When separated water droplets condense on the surface of a composite insulator,the electrical field on the insulator surface is distorted.In turn,such distortions change the trajectories of pollution particles.In this...When separated water droplets condense on the surface of a composite insulator,the electrical field on the insulator surface is distorted.In turn,such distortions change the trajectories of pollution particles.In this study,the COMSOL software is used to simulate such a process for the FXBW4-10/100 composite insulator with or without water droplets condensation under a 10 kV DC voltage.The influence of the wind speed and particles concentration on the contamination characteristics of the considered 110 kV insulator is analyzed.The results show that:1)in the presence of water droplets on the insulator surface,the ratio of electrical field force and gravity acting on the particles is large;2)the contamination on the insulator surface increases with the wind speed;3)when the wind speed is small,the relationship between the contamination amount and the pollution concentration is essentially linear.展开更多
Constructing impermeable curtains to contain contaminant in aquifers is a costly and complex process that can impact the structure integrity of aquifer systems.Are impermeable curtains necessary for a groundwater cont...Constructing impermeable curtains to contain contaminant in aquifers is a costly and complex process that can impact the structure integrity of aquifer systems.Are impermeable curtains necessary for a groundwater contaminant remediation project?This study evaluates the necessity of impermeable curtains for groundwater contaminant remediation projects.Specifically,it considers remediation efforts based on the Pump and Treat(PAT)technique under various hydrogeological conditions and contaminant properties,comparing the total remediation cost and effectiveness.To further investigate,a multi-objective simulation and optimization model,utilizing the Multi-Objective Fast Harmony Search(MOFHS)algorithm,was employed to identify optimal groundwater remediation system designs that without impermeable curtains.Both a two-dimensional(2-D)hypothetical example and a three-dimensional(3-D)field example were used to assess the necessity of constructing impermeable curtains.The 2-D hypothetical example demonstrated that the installation of impermeable curtain is justified only when the dispersivity(αL)of the contaminant reaches 100 meters.In most cases,particularly at sites with porosity(n)under 0.3,alternative,more cost-effective,and efficient remediation strategies may be available,making impermeable barriers unnecessary.The optimization results of the 3-D field example further corroborate the conclusions derived from the 2-D hypothetical example.These findings provide valuable guidance for more scientifically informed,reasonable,and cost-effective groundwater contaminant remediation projects.展开更多
Due to rapid urbanization and industrialization, heavy metals in road-deposited sediments（RDSs） of parks are emitted into the terrestrial, atmospheric, and water environment, and have a severe impact on residents＇ ...Due to rapid urbanization and industrialization, heavy metals in road-deposited sediments（RDSs） of parks are emitted into the terrestrial, atmospheric, and water environment, and have a severe impact on residents＇ and tourists＇ health. To identify the distribution and characteristic of heavy metals in RDS and to assess the road environmental quality in Chinese parks, samples were collected from Beijing Olympic Park in the present study. The results indicated that particles with small grain size（〈150 μm） were the dominant fraction. The length of dry period was one of the main factors affecting the particle size distribution, as indicated by the variation of size fraction with the increase of dry days. The amount of heavy metal（i.e., Cu, Zn, Pb and Cd） content was the largest in particles with small size（〈150 μm） among all samples. Specifically, the percentage of Cu, Zn, Pb and Cd in these particles was 74.7%, 55.5%, 56.6% and 71.3%, respectively.Heavy metals adsorbed in sediments may mainly be contributed by road traffic emissions. The contamination levels of Pb and Cd were higher than Cu and Zn on the basis of the mean heavy metal contents. Specifically, the geoaccumulation index（I geo） decreased in the order：Cd〉Pb〉Cu〉Zn. This study analyzed the mobility of heavy metals in sediments using partial sequential extraction with the Tessier procedure. The results revealed that the apparent mobility and potential metal bioavailability of heavy metals in the sediments, based on the exchangeable and carbonate fractions, decreased in the order： Cd〉Zn≈Pb〉Cu.展开更多
基金Science and Technology Project of State Grid Corporation(GY7111053)[www.sgcc.com.cn]。
文摘When separated water droplets condense on the surface of a composite insulator,the electrical field on the insulator surface is distorted.In turn,such distortions change the trajectories of pollution particles.In this study,the COMSOL software is used to simulate such a process for the FXBW4-10/100 composite insulator with or without water droplets condensation under a 10 kV DC voltage.The influence of the wind speed and particles concentration on the contamination characteristics of the considered 110 kV insulator is analyzed.The results show that:1)in the presence of water droplets on the insulator surface,the ratio of electrical field force and gravity acting on the particles is large;2)the contamination on the insulator surface increases with the wind speed;3)when the wind speed is small,the relationship between the contamination amount and the pollution concentration is essentially linear.
基金supported by the National Key Research and Development Program of China(Grant No.2022YFC3702200)the National Natural Science Foundation of China(Grant Nos.42372279 and U2267218)the Natural Science Foundation of Anhui Province(Grant No.JZ2022AKZR0451).
文摘Constructing impermeable curtains to contain contaminant in aquifers is a costly and complex process that can impact the structure integrity of aquifer systems.Are impermeable curtains necessary for a groundwater contaminant remediation project?This study evaluates the necessity of impermeable curtains for groundwater contaminant remediation projects.Specifically,it considers remediation efforts based on the Pump and Treat(PAT)technique under various hydrogeological conditions and contaminant properties,comparing the total remediation cost and effectiveness.To further investigate,a multi-objective simulation and optimization model,utilizing the Multi-Objective Fast Harmony Search(MOFHS)algorithm,was employed to identify optimal groundwater remediation system designs that without impermeable curtains.Both a two-dimensional(2-D)hypothetical example and a three-dimensional(3-D)field example were used to assess the necessity of constructing impermeable curtains.The 2-D hypothetical example demonstrated that the installation of impermeable curtain is justified only when the dispersivity(αL)of the contaminant reaches 100 meters.In most cases,particularly at sites with porosity(n)under 0.3,alternative,more cost-effective,and efficient remediation strategies may be available,making impermeable barriers unnecessary.The optimization results of the 3-D field example further corroborate the conclusions derived from the 2-D hypothetical example.These findings provide valuable guidance for more scientifically informed,reasonable,and cost-effective groundwater contaminant remediation projects.
基金supported by the Beijing Municipal Natural Science Foundation (No. 8142013)the Philosophical and Social Science Planning Program of Beijing (No. 13CSC010)
文摘Due to rapid urbanization and industrialization, heavy metals in road-deposited sediments（RDSs） of parks are emitted into the terrestrial, atmospheric, and water environment, and have a severe impact on residents＇ and tourists＇ health. To identify the distribution and characteristic of heavy metals in RDS and to assess the road environmental quality in Chinese parks, samples were collected from Beijing Olympic Park in the present study. The results indicated that particles with small grain size（〈150 μm） were the dominant fraction. The length of dry period was one of the main factors affecting the particle size distribution, as indicated by the variation of size fraction with the increase of dry days. The amount of heavy metal（i.e., Cu, Zn, Pb and Cd） content was the largest in particles with small size（〈150 μm） among all samples. Specifically, the percentage of Cu, Zn, Pb and Cd in these particles was 74.7%, 55.5%, 56.6% and 71.3%, respectively.Heavy metals adsorbed in sediments may mainly be contributed by road traffic emissions. The contamination levels of Pb and Cd were higher than Cu and Zn on the basis of the mean heavy metal contents. Specifically, the geoaccumulation index（I geo） decreased in the order：Cd〉Pb〉Cu〉Zn. This study analyzed the mobility of heavy metals in sediments using partial sequential extraction with the Tessier procedure. The results revealed that the apparent mobility and potential metal bioavailability of heavy metals in the sediments, based on the exchangeable and carbonate fractions, decreased in the order： Cd〉Zn≈Pb〉Cu.
