Concentration Distribution Characteristics Research Articles

Measurement-based evaluation of the effect of an over-track-exhaust ventilation system on the particulate matter concentration and size distribution in a subway

To reveal the influence of an over-track-exhaust (OTE) system on particulate matter (PM) concentration and size distribution in underground stations, field measurements were performed at a subway station both in the tunnel ventilation and non-ventilation seasons. By regulating the operating conditions of the OTE system and analyzing different particle size ranges, the characteristics of PM concentration and particulate size distribution under different OTE conditions were obtained. The results show that the normal operation of the OTE system slightly reduces PM concentration, but the effect is negligible. However, it was found that PM concentration increases under long-time operation of the OTE system if the ambient air quality is poor. When the OTE system is operating, the removal efficiencies of particles larger than 2.5 μm are relatively higher. However, the proportion of fine particles (<PM2.5) increases because more fine particles enter the station owing to negative pressure. Correlation analyses of different zones also showed the same result and identified the PM source for each zone. Moreover, the variation trends of the daily average concentration of PM in each zone are in accordance with the ambient environment; thus, the external environment may have a strong influence on subway air quality.

Coupling control on pillar stress concentration and surface cracks in shallow multi-seam mining

In order to ensure safe mining and reduce surface damage in shallow multi-seam mining, the failure characteristics of interburden strata with different coal pillars offset distances between pillars in the upper and lower seams, the distribution characteristics of stress concentration in coal pillars, and the development characteristics of stratum cracks and subsidence were investigated by physical and UDEC2D simulation. Meanwhile, the effect of different coal pillar offset distances on stress concentration of coal pillar and development of stratum cracks were studied. Based on those results, a formula for safe mining and reducing surface damage was established, which provided a theoretical basis for safe and environmentally friendly mining in shallow multi-seam. According to the results, the optimal coal pillar offset distance (the side to side horizontal distance of the upper and lower coal pillars) between the upper and lower coal seams was developed to reduce the stress concentration of coal pillars and surface damage. The results of this study have been applied in Ningtiaota coal mine and have achieved good results in safe and environmentally friendly mining.

Experimental analysis of spray behavior and lubrication performance under twin-fluid atomization

Abstract The spray behavior of a twin-fluid nozzle (TFN) can seriously affect lubrication performance, cutting fluid consumption and tool life during the manufacturing process. It is important to study the spray behavior and droplet size distribution characteristics of twin-fluid atomization to improve machining performance and reduce environmental pollution. In the current study, first, via a phase Doppler method, the spatial distribution of spray behavior of a TFN with and without a self-excited vibrating cavity (SVC) is analyzed and compared. Then, under various gas-to-liquid mass ratio values, the counts percent and cumulative distributions of droplets of a TFN with different SVC structures are further investigated. In addition, comparative investigations of the effects of different TFNs on the lubrication performance are conducted. The results show that the SVC structural parameter and gas-to-liquid mass ratio have an important influence on the secondary atomization of a TFN with an SVC, which significantly affects the spray behavior and droplet size distribution characteristics. The velocity differences between the gas-liquid two phases and the strong turbulence around the SVC are the key factors affecting the secondary atomization. The SVC can significantly increase the spatial coverage of droplets and improve the droplet spatial distribution characteristics of diameter and number concentration. The TFN with an improved SVC has better spray behavior and droplet size distribution characteristics, resulting in reductions in tool wear, cutting temperature and surface roughness of approximately 24.84 %, 21.24 % and 31.86 %, respectively, compared with the TFN without an SVC.

Hydrochemical composition, distribution, and sources of typical organic pollutants and metals in Lake Bangong Co, Tibet.

Lake Bangong Co is a special lake in western Tibet, with characteristics of increased salinity from the eastern area to the western area. Due to its remote location and poor environmental conditions, there are few background data on the water environment of this lake. In this study, the water chemical composition of Lake Bangong Co was studied, and the concentration levels, distribution characteristics, and pollution sources of polycyclic aromatic hydrocarbons (PAHs), phthalic acid esters (PAEs), and metals (As, Pb, Cr, Mn, Cu, Cd, Ni, and Zn) were investigated. The hydrochemical characteristics of the lake showed significant spatial differences. Conductivity, salinity, degree of mineralization, total hardness, Cl-, and SO42- generally increased from the eastern part to the western part. Most water quality parameters met the class III standards of the Chinese surface water standards; however, the Cl- and SO42- concentrations in the western part exceeded the surface water standard limits. ΣPAH and ΣPAE concentrations in lake water have no significant relationship with hydrochemical parameters. Among the 16 target PAHs, 4 PAH monomers with a (5 + 6)-ring were not detected in the lake water. The main sources of PAHs included emissions from biomass combustion, petroleum volatilization, and automobile exhaust. Six PAE monomers were detected at all sampling sites with relatively low concentrations, and di-2-ethylhexyl phthalate (DEHP) and di-n-butyl phthalate (DBP) were the main pollutants. The main source of PAEs was domestic waste, which might be related to increasing human activities in this area recently. In general, the concentrations of metals in the water of Lake Bangong Co were lower than those in the regions affected by anthropogenic activities except As. The results of PCA showed that As, Cu, and Cr mainly originated from natural sources; Pb, Mn, and Cr came from both natural and anthropogenic sources; and Cd was highly likely from anthropogenic sources.

Therapeutic Drug Monitoring and Nephrotoxicity of Teicoplanin Therapy in Chinese Children: A Retrospective Study.

PurposeThis study aims to 1) describe the distribution characteristics of teicoplanin trough concentration (Cmin) and explore the related influencing factors and 2) evaluate the nephrotoxicity of teicoplanin in children.Patients and MethodsA cohort of children who were treated with teicoplanin intravenously were included in this retrospective study. Regression analysis was performed to explore the factors associated with the fluctuations of teicoplanin Cmin and the development of nephrotoxicity. Classification and regression tree analysis was used to identify the population at high risk for teicoplanin nephrotoxicity.ResultsA total of 269 plasma samples from 186 children were collected. Underexposure (Cmin < 10 mg/L) was documented in 52.7% of cases. The Cmin/dose after administering the loading dose was strongly associated with age (P = 0.008), weight (P = 0.039), and serum creatinine (P = 0.022). The Cmin/dose after administering the maintenance dose was strongly associated with gender (P = 0.014) and serum creatinine (P = 0.006). Cmin (P = 0.012) and the concomitant treatment with amphotericin B (P = 0.001) were the independent risk factors for teicoplanin-related nephrotoxicity. Children who were concomitantly treated by amphotericin B with teicoplanin Cmin > 9.81 mg/L or patients with teicoplanin Cmin > 21.94 mg/L were at high risk for nephrotoxicity.ConclusionThe fluctuations of teicoplanin Cmin could be affected by age, weight, gender, and serum creatinine. Cmin and concomitant treatment with amphotericin B were the independent risk factors for nephrotoxicity. We suggested that the therapeutic drug monitoring of teicoplanin should be performed in children.

Inversion and distribution of total suspended matter in water based on remote sensing images-A case study on Yuqiao Reservoir, China.

In this paper, Yuqiao Reservoir is taken as the research object. The total suspended matter (TSM) produced by the economic development in the upper reaches of the reservoir and its surrounding areas has brought great ecological harm to the safe operation of the reservoir. Satellite remote sensing technology provides a good way to obtain the temporal and spatial variation of TSM in the study area. Two field surveys were carried out in the Yuqiao Reservoir, a total of 44 sampling points collected in the two tests. The spectral data and concentration of TSM were obtained. We developed and validated a robust empirical model to estimate the concentration of TSM in the water of the Yuqiao Reservoir for the first time. The TSM distribution map of the Yuqiao Reservoir in 2013-2018 is retrieved based on Landsat 8 OLI images. This paper analyzes the spatial distribution characteristics of TSM concentration in the Yuqiao Reservoir for several years, as well as the interannual, seasonal, and monthly variation laws and development trends. The results show that the spatial distribution of TSM in Yuqiao Reservoir shows a decreasing trend from the periphery to the center; the interannual changes are mainly as follows: The annual change trend of TSM in Yuqiao Reservoir is not obvious; the seasonal changes are significant: the highest in summer (higher than 40mg/L), the second in autumn, and the lowest in spring and winter (lower than 15mg/L); and the monthly changes show regular fluctuations: In a year cycle, the concentration of TSM generally shows an inverted V-shaped trend; that is, TSM increases gradually from January to August and decreases gradually from August to December. The research results of this paper can be applied to other similar types of land water bodies, which will promote the wide application of Landsat 8 OLI images in the monitoring of TSM in lakes, rivers, and reservoirs in different regions across China, and provide data support for the scientific management of the safe operation of research areas. PRACTITIONER POINTS: The monitoring model of TSM in Yuqiao Reservoir was built for the first time. Temporal and spatial analysis of TSM concentration in Yuqiao Reservoir for the first time. The concentration of TSM is in Yuqiao Reservoir greatly affected by wind speed and precipitation.

Study of the generation and diffusion of bioaerosol under two aeration conditions

Given that studies on actual sewage treatment plants are often affected by environmental conditions, it is challenging to clearly understand the associated bioaerosol generation and diffusion characteristics during the aeration process. Therefore, to enhance understanding in this regard, in this study, bioaerosol generator was used to simulate bioaerosol generation and diffusion under two aeration modes, i.e., bubble bottom aeration and brush surface aeration. The total concentration range of culturable bacteria in the bioaerosol produced by bubble bottom aeration and that produced by brush surface aeration were 300–3000 CFU/m3. Under bubble bottom aeration, the generated bioaerosol was symmetrically distributed around the source point, whereas under brush surface aeration, it was primarily distributed in the forward direction of the rotating brush surface. These bioaerosols from bubble bottom aeration predominantly consisted of particles with sizes below 3.3 μm, particularly those with sizes in the range 1.1–2.1 μm. On the contrary, the bioaerosols produced via brush surface aeration predominantly consisted of particles with sizes above 3.3 μm. The distribution characteristics of population structure in the two aeration modes were consistent with the distribution characteristics of concentration in the corresponding models. Additionally, the results showed that when the aeration process is unaffected by environmental conditions (particle matters, wind direct, wind speed, etc.), the bioaerosol components originate primarily from the parent sewage or sludge, and do not diffuse far from the source point. Therefore, source reduction (capping or sealing) can be recommended as the primary control strategy for bioaerosols in sewage treatment plants. The adoption of such measures will significantly limit the diffusion of bioaerosols, thereby reducing the potential risks associated with human exposure.

Evaluation of particulate matter concentrations according to cooking activity in a residential environment.

This study aimed to determine the ventilation conditions required for suitable indoor air quality management during cooking in a typical South Korean residential home. We measured the concentrations of particulate matter (PM10) and fine particulate matter (PM2.5) under different ventilation conditions during the cooking of different food materials in the kitchen of a multi-family house, which is the representative residential space in South Korea. Pork belly and mackerel, which are the staple meat and fish products of Korean people, were prepared (200g of each) and cooked via roasting. The PM10 and PM2.5 concentrations were measured three times for 1h at 1min intervals under twelve ventilation conditions. To investigate the PM10 and PM2.5 concentration distribution characteristics and the reduction effect according to ventilation condition, the ratio of the concentration during cooking to the initial concentration was calculated for each condition. Factors causing the emission of PM10 and PM2.5 for each food material and under each ventilation condition were analyzed using principal component analysis and verified using one-way analysis of variance and post hoc analysis. The PM10 and PM2.5 concentrations generated during the cooking of pork belly and mackerel reached their maximum values when no ventilation was used. Under this condition, PM10 concentrations were 246.27 and 1227.71μg/m3 while the PM2.5 concentrations were 161.93 and 760.82μg/m3 for pork belly and mackerel cooking, respectively. The PM10 and PM2.5 concentrations were also found to be high when a range hood and air cleaner were used, indicating that it is necessary to improve the performance of ventilation devices and to use appropriate ventilation methods. The use of natural ventilation exhibited a high PM10 and PM2.5 reduction effect compared with the ventilation conditions that used ventilation devices. Using natural ventilation together with ventilation devices was found to be the most effective method of reducing the PM10 and PM2.5 generated during cooking. In conclusion, PM10 and PM2.5 concentrations generated during the cooking of pork belly and mackerel varied depending on the ventilation condition, but they were high when inappropriate ventilation methods were used. Therefore, using appropriate ventilation conditions is effective in reducing PM10 and PM2.5 generated during cooking.

Study on the Distribution of Surface Chlorophyll-a and Subsurface Chlorophyll Maximum in the Southeastern Yellow Sea According to the Typhoon Paths and Water Masses

The influences of physiochemical processes on the distribution of surface chlorophyll-a (Chl-a) and subsurface chlorophyll maximum (SCM) were investigated in the southeastern Yellow Sea (YS) during summer in 2010–2013. The paths of typhoons from 2010 to 2012 were different, resulting in different patterns of surface Chl-a and the SCM layer. Surface Chl-a appeared in high concentrations at the coastal area in 2010 and 2012, and at all stations in 2011. The SCM layer descended in the central area in 2012 and rose in the coastal area in 2010, and lifted at all stations in 2011. The SCM layer was shallower from the open sea located at the Yellow Sea Cold Water to the coastal area due to tidal fronts and topographic properties. As a result, the distribution characteristics of Chl-a concentration according to typhoon paths and water masses may affect the marine ecosystem in the YS.

Metro train carriage combustion behaviors – Full-scale experiment study

A full-size metro train carriage (internal dimensions 19.1 m × 3.0 m × 2.65 m) is burned to investigate the fire growth process during the initial-3-minute. The heat release rate (HRR), window glass rupture characteristics, fire smoke concentration and inside temperature distribution characteristics are investigated quantitatively. The experiment results show that total heat release (THR) can be up to 1009.49 MJ in 3 mins. It is observed that the fire during the initial-3-minute can be divided into three stages. The t2 fire, linear growth fire and stable fire are all observed in the initial-3-minute, and a series of fitted HRR is achieved for the three stages. The fire is found to be ventilation controlled after about 26 s, and a formula computing peak stable HRR with known ventilation condition is proposed. The trend of inner carriage smoke temperature, CO2 and CO concentration is investigated to evaluate harm to passengers, and the production coefficient curves of gases are also analyzed. The CO concentration measured by calorimetric system has been fitted by formulas in three stages. The proposed formulas can provide reference for risk assessment, evacuation planning as well as fire rescue.

Numerical study on DPM dispersion and distribution in an underground development face based on dynamic mesh

In 2012, the International Agency for Research on Cancer (IARC) classified diesel particulate matter (DPM) as a carcinogen to human. With the increased usage of diesel equipment in underground mines, miners have a high risk of over-exposure to DPM, which has drawn many concerns from the public. This study used computational fluid dynamics (CFD) to analyse the DPM dispersion and concentration distribution characteristics in an underground development face based on an onsite experiment. The DPM emitted from a moving loader under a forcing auxiliary ventilation system was simulated. The motion of the load-haul-dump (LHD) in the tunnel was represented by a dynamic mesh method. The species transport approach was applied to study the DPM behaviours. High DPM concentration zones were then identified based on the simulation results. The results could provide guidelines for work practices and be helpful to an optimum auxiliary ventilation design to reduce underground miner exposure.

Spray characteristics of direct injection injectors with different nozzle configurations under flash-boiling conditions

This investigation utilized four gasoline direct injection (GDI) injectors with different nozzle lengths and step hole diameters to analyze the influences of nozzle structure on the superheated plume and spray collapse under different superheat degrees. The spray behaviors of were recorded by using high-speed shadowgraphs. In addition, the spray concentration distribution, spray development, and spray swelling characteristics under different superheat conditions were analyzed. The experimental results showed that hole length and step hole diameter affected the widths of the spray plumes, which then affected the spray characteristics. Wider spray plumes enhance plume interactions and promote reduced spray penetration. This causes spray to enter the transition regime at a lower degree of superheat. In addition, the transition regime exhibits better spray characteristics than the subcooled and flare flash boiling regimes. Injector with smaller hole length and larger step hole diameter exhibits stronger adaptability while utilizing the remarkable spray characteristics in the transition regime, owing to the greater length of the spray transition regime.

Characteristics and Source of Dissolved Organic Matter in Lake Hulun, A Large Shallow Eutrophic Steppe Lake in Northern China

Lake Hulun, the fifth largest lake in China, is a typical eutrophic steppe lake located in the Hulun Buir Prairie. The dissolved organic matter (DOM) in the water of Lake Hulun has a high concentration. However, little is known about the occurrence characteristics and source of the DOM in Lake Hulun. The spatial and temporal distribution characteristics of DOM concentration in Lake Hulun were thoroughly surveyed, and the optical characteristics, fluorescence components and sources of DOM were analyzed by excitation emission matrix (EMM) and parallel factor analysis (PARAFAC) technology. The DOM concentration was 6.46–42.87 mg C/L, and was highest in summer and lowest in winter. The difference in the spatial distribution of DOM in winter was significant due to the ice over, and showed a trend where the concentration near the shore was higher than that in the center of the lake. Three humic-like components and one component consisting of a mixture of humic-like and protein-like substances of DOM were identified, with the former being prevalent. The humification index of DOM was 2.22–9.92, indicating that the DOM has a high degree of humification. The DOM is mainly derived from terrestrial sources, with the highest proportion (91.0% ± 8.1%) found in winter and the lowest (66.2% ± 7.7%) in summer. Given that the DOM in Lake Hulun is mainly dominated by humic-like components with a high degree humification, the DOM may have low bioactivity. However, this is just a preliminary analysis and judgment, and it is necessary to conduct other experiments such as biodegradation experiments to further study the bioavailability of DOM in Lake Hulun.

On-site investigation of the concentration and size distribution characteristics of airborne fungi in a university library

It is important to investigate fungal air quality in libraries because they represent a complex indoor environment. The aim of the study was to quantitatively investigate airborne fungal contamination levels based on field measurements in autumn and winter in four selected library rooms (compact stack, lending room, reading room, study room) in a university library building, as well as the effects of several factors on the culturability of airborne fungi. Airborne fungal levels varied by room, with the highest fungal levels in the reading room (634 ± 275 CFU/m3) and the lowest in the lending room (486 ± 177 CFU/m3). Airborne fungal concentrations were significantly different with seasonal variation (p < 0.05) for all rooms except for the reading room. The size distribution analysis showed that the most airborne fungi were 1.1–3.2 μm in size; based on the schematic diagram of the human respiratory system, more than 80% of airborne fungi could be deposited in the lower respiratory tract (0.65–4.7 μm). Indoor/outdoor airborne fungal concentration ratios were below 1.0 for all four rooms during autumn and winter, showing that outdoor fungi are the main source of indoor fungi. Pearson correlations showed that the fungal concentration was significantly positively correlated with both temperature (r = 0.531, p < 0.05) and relative humidity (r = 0.555, p < 0.05). Indoor temperature, indoor relative humidity and number of open windows significantly positively affected airborne fungal concentration in a multiple linear regression model (p < 0.05). This paper provides fundamental data on fungal contamination that can help experts in indoor air quality to develop guidelines for airborne fungi in libraries and create a safe environment for library patrons and staff.

Variation Characteristics of Mass Concentration of Inhalable Particles in Qingdao, China

The geographical condition of Qingdao, China is relatively special; the transport of various inland pollutants, the emissions of marine aerosol and local pollutants will have an impact on the changes of atmospheric aerosol concentration. By using the stability classification method, trajectory clustering analysis and the NOAA HYSPLIT model, the seasonal distribution characteristics of atmospheric inhalable particulate matter concentration in Qingdao, China and its relationship with meteorological conditions, mixed layer height, and the seasonal characteristics of Qingdao pollutant transport were analyzed. The results show that the variation trends of PM2.5 and PM10 were about the same, and there are obvious seasonal differences, which are high in winter and spring, and low in summer and autumn. The concentration of inhalable particulate matter has a negative correlation with temperature, wind speed and relative humidity. The concentration of inhalable particulate matter is distinct in different relative humidity ranges. When the wind speed is less than 3 - 4 m/s, there are more inhalable particles, while the mass concentration shows obvious reduction with the wind speed more than 4 m/s. There is a significant negative correlation between the mass concentration of pollutants and the daily maximum mixed layer height. The larger the concentration of pollutants, the smaller the thickness of the daily largest mixed layer. Conversely, the smaller the mass concentration of pollutants, the larger the thickness of the daily largest mixed layer. The pollutant transport in Qingdao has obvious seasonal characteristics. The air mass in spring, autumn and winter is mainly medium-long distance transport from Mongolia and southern Russia, and medium-short distance transport from Inner Mongolia and northeast of China. The source of air masses in summer is mainly transported from the eastern and sea areas.

兰州市SO2时空动态分布特征及其与城市生态系统的关系

PDF HTML阅读 XML下载 导出引用 引用提醒 兰州市SO2时空动态分布特征及其与城市生态系统的关系 DOI: 10.5846/stxb201903220542 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家重点研发计划项目（2016YFC0500907）；甘肃省重点研发计划（17YF1FA120）；兰州市科技计划（2017RC69） Spatial and temporal dynamic distribution characteristics of SO2 in Lanzhou City and its relation with urban ecosystem Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:强化城市大气污染物多尺度监测手段，辨识污染物时空演变规律及其与城市生态系统各要素间的相互关系，可为城市大气环境质量综合管控提供科学依据。利用OMI、EOS/MODIS卫星影像及其他统计类数据，在分析了兰州市2006-2016年对流层SO2柱浓度的时空分布特征基础上，进一步探讨了NDVI、工业总产值、汽车保有量等城市自然经济社会生态要素的结构变化与SO2浓度变化的关系。结果表明：1）兰州市对流层SO2空间分布不均，呈现出以河谷低海拔区域分布为中心，向西北、东南山地两侧递减的"倒U"形格局；2）近10年内，兰州市大气SO2柱浓度值在0.033-0.25（多布森单位）之间，总体呈下降趋势，年均降幅为14%，降速为0.02（多布森单位）/a；3）兰州市大气SO2柱浓度变化特征与城市工业生产和交通因素关系密切，又受地形、季节风向等气象气候条件制约；4）兰州市NDVI指数与大气SO2柱浓度值相关性明显，兰州市植被覆盖度较低，植被指数为0.09-0.66，对SO2净化能力有限。综合以上结果，本研究认为，通过调控城市社会、经济、自然生态系统结构，并适当采用基因工程等科学技术来增加地表植被覆盖量，是下一步兰州市大气环境质量管理的重要举措之一。 Abstract:Strengthen the methods of multi-scale monitoring for urban air pollutants, identified the temporal and spatial development of pollutants and their relationships with the elements of urban ecosystem can provide a scientific basis for comprehensive management and control of urban air quality. This research analyzed the temporal and spatial distribution characteristics of SO2 column concentration in the troposphere of Lanzhou City from 2006 to 2016, based on OMI, EOS/MODIS satellite images, and other statistical data. The paper further discussed the relationship between the SO2 concentration and urban structural changes of natural, economic, and social elements, such as NDVI, industrial production, car parc. The results showed that 1) the spatial distribution of SO2 presented an inhomogeneous characteristic in the troposphere in Lanzhou city, which showed an inverted U-shaped pattern with the low elevation of the valley as the center and decreased on both sides of the northwest and southeast mountain areas. 2) In the past 10 years, the concentration of SO2 column in Lanzhou was between 0.033-0.25 Dobson unit. It showed the downward trend with an average annual decline of 14%, and with the declining rate of 0.02 Dobson unit/a. 3) The characteristics of atmospheric SO2 column concentration change of Lanzhou city were closely related to urban industrial production and traffic factors, and also restricted by the meteorological and climatic conditions such as topography and seasonal wind direction. 4) The NDVI index of Lanzhou city was significantly correlated with the concentration of atmospheric SO2 column. Lanzhou city had a low vegetation coverage, with the vegetation index of 0.09-0.66. It had a limited ability to purify SO2. Based on the above results, we consider that it is one of the important measures for Lanzhou's atmospheric environmental quality management to increase the surface vegetation coverage by adjusting the structure of urban social, economic, and natural ecosystems, and using appropriate science and technology such as genetic engineering. 参考文献 相似文献 引证文献

An eigenvector spatial filtering based spatially varying coefficient model for PM2.5 concentration estimation: A case study in Yangtze River Delta region of China

Ordinary interpolation using PM2.5 ground monitoring observations can seldom reveal the PM2.5 concentration distribution characteristics due to the uneven distribution of monitoring stations and because ordinary linear regression often neglects the spatial autocorrelation among geographical locations. In this study, we developed an eigenvector spatial filtering based spatially varying coefficient (ESF-SVC) model to estimate ground PM2.5 concentration. To generate and analyze the spatiotemporal distribution of PM2.5 concentration in the China's Yangtze River Delta (YRD) region, ESF-SVC model which uses a set of satellite remote sensing data, factory locations, and road networks, was fitted at different time scales from December 2015 to November 2016. Comparisons among the ESF-SVC, eigenvector spatial filtering (ESF) and geographically weighted regression (GWR) models suggest that the ESF-SVC model with an average annual and seasonal adjusted R2 of 0.684, is 10.3 and 13.8% higher than the GWR and ESF models, respectively. The average annual and seasonal cross validation root mean square error (RMSE) of the ESF-SVC models lower than the GWR and ESF models. PM2.5 concentration distribution maps for annual and seasonal were produced to illustrate YRD region's spatiotemporal characteristics. In summary, an ESF-SVC model offers a reliable approach for PM2.5 concentrations estimation in large area.

China’s corridors-in-the-sky design and space-time congestion identification and the influence of air routes’ traffic flow

With rapid development of air transportation, the airspace structure of the future will need to be flexible and dynamic to accommodate the increase in traffic demand. The corridors-in-the-sky has become a new technology to support the full exploitation and utilization of airspace resources. This paper proposes a method of designing corridor, identifying congestion state, and analyzing the influence of air routes’ traffic flow. From this, we have reached a number of conclusions. (1) The congestion periods present the multi-peak “wavy” scattered distributions and the peaks back-end agglomeration characteristics in the whole day. (2) The congestion segments present the structural characteristics of unbalanced coverage and concentrated distribution to the crossing points. The corridors with high congestion level present as an italic “N-shaped” frame, which presents incomplete penetration of short segments. (3) For the temporal and spatial interaction, there are two types of congestion segments, and there are some common congestion periods in different congestion segments of multiple corridors. The high-density air route plays a relatively decisive role in corridor congestion, and the influence of two directions is unbalanced. This research can provide a basis for the dynamic evaluation of China’s airspace resources and corridors construction in the future.

The Influence of Multi-Scale Atmospheric Circulation on Severe Haze Events in Autumn and Winter in Shanghai, China

Severe haze events have many adverse effects on agricultural production and human activity. Haze events are often associated with specific patterns of atmospheric circulation. Therefore, studying the relationship between atmospheric circulation and haze is particularly important for early warning and forecasting of urban haze events. In order to study the relationship between multi-scale atmospheric circulation and severe haze events in autumn and winter in Shanghai, China, we used a T-mode objective classification method to classify autumn and winter atmospheric circulation patterns into six types based on sea level pressure data from 2007 to 2016 in the Shanghai area. For the period between September 2016 and February 2017, we used the Allwine–Whiteman method to classify the local wind in Shanghai into three categories: stagnation, recirculation, and ventilation. By further studying the PM2.5 concentration distribution, visibility distribution, and other meteorological characteristics of each circulation type (CT) and local wind field type, we found that the Shanghai area is most prone to severe haze when exposed to certain circulation patterns (CT1, CT2, and CT4), mainly associated to the cold air activity and the displacement of the high pressure system relative to Shanghai. We also found that the local wind fields in the Shanghai area are dominated by recirculation and stagnation events. These conclusions were further verified by studying a typical pollution process in Shanghai in November 2016 and the pollutant diffusion path using the HYSPLIT (Hybrid Single Particle Lagrangian Integrated Trajectory model) simulation model.

Study on the control effect of two different forms of side suction hoods on pollutants

A suitable exhaust hood form has a great influence on the control effect of pollutants. This paper uses CFD technology to numerically simulate the airflow distribution characteristics and pollutant concentration distribution characteristics of the side hood before and after improvement. The results show that: (1) The airflow of the improved side suction hood is introduced from the front of hood to make the fresh air pass through the breathing area first and then takes away the hazardous substances, which is beneficial to the breathing health of workers. (2) When the exhaust velocity (V) is more than 3.5m/s, with the increase of the exhaust velocity, the concentration hazardous substances at each control point of the two forms of exhaust hood tends to be stable gradually. (3) When the exhaust velocity is less than 3.5m/s, the control effect of side suction hood with baffle is better than that without baffle, and the percentage of hazardous substances concentration at the same control point can be reduced by 12%-29%, or even higher.