acta Scientiae Circumstantiae, 10.13671/j.hjkxxb.2014.0728, 35, 1, 56-64, 2015.01, In this study, ensemble forecast combined with linear regression method is used to reduce the uncertainty in air quality models. Firstly, the PM10 forecasts by three models (NAQPMS, CAMx and CMAQ) in EMS-Beijing are evaluated over Beijing areas. In order to improve the forecast performance, the linear regression method (REG) is used to combine the forecast results of the three models and is compared with the ensemble mean method. The results show that for single model forecast, great difference exists among different models and no model performs much better for all statistic indexes than the other two models. Overall, CMAQ performs better in tendency prediction, while NAQPMS has smaller root mean square errors than the other two models. Ensemble mean method presents poor performance in improving the PM10 forecasts from the three models. On the other hand, REG brings significant improvement of the PM10 forecast. When an appropriate training length (36 days) is applied, the root mean square errors of PM10 forecast over 28 stations of Beijing is reduced by 32%~43% when using REG and the bias decreased considerably to 5.8 μgï¿½m-3. This result implies that REG can greatly improve forecast performance than single model and ensemble mean forecast. Furthermore, the REG also greatly improve capturing of pollution episode forecast..|
|34.||Zi Fa Wang, Jie Li, Zhe Wang, Wen Yi Yang, Xiao Tang, Bao Zhu Ge, Pin Zhong Yan, Li Li Zhu, Xue Shun Chen, Huan Sheng Chen, Wei Wand, Jian Jun Li, Bing Liu, Xiao Yan Wang, Wei Wand, Yi Lin Zhao, Ning Lu, De Bin Su, Modeling study of regional severe hazes over mid-eastern China in January 2013 and its implications on pollution prevention and control, Science China Earth Sciences, 10.1007/s11430-013-4793-0, 57, 1, 3-13, 2014.01, The Nested Air Quality Prediction Model System (NAQPMS) was used to investigate the temporal and spatial variations of PM2.5 over tropospheric central eastern China in January 2013. The impact of regional transport and its implications on pollution prevention and control were also examined. Comparison between simulated and observed PM2.5 showed NAQPMS was able to reproduce the evolution of PM2.5 during heavy haze episodes. The results indicated that regional transport of PM2.5 played an important role in regional haze episodes in the city cluster including Hebei, Beijing and Tianjin (HBT). The cross-city clusters transport outside HBT and transport among cities inside HBT contributed 20%–35% and 26%–35% of PM2.5 as compared with local emission, in HBT respectively. To meet the Air Quality Standards for Grade II, 90%, 90% and 65% of emissions would have to be cut down in Hebei, Tianjin and Beijing, if non-control strategy was taken in the surrounding city clusters of HBT. This implicated that control of emissions in one city cluster is not sufficient to reduce regional haze events, and joint efforts among city clusters are essential. Besides regional transports, two-way feedback between boundary-layer evolution and PM2.5 also significantly contributed to the formation of heavy hazes, which contributed 30% of monthly average PM2.5 concentration in HBT..|