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Characteristics and sources of PM2.5 in typical atmospheric pollution episodes in Beijing
WANG Zhi-juan1,HAN Li-hui1,CHEN Xu-feng2,CHENG Shui-yuan1,LI Yue1,TIAN Chuan1,XIE Hui1(1 College of Environmental & Energy Engineering,Beijing University of Technology,Beijing 100124,China;2 Tangshan Environmental Monitoring Station,Tangshan 063000,Hebei,China)To study the characteristics and sources of PM2.5 in typical atmospheric pollution episodes during winter and spring in Beijing,the samples of PM2.5 were collected at the air quality monitoring site during winter and spring from 12/2010 to 03/2011.The periods are typical seasons for two types of heavy air pollution,i.e.haze and dust to happen often.Concentration of PM2.5,elements,water soluble ions and organic and elemental carbons of PM2.5 were analyzed for typical haze,dust,unpolluted weather during winter and spring.The results indicated that daily concentrations of PM2.5 during haze and dust days were up to 301.8 μg/m3 and 284.8 μg/m3,that were 8.62 and 8.14 times of the daily standard of EPA.Enrichment factor method was used to analyze the natural sources or anthropogenic sources of different elements during non heavy air pollution periods.Polluting elements S,Cu,Zn,As,Se,Cd,Sb,Pb were mainly released from coal combustion,motor vehicle exhaust and waste burnt;while Na,Mg,Al,Ca,Fe were main crustal elements.NH+4,NO-3,SO2-4 were found to be the dominant ionic species of PM2.5.The value of OC/EC(4.085) exceeded 2 suggesting that the OC of Beijing during haze belongs to secondary pollution source.Concentrations of anthropogenic source elements S,Cu,Zn,As,Se,Cd,Sb,Pb in PM2.5during haze were higher than that of unpolluted weather and dust.The concentrations of secondary inorganic particles NH+4,NO-3,SO2-4 and secondary organic carbons of PM2.5 during haze were higher than that of another two types of weather.Concentrations of crustal elements Na,Mg,Al,Ca,Fe during dust days were higher than that of unpolluted weather and haze.PM2.5 were mainly released from coal combustion and industry,secondary reaction,soil,motor vehicle and waste burnt during winter and spring.Contribution of secondary reaction was higher than other sources during haze,while contribution of soil was higher than others during dust.
Research on the influencing factors of improving the resilience of emergency supply chain in the context of disasters
QIAN Cun-hua;CHEN Hai-bin;ZHOU Jun-gui;Improving the resilience of the emergency supply chain in the context of disasters is of great significance for improving disaster reduction and relief capabilities. This paper aims at the characteristics of emergency supply chains such as urgency, uncertainty, and government organization guarantee under sudden disasters, and finds out 16 factors that affect the resilience of emergency supply chains from five aspects of supply chain procurement system, transportation system, warehousing system and organization guarantee system, and information system. Then we use DEMATEL(decision experiment analysis method) to calculate the comprehensive impact matrix and solve the impact degree, affected degree, and centrality. The reason degree and hierarchical structure chart, and the ISM(Interpretative Structure Model) method are used to calculate the reachability matrix, and the multi-level recursive structure model of the influencing factors of the resilience of the emergency supply chain is built after the hierarchical classification. Then, the comprehensive analysis is conducted based on the results of the DEMATEL-ISM integrated modeling method. The results show that the influencing factors of the resilience of the emergency supply chain can be divided into 6 levels and 4 levels, in which the governance capacity of the local government is the fundamental influencing factor. Transport network management capability, infrastructure construction level, and information collaboration capability are indirect influencing factors; The storage capacity of emergency materials, warehouse throughput efficiency, transportation timeliness, and fault recovery capability are the direct influencing factors. Finally, according to the research results, it provides corresponding suggestions for maintaining the long-term operation of the emergency supply chain system and puts forward priority strategies and resource allocation strategies for improving the resilience of the emergency supply chain in the context of disasters, providing a theoretical basis for improving the resilience of the emergency supply chain.
Decomposition of influencing factors and peak prediction of carbon emissions in China
CHEN Tao;LI Xiaoyang;CHEN Bin;This paper aims to explore the influencing factors of China's carbon emissions and forecast the peak of carbon emissions. Firstly, Logarithmic Mean Divisia Index(LMDI) is used to evaluate the contribution value and contribution rate of energy emission intensity, energy structure, energy intensity, and economic development to the change of per capita carbon emission from 2011 to 2019. Secondly, according to the latest relevant national policies and scheduled development goals, the scenario analysis method is used to define the population changes, GDP, urbanization, the proportion of the secondary industry, and energy intensity respectively, and three different scenarios are set to increase the comprehensiveness and accuracy of the forecast results. Finally, the STIRPAT(Stochastic Impacts by Regression on Population, Affluence, and Technology) trained by ridge Regression is adopted to forecast carbon emissions in future years. The results show that:(1) From 2011 to 2019, China's per capita carbon emissions increased by 1.09 t cumulatively, among which economic development played a major role, and the cumulative contribution was about 5.61 t; However, the optimization of energy structure and the reduction of energy intensity play an inhibitory role, and the cumulative contributions are about-0.66 t and-3.86 t, respectively.(2) All three scenarios achieve a carbon peak before 2030, among which the CO2 emissions in the baseline scenario will reach the peak in 2027, about 11.087 billion tons, and the per capita CO2 emissions will be 7.69 tons. In the low emission reduction scenario, CO2 emissions will peak in 2029 at about 11.204 billion tons, with per capita CO2 emissions of 7.75 tons. In the high emission reduction scenario, the peak CO2 emission occurs in 2024, which is about 10.990 billion tons, and the per capita CO2 emission is 7.72 tons. The prediction of this result is consistent with the development trend and can provide a reference for the realization of the carbon peak in China.
Comprehensive evaluation method for the railway safety based on the entropy method and the grey relation analysis
FENG Yun-qing;LI Xue-mei;LI Xue-wei;School of Economics and Management,Beijing Jiaotong University;Firstly,this paper has set up two railway safety evaluation systems from the prediction and the result aspects separately based on the analysis of the railway operation safety factors. Secondly,the entropy method has been adopted to calculate the weight of each index that affects the railway safety from the prediction and the result perspective individually. From the weight calculation we can see that the "human factor"is the dominant factor that may lead to railway accidents. Besides,from the perspective of the railway safety consequences,"the damage of railway accidents " factor impacts the most on the railway safety goals. Thirdly,combined with the weight of each index from the prediction perspective,the grey relation grade of the railway safety is calculated using the grey relation analysis during the period from 1985 to 2007 and a railway safety curve was drawn to reflect the trend of the railway safety development. From the above results,it can be concluded that there are three stages in our railway safety development in the past 23 years. The first stage is from 1985 to 1990. In this stage,the railway safety level is low and has a trend of decline because of the low level of technical equipment and management. The second stage is from 1991 to 2000,the level of the railway safety get a great improvement. Although the safety data in some year has fluctuated,the overall trend has improved a lot. The third stage is from 2001 to 2007. Since 2001,the gray correlation degree of the railway safety is over 0. 8 and enters into a steady period. In general,the overall level of China's railway safety obtained an obvious improvement and the overall railway safety in China has reached a high level.
Application of combination weighting and TOPSIS in the assessment of urban regional resilience under flood disaster
MENG Xiao-jing;CHEN Xin;CHEN Jia-jing;YANG Hong-gang;To quantitatively assess the ability of urban regions to cope with rainstorm flood disasters, the assessment index system of urban resilience under flood disasters was established based on resilient city ideas. 21 indicators were determined from the three attributes of resistance, adaptability, and recovery, as well as the four dimensions of economy, society, ecological environment, and infrastructure. Based on the principle of minimum relative information entropy, the combined weights of indicators were determined by the Analytic Hierarchy Process(AHP) and Criteria Importance Though Intercrieria Correlation(CRITIC). The assessment model of urban resilience was established using the Technique for Order Preference by Similarity to the Ideal Solution(TOPSIS). Taking Xi'an as an example, the resilience of resistance, adaptability, and recovery attributes and the resilience of economic, social, ecological environment and infrastructure dimensions were evaluated in six areas including Xincheng District, Beilin District, Lianhu District, Baqiao District, Weiyang District, and Yanta District. The level of urban regional resilience was obtained. The results show that the attribute of resistance and adaptability are the main factors that affect the level of urban resilience. The dimension of ecological environment and infrastructure have a greater influence on the urban resilience level, while the dimension of economy and society have little influence on the urban resilience level. The resilience levels varied greatly among regions. The levels of resilience of resistance, adaptability, and recovery attributes are highest in Baqiao District. The level of economic resilience is highest in Yanta District, and all dimensions of resilience are weak in Beilin District and Lianhu District. Moreover, the resilience rating of Baqiao District is Class III, the resilience rating of Xincheng District and Weiyang District is Class II, and the resilience rating of Beilin District, Lianhu District, and Yanta District is Class I. The assessment results provide a reference for improving urban resilience and reducing flood disaster risk.
Research advance review for low-temperature NH3-SCR catalysts
LIU Ting1,WANG Ting-chun1,WU Rui-qing1,SHEN Bo-xiong2(1 Sinopec research institute of safety engineering,Qingdao 266071,China;2 College of Environmental Science and Engineering,Nankai University,Tianjing 300071,China)The present paper is aimed to give a summary and commentary on the research advances for low-temperature NH3-SCR catalysts,such as the selective catalytic reduction(SCR) of NOx with NH3 at low temperature.The catalysts mentioned above usually serve as a promising technique for NOx removal from the flue gases.When preparing this paper,we have searched through the comprehensive literatures dedicated to the field of low-temperature NH3-SCR catalysts.An outstanding example in this way is MnOx-based catalysts,VOx-based catalysts,another kind,as we mentioned about,and some other metal oxide-based catalysts.These catalysts with high surface area and well amorphous structure all display high catalytic activities for low-temperature SCR of NOx with NH3.The study of the mechanism and impact of SCR of NOx with NH3 at low temperature on CeO2 modified MnOx-based catalysts indicates that the adsorption of NH3,O2 and NOx for the catalysts play an important role in the low-temperature catalytic series along with SCR of NOx with NH3.The SCR reaction of NOx and NH3 to the CeO2 modified MnOx-based catalysts also prove to carry on the ER mechansm and LH mechanism.Research activities in this way indicate that preparing methods of catalysts,the catalyst support,and the modified metal oxide may all have strong impact on the catalytic activities for low-temperature SCR of NOx with NH3.The reaction of NH2— and gas NO,and then the composed NH2NO all tend to further decompose to give N2 and H2O and then resulted in a typical SCR mechanism reported for CeO2 modified MnOx-based catalysts.In this paper,we have also made a discussion over the deactivation mechanism of low-temperature NH3-SCR catalysts due to their reaction to water vapor and sulfur dioxide in the flue gases.The competitive adsorption of the water vapor with the reaction gases on the surface of the catalysts tends to decrease the catalytic function of the low-temperature catalysts.And,water vapor and sulfur dioxide in the flue gases may have a combined effect on the catalytic activity of the low-temperature catalysts.Besides,the resulted sulfates with the presence of water vapor and sulfur dioxide are likely to deposit on the surface of the catalysts and result in the deactivation of the low-temperature NH3-SCR catalysts.Future research tendency in the above-said key areas will surely bring great benefits to the development of such catalysts.
Safety risk assessment and three-dimensional path planning for UAV in complex urban low-altitude airspace
XIE Hua;HAN Site;YIN Jianan;JI Xiaohui;YANG Yichen;To meet the pressing need for improved safety and efficiency of low-altitude Unmanned Aerial Vehicle(UAV) flights in complex urban environments, a method for complex urban low-altitude UAV safety risk assessment and three-dimensional(3D) path planning is proposed. Firstly, based on a hierarchical structure of origin/destination/warning boundaries, UAV out-of-bounds conflict rate and buffer airspace occupancy ratio indicators are designed. An optimization model for UAV geofence safety buffer distance is established, and the optimal buffer distance of 28.90 m is scientifically calibrated, serving as the basis for setting the optimal grid granularity of 30 m for the low-altitude airspace. Then, a UAV risk map consisting of a population density layer, sheltered layer, and obstacle layer is constructed. A risk-to-ground assessment model for UAVs is established for two descent modes: ballistic descent and uncontrolled glide, generating a fine-grained and composite urban low-altitude probability risk map. Finally, initial planning, optimization reconstruction, and simulation experiments are conducted for UAV 3D path utilizing geofences, probability risk map, and Jump Point Search algorithm. The effectiveness of the 3D path planning method is verified, and the parameter sensitivity of the path planning model is analyzed. Experimental results demonstrate that the casualty risk of fixed-wing UAVs is 3 to 50 times higher than that of rotary-wing UAVs, and the casualty risk of ballistic descent mode is 5 to 75 times higher than that of uncontrolled glide de-scent mode. Compared to the A* algorithm, the Jump Point Search algorithm effectively reduces the number of turns and solution time for flight paths, making it more suitable for planning UAV flight paths. Compared to the method without a risk map, UAV path planning based on a risk map reduces 50% of high-risk nodes, with an increase in path length of only 7.2% and 11.4%. The overall casualty risk of path nodes is significantly reduced, effectively ensuring the safety of UAV operations and demonstrating significant effectiveness in executing long-distance missions. The research findings provide a theoretical basis and methodological support for the formulation of flight plans and safety operation supervision for complex urban low-altitude UAV flights.
REVIEW OF THE RESEARCHES OF CONSTRUCTION SAFETY MANAGEMENT
FANG Dong-ping, HUANG Xin-yu & John C.W. Wong (Tsinghua-Gammon Construction Safety Research Center, Tsinghua University, Beijing 100081, China)Construction industry is of great significance to the economic growth in most countries. However, due to the distinct characteristics,its performance of safety and health has long been unacceptable, and constrains the continuous improvement of productivity and quality as well as the reputation and sustainable development of the industry. In China, researches on construction safety have long been behind the development of construction industry. Safety records of construction industry in China are far from being satisfactory. It is estimated that in China, over 3 000 workers are killed and billions of Chinese currency RMB are lost each year because of accidents in situ. As nearly 35 000 000 labors are employed in construction industry in China, the improvement of safety condition will save thousands of lives and billions of RMB each year. Therefore, research work on safety management is an urgent demand, especially in the aspect of management. In the present paper, advanced research works in construction safety management are reviewed in the aspects of culture, cost, and organization respectively.First,the safety culture of construction and the functions of all sides participating in the project of construction are dicussed.The attention is paid to the Total Safety Cufture.Second,the present state of the counting of cost and profit of constructron safety are reviewed.In order to calculate the cost and profit of construction safety,the indirect loss using different methods is discussed in detail.Thirdly,the progresses in management and organization of construction safety are summerized. Theories such as TSM(Total Safety Management) is discussed. Suggestions for further researches and investigation of construction safety are brought out as follows: (1) Make full use of the existing resources of construction industry to improve safety management based on the quantitative and qualitative analysis of factors influencing safety performance in situ; (2) Thoroughly investigate into the true cost and benefit of construction safety in order to harmonize safety with quality, schedule and cost when conflicts between them occur; (3) Safety culture in different levels are essential to the goal of "zero accident" in situ, researches into cultural effects on safety psychology and performance of workers will certainly help workers to work more safely; (4) Technological development, especially in the aspect of construction machinery, should be carefully designed and studied in order to eliminate the risks of accidents.
Research on the urban resilience assessment for critical infrastructure interdependency
ZHOU Fang;ZHAO Wei;HU Xiang-kui;WANG Jiang-tao;XU Qing-wei;This article explores potential threats affecting urban resilience from the perspective of infrastructure coupling. This paper demonstrates the impact of infrastructure interdependency on urban resilience from two perspectives: weakening and improving. The interdependency of infrastructure makes the urban key infrastructure system closely linked and very fragile, which is also the key factor affecting urban resilience. The interdependency of infrastructure leads to the propagation of small disturbances across the systems, thereby causing serious consequences. This study mainly focuses on the functional interdependency and geographic interdependency in the coupling relationship of infrastructure. The method of complex network is used to build the urban infrastructure of multi-layered relations and simulate the coupling process. The giant connected component is taken as the evaluation basis of urban resilience. This paper takes the power network, water supply network, and gas network of a city in China as an example. A case study in this paper establishes a three-tier urban network evaluation model of urban resilience considering the geographical interdependency and the functional coupling relationship. The results show that the interdependency can lead to cascading failures, which rapidly spread from one system to another. Eventually, cascading failures lead to a large-scale impact on the city, which manifests in the sudden weakening of urban resilience. By controlling and optimizing the functional interdependency or controlling the geographical interdependency, it is expected to reduce the occurrence of cascading failures. These two control strategies significantly reduce the propagation process of adverse failures in a certain region, that is, to effectively improve the urban resilience.
Simulation study on the efficacy of policies regarding retired new energy vehicle batteries
WEI Lang;WANG Cuixia;LI Yaqin;This paper aims to explore the effectiveness of incentive policies aimed at promoting the recycling of retired New Energy Vehicle Batteries(NEVBs) in China. Taking into account the current state of China's NEVBs recycling industry, a system dynamics model integrating costs and benefits was constructed to simulate the trajectory of China's NEVBs recycling from 2018 to 2035. Additionally, multi-scenario policy simulations were conducted to evaluate the effectiveness of three typical policies: promoting technological innovation, offering subsidies and tax incentives, and advancing cascade utilization. The findings indicate that:(1) Recycling of NEVBs offers both economic and environmental advantages. Nevertheless, the economic feasibility of the industry's initial phase is relatively modest, with an anticipated return on investment of below 10% before 2026.(2) In comparison to the baseline scenario devoid of policy intervention, the policy aimed at promoting technological innovation demonstrates effectiveness in boosting metal resource recycling and lowering recycling unit costs. This reduction in costs and enhancement in efficiency are anticipated to foster sustainable industrial progress. By 2035, it is projected that lithium metal recovery could increase by 25.3%.(3) The subsidy and tax rebate policy could effectively boost the investment return rate, thereby incentivizing enterprises to expand their recycling capacity. Offering a unit recycling subsidy of 10-15 yuan per kilowatt-hour can notably boost the recovery volume of NEVBs.(4) The policy of advancing cascaded utilization can better harness the remaining value of retired batteries, thereby reducing their lifecycle carbon emissions. Under the scenario of increasing the cascaded utilization rate to 50%, it is projected that by 2035, nearly 4.3 million tons of carbon emissions could be reduced.(5) The impact of the three policies exhibits a coupling effect, resulting in the recovery of decommissioned batteries in 2035 reaching close to 8 million tons under the combined scenario. Based on the policy simulation results, recommendations are proposed to promote the development of China's new energy vehicle battery recycling industry.