The mercury removals by existing pollution control devices and the mass balances of mercury in four coal-fired power plants of China were carried out based on a measurement method with the aluminum matrix sorbent.All ...The mercury removals by existing pollution control devices and the mass balances of mercury in four coal-fired power plants of China were carried out based on a measurement method with the aluminum matrix sorbent.All the plants are equipped with a cold-side electrostatic precipitator （ESP） and a wet flue gas desulfurization （FGD） in series.During the course of coal stream,the samples,such as coal,bottom ash,fly ash,gypsum and flue gas,were collected.The Hg concentrations in coals were measured by CVAAS after appropriate preparation and acid digestion.Other solid samples were measured by the RA-915 ＋ Zeeman Mercury Spectrometer.The vapor phase Hg was collected by a sorbent trap from flue gas and then measured using CVAAS followed by acid leaching.The mercury mass balances were estimated in this study were 91.6%,77.1%,118% and 85.8% for the four power plants,respectively.The total Hg concentrations in the stack gas were ranged from 1.56–5.95 μg/m 3.The relative distribution of Hg in bottom ash,ESP,WFGD and stack discharged were ranged between 0.110%–2.50%,2.17%–23.4%,2.21%–87.1%,and 21.8%–72.7%,respectively.The distribution profiles were varied with the coal type and the operation conditions.The Hg in flue gas could be removed by ESP and FGD systems with an average removal efficiency of 51.8%.The calculated average emission factor was 0.066 g/ton and much lower than the results obtained ten years ago.展开更多
为探究不同距离下充水溶洞对岩溶隧道突涌水灾变演化的过程,基于扫描电子显微镜(scanning electron microscope,SEM)对研究区的灰岩进行微观结构表征分析,再采用岩石破裂过程分析软件RFPA^(2D)-Flow建立数值模型,模拟不同距离溶洞对隧...为探究不同距离下充水溶洞对岩溶隧道突涌水灾变演化的过程,基于扫描电子显微镜(scanning electron microscope,SEM)对研究区的灰岩进行微观结构表征分析,再采用岩石破裂过程分析软件RFPA^(2D)-Flow建立数值模型,模拟不同距离溶洞对隧道开挖的影响。试验结果表明:通过SEM观察发现,灰岩矿物内部晶体颗粒分布不均匀,形状不规则,存在溶蚀孔隙较为发育。隧道在开挖扰动过程中,不同距离下溶洞对隧道围岩破坏过程影响显著,当相对距离为1 m时,溶洞周围围岩单元损伤最严重,2 m时次之,处于临界状态,3 m时最小。整个开挖过程大致可分为3个阶段:压密阶段、裂缝扩展阶段、失稳破坏阶段。根据声发射总能量与声发射计数的趋势变化,可以清晰反映出在隧道突涌水的灾变演化情况。研究成果对富水岩溶隧道突涌水的防预和处治提供给理论指导。展开更多
The source apportionment of PM2.5 is essential for pollution prevention.In view of the weaknesses of individual models,we proposed an integrated chemical mass balancesource emission inventory(CMB-SEI)model to acquire ...The source apportionment of PM2.5 is essential for pollution prevention.In view of the weaknesses of individual models,we proposed an integrated chemical mass balancesource emission inventory(CMB-SEI)model to acquire more accurate results.First,the SEI of secondary component precursors(SO2,NOx,NH3,and VOCs)was compiled to acquire the emission ratios of these sources for the precursors.Then,a regular CMB simulation was executed to obtain the contributions of primary particle sources and secondary components(SO4^2-,NO3^-3,NH4^+,and SOC).Afterwards,the contributions of secondary components were apportioned into primary sources according to the source emission ratios.The final source apportionment results combined the contributions of primary sources by CMB and SEI.This integrated approach was carried out via a case study of three coastal cities(Zhoushan,Taizhou,and Wenzhou;abbreviated WZ,TZ,and ZS)in Zhejiang Province,China.The regular CMB simulation results showed that PM2.5 pollution was mainly affected by secondary components and mobile sources.The SEI results indicated that electricity,industrial production and mobile sources were the largest contributors to the emission of PM2.5 gaseous precursors.The simulation results of the CMB-SEI model showed that PM2.5 pollution in the coastal areas of Zhejiang Province presented complex pollution characteristics dominated by mobile sources,electricity production sources and industrial production sources.Compared to the results of the CMB and SEI models alone,the CMB-SEI model completely apportioned PM2.5 to primary sources and simultaneously made the results more accurate and reliable in accordance with local industrial characteristics.展开更多
The characteristics of joints are crucial factors which influence the penetration efficiency of tunnel boring machine(TBM).Based on the theoretical study,numerical simulation and experimental research,many researchers...The characteristics of joints are crucial factors which influence the penetration efficiency of tunnel boring machine(TBM).Based on the theoretical study,numerical simulation and experimental research,many researchers have studied the interaction between TBM disc cutters and jointed rock mass.However,in most of these works,the effect of joint on rock fragmentation by double disc cutter has been scarcely investigated.Thus,the effects of joint orientation and joint space on rock fragmentation by double disc cutter are highlighted in this study.During the test,jointed concrete specimens are adopted to simulate jointed rock mass.Improved RYL-600rock shear rheological instrument was employed during the indentation process under disc cutters,and acoustic emission location system was used to analyze the rock damage and physical deterioration.The results show that there are four failure modes and three modes of crack initiation and propagation in jointed rock mass.It is concluded that the existing joint planes have obviously restrained the crack initiation and propagation during the rock fragmentation process.The results also indicate that samples are damaged most seriously when joint orientation equals60°,which is proved to be the optimum joint orientation in TBM penetration.展开更多
Stars with initial masses in the range of 8-25 solar masses are thought to end their lives as hydrogen-rich supernovae(SNeⅡ).Based on the pre-explosion images of Hubble space telescope(HST)and Spitzer space telescope...Stars with initial masses in the range of 8-25 solar masses are thought to end their lives as hydrogen-rich supernovae(SNeⅡ).Based on the pre-explosion images of Hubble space telescope(HST)and Spitzer space telescope,we place tight constraints on the progenitor candidate of type IIP SN 2023ixf in Messier 101.Fitting of the spectral energy distribution(SED)of its progenitor with dusty stellar spectral models results in an estimation of the effective temperature as 3091+422-258K.The luminosity is estimated as lg(L/L⊙)~4.83,consistent with a red supergiant(RSG)star with an initial mass of 12-1+2M⊙.The derived mass loss rate(6×10^(-6)-9×10^(-6)M⊙yr^(-1))is much lower than that inferred from the flash spectroscopy of the SN,suggesting that the progenitor experienced a sudden increase in mass loss when approaching the final explosion.In the infrared bands,significant deviation from the range of regular RSGs in the color-magnitude diagram and period-luminosity space of the progenitor star indicates enhanced mass loss and dust formation.Combined with new evidence of polarization at the early phases of SN 2023ixf,such a violent mass loss is likely a result of binary interaction.展开更多
Brake wear is an important but unregulated vehicle-related source of atmospheric particulate matter(PM).The single-particle spectral fingerprints of brake wear particles(BWPs)provide essential information for understa...Brake wear is an important but unregulated vehicle-related source of atmospheric particulate matter(PM).The single-particle spectral fingerprints of brake wear particles(BWPs)provide essential information for understanding their formation mechanism and atmospheric contributions.Herein,we obtained the single-particle mass spectra of BWPs by combining a brake dynamometer with an online single particle aerosol mass spectrometer and quantified real-world BWP emissions through a tunnel observation in Tianjin,China.The pure BWPs mainly include three distinct types of particles,namely,Bacontaining particles,mineral particles,and carbon-containing particles,accounting for 44.2%,43.4%,and 10.3%of the total BWP number concentration,respectively.The diversified mass spectra indicate complex BWP formation pathways,such as mechanical,phase transition,and chemical processes.Notably,the mass spectra of Ba-containing particles are unique,which allows them to serve as an excellent indicator for estimating ambient BWP concentrations.By evaluating this indicator,we find that approximately 4.0%of the PM in the tunnel could be attributable to brake wear;the real-world fleet-average emission factor of 0.28 mg km1 veh1 is consistent with the estimation obtained using the receptor model.The results presented herein can be used to inform assessments of the environmental and health impacts of BWPs to formulate effective emissions control policies.展开更多
近年来,药物和个人护理品(Pharmaceuticals and Personal Care Products,PPCPs)在饮用水、污水及自然水体中被频繁检出,对生态及人类健康有潜在的不利影响。污水处理厂是PPCPs进入环境的主要途径之一,研究PPCPs在污水处理厂中的赋存与...近年来,药物和个人护理品(Pharmaceuticals and Personal Care Products,PPCPs)在饮用水、污水及自然水体中被频繁检出,对生态及人类健康有潜在的不利影响。污水处理厂是PPCPs进入环境的主要途径之一,研究PPCPs在污水处理厂中的赋存与去除具有重要意义。使用高效液相色谱-串联质谱联用仪(LC-MS/MS)分析了武汉市5个不同工艺污水处理厂中14种PPCPs的浓度和去除效率。结果表明:各污水处理厂进水中共检出13种PPCPs,总浓度范围为1 471~2 077 ng/L;污水处理厂对大部分目标污染物的总去除效率达到80%以上,在生物处理工艺阶段污染物的去除效率最好,去除机制主要是污泥的吸附和微生物的降解;各污水处理厂进水中PPCPs的质量负荷范围较高(>103.0 g/d),出水中PPCPs的排放量明显降低(<36.3 g/d)。展开更多
基金supported by the National High-Tech Research and Development Program (863) of China(No.2007AA06Z340)
文摘The mercury removals by existing pollution control devices and the mass balances of mercury in four coal-fired power plants of China were carried out based on a measurement method with the aluminum matrix sorbent.All the plants are equipped with a cold-side electrostatic precipitator （ESP） and a wet flue gas desulfurization （FGD） in series.During the course of coal stream,the samples,such as coal,bottom ash,fly ash,gypsum and flue gas,were collected.The Hg concentrations in coals were measured by CVAAS after appropriate preparation and acid digestion.Other solid samples were measured by the RA-915 ＋ Zeeman Mercury Spectrometer.The vapor phase Hg was collected by a sorbent trap from flue gas and then measured using CVAAS followed by acid leaching.The mercury mass balances were estimated in this study were 91.6%,77.1%,118% and 85.8% for the four power plants,respectively.The total Hg concentrations in the stack gas were ranged from 1.56–5.95 μg/m 3.The relative distribution of Hg in bottom ash,ESP,WFGD and stack discharged were ranged between 0.110%–2.50%,2.17%–23.4%,2.21%–87.1%,and 21.8%–72.7%,respectively.The distribution profiles were varied with the coal type and the operation conditions.The Hg in flue gas could be removed by ESP and FGD systems with an average removal efficiency of 51.8%.The calculated average emission factor was 0.066 g/ton and much lower than the results obtained ten years ago.
基金supported by the National Key Research and Development Program of China(No.2018YFC0214102)。
文摘The source apportionment of PM2.5 is essential for pollution prevention.In view of the weaknesses of individual models,we proposed an integrated chemical mass balancesource emission inventory(CMB-SEI)model to acquire more accurate results.First,the SEI of secondary component precursors(SO2,NOx,NH3,and VOCs)was compiled to acquire the emission ratios of these sources for the precursors.Then,a regular CMB simulation was executed to obtain the contributions of primary particle sources and secondary components(SO4^2-,NO3^-3,NH4^+,and SOC).Afterwards,the contributions of secondary components were apportioned into primary sources according to the source emission ratios.The final source apportionment results combined the contributions of primary sources by CMB and SEI.This integrated approach was carried out via a case study of three coastal cities(Zhoushan,Taizhou,and Wenzhou;abbreviated WZ,TZ,and ZS)in Zhejiang Province,China.The regular CMB simulation results showed that PM2.5 pollution was mainly affected by secondary components and mobile sources.The SEI results indicated that electricity,industrial production and mobile sources were the largest contributors to the emission of PM2.5 gaseous precursors.The simulation results of the CMB-SEI model showed that PM2.5 pollution in the coastal areas of Zhejiang Province presented complex pollution characteristics dominated by mobile sources,electricity production sources and industrial production sources.Compared to the results of the CMB and SEI models alone,the CMB-SEI model completely apportioned PM2.5 to primary sources and simultaneously made the results more accurate and reliable in accordance with local industrial characteristics.
基金Project(11772358) supported by the National Natural Science Foundation of ChinaProject(2013CB035401) supported by the National Basic Research Program of ChinaProject(2015zzts262) supported by the Fundamental Research Funds for the Central Universities,China
文摘The characteristics of joints are crucial factors which influence the penetration efficiency of tunnel boring machine(TBM).Based on the theoretical study,numerical simulation and experimental research,many researchers have studied the interaction between TBM disc cutters and jointed rock mass.However,in most of these works,the effect of joint on rock fragmentation by double disc cutter has been scarcely investigated.Thus,the effects of joint orientation and joint space on rock fragmentation by double disc cutter are highlighted in this study.During the test,jointed concrete specimens are adopted to simulate jointed rock mass.Improved RYL-600rock shear rheological instrument was employed during the indentation process under disc cutters,and acoustic emission location system was used to analyze the rock damage and physical deterioration.The results show that there are four failure modes and three modes of crack initiation and propagation in jointed rock mass.It is concluded that the existing joint planes have obviously restrained the crack initiation and propagation during the rock fragmentation process.The results also indicate that samples are damaged most seriously when joint orientation equals60°,which is proved to be the optimum joint orientation in TBM penetration.
基金supported by the National Natural Science Foundation of China(Grant Nos.12288102,12033003,and 11633002)the Ma Huateng Foundation+4 种基金the Scholar Program of Beijing Academy of Science and Technology(Grant No.DZ:BS202002)the Tencent Xplorer Prizesponsored(in part)by the Chinese Academy of Sciences(CAS)through a grant to the CAS South America Center for Astronomy(CASSACA)in Santiago,ChileFunding for the LJT has been provided by the CAS and the People’s Government of Yunnan Province。
文摘Stars with initial masses in the range of 8-25 solar masses are thought to end their lives as hydrogen-rich supernovae(SNeⅡ).Based on the pre-explosion images of Hubble space telescope(HST)and Spitzer space telescope,we place tight constraints on the progenitor candidate of type IIP SN 2023ixf in Messier 101.Fitting of the spectral energy distribution(SED)of its progenitor with dusty stellar spectral models results in an estimation of the effective temperature as 3091+422-258K.The luminosity is estimated as lg(L/L⊙)~4.83,consistent with a red supergiant(RSG)star with an initial mass of 12-1+2M⊙.The derived mass loss rate(6×10^(-6)-9×10^(-6)M⊙yr^(-1))is much lower than that inferred from the flash spectroscopy of the SN,suggesting that the progenitor experienced a sudden increase in mass loss when approaching the final explosion.In the infrared bands,significant deviation from the range of regular RSGs in the color-magnitude diagram and period-luminosity space of the progenitor star indicates enhanced mass loss and dust formation.Combined with new evidence of polarization at the early phases of SN 2023ixf,such a violent mass loss is likely a result of binary interaction.
基金supported by the National key research and development program of China(2022YFE0135000)the Tianjin Science and Technology Plan Project(19YFZCSF00960)+2 种基金the National Natural Science Foundation of China(42177084,42175123,42107114,42107125)the Natural Science Foundation of Tianjin(20JCYBJC01270)the Fundamental Research Funds for the Central Universities(63221411).
文摘Brake wear is an important but unregulated vehicle-related source of atmospheric particulate matter(PM).The single-particle spectral fingerprints of brake wear particles(BWPs)provide essential information for understanding their formation mechanism and atmospheric contributions.Herein,we obtained the single-particle mass spectra of BWPs by combining a brake dynamometer with an online single particle aerosol mass spectrometer and quantified real-world BWP emissions through a tunnel observation in Tianjin,China.The pure BWPs mainly include three distinct types of particles,namely,Bacontaining particles,mineral particles,and carbon-containing particles,accounting for 44.2%,43.4%,and 10.3%of the total BWP number concentration,respectively.The diversified mass spectra indicate complex BWP formation pathways,such as mechanical,phase transition,and chemical processes.Notably,the mass spectra of Ba-containing particles are unique,which allows them to serve as an excellent indicator for estimating ambient BWP concentrations.By evaluating this indicator,we find that approximately 4.0%of the PM in the tunnel could be attributable to brake wear;the real-world fleet-average emission factor of 0.28 mg km1 veh1 is consistent with the estimation obtained using the receptor model.The results presented herein can be used to inform assessments of the environmental and health impacts of BWPs to formulate effective emissions control policies.
文摘近年来,药物和个人护理品(Pharmaceuticals and Personal Care Products,PPCPs)在饮用水、污水及自然水体中被频繁检出,对生态及人类健康有潜在的不利影响。污水处理厂是PPCPs进入环境的主要途径之一,研究PPCPs在污水处理厂中的赋存与去除具有重要意义。使用高效液相色谱-串联质谱联用仪(LC-MS/MS)分析了武汉市5个不同工艺污水处理厂中14种PPCPs的浓度和去除效率。结果表明:各污水处理厂进水中共检出13种PPCPs,总浓度范围为1 471~2 077 ng/L;污水处理厂对大部分目标污染物的总去除效率达到80%以上,在生物处理工艺阶段污染物的去除效率最好,去除机制主要是污泥的吸附和微生物的降解;各污水处理厂进水中PPCPs的质量负荷范围较高(>103.0 g/d),出水中PPCPs的排放量明显降低(<36.3 g/d)。
