Ammonia(NH3)has been widely recognized as a key precursor of atmospheric secondary aerosol formation.Vehicle emission is a major source of urban atmospheric NH3.With the tightening of emission standards and the growin...Ammonia(NH3)has been widely recognized as a key precursor of atmospheric secondary aerosol formation.Vehicle emission is a major source of urban atmospheric NH3.With the tightening of emission standards and the growing trend of vehicle fleet electrification,it is imperative to update the emission factors for NH3 from real-world on-road fleets.In this study,a tunnel measurement was conducted in the urban area of Tianjin,China.The fleet-average NH3 emission factor(EF)was 11.2 mg/(km·veh),significantly lower than those in previous studies,showing the benefit of emission standard updating.Through a multiple linear regression analysis,the EFs of light-duty gasoline vehicles,light-duty diesel vehicles,and heavy-duty diesel vehicles(HDDVs)were estimated to be 5.7±0.6 mg/(km·veh),40.8±5.1 mg/(km·veh),and 160.2±16.6 mg/(km·veh),respectively.Based on the results from this study,we found that HDDVs,which comprise<3%of the total vehicles may contribute approximately 22%of total NH3 emissions in Tianjin.Our results highlight NH3 emissions from HDDVs,a previously potentially overlooked source of NH3 emissions in urban areas.The actual on-road NH3 emissions from HDDVs may exceed current expectations,posing a growing concern for the future.展开更多
The rapid development of magnetic materials provides the possibility for the application of permanent magnet stirring(PMS).Numerical and experimental investigations were employed with respect to the solidification pro...The rapid development of magnetic materials provides the possibility for the application of permanent magnet stirring(PMS).Numerical and experimental investigations were employed with respect to the solidification process of the Al—2Sc alloy controlled by a novel PMS using NdFeB permanent magnets under various rotation speeds(0,50,100 and 150 r/min).The simulated results reveal that the maximum electromagnetic force increases proportionally from 4.14 to 12.39 kN/m^(3)and the maximum tangential velocity increases from 0.13 to 0.36 m/s when the rotation speed of PMS enhances from 50 to 150 r/min in the ingot melt.Besides,the experimental results demonstrate that PMS can achieve a uniform distribution of blocky Al_(3)Sc precipitated phase in the longitudinal direction under the impact of a forced fluid flow.Moreover,increasing rotation speed of PMS is beneficial to refining aluminum grain size significantly and decreasing the texture intensity in the alloy.In addition,the Brinell hardness of Al-2Sc alloy is increased by 33%to 27.8 HB and the tensile strength is enhanced by 34%-128.2 MPa,due to the improved distribution of the strengthening Al_(3)SC phase and the grain refinement of Al matrix under the impact of PMS.This work provides an effective application of NdFeB permanent magnets in the metal cast field.展开更多
To investigate the response of Roadside Monitoring Stations(RSs)to traffic-related air pollution,traffic and pollutant characteristics,influencing factors,and potential source characterization in Tianjin,China were de...To investigate the response of Roadside Monitoring Stations(RSs)to traffic-related air pollution,traffic and pollutant characteristics,influencing factors,and potential source characterization in Tianjin,China were determined based on roadside monitoring of real-world data conducted at RSs in 2022.The diurnal variation trend of pollutants at RSs was consistent with that at the National Monitoring Station(NM),with notably higher pollutant fluctuations during the morning and evening peak traffic times at RSs,where the average diurnal concentration was 41.46%higher than that at the NM.The generalized additive model(GAM)for nitrogen oxides(NO_(x))and carbon monoxide(CO),responding to themultiple influencing factors,performed well at RSs,with deviance explained by 86.6%and 61.4%,respectively.The synergistic effects of wind direction and speed contributed to most of the variations in NO_(x) and CO,which were 14.74%and 12.87%,respectively.Pollutant concentrations were highest under windless conditions,with pollutants originating primarily from local vehicle emissions.The model results indicated that medium-duty truck(MDT)traffic flow predominantly contributed to the variability in NO_(x) emissions,whereas passenger car(PC)traffic flow was the primary source of CO emissions from traffic variables.MDTs should be the focus of urban NO_(x) traffic emissions control.Potential-source analysis validated the results obtained from the GAM,and both analyses showed that RSs can better characterize traffic-related air pollutants.Furthermore,more stringent emission standards have effectively mitigated the release of pollutants from motor vehicles and contributed to the modernization of vehicle fleet composition,effectively decreasing CO concentrations.展开更多
Traffic vehicles, many of which are powered by port fuel injection(PFI) engines, are major sources of particulate matter in the urban atmosphere. We studied particles from the emission of a commercial PFI-engine vehic...Traffic vehicles, many of which are powered by port fuel injection(PFI) engines, are major sources of particulate matter in the urban atmosphere. We studied particles from the emission of a commercial PFI-engine vehicle when it was running under the states of cold start, hot start, hot stabilized running, idle and acceleration, using a transmission electron microscope and an energy-dispersive X-ray detector. Results showed that the particles were mainly composed of organic, soot, and Ca-rich particles, with a small amount of S-rich and metal-containing particles, and displayed a unimodal size distribution with the peak at 600 nm. The emissions were highest under the cold start running state, followed by the hot start, hot stabilized, acceleration, and idle running states. Organic particles under the hot start and hot stabilized running states were higher than those of other running states. Soot particles were highest under the cold start running state. Under the idle running state, the relative number fraction of Ca-rich particles was high although their absolute number was low. These results indicate that PFI-engine vehicles emit substantial primary particles,which favor the formation of secondary aerosols via providing reaction sites and reaction catalysts, as well as supplying soot, organic, mineral and metal particles in the size range of the accumulation mode. In addition, the contents of Ca, P, and Zn in organic particles may serve as fingerprints for source apportionment of particles from PFI-engine vehicles.展开更多
Knowledge of particle number size distribution（PND） and new particle formation（NPF）events in Southern China is essential for mitigation strategies related to submicron particles and their effects on regional air q...Knowledge of particle number size distribution（PND） and new particle formation（NPF）events in Southern China is essential for mitigation strategies related to submicron particles and their effects on regional air quality,haze,and human health.In this study,seven field measurement campaigns were conducted from December 2013 to May 2015 using a scanning mobility particle sizer（SMPS） at four sites in Southern China,including three urban sites and one background site.Particles were measured in the size range of15-515 nm,and the median particle number concentrations（PNCs） were found to vary in the range of 0.3× 10~4-2.2 × 10~4 cn^（-3） at the urban sites and were approximately 0.2 × 10~4 cm^（-3） at the background site.The peak diameters at the different sites varied largely from 22 to 102 nm.The PNCs in the Aitken mode（25-100 nm） at the urban sites were up to 10 times higher than they were at the background site,indicating large primary emissions from traffic at the urban sites.The diurnal variations of PNCs were significantly influenced by both rush hour traffic at the urban sites and NPF events.The frequencies of NPF events at the different sites were0%-30%,with the highest frequency occurring at an urban site during autumn.With higher SO_2 concentrations and higher ambient temperatures being necessary,NPF at the urban site was found to be more influenced by atmospheric oxidizing capability,while NPF at the background site was limited by the condensation sink.This study provides a unique dataset of particle number and size information in various environments in Southern China,which can help understand the sources,formation,and the climate forcing of aerosols in this quickly developing region,as well as help constrain and validate NPF modeling.展开更多
Light-duty gasoline vehicles have drawn public attention in China due to their significant primary emissions of particulate matter and volatile organic compounds（VOCs）. However,little information on secondary aeroso...Light-duty gasoline vehicles have drawn public attention in China due to their significant primary emissions of particulate matter and volatile organic compounds（VOCs）. However,little information on secondary aerosol formation from exhaust for Chinese vehicles and fuel conditions is available. In this study, chamber experiments were conducted to quantify the potential of secondary aerosol formation from the exhaust of a port fuel injection gasoline engine. The engine and fuel used are common in the Chinese market, and the fuel satisfies the China V gasoline fuel standard. Substantial secondary aerosol formation was observed during a 4–5 hr simulation, which was estimated to represent more than 10 days of equivalent atmospheric photo-oxidation in Beijing. As a consequence, the extreme case secondary organic aerosol（SOA） production was 426 ± 85 mg/kg-fuel, with high levels of precursors and OH exposure. The low hygroscopicity of the aerosols formed inside the chamber suggests that SOA was the dominant chemical composition. Fourteen percent of SOA measured in the chamber experiments could be explained through the oxidation of speciated single-ring aromatics. Unspeciated precursors, such as intermediate-volatility organic compounds and semi-volatile organic compounds, might be significant for SOA formation from gasoline VOCs. We concluded that reductions of emissions of aerosol precursor gases from vehicles are essential to mediate pollution in China.展开更多
Intermediate and semi-volatility organic compounds(I/SVOCs)are crucial precursors for secondary organic aerosols(SOA).Vehicles are major sources of I/SVOCs,yet their emission profiles remain insufficiently characteriz...Intermediate and semi-volatility organic compounds(I/SVOCs)are crucial precursors for secondary organic aerosols(SOA).Vehicles are major sources of I/SVOCs,yet their emission profiles remain insufficiently characterized.We conducted dynamometer tests on eight in-use gasoline and diesel vehicles(DVs),employing non-targeted analysis with comprehensive two-dimensional gas chromatography coupled with high-resolution mass spectrometry(GC×GC-TOFMS)to investigate vehicular I/SVOC emissions at the molecular level.A total of 438 and 424 compounds were identified and(semi)-quantified in the gas and particle phases,respectively.DVs exhibited higher emission factors(376.7±74.9 mg/(kg·fuel))compared to gasoline vehicles(GVs)(114.4±42.1 mg/(kg·fuel))across both phases.Alkanes(29.7%-41.9%),single-ring aromatics(2.6%-29.8%),and cycloalkanes(1.0%-13.1%)were dominant I/SVOCs groups.Oxygenated I/SVOCs were more abundant in particulate phases(40.3%-56.8%)than in gas phases(14.4%-15.3%).Upgrading emission standards reduced organic emissions by 89.2%from China IV to China VI for DVs,particularly in the particle phase.Coldstart conditions resulted in higher I/SVOC emissions(528.4 mg/(kg·fuel))than hot-starts(224.8 mg/(kg·fuel))due to reduced combustion efficiency and suboptimal after-treatment performance at low temperatures.Our composition-based SOA estimation method improved SOA predictions by 1.5 and 1.2 times for diesel and GVs,respectively,compared to the traditional bin approach.These findings provide valuable insights into the molecular composition of vehicular I/SVOCs and their environmental impacts.展开更多
Severe haze pollution occurs frequently in the winter over the Beijing-Tianjin-Hebei(BTH)region(China),exerting profound impacts on air quality,visibility,and human health.The Chinese Government has taken strict mitig...Severe haze pollution occurs frequently in the winter over the Beijing-Tianjin-Hebei(BTH)region(China),exerting profound impacts on air quality,visibility,and human health.The Chinese Government has taken strict mitigation actions since 2013 and has achieved a significant reduction in the annual mean PM2.5 concentration over this region.However,the level of secondary aerosols during heavy haze episodes showed little decrease during this period.During heavy haze episodes,the concentrations of secondary aerosol components,including sulfate,nitrate and secondary organics,in aerosol particles increase sharply,acting as the main contributors to aerosol pollution.To achieve effective control of particle pollution in the BTH region,the precise and complete secondary aerosol formation mechanisms have been investigated,and advances have been made about the mechanisms of gas phase reaction,nucleation and heterogeneous reactions in forming secondary aerosols.This paper reviews the research progress in aerosol chemistry during haze pollution episodes in the BTH region,lays out the challenges in haze formation studies,and provides implications and directions for future research.展开更多
The transport sector is a significant energy consumer and a major contributor to urban air pollution.At present,the substitution of cleaner fuel is one feasible way to deal with the growing energy demand and environme...The transport sector is a significant energy consumer and a major contributor to urban air pollution.At present,the substitution of cleaner fuel is one feasible way to deal with the growing energy demand and environmental pollution.Methanol has been recognized as a good alternative to gasoline due to its good combustion performance.In the past decades,many studies have investigated exhaust emissions using methanol-gasoline blends.However,the conclusions derived from different studies vary significantly,and the explanations for the effects of methanol blending on exhaust emissions are also inconsistent.This review summarizes the characteristics of CO,HC,NO_(x),CO_(2),and particulate emissions from methanol-gasoline blended fuels and pure methanol fuel.CO,HC,CO_(2),particle mass(PM),and particle number(PN)emissions decrease when methanol-blended fuel is used in place of gasoline fuel.NO_(x) emission either decreases or increases depending on the test conditions,i.e.,methanol content.Furthermore,this review synthesizes the mechanisms by which methanol-blended fuel influences pollutant emissions.This review provides insight into the pollutant emissions from methanol-blended fuel,which will aid policymakers in making energy strategy decisions that take urban air pollution,climate change,and energy security into account.展开更多
A single particle aerosol mass spectrometer(SPAMS)was used to accurately quantify the contribution of vehicle non-exhaust emissions to particulate matter at typical road environment.The PM_(2.5),black carbon,meteorolo...A single particle aerosol mass spectrometer(SPAMS)was used to accurately quantify the contribution of vehicle non-exhaust emissions to particulate matter at typical road environment.The PM_(2.5),black carbon,meteorological parameters and traffic flow were recorded during the test period.The daily trend for traffic flow and speed on TEDA Street showed obvious“M”and“W”characteristics.6.3 million particles were captured via the SPAMS,including 1.3 million particles with positive and negative spectral map information.Heavy Metal,High molecular Organic Carbon,Organic Carbon,Mixed Carbon,Elemental Carbon,Rich Potassium,Levo-rotation Glucose,Rich Na,SiO_(3) and other categories were analyzed.The particle number concentration measured by SPAMS showed a good linear correlation with the mass concentrations of PM_(2.5) and BC,which indicates that the particulate matter captured by the SPAMS reflects the pollution level of fine particulate matter.EC,ECOC,OC,HM and crustal dust components were found to show high values from 7:00–9:00 AM,showing that these chemical components are directly or indirectly related to vehicle emissions.Based on the PMF model,7 major factors are resolved.The relative contributions of each factor were determined:vehicle exhaust emission(44.8%),coal-fired source(14.5%),biomass combustion(12.2%),crustal dust(9.4%),ship emission(9.0%),tires wear(6.6%)and brake pads wear(3.5%).The results show that the contribution of vehicle non-exhaust to particulate matter at roadside environment is approximately 10.1%.Vehicle non-exhaust emissions are the focus of future research in the vehicle pollutant emission control field.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
Measurements studies have shown that the absorption of radiation by black carbon(BC)increases as the particles age.However,there are significant discrepancies between the measured and modeled absorption enhancement(E_...Measurements studies have shown that the absorption of radiation by black carbon(BC)increases as the particles age.However,there are significant discrepancies between the measured and modeled absorption enhancement(E_(abs)),largely due to the simplifications used in modeling the mixing states and shape diversities.We took advantage of chamber experiments on BC aging and developed an efficient method to resolve the particle shape based on the relationship between the coating fraction(ΔD_(ve)/D_(ve),0)and fractal dimension(D_(f)),which can also reflect the variations of D_(f)during the whole BC aging process.BC with externally and partly mixed states(0≤ΔD_(ve)/D_(ve),0≤0.5)can be considered to be uniformly distributed with the D_(f)values of 1.8–2.1,whereas the Df values are constrained in the range 2.2–2.8 for fully mixed states(ΔD_(ve)/D_(ve),0>0.5).The morphological parameters(i.e.,the effective density and the dynamic shape factor)were compared with the measured values to verify the simulated morphology.The simulated mean deviations of morphological parameters were smaller than 8%for the method resolving the particle shape.By applying a realistic shape and refractive index,the mass absorption cross for fully mixed states can be improved by 11%compared with a simplified core–shell model.Based on our understanding of the influence of D_(f)andΔD_(ve)/D_(ve),0 on E_(abs),we propose a two-stage calibration equation to correct the E_(abs)values estimated by the core–shell model,which reduces the simulation error in the Mie calculation by 6%–14%.展开更多
The strong metal-support interaction(SMSI)in supported catalysts plays a dominant role in catalytic degradation,upgrading,and remanufacturing of environmental pollutants.Previous studies have shown that SMSI is crucia...The strong metal-support interaction(SMSI)in supported catalysts plays a dominant role in catalytic degradation,upgrading,and remanufacturing of environmental pollutants.Previous studies have shown that SMSI is crucial in supported catalysts'activity and stability.However,for redox reactions catalyzed in environmental catalysis,the enhancement mechanism of SMSI-induced oxygen vacancy and electron transfer needs to be clarified.Additionally,the precise control of SMSI interface sites remains to be fully understood.Here we provide a systematic review of SMSI's catalytic mechanisms and control strategies in purifying gaseous pollutants,treating organic wastewater,and valorizing biomass solid waste.We explore the adsorption and activation mechanisms of SMSI in redox reactions by examining interfacial electron transfer,interfacial oxygen vacancy,and interfacial acidic sites.Furthermore,we develop a precise regulation strategy of SMSI from systematical perspectives of interface effect,crystal facet effect,size effect,vip ion doping,and modification effect.Importantly,we point out the drawbacks and breakthrough directions for SMSI regulation in environmental catalysis,including partial encapsulation strategy,size optimization strategy,interface oxygen vacancy strategy,and multi-component strategy.This review article provides the potential applications of SMSI and offers guidance for its controlled regulation in environmental catalysis.展开更多
Using a multiphase difference-in-differences model, this study investigates the relationship between export trade and the corporate technological innovation of listed companies. It reveals that engaging in export trad...Using a multiphase difference-in-differences model, this study investigates the relationship between export trade and the corporate technological innovation of listed companies. It reveals that engaging in export trade increases corporate innovation input and output. In terms of patent output, export trade greatly promotes the output of invention patents and utility model patents with a high technological content. These conclusions remain valid after a series of robustness and endogeneity tests. Regarding the mechanisms of the observed relationships, export trade stimulates corporate technological innovation mainly by realizing economies of scale and increasing risk-taking. The positive correlation between export trade and corporate technological innovation is strongest among state-owned enterprises, non-high-tech enterprises, enterprises based in central and eastern China, enterprises engaged in general trade, and enterprises exporting to developed economies. Given the growing trade frictions ongoing at the time of writing, the conclusions of this study provide vital practical guidance and empirical evidence for a national strategy of innovation-driven development.展开更多
基金supported by the National key research and development program of China(No.2022YFE0135000)the National Natural Science Foundation of China(No.42175123)the Natural Science Foundation of Tianjin(No.23JCJQJC00170).
文摘Ammonia(NH3)has been widely recognized as a key precursor of atmospheric secondary aerosol formation.Vehicle emission is a major source of urban atmospheric NH3.With the tightening of emission standards and the growing trend of vehicle fleet electrification,it is imperative to update the emission factors for NH3 from real-world on-road fleets.In this study,a tunnel measurement was conducted in the urban area of Tianjin,China.The fleet-average NH3 emission factor(EF)was 11.2 mg/(km·veh),significantly lower than those in previous studies,showing the benefit of emission standard updating.Through a multiple linear regression analysis,the EFs of light-duty gasoline vehicles,light-duty diesel vehicles,and heavy-duty diesel vehicles(HDDVs)were estimated to be 5.7±0.6 mg/(km·veh),40.8±5.1 mg/(km·veh),and 160.2±16.6 mg/(km·veh),respectively.Based on the results from this study,we found that HDDVs,which comprise<3%of the total vehicles may contribute approximately 22%of total NH3 emissions in Tianjin.Our results highlight NH3 emissions from HDDVs,a previously potentially overlooked source of NH3 emissions in urban areas.The actual on-road NH3 emissions from HDDVs may exceed current expectations,posing a growing concern for the future.
基金Project supported by the Natural Science Foundation of Hunan Province(2024JJ4056)the Key Project of Guangxi Zhuang Autonomous Region(AB22080089)the Government of Chongzuo,Guangxi Zhuang Autonomous Region(FA20210716)。
文摘The rapid development of magnetic materials provides the possibility for the application of permanent magnet stirring(PMS).Numerical and experimental investigations were employed with respect to the solidification process of the Al—2Sc alloy controlled by a novel PMS using NdFeB permanent magnets under various rotation speeds(0,50,100 and 150 r/min).The simulated results reveal that the maximum electromagnetic force increases proportionally from 4.14 to 12.39 kN/m^(3)and the maximum tangential velocity increases from 0.13 to 0.36 m/s when the rotation speed of PMS enhances from 50 to 150 r/min in the ingot melt.Besides,the experimental results demonstrate that PMS can achieve a uniform distribution of blocky Al_(3)Sc precipitated phase in the longitudinal direction under the impact of a forced fluid flow.Moreover,increasing rotation speed of PMS is beneficial to refining aluminum grain size significantly and decreasing the texture intensity in the alloy.In addition,the Brinell hardness of Al-2Sc alloy is increased by 33%to 27.8 HB and the tensile strength is enhanced by 34%-128.2 MPa,due to the improved distribution of the strengthening Al_(3)SC phase and the grain refinement of Al matrix under the impact of PMS.This work provides an effective application of NdFeB permanent magnets in the metal cast field.
基金supported by the National Key Research and Development Program of China(Nos.2023YFC3707301 and 2023YFC3705400)the Fundamental Research Funds for the Central Universities(Nos.ZB23003425 and 63211075)。
文摘To investigate the response of Roadside Monitoring Stations(RSs)to traffic-related air pollution,traffic and pollutant characteristics,influencing factors,and potential source characterization in Tianjin,China were determined based on roadside monitoring of real-world data conducted at RSs in 2022.The diurnal variation trend of pollutants at RSs was consistent with that at the National Monitoring Station(NM),with notably higher pollutant fluctuations during the morning and evening peak traffic times at RSs,where the average diurnal concentration was 41.46%higher than that at the NM.The generalized additive model(GAM)for nitrogen oxides(NO_(x))and carbon monoxide(CO),responding to themultiple influencing factors,performed well at RSs,with deviance explained by 86.6%and 61.4%,respectively.The synergistic effects of wind direction and speed contributed to most of the variations in NO_(x) and CO,which were 14.74%and 12.87%,respectively.Pollutant concentrations were highest under windless conditions,with pollutants originating primarily from local vehicle emissions.The model results indicated that medium-duty truck(MDT)traffic flow predominantly contributed to the variability in NO_(x) emissions,whereas passenger car(PC)traffic flow was the primary source of CO emissions from traffic variables.MDTs should be the focus of urban NO_(x) traffic emissions control.Potential-source analysis validated the results obtained from the GAM,and both analyses showed that RSs can better characterize traffic-related air pollutants.Furthermore,more stringent emission standards have effectively mitigated the release of pollutants from motor vehicles and contributed to the modernization of vehicle fleet composition,effectively decreasing CO concentrations.
基金supported by the Projects of International Cooperation and Exchanges of National Science Foundation of China (No.41571130031)the National Basic Research Program of China (No.2013CB228503)partly supported by a Grant-in-Aid for Scientific Research (B) (No.16H02942) from the JSPS
文摘Traffic vehicles, many of which are powered by port fuel injection(PFI) engines, are major sources of particulate matter in the urban atmosphere. We studied particles from the emission of a commercial PFI-engine vehicle when it was running under the states of cold start, hot start, hot stabilized running, idle and acceleration, using a transmission electron microscope and an energy-dispersive X-ray detector. Results showed that the particles were mainly composed of organic, soot, and Ca-rich particles, with a small amount of S-rich and metal-containing particles, and displayed a unimodal size distribution with the peak at 600 nm. The emissions were highest under the cold start running state, followed by the hot start, hot stabilized, acceleration, and idle running states. Organic particles under the hot start and hot stabilized running states were higher than those of other running states. Soot particles were highest under the cold start running state. Under the idle running state, the relative number fraction of Ca-rich particles was high although their absolute number was low. These results indicate that PFI-engine vehicles emit substantial primary particles,which favor the formation of secondary aerosols via providing reaction sites and reaction catalysts, as well as supplying soot, organic, mineral and metal particles in the size range of the accumulation mode. In addition, the contents of Ca, P, and Zn in organic particles may serve as fingerprints for source apportionment of particles from PFI-engine vehicles.
基金supported by the National Natural Science Foundation of China(Nos.U1301234,21277003)the Shenzhen Science&Technology Plan,and the Ministry of Science and Technology of China(No.2013CB228503)
文摘Knowledge of particle number size distribution（PND） and new particle formation（NPF）events in Southern China is essential for mitigation strategies related to submicron particles and their effects on regional air quality,haze,and human health.In this study,seven field measurement campaigns were conducted from December 2013 to May 2015 using a scanning mobility particle sizer（SMPS） at four sites in Southern China,including three urban sites and one background site.Particles were measured in the size range of15-515 nm,and the median particle number concentrations（PNCs） were found to vary in the range of 0.3× 10~4-2.2 × 10~4 cn^（-3） at the urban sites and were approximately 0.2 × 10~4 cm^（-3） at the background site.The peak diameters at the different sites varied largely from 22 to 102 nm.The PNCs in the Aitken mode（25-100 nm） at the urban sites were up to 10 times higher than they were at the background site,indicating large primary emissions from traffic at the urban sites.The diurnal variations of PNCs were significantly influenced by both rush hour traffic at the urban sites and NPF events.The frequencies of NPF events at the different sites were0%-30%,with the highest frequency occurring at an urban site during autumn.With higher SO_2 concentrations and higher ambient temperatures being necessary,NPF at the urban site was found to be more influenced by atmospheric oxidizing capability,while NPF at the background site was limited by the condensation sink.This study provides a unique dataset of particle number and size information in various environments in Southern China,which can help understand the sources,formation,and the climate forcing of aerosols in this quickly developing region,as well as help constrain and validate NPF modeling.
基金supported by the National Key Basic Research and Development Program (No. 2013CB228500)the National Basic Research Program (973) of China (Nos. 2013CB228503, 2013CB228502)+3 种基金National Natural Science Foundation of China (Nos. 91544214, 51636003)the Strategic Priority Research Program of Chinese Academy of Sciences (No. XDB05010500)China Postdoctoral Science Foundation (No. 2015M580929)the State Key Lab of Automotive Safety and Energy at Tsinghua University for their support for the experiments
文摘Light-duty gasoline vehicles have drawn public attention in China due to their significant primary emissions of particulate matter and volatile organic compounds（VOCs）. However,little information on secondary aerosol formation from exhaust for Chinese vehicles and fuel conditions is available. In this study, chamber experiments were conducted to quantify the potential of secondary aerosol formation from the exhaust of a port fuel injection gasoline engine. The engine and fuel used are common in the Chinese market, and the fuel satisfies the China V gasoline fuel standard. Substantial secondary aerosol formation was observed during a 4–5 hr simulation, which was estimated to represent more than 10 days of equivalent atmospheric photo-oxidation in Beijing. As a consequence, the extreme case secondary organic aerosol（SOA） production was 426 ± 85 mg/kg-fuel, with high levels of precursors and OH exposure. The low hygroscopicity of the aerosols formed inside the chamber suggests that SOA was the dominant chemical composition. Fourteen percent of SOA measured in the chamber experiments could be explained through the oxidation of speciated single-ring aromatics. Unspeciated precursors, such as intermediate-volatility organic compounds and semi-volatile organic compounds, might be significant for SOA formation from gasoline VOCs. We concluded that reductions of emissions of aerosol precursor gases from vehicles are essential to mediate pollution in China.
基金supported by the National Key Research and Development Program of China(Nos.2023YFC3706201 and 2022YFE0135000)the National Natural Science Foundation of China(Nos.42175123 and 42311530112)the Fundamental Research Funds for the Central Universities of China(Nos.63241318,63241322,and 63243126).
文摘Intermediate and semi-volatility organic compounds(I/SVOCs)are crucial precursors for secondary organic aerosols(SOA).Vehicles are major sources of I/SVOCs,yet their emission profiles remain insufficiently characterized.We conducted dynamometer tests on eight in-use gasoline and diesel vehicles(DVs),employing non-targeted analysis with comprehensive two-dimensional gas chromatography coupled with high-resolution mass spectrometry(GC×GC-TOFMS)to investigate vehicular I/SVOC emissions at the molecular level.A total of 438 and 424 compounds were identified and(semi)-quantified in the gas and particle phases,respectively.DVs exhibited higher emission factors(376.7±74.9 mg/(kg·fuel))compared to gasoline vehicles(GVs)(114.4±42.1 mg/(kg·fuel))across both phases.Alkanes(29.7%-41.9%),single-ring aromatics(2.6%-29.8%),and cycloalkanes(1.0%-13.1%)were dominant I/SVOCs groups.Oxygenated I/SVOCs were more abundant in particulate phases(40.3%-56.8%)than in gas phases(14.4%-15.3%).Upgrading emission standards reduced organic emissions by 89.2%from China IV to China VI for DVs,particularly in the particle phase.Coldstart conditions resulted in higher I/SVOC emissions(528.4 mg/(kg·fuel))than hot-starts(224.8 mg/(kg·fuel))due to reduced combustion efficiency and suboptimal after-treatment performance at low temperatures.Our composition-based SOA estimation method improved SOA predictions by 1.5 and 1.2 times for diesel and GVs,respectively,compared to the traditional bin approach.These findings provide valuable insights into the molecular composition of vehicular I/SVOCs and their environmental impacts.
基金supported by the National Natural Science Foundation of China(Grant Nos.91844301 and 91544214)National Research Program for Key Issues in Air Pollution Control(DQGG0103)National Key Research and Development Program of China(No.2016YFC0202000:Task 3)。
文摘Severe haze pollution occurs frequently in the winter over the Beijing-Tianjin-Hebei(BTH)region(China),exerting profound impacts on air quality,visibility,and human health.The Chinese Government has taken strict mitigation actions since 2013 and has achieved a significant reduction in the annual mean PM2.5 concentration over this region.However,the level of secondary aerosols during heavy haze episodes showed little decrease during this period.During heavy haze episodes,the concentrations of secondary aerosol components,including sulfate,nitrate and secondary organics,in aerosol particles increase sharply,acting as the main contributors to aerosol pollution.To achieve effective control of particle pollution in the BTH region,the precise and complete secondary aerosol formation mechanisms have been investigated,and advances have been made about the mechanisms of gas phase reaction,nucleation and heterogeneous reactions in forming secondary aerosols.This paper reviews the research progress in aerosol chemistry during haze pollution episodes in the BTH region,lays out the challenges in haze formation studies,and provides implications and directions for future research.
基金supported by the Tianjin Science and Technology Plan Project(China)(Nos.18PTZWHZ00120,19YFZCSF 00960,20YFZCSN01000,20JCYBJC01270)The Fundamental Research Funds for the Central University of China(Nos.63213074,63211075).
文摘The transport sector is a significant energy consumer and a major contributor to urban air pollution.At present,the substitution of cleaner fuel is one feasible way to deal with the growing energy demand and environmental pollution.Methanol has been recognized as a good alternative to gasoline due to its good combustion performance.In the past decades,many studies have investigated exhaust emissions using methanol-gasoline blends.However,the conclusions derived from different studies vary significantly,and the explanations for the effects of methanol blending on exhaust emissions are also inconsistent.This review summarizes the characteristics of CO,HC,NO_(x),CO_(2),and particulate emissions from methanol-gasoline blended fuels and pure methanol fuel.CO,HC,CO_(2),particle mass(PM),and particle number(PN)emissions decrease when methanol-blended fuel is used in place of gasoline fuel.NO_(x) emission either decreases or increases depending on the test conditions,i.e.,methanol content.Furthermore,this review synthesizes the mechanisms by which methanol-blended fuel influences pollutant emissions.This review provides insight into the pollutant emissions from methanol-blended fuel,which will aid policymakers in making energy strategy decisions that take urban air pollution,climate change,and energy security into account.
基金supported by the National Natural Science Foundation of China(Nos.42107114 and 42177084)the Tianjin Science and Technology Plan Project(No.20YFZCSN01000)the Fundamental Research Funds for the Central Universities(No.63221411).
文摘A single particle aerosol mass spectrometer(SPAMS)was used to accurately quantify the contribution of vehicle non-exhaust emissions to particulate matter at typical road environment.The PM_(2.5),black carbon,meteorological parameters and traffic flow were recorded during the test period.The daily trend for traffic flow and speed on TEDA Street showed obvious“M”and“W”characteristics.6.3 million particles were captured via the SPAMS,including 1.3 million particles with positive and negative spectral map information.Heavy Metal,High molecular Organic Carbon,Organic Carbon,Mixed Carbon,Elemental Carbon,Rich Potassium,Levo-rotation Glucose,Rich Na,SiO_(3) and other categories were analyzed.The particle number concentration measured by SPAMS showed a good linear correlation with the mass concentrations of PM_(2.5) and BC,which indicates that the particulate matter captured by the SPAMS reflects the pollution level of fine particulate matter.EC,ECOC,OC,HM and crustal dust components were found to show high values from 7:00–9:00 AM,showing that these chemical components are directly or indirectly related to vehicle emissions.Based on the PMF model,7 major factors are resolved.The relative contributions of each factor were determined:vehicle exhaust emission(44.8%),coal-fired source(14.5%),biomass combustion(12.2%),crustal dust(9.4%),ship emission(9.0%),tires wear(6.6%)and brake pads wear(3.5%).The results show that the contribution of vehicle non-exhaust to particulate matter at roadside environment is approximately 10.1%.Vehicle non-exhaust emissions are the focus of future research in the vehicle pollutant emission control field.
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.
基金supported by the National Key R&D Program of China(2018YFC0213800)the National Natural Science Foundation of China(Grant No.42021004)the open fund of the Jiangsu Key Laboratory of Atmospheric Environment Monitoring and Pollution Control(China)(KHK1908).
文摘Measurements studies have shown that the absorption of radiation by black carbon(BC)increases as the particles age.However,there are significant discrepancies between the measured and modeled absorption enhancement(E_(abs)),largely due to the simplifications used in modeling the mixing states and shape diversities.We took advantage of chamber experiments on BC aging and developed an efficient method to resolve the particle shape based on the relationship between the coating fraction(ΔD_(ve)/D_(ve),0)and fractal dimension(D_(f)),which can also reflect the variations of D_(f)during the whole BC aging process.BC with externally and partly mixed states(0≤ΔD_(ve)/D_(ve),0≤0.5)can be considered to be uniformly distributed with the D_(f)values of 1.8–2.1,whereas the Df values are constrained in the range 2.2–2.8 for fully mixed states(ΔD_(ve)/D_(ve),0>0.5).The morphological parameters(i.e.,the effective density and the dynamic shape factor)were compared with the measured values to verify the simulated morphology.The simulated mean deviations of morphological parameters were smaller than 8%for the method resolving the particle shape.By applying a realistic shape and refractive index,the mass absorption cross for fully mixed states can be improved by 11%compared with a simplified core–shell model.Based on our understanding of the influence of D_(f)andΔD_(ve)/D_(ve),0 on E_(abs),we propose a two-stage calibration equation to correct the E_(abs)values estimated by the core–shell model,which reduces the simulation error in the Mie calculation by 6%–14%.
基金National Key Research and Development Program of China(2022YFE0135000)National Natural Science Foundation of China(42175123、42107125)Fundamental Research Funds for the Central Universities,Nankai University(63231205).
文摘The strong metal-support interaction(SMSI)in supported catalysts plays a dominant role in catalytic degradation,upgrading,and remanufacturing of environmental pollutants.Previous studies have shown that SMSI is crucial in supported catalysts'activity and stability.However,for redox reactions catalyzed in environmental catalysis,the enhancement mechanism of SMSI-induced oxygen vacancy and electron transfer needs to be clarified.Additionally,the precise control of SMSI interface sites remains to be fully understood.Here we provide a systematic review of SMSI's catalytic mechanisms and control strategies in purifying gaseous pollutants,treating organic wastewater,and valorizing biomass solid waste.We explore the adsorption and activation mechanisms of SMSI in redox reactions by examining interfacial electron transfer,interfacial oxygen vacancy,and interfacial acidic sites.Furthermore,we develop a precise regulation strategy of SMSI from systematical perspectives of interface effect,crystal facet effect,size effect,vip ion doping,and modification effect.Importantly,we point out the drawbacks and breakthrough directions for SMSI regulation in environmental catalysis,including partial encapsulation strategy,size optimization strategy,interface oxygen vacancy strategy,and multi-component strategy.This review article provides the potential applications of SMSI and offers guidance for its controlled regulation in environmental catalysis.
基金financial support from the National Natural Science Foundation of China(No.71972091)
文摘Using a multiphase difference-in-differences model, this study investigates the relationship between export trade and the corporate technological innovation of listed companies. It reveals that engaging in export trade increases corporate innovation input and output. In terms of patent output, export trade greatly promotes the output of invention patents and utility model patents with a high technological content. These conclusions remain valid after a series of robustness and endogeneity tests. Regarding the mechanisms of the observed relationships, export trade stimulates corporate technological innovation mainly by realizing economies of scale and increasing risk-taking. The positive correlation between export trade and corporate technological innovation is strongest among state-owned enterprises, non-high-tech enterprises, enterprises based in central and eastern China, enterprises engaged in general trade, and enterprises exporting to developed economies. Given the growing trade frictions ongoing at the time of writing, the conclusions of this study provide vital practical guidance and empirical evidence for a national strategy of innovation-driven development.
