This work examines the influence of preparation methods on the physicochemical properties and catalytic performance of MnOx‐CeO2 catalysts for selective catalytic reduction of NO by NH3 (NH3‐SCR) at low temperature....This work examines the influence of preparation methods on the physicochemical properties and catalytic performance of MnOx‐CeO2 catalysts for selective catalytic reduction of NO by NH3 (NH3‐SCR) at low temperature. Five different methods, namely, mechanical mixing, impregnation,hydrothermal treatment, co‐precipitation, and a sol‐gel technique, were used to synthesizeMnOx‐CeO2 catalysts. The catalysts were characterized in detail, and an NH3‐SCR model reaction waschosen to evaluate the catalytic performance. The results showed that the preparation methodsaffected the catalytic performance in the order: hydrothermal treatment > sol‐gel > co‐precipitation> impregnation > mechanical mixing. This order correlated with the surface Ce3+ and Mn4+ content,oxygen vacancies and surface adsorbed oxygen species concentration, and the amount of acidic sitesand acidic strength. This trend is related to redox interactions between MnOx and CeO2. The catalystformed by a hydrothermal treatment exhibited excellent physicochemical properties, optimal catalyticperformance, and good H2O resistance in NH3‐SCR reaction. This was attributed to incorporationof Mnn+ into the CeO2 lattice to form a uniform ceria‐based solid solution (containing Mn‐O‐Cestructures). Strengthening of the electronic interactions between MnOx and CeO2, driven by thehigh‐temperature and high‐pressure conditions during the hydrothermal treatment also improved the catalyst characteristics. Thus, the hydrothermal treatment method is an efficient and environment‐friendly route to synthesizing low‐temperature denitrification (deNOx) catalysts.展开更多
Thermally stable Zr4+, Al3+, and Si4+ cations were incorporated into the lattice of CeO2 nano‐rods (i.e., CeO2‐NR) in order to improve the specific surface area. The undoped and Zr4+, Al3+, and Si4+ doped nano‐rods...Thermally stable Zr4+, Al3+, and Si4+ cations were incorporated into the lattice of CeO2 nano‐rods (i.e., CeO2‐NR) in order to improve the specific surface area. The undoped and Zr4+, Al3+, and Si4+ doped nano‐rods were used as supports to prepare MnOx/CeO2‐NR, MnOx/CZ‐NR, MnOx/CA‐NR, and MnOx/CS‐NR catalysts, respectively. The prepared supports and catalysts were comprehensively characterized by transmission electron microscopy (TEM), high‐resolution TEM, X‐ray diffraction, Raman and N2‐physisorption analyses, hydrogen temperature‐programmed reduction, ammonia temperature‐programmed desorption, in situ diffuse reflectance infrared Fourier‐transform spectroscopic analysis of the NH3 adsorption, and X‐ray photoelectron spectroscopy. Moreover, the catalytic performance and H2O+SO2 tolerance of these samples were evaluated through NH3‐selective catalytic reduction (NH3‐SCR) in the absence or presence of H2O and SO2. The obtained results show that the MnOx/CS‐NR catalyst exhibits the highest NOx conversion and the lowest N2O concentration, which result from the largest number of oxygen vacancies and acid sites, the highest Mn4+ content, and the lowest redox ability. The MnOx/CS‐NR catalyst also presents excellent resistance to H2O and SO2. All of these phenomena suggest that Si4+ is the optimal dopant for the MnOx/CeO2‐NR catalyst.展开更多
China national air quality monitoring network has become the core data source for air quality assessment and management in China.However,during network construction,the significant change in numbers of monitoring site...China national air quality monitoring network has become the core data source for air quality assessment and management in China.However,during network construction,the significant change in numbers of monitoring sites with time is easily ignored,which brings uncertainty to air quality assessments.This study aims to analyze the impact of change in numbers of stations on national and regional air quality assessments in China during 2013-18.The results indicate that the change in numbers of stations has different impacts on fine particulate matter(PM_(2.5))and ozone concentration assessments.The increasing number of sites makes the estimated national and regional PM_(2.5) concentration slightly lower by 0.6−2.2μg m^(−3) and 1.4−6.0μg m^(−3) respectively from 2013 to 2018.The main reason is that over time,the monitoring network expands from the urban centers to the suburban areas with low population densities and pollutant emissions.For ozone,the increasing number of stations affects the long-term trends of the estimated concentration,especially the national trends,which changed from a slight upward trend to a downward trend in 2014−15.Besides,the impact of the increasing number of sites on ozone assessment exhibits a seasonal difference at the 0.05 significance level in that the added sites make the estimated concentration higher in winter and lower in summer.These results suggest that the change in numbers of monitoring sites is an important uncertainty factor in national and regional air quality assessments,that needs to be considered in long-term concentration assessment,trend analysis,and trend driving force analysis.展开更多
The attainment of suitable ambient air quality standards is a matter of great concern for successfully hosting the ⅩⅩⅣ Olympic Winter Games(OWG). Transport patterns and potential sources of pollutants in Zhangjiako...The attainment of suitable ambient air quality standards is a matter of great concern for successfully hosting the ⅩⅩⅣ Olympic Winter Games(OWG). Transport patterns and potential sources of pollutants in Zhangjiakou(ZJK) were investigated using pollutant monitoring datasets and a dispersion model. The PM_(2.5) concentration during February in ZJK has increased slightly(28%) from 2018 to 2021, mostly owing to the shift of main potential source regions of west-central Inner Mongolia and Mongolian areas(2015–18) to the North China Plain and northern Shanxi Province(NCPS) after 2018.Using CO as an indicator, the relative contributions of the different regions to the receptor site(ZJK) were evaluated based on the source-receptor-relationship method(SRR) and an emission inventory. We found that the relative contribution of pollutants from NCPS increased from 33% to 68% during 2019–21. Central Inner Mongolia(CIM) also has an important impact on ZJK under unfavorable weather conditions. This study demonstrated that the effect of pollution control measures in the NCPS and CIM should be strengthened to ensure that the air quality meets the standard during the ⅩⅩⅣ OWG.展开更多
NH_(3)-SCR(SCR:Selective catalytic reduction)is an effective technology for the de-NO_(x)process from both mobile and stationary pollution sources,and the most commonly used catalysts are the vanadia-based catalysts.A...NH_(3)-SCR(SCR:Selective catalytic reduction)is an effective technology for the de-NO_(x)process from both mobile and stationary pollution sources,and the most commonly used catalysts are the vanadia-based catalysts.An innovative V_(2)O_(5)-CeO_(2)/TaTiO_(x)catalyst for NO_(x)removal was prepared in this study.The influences of Ce and Ta in the V_(2)O_(5)-CeO_(2)/TaTiO_(x)catalyst on the SCR performance and physicochemical properties were investigated.The V_(2)O_(5)-CeO_(2)/TaTiO_(x)catalyst not only exhibited excellent SCR activity in a wide temperature window,but also presented strong resistance to H_(2)Oand SO_(2)at 275◦C.A series of characterizationmethods was used to study the catalysts,including H2-temperature programmed reduction,X-ray photoelectron spectroscopy,NH_(3)-temperature programmed desorption,etc.It was discovered that a synergistic effect existed between Ce and Ta species.The introduction of Ce and Ta enlarged the specific surface area,increased the amount of acid sites and the ratio of Ce^(3+),(V^(3+)+V^(4+))and Oα,and strengthened the redox capability which were related to synergistic effect between Ce and Ta species,significantly improving the NH_(3)-SCR activity.展开更多
About 70%of the flue gas in the iron-steel industry has achieved multi-pollutant ultra-low emissions in China until 2023,and then the blast furnace gas purification has become the control step and bottleneck.Our resea...About 70%of the flue gas in the iron-steel industry has achieved multi-pollutant ultra-low emissions in China until 2023,and then the blast furnace gas purification has become the control step and bottleneck.Our research group has designed and constructed the world’s first blast furnace gas desulfurization pilot plant with the scale of 2000 Nm^(3)/h in October 2021.The pilot plant is a two-step combined desulfurization device including catalytic hydrolysis of carbonyl sulfur(COS)and absorption-oxidation of H_(2)S,continuously running for 120 days.In the hydrolysis system,one reason for catalyst deactivation has been verified from the sulfur deposition.HCN in blast furnace gas can be hydrolyzed on the hydrolysis catalyst to produce the nitrogen deposition,which is one of the reasons for catalyst deactivation and has never been found in previous studies.The deposition forms of S and N elements are determined,S element forms elemental sulfur and sulfate,while N element forms-NH_(2)and NH_(4)^(+).In the absorption-oxidation system,the O_(2)loading and the residence time have been optimized to control the oxidation of HS^(−)to produce elemental sulfur instead of by-product S_(2)O_(3)^(2−).The balance and distribution of S and N elements have been calculated for thewholemulti-phase system,approximately 84.4%of the sulfur is converted to solid sulfur product,about 1.3%of the sulfur and 19.2%of N element are deposited on the hydrolysis catalyst.The pilot plant provides technical support formulti-pollutant control of blast furnace.展开更多
Cerium and cobalt loaded Co-Ce/TiO_(2)catalyst prepared by impregnation method was investigated for photothermal catalytic toluene oxidation.Based on catalyst characterizations(XPS,EPR and H2-TPR),redox cycle between ...Cerium and cobalt loaded Co-Ce/TiO_(2)catalyst prepared by impregnation method was investigated for photothermal catalytic toluene oxidation.Based on catalyst characterizations(XPS,EPR and H2-TPR),redox cycle between Co and TiO_(2)(Co^(2+)+Ti^(4+)↔Co^(3+)+Ti^(3+))results in the formation of Co^(3+),Ti^(3+)and oxygen vacancies,which play important roles in toluene catalytic oxidation reaction.The introduction of Ce brings in the dual redox cycles(Co^(2+)+Ti^(4+)↔Co^(3+)+Ti^(3+),Co^(2+)+Ce4+↔Co^(3+)+Ce3+),further promoting the elevation of reaction sites amount.Under full spectrum irradiation with light intensity of 580mW/cm^(2),Co-Ce/TiO_(2)catalyst achieved 96%of toluene conversion and 73%of CO_(2)yield,obviously higher than Co/P25 and Co/TiO_(2).Co-Ce/TiO_(2)efficiently maintains 10-hour stability test under water vapor conditions and exhibits better photothermal catalytic performance than counterparts under different wavelengths illumination.Photothermal catalytic reaction displays improved activities compared with thermal catalysis,which is attributed to the promotional effect of light including photocatalysis and light activation of reactive oxygen species.展开更多
On-line chemical characterization of atmospheric particulate matter(PM)with soft ionization technique and ultrahigh-resolution Mass Spectrometry(UHRMS)provides molecular information of organic constituents in real tim...On-line chemical characterization of atmospheric particulate matter(PM)with soft ionization technique and ultrahigh-resolution Mass Spectrometry(UHRMS)provides molecular information of organic constituents in real time.Here we describe the development and application of an automatic measurement system that incorporates PM_(2.5)sampling,thermal desorption,atmospheric pressure photoionization,and UHRMS analysis.Molecular formulas of detected organic compounds were deducted from the accurate(±10 ppm)molecular weights obtained at a mass resolution of 100,000,allowing the identification of small organic compounds in PM_(2.5).Detection efficiencies of 28 standard compounds were determined and we found a high sensitivity and selectivity towards organic amines with limits of detection below 10 pg.As a proof of principle,PM_(2.5)samples collected off-line in winter in the urban area of Beijing were analyzed using the Ionization Module and HRMS of the system.The automatic system was then applied to conduct on-line measurements during the summer time at a time resolution of 2 hr.The detected organic compounds comprised mainly CHON and CHN compounds below 350 m/z.Pronounced seasonal variations in elemental composition were observed with shorter carbon backbones and higher O/C ratios in summer than that in winter.This result is consistent with stronger photochemical reactions and thus a higher oxidation state of organics in summer.Diurnal variation in signal intensity of each formula provides crucial information to reveal its source and formation pathway.In summary,the automatic measurement system serves as an important tool for the on-line characterization and identification of organic species in PM_(2.5).展开更多
The pollution of atmospheric ozone in China shows an obvious upward trend in the past decade.However,the studies on the atmospheric oxidation capacity and O_(3)formation in four seasons in the southeastern coastal reg...The pollution of atmospheric ozone in China shows an obvious upward trend in the past decade.However,the studies on the atmospheric oxidation capacity and O_(3)formation in four seasons in the southeastern coastal region of China with the rapid urbanization remain limited.Here,a four-season field observation was carried out in a coastal city of southeast China,using an observation-based model combining with the Master Chemical Mechanism,to explore the atmospheric oxidation capacity(AOC),radical chemistry,O_(3)formation pathways and sensitivity.The results showed that the average net O_(3)production rate(14.55 ppbv/hr)in summer was the strongest,but the average O_(3)concentrations in autumn was higher.The AOC and ROx levels presented an obvious seasonal pattern with the maximum value in summer,while the OH reactivity in winter was the highest with an average value of 22.75 sec^(-1).The OH reactivity was dominated by oxygenated VOCs(OVOCs)(30.6%-42.8%),CO(23.2%-26.8%),NO_(2)(13.6%-22.0%),and alkenes(8.4%-12.5%)in different seasons.HONO photolysis dominated OH primary source on daytime in winter,while in other seasons,HONO photolysis in the morning and ozone photolysis in the afternoon contributed mostly.Sensitivity analysis indicated that O_(3)production was controlled by VOCs in spring,autumn and winter,but a VOC-limited and NOx-limited regime in summer,and alkene and aromatic species were the major controlling factors to O_(3)formation.Overall,the study characterized the atmospheric oxidation capacity and elucidated the controlling factors for O_(3)production in the coastal area with the rapid urbanization in China.展开更多
Severe haze pollution that occurred in January 2014 in Wuhan was investigated. The factors leading to Wuhan’s PM2.5 pollution and the characteristics and formation mechanism were found to be significantly different f...Severe haze pollution that occurred in January 2014 in Wuhan was investigated. The factors leading to Wuhan’s PM2.5 pollution and the characteristics and formation mechanism were found to be significantly different from other megacities, like Beijing. Both the growth rates and decline rates of PM2.5 concentrations in Wuhan were lower than those in Beijing, but the monthly PM2.5 value was approximately twice that in Beijing. Furthermore, the sharp increases of PM2.5 concentrations were often accompanied by strong winds. A high-precision modeling system with an online source-tagged method was established to explore the formation mechanism of five haze episodes. The long-range transport of the polluted air masses from the North China Plain (NCP) was the main factor leading to the sharp increases of PM2.5 concentrations in Wuhan, which contributed 53.4% of the monthly PM2.5 concentrations and 38.5% of polluted days. Furthermore, the change in meteorological conditions such as weakened winds and stable weather conditions led to the accumulation of air pollutants in Wuhan after the long-range transport. The contribution from Wuhan and surrounding cities to the PM2.5 concentrations was determined to be 67.4% during this period. Under the complex regional transport of pollutants from surrounding cities, the NCP, East China, and South China, the five episodes resulted in 30 haze days in Wuhan. The findings reveal important roles played by transregional and intercity transport in haze formation in Wuhan.展开更多
To investigate how the physicochemical properties and NH3‐selective catalytic reduction(NH3‐SCR)performance of supported ceria‐based catalysts are influenced as a function of support type,a series of CeO2/SiO2,CeO2...To investigate how the physicochemical properties and NH3‐selective catalytic reduction(NH3‐SCR)performance of supported ceria‐based catalysts are influenced as a function of support type,a series of CeO2/SiO2,CeO2/γ‐Al2O3,CeO2/ZrO2,and CeO2/TiO2catalysts were prepared.The physicochemical properties were probed by means of X‐ray diffraction,Raman spectroscopy,Brunauer‐Emmett‐Teller surface area measurements,X‐ray photoelectron spectroscopy,H2‐temperature programmed reduction,and NH3‐temperature programmed desorption.Furthermore,the supported ceria‐based catalysts'catalytic performance and H2O+SO2tolerance were evaluated by the NH3‐SCR model reaction.The results indicate that out of the supported ceria‐based catalysts studied,the CeO2/γ‐Al2O3catalyst exhibits the highest catalytic activity as a result of having a high relative Ce3+/Ce4+ratio,optimum reduction behavior,and the largest total acid site concentration.Finally,the CeO2/γ‐Al2O3catalyst also presents excellent H2O+SO2tolerance during the NH3‐SCR process.展开更多
The vertical observation of volatile organic compounds(VOCs)is an important means to clarify the mechanisms of ozone formation.To explore the vertical evolution of VOCs in summer,a field campaign using a tethered ball...The vertical observation of volatile organic compounds(VOCs)is an important means to clarify the mechanisms of ozone formation.To explore the vertical evolution of VOCs in summer,a field campaign using a tethered balloon during summer photochemical pollution was conducted in Shijiazhuang from 8 June to 3 July 2019.A total of 192 samples were collected,23 vertical profiles were obtained,and the concentrations of 87 VOCs were measured.The range of the total VOC concentration was 41-48 ppbv below 600 m.It then slightly increased above 600 m,and rose to 58±52 ppbv at 1000 m.The proportion of alkanes increased with height,while the proportions of alkenes,halohydrocarbons and acetylene decreased.The proportion of aromatics remained almost unchanged.A comparison with the results of a winter field campaign during 8-16 January 2019 showed that the concentrations of all VOCs in winter except for halohydrocarbons were more than twice those in summer.Alkanes accounted for the same proportion in winter and summer.Alkenes,aromatics,and acetylene accounted for higher proportions in winter,while halohydrocarbons accounted for a higher proportion in summer.There were five VOC sources in the vertical direction.The proportions of gasoline vehicular emissions+industrial sources and coal burning were higher in winter.The proportions of biogenic sources+long-range transport,solvent usage,and diesel vehicular emissions were higher in summer.From the surface to 1000 m,the proportion of gasoline vehicular emissions+industrial sources gradually increased.展开更多
With the coming of the“14th Five-Year Plan,”the coordinated control of particulate matter with an aerodynamic diameter no greater than 2.5 lm(PM_(2.5))and O_(3) has become a major issue of air pollution prevention a...With the coming of the“14th Five-Year Plan,”the coordinated control of particulate matter with an aerodynamic diameter no greater than 2.5 lm(PM_(2.5))and O_(3) has become a major issue of air pollution prevention and control in China.The stereoscopic monitoring of regional PM_(2.5) and O_(3) and their precursors is crucial to achieve coordinated control.However,current monitoring networks are currently inadequate for monitoring the vertical profiles of both PM_(2.5) and O_(3) simultaneously and support air quality control.The University of Science and Technology of China(USTC)has established a nationwide ground-based hyperspectral stereoscopic remote sensing network based on multi-axis differential optical absorption spectroscopy(MAX-DOAS)since 2015.This monitoring network provides a significant opportunity for the regional coordinated control of PM_(2.5) and O_(3) in China.One-year vertical profiles of aerosol,NO_(2) and HCHO monitored from four MAX-DOAS stations installed in four megacities(Beijing,Shanghai,Shenzhen,and Chongqing)were used to characterize their vertical distribution differences in four key regions,Jing–Jin–Ji(JJJ),Yangtze River Delta(YRD),Pearl River Delta(PRD),and Sichuan Basin(SB),respectively.The normalized and yearly averaged aerosol vertical profiles below 400 m in JJJ and PRD exhibit a box shape and a Gaussian shape,respectively,and both show exponential shapes in YRD and SB.The NO_(2) vertical profiles in four regions all exhibit exponential shapes because of vehicle emissions.The shape of the HCHO vertical profile in JJJ and PRD was Gaussian,whereas an exponential shape was shown in YRD and SB.Moreover,a regional transport event occurred at an altitude of 600–1000 m was monitored in the southwest–northeast pathway of the North China Plain(NCP)by five MAX-DOAS stations(Shijiazhuang(SJZ),Wangdu(WD),Nancheng(NC),Chinese Academy of Meteorological Sciences(CAMS),and University of Chinese Academy of Sciences(UCAS))belonging to the above network.The aerosol optical depths(AOD)in these five stations decreased in the order of SJZ>WD>NC>CAMS>UCAS.The short-distance regional transport of NO2 in the 700–900 m layer was monitored between WD and NC.As an important precursor of secondary aerosol,the peak of NO_(2) air mass in WD and NC all occurred 1 h earlier than that of aerosol.This was also observed for the short-distance regional transport of HCHO in the 700–900 m layer between NC and CAMS,which potentially affected the O_(3) concentration in Beijing.Finally,CAMS was selected as a typical site to determine the O_(3)–NO_(x)–volatile organic compounds(VOCs)sensitivities in vertical space.We found the production of O_(3) changed from predominantly VOCs-limited conditions to mainly mixed VOCs–NO_(x)-limited condition from the 0–100 m layer to the 200–300 m layer.In addition,the downward transport of O_(3) could contribute to the increase of ground surface O_(3) concentration.This ground-based hyperspectral stereoscopic remote sensing network provide a promising strategy to support management of PM_(2.5) and O_(3) and their precursors and conduct attribution of sources.展开更多
Three-month wind profiles, 260 m PM_1 concentrations [i.e., particulate matter(PM) with an aerodynamic diameter ≤1μm], and carrier-to-noise ratio data at two Beijing sites 55 km apart(urban and suburban) were collec...Three-month wind profiles, 260 m PM_1 concentrations [i.e., particulate matter(PM) with an aerodynamic diameter ≤1μm], and carrier-to-noise ratio data at two Beijing sites 55 km apart(urban and suburban) were collected to analyze the characteristics of low-level nocturnal wind and PM in autumn and winter. Three mountain-plain wind events with wind shear were selected for analysis. The measurements indicated that the maximum wind speeds of the northerly weak low-level jet(LLJ) below 320 m at the suburban site were weaker than those at the urban site, and the LLJ heights and depths at the suburban site were lower than those at the urban site. The nocturnal 140 m mean vertical velocities and the variations in vertical velocity at the urban site were larger than those at the suburban site. A nocturnal breeze with a weak LLJ of ～3 m s^(-1) noticeably offset nocturnal PM transport due to southerly flow and convergence within the northern urban area of Beijing. Characteristics of the nocturnal LLJ, such as start-up time, structure, intensity, and duration, were important factors in determining the decrease in the nocturnal horizontal range and site-based low-level variations in PM.展开更多
A field experiment of nocturnal mountain wind and corresponding particulate matter （PM） evolution under weak synoptic forcing at five sites within urban Beijing was conducted using a moving Doppler wind lidar and a ...A field experiment of nocturnal mountain wind and corresponding particulate matter （PM） evolution under weak synoptic forcing at five sites within urban Beijing was conducted using a moving Doppler wind lidar and a fixed tower. Clear wind shear and zero-horizontal-wind zones at 40-320 m above the ground with a delay of 1.5 h were found at two sites between 20 km from north to south urban Beijing. The wind speed and height of the low-level jet at the north urban Beijing site were greater than those at the east urban Beijing site. The average horizontal distribution of low-level PM at 240 m was similar to the ground-level PM at night. The PM2.s （aerodynamic diameter ≤2.5 μm） accumulation center showed no abrupt changes with a shift in wind direction until the northerly wind jet arrived.展开更多
Multiaxis differential absorption spectroscopy(MAX-DOAS)is a newly developed advanced vertical profile detection method,but the vertical nitrogen dioxide(NO_(2))profiles measured by MAX-DOAS have not yet been fully ve...Multiaxis differential absorption spectroscopy(MAX-DOAS)is a newly developed advanced vertical profile detection method,but the vertical nitrogen dioxide(NO_(2))profiles measured by MAX-DOAS have not yet been fully verified.In this study,we perform MAX-DOAS and tower gradient observations to simultaneously acquire tropospheric NO_(2)observations in the Beijing urban area from 1 April to 31 May 2019.The average values of the tropospheric NO_(2)vertical column densities measured by MAX-DOAS and the tropospheric monitoring instrument are 15.8×1015 and 12.4×1015 molecules cm−2,respectively,and the correlation coefficient R reaches 0.87.The MAX-DOAS measurements are highly consistent with the tower-based in situ measurements,and the correlation coefficients R from the ground to the upper air are 0.89(60 m),0.87(160 m),and 0.76(280 m).MAX-DOAS accurately measures the trend of NO_(2)vertical profile changes,although a large underestimation occurs by a factor of two.By analyzing the NO_(2)vertical profile,the NO_(2)concentration reveals an exponential decrease with height.The NO_(2)vertical profile also coincides with the evolution of the boundary layer height.The study shows that the NO_(2)over Beijing mainly originates from local sources and occurs in the boundary layer,and its vertical evolution pattern has an important guiding significance to better understand nitrate production and ozone pollution.展开更多
Based on online observations of fine particulate matter(PM2.5) for five consecutive years from January 2013 to December 2017 in Beijing, combined with simultaneous measurement of gaseous precursors and meteorological ...Based on online observations of fine particulate matter(PM2.5) for five consecutive years from January 2013 to December 2017 in Beijing, combined with simultaneous measurement of gaseous precursors and meteorological parameters, the evolution and meteorological causes of fineparticle explosive growth(FPEG) events were analyzed. During the 5-year observation period,132 FPEG events were observed and these events were further divided into three types(3-, 6-, and 9-h events) according to their evolution duration. The majority of FPEG events were observed in winter under the conditions of higher gas precursor concentrations and unfavorable meteorological conditions. The average concentration of PM2.5 during winter FPEG events changed little from 2013 to 2016, whereas it decreased significantly in 2017, in accordance with the similar variation of gaseous species(SO2, NO2, and CO). In addition, the higher wind speeds and lowest relative humidity observed in 2017 were also conducive to the decrease in PM2.5. The evolutions of FPEG events and normal haze episodes were analyzed, revealing that the rate of increase in NO2 was much greater than that of SO2, suggesting more of a contribution from mobile sources than stationary sources. The polar Plot results suggest that the transportation from the southeast area of Beijing plays a major role in the formation of 3-h events, whereas local emissions is the main contributory factor for 9-h events and normal haze episodes. However, further quantitative analysis regarding the contributions of these factors is still needed.展开更多
1.Introduction In recent years,the air quality in China has improved significantly.In many cities,however,the concentration of fine particulate matter(PM_(2.5))remains higher than the secondary-level national ambient ...1.Introduction In recent years,the air quality in China has improved significantly.In many cities,however,the concentration of fine particulate matter(PM_(2.5))remains higher than the secondary-level national ambient air quality standard(NAAQS level-2,35μg·m^(-3),GB3095-2012[1])and much higher than the first-level NAAQS(15μg·m^(-3),GB3095-2012[1])and the World Health Organization(WHO)air quality guidelines(5μg·m^(-3)).展开更多
In recent years,China has implemented several measures to improve air quality.The Beijing-Tianjin-Hebei(BTH)region is one area that has suffered from the most serious air pollution in China and has undergone huge chan...In recent years,China has implemented several measures to improve air quality.The Beijing-Tianjin-Hebei(BTH)region is one area that has suffered from the most serious air pollution in China and has undergone huge changes in air quality in the past few years.How to scientifically assess these change processes remain the key issue in further improving the air quality over this region in the future.To evaluate the changes in major air pollutant emissions over this region,this paper employs ensemble Kalman filtering(EnKF)for integrating the national ground monitoring pollutant observation data and the Nested Air Quality Prediction Modeling System(NAQPMS)simulation data to inversely estimate the emission rates of SO_(2),NOX,CO,and primary PM_(2.5)over BTH region in February from 2014 to 2019.The results show that SO_(2),NOX,CO,and primary PM_(2.5)emissions in the BTH region decreased in February from 2014 to 2019 by 83%,37%,41%,and 42%,while decreases in Beijing during this period were 86%,67%,59%,and 65%,respectively.Compared with the prior emission inventory,the inversion emission inventory reduces the uncertainty of multi-pollutant simulation in the BTH region,with simulated root mean square errors of the monthly average concentrations of SO_(2),NOX,PM_(2.5),and CO reduced by 41%,30%,31%,and 22%,respectively.The average uncertainties of SO_(2),NOX,PM_(2.5),and CO inversion emissions in2014-19 are±14.03%yr^(-1),±28.91%yr^(-1),±126.15%yr^(-1),and±43.58%yr^(-1).Compared with the uncertainty of MEIC emission,the uncertainties of all species changed by+2%yr^(-1),-2%yr^(-1),-26%yr^(-1),and-4%yr^(-1),respectively.The spatial distribution results illustrate that air pollutant emissions are mainly distributed over the eastern and southern BTH regions.The spatial gap between the inversion emissions and MEIC emissions was further closed in 2019 compared to 2014.The results of this paper can provide a new reference for assessing changes in air pollution emissions over the BTH region in recent years and validating a bottom-up emission inventory.展开更多
A series of Co-based oxide catalysts were prepared by calcining hydrotalcite precursors in different atmospheres and studied for HCHO catalytic oxidation. The N2-calcined catalyst exhibits enhanced HCHO oxidation and ...A series of Co-based oxide catalysts were prepared by calcining hydrotalcite precursors in different atmospheres and studied for HCHO catalytic oxidation. The N2-calcined catalyst exhibits enhanced HCHO oxidation and superior stability. On the basis of H2-TPR, X-ray photoelectron spectroscopy, and Raman characterizations, this can be ascribed to better redox ability, octahedrally coordinated Co2+ ions derived from the CoO phase, and other surface oxygen species, such as O2– or O–. The extra octahedrally coordinated Co2+ ions may reside in a more open framework site than the inactive tetrahedrally coordinated Co2+ ions. This species of Co2+ can easily make contact with oxygen and oxidize. The surface oxygen species, along with the octahedrally coordinated Co2+ ions, and a part of the Co3+ species constitute the Co2+-oxygen species-Co3+ sites, which enhance the catalytic activities. According to DRIFTS, Co2+-oxygen species-Co3+ makes oxidation of HCHO and conversion of DOM to formate easier.展开更多
基金supported by the National Natural Science Foundation of China (No. 21507130)the Open Project Program of Beijing National Laboratory for Molecular Sciences (No. 20140142)+3 种基金the Open Project Program of Chongqing Key Laboratory of Environmental Materials and Remediation Technology from Chongqing University of Arts and Sciences (No. CEK1405)the Open Project Program of Jiangsu Key Laboratory of Vehicle Emissions Control (No. OVEC001)the Open Project Program of Chongqing Key Laboratory of Catalysis and Functional Organic Molecules from Chongqing Technology and Business University (1456029)the Chongqing Science & Technology Commission (Nos. cstc2016jcyj A0070, cstc2014pt-gc20002, cstckjcxljrc13)~~
文摘This work examines the influence of preparation methods on the physicochemical properties and catalytic performance of MnOx‐CeO2 catalysts for selective catalytic reduction of NO by NH3 (NH3‐SCR) at low temperature. Five different methods, namely, mechanical mixing, impregnation,hydrothermal treatment, co‐precipitation, and a sol‐gel technique, were used to synthesizeMnOx‐CeO2 catalysts. The catalysts were characterized in detail, and an NH3‐SCR model reaction waschosen to evaluate the catalytic performance. The results showed that the preparation methodsaffected the catalytic performance in the order: hydrothermal treatment > sol‐gel > co‐precipitation> impregnation > mechanical mixing. This order correlated with the surface Ce3+ and Mn4+ content,oxygen vacancies and surface adsorbed oxygen species concentration, and the amount of acidic sitesand acidic strength. This trend is related to redox interactions between MnOx and CeO2. The catalystformed by a hydrothermal treatment exhibited excellent physicochemical properties, optimal catalyticperformance, and good H2O resistance in NH3‐SCR reaction. This was attributed to incorporationof Mnn+ into the CeO2 lattice to form a uniform ceria‐based solid solution (containing Mn‐O‐Cestructures). Strengthening of the electronic interactions between MnOx and CeO2, driven by thehigh‐temperature and high‐pressure conditions during the hydrothermal treatment also improved the catalyst characteristics. Thus, the hydrothermal treatment method is an efficient and environment‐friendly route to synthesizing low‐temperature denitrification (deNOx) catalysts.
基金supported by National Natural Science Foundation of China (21876168, 21507130)Youth Innovation Promotion Association of CAS (2019376)the Chongqing Science & Technology Commission (cstc2016jcyjA0070, cstckjcxljrc13)~~
文摘Thermally stable Zr4+, Al3+, and Si4+ cations were incorporated into the lattice of CeO2 nano‐rods (i.e., CeO2‐NR) in order to improve the specific surface area. The undoped and Zr4+, Al3+, and Si4+ doped nano‐rods were used as supports to prepare MnOx/CeO2‐NR, MnOx/CZ‐NR, MnOx/CA‐NR, and MnOx/CS‐NR catalysts, respectively. The prepared supports and catalysts were comprehensively characterized by transmission electron microscopy (TEM), high‐resolution TEM, X‐ray diffraction, Raman and N2‐physisorption analyses, hydrogen temperature‐programmed reduction, ammonia temperature‐programmed desorption, in situ diffuse reflectance infrared Fourier‐transform spectroscopic analysis of the NH3 adsorption, and X‐ray photoelectron spectroscopy. Moreover, the catalytic performance and H2O+SO2 tolerance of these samples were evaluated through NH3‐selective catalytic reduction (NH3‐SCR) in the absence or presence of H2O and SO2. The obtained results show that the MnOx/CS‐NR catalyst exhibits the highest NOx conversion and the lowest N2O concentration, which result from the largest number of oxygen vacancies and acid sites, the highest Mn4+ content, and the lowest redox ability. The MnOx/CS‐NR catalyst also presents excellent resistance to H2O and SO2. All of these phenomena suggest that Si4+ is the optimal dopant for the MnOx/CeO2‐NR catalyst.
基金supported by the National Natural Science Foundation(Grant Nos.41875164&92044303)the National Key Research and Development Plan(Grant No.YS2020YFA060022).
文摘China national air quality monitoring network has become the core data source for air quality assessment and management in China.However,during network construction,the significant change in numbers of monitoring sites with time is easily ignored,which brings uncertainty to air quality assessments.This study aims to analyze the impact of change in numbers of stations on national and regional air quality assessments in China during 2013-18.The results indicate that the change in numbers of stations has different impacts on fine particulate matter(PM_(2.5))and ozone concentration assessments.The increasing number of sites makes the estimated national and regional PM_(2.5) concentration slightly lower by 0.6−2.2μg m^(−3) and 1.4−6.0μg m^(−3) respectively from 2013 to 2018.The main reason is that over time,the monitoring network expands from the urban centers to the suburban areas with low population densities and pollutant emissions.For ozone,the increasing number of stations affects the long-term trends of the estimated concentration,especially the national trends,which changed from a slight upward trend to a downward trend in 2014−15.Besides,the impact of the increasing number of sites on ozone assessment exhibits a seasonal difference at the 0.05 significance level in that the added sites make the estimated concentration higher in winter and lower in summer.These results suggest that the change in numbers of monitoring sites is an important uncertainty factor in national and regional air quality assessments,that needs to be considered in long-term concentration assessment,trend analysis,and trend driving force analysis.
基金the National Key Scientific and Technological Infrastructure project “Earth System Science Numerical Simulator Facility” (Earth Lab)
文摘The attainment of suitable ambient air quality standards is a matter of great concern for successfully hosting the ⅩⅩⅣ Olympic Winter Games(OWG). Transport patterns and potential sources of pollutants in Zhangjiakou(ZJK) were investigated using pollutant monitoring datasets and a dispersion model. The PM_(2.5) concentration during February in ZJK has increased slightly(28%) from 2018 to 2021, mostly owing to the shift of main potential source regions of west-central Inner Mongolia and Mongolian areas(2015–18) to the North China Plain and northern Shanxi Province(NCPS) after 2018.Using CO as an indicator, the relative contributions of the different regions to the receptor site(ZJK) were evaluated based on the source-receptor-relationship method(SRR) and an emission inventory. We found that the relative contribution of pollutants from NCPS increased from 33% to 68% during 2019–21. Central Inner Mongolia(CIM) also has an important impact on ZJK under unfavorable weather conditions. This study demonstrated that the effect of pollution control measures in the NCPS and CIM should be strengthened to ensure that the air quality meets the standard during the ⅩⅩⅣ OWG.
基金supported by the National Natural Science Foundation of China(Nos.22276182 and 22188102)the Natural Science Foundation of Fujian Province,China(No.2023J06048)the Youth Innovation Promotion Association of Chinese Academy of Sciences(No.2021303).
文摘NH_(3)-SCR(SCR:Selective catalytic reduction)is an effective technology for the de-NO_(x)process from both mobile and stationary pollution sources,and the most commonly used catalysts are the vanadia-based catalysts.An innovative V_(2)O_(5)-CeO_(2)/TaTiO_(x)catalyst for NO_(x)removal was prepared in this study.The influences of Ce and Ta in the V_(2)O_(5)-CeO_(2)/TaTiO_(x)catalyst on the SCR performance and physicochemical properties were investigated.The V_(2)O_(5)-CeO_(2)/TaTiO_(x)catalyst not only exhibited excellent SCR activity in a wide temperature window,but also presented strong resistance to H_(2)Oand SO_(2)at 275◦C.A series of characterizationmethods was used to study the catalysts,including H2-temperature programmed reduction,X-ray photoelectron spectroscopy,NH_(3)-temperature programmed desorption,etc.It was discovered that a synergistic effect existed between Ce and Ta species.The introduction of Ce and Ta enlarged the specific surface area,increased the amount of acid sites and the ratio of Ce^(3+),(V^(3+)+V^(4+))and Oα,and strengthened the redox capability which were related to synergistic effect between Ce and Ta species,significantly improving the NH_(3)-SCR activity.
基金supported by the Key Research and Development Program of Hebei Province(No.21373702D)the Key Science and Technology Program of HBIS Group Co.,Ltd.(No.HG2021117)+1 种基金the National Natural Science Foundation of China(No.52370124)the National Key R&D Program of China(No.2023YFC3707003).
文摘About 70%of the flue gas in the iron-steel industry has achieved multi-pollutant ultra-low emissions in China until 2023,and then the blast furnace gas purification has become the control step and bottleneck.Our research group has designed and constructed the world’s first blast furnace gas desulfurization pilot plant with the scale of 2000 Nm^(3)/h in October 2021.The pilot plant is a two-step combined desulfurization device including catalytic hydrolysis of carbonyl sulfur(COS)and absorption-oxidation of H_(2)S,continuously running for 120 days.In the hydrolysis system,one reason for catalyst deactivation has been verified from the sulfur deposition.HCN in blast furnace gas can be hydrolyzed on the hydrolysis catalyst to produce the nitrogen deposition,which is one of the reasons for catalyst deactivation and has never been found in previous studies.The deposition forms of S and N elements are determined,S element forms elemental sulfur and sulfate,while N element forms-NH_(2)and NH_(4)^(+).In the absorption-oxidation system,the O_(2)loading and the residence time have been optimized to control the oxidation of HS^(−)to produce elemental sulfur instead of by-product S_(2)O_(3)^(2−).The balance and distribution of S and N elements have been calculated for thewholemulti-phase system,approximately 84.4%of the sulfur is converted to solid sulfur product,about 1.3%of the sulfur and 19.2%of N element are deposited on the hydrolysis catalyst.The pilot plant provides technical support formulti-pollutant control of blast furnace.
基金supported by the Science and Technology Planning Project of Xiamen(No.3502Z20226022)the National Natural Science Foundation of China(Nos.22376193 and 22176187).
文摘Cerium and cobalt loaded Co-Ce/TiO_(2)catalyst prepared by impregnation method was investigated for photothermal catalytic toluene oxidation.Based on catalyst characterizations(XPS,EPR and H2-TPR),redox cycle between Co and TiO_(2)(Co^(2+)+Ti^(4+)↔Co^(3+)+Ti^(3+))results in the formation of Co^(3+),Ti^(3+)and oxygen vacancies,which play important roles in toluene catalytic oxidation reaction.The introduction of Ce brings in the dual redox cycles(Co^(2+)+Ti^(4+)↔Co^(3+)+Ti^(3+),Co^(2+)+Ce4+↔Co^(3+)+Ce3+),further promoting the elevation of reaction sites amount.Under full spectrum irradiation with light intensity of 580mW/cm^(2),Co-Ce/TiO_(2)catalyst achieved 96%of toluene conversion and 73%of CO_(2)yield,obviously higher than Co/P25 and Co/TiO_(2).Co-Ce/TiO_(2)efficiently maintains 10-hour stability test under water vapor conditions and exhibits better photothermal catalytic performance than counterparts under different wavelengths illumination.Photothermal catalytic reaction displays improved activities compared with thermal catalysis,which is attributed to the promotional effect of light including photocatalysis and light activation of reactive oxygen species.
基金supported by the National Natural Science Foundation of China(No.41805105)。
文摘On-line chemical characterization of atmospheric particulate matter(PM)with soft ionization technique and ultrahigh-resolution Mass Spectrometry(UHRMS)provides molecular information of organic constituents in real time.Here we describe the development and application of an automatic measurement system that incorporates PM_(2.5)sampling,thermal desorption,atmospheric pressure photoionization,and UHRMS analysis.Molecular formulas of detected organic compounds were deducted from the accurate(±10 ppm)molecular weights obtained at a mass resolution of 100,000,allowing the identification of small organic compounds in PM_(2.5).Detection efficiencies of 28 standard compounds were determined and we found a high sensitivity and selectivity towards organic amines with limits of detection below 10 pg.As a proof of principle,PM_(2.5)samples collected off-line in winter in the urban area of Beijing were analyzed using the Ionization Module and HRMS of the system.The automatic system was then applied to conduct on-line measurements during the summer time at a time resolution of 2 hr.The detected organic compounds comprised mainly CHON and CHN compounds below 350 m/z.Pronounced seasonal variations in elemental composition were observed with shorter carbon backbones and higher O/C ratios in summer than that in winter.This result is consistent with stronger photochemical reactions and thus a higher oxidation state of organics in summer.Diurnal variation in signal intensity of each formula provides crucial information to reveal its source and formation pathway.In summary,the automatic measurement system serves as an important tool for the on-line characterization and identification of organic species in PM_(2.5).
基金funded by the Cultivating Project of Strategic Priority Research Program of Chinese Academy of Sciences (No.XDPB1903)the Science and Technology Department of Fujian Province (No.2022L3025)+1 种基金the National Natural Science Foundation of China (No.U22A20578&42277091)the Center for Excellence in Regional Atmospheric Environment Project (No.E0L1B20201)。
文摘The pollution of atmospheric ozone in China shows an obvious upward trend in the past decade.However,the studies on the atmospheric oxidation capacity and O_(3)formation in four seasons in the southeastern coastal region of China with the rapid urbanization remain limited.Here,a four-season field observation was carried out in a coastal city of southeast China,using an observation-based model combining with the Master Chemical Mechanism,to explore the atmospheric oxidation capacity(AOC),radical chemistry,O_(3)formation pathways and sensitivity.The results showed that the average net O_(3)production rate(14.55 ppbv/hr)in summer was the strongest,but the average O_(3)concentrations in autumn was higher.The AOC and ROx levels presented an obvious seasonal pattern with the maximum value in summer,while the OH reactivity in winter was the highest with an average value of 22.75 sec^(-1).The OH reactivity was dominated by oxygenated VOCs(OVOCs)(30.6%-42.8%),CO(23.2%-26.8%),NO_(2)(13.6%-22.0%),and alkenes(8.4%-12.5%)in different seasons.HONO photolysis dominated OH primary source on daytime in winter,while in other seasons,HONO photolysis in the morning and ozone photolysis in the afternoon contributed mostly.Sensitivity analysis indicated that O_(3)production was controlled by VOCs in spring,autumn and winter,but a VOC-limited and NOx-limited regime in summer,and alkene and aromatic species were the major controlling factors to O_(3)formation.Overall,the study characterized the atmospheric oxidation capacity and elucidated the controlling factors for O_(3)production in the coastal area with the rapid urbanization in China.
基金supported by the National Key R&D Program (Grant Nos. 2017YFC0212603 and 2017YFC0212604)the Chinese Academy of Sciences Strategic Priority Research Program (Grant No. XDA19040201)the National Natural Science Foundation of China (Grant Nos. 41575128 and 41620104008)
文摘Severe haze pollution that occurred in January 2014 in Wuhan was investigated. The factors leading to Wuhan’s PM2.5 pollution and the characteristics and formation mechanism were found to be significantly different from other megacities, like Beijing. Both the growth rates and decline rates of PM2.5 concentrations in Wuhan were lower than those in Beijing, but the monthly PM2.5 value was approximately twice that in Beijing. Furthermore, the sharp increases of PM2.5 concentrations were often accompanied by strong winds. A high-precision modeling system with an online source-tagged method was established to explore the formation mechanism of five haze episodes. The long-range transport of the polluted air masses from the North China Plain (NCP) was the main factor leading to the sharp increases of PM2.5 concentrations in Wuhan, which contributed 53.4% of the monthly PM2.5 concentrations and 38.5% of polluted days. Furthermore, the change in meteorological conditions such as weakened winds and stable weather conditions led to the accumulation of air pollutants in Wuhan after the long-range transport. The contribution from Wuhan and surrounding cities to the PM2.5 concentrations was determined to be 67.4% during this period. Under the complex regional transport of pollutants from surrounding cities, the NCP, East China, and South China, the five episodes resulted in 30 haze days in Wuhan. The findings reveal important roles played by transregional and intercity transport in haze formation in Wuhan.
基金supported by the National Natural Science Foundation of China (21507130)the Chongqing Science and Technology Commission (cstc2016jcyjA 0070,cstc2014pt-gc20002,cstc2014yykfC 20003,cstckjcxljrc13)the Open Project Program of Chongqing Key Laboratory of Ca-talysis and Functional Organic Molecules from Chongqing Technology and Business University (1456029)~~
文摘To investigate how the physicochemical properties and NH3‐selective catalytic reduction(NH3‐SCR)performance of supported ceria‐based catalysts are influenced as a function of support type,a series of CeO2/SiO2,CeO2/γ‐Al2O3,CeO2/ZrO2,and CeO2/TiO2catalysts were prepared.The physicochemical properties were probed by means of X‐ray diffraction,Raman spectroscopy,Brunauer‐Emmett‐Teller surface area measurements,X‐ray photoelectron spectroscopy,H2‐temperature programmed reduction,and NH3‐temperature programmed desorption.Furthermore,the supported ceria‐based catalysts'catalytic performance and H2O+SO2tolerance were evaluated by the NH3‐SCR model reaction.The results indicate that out of the supported ceria‐based catalysts studied,the CeO2/γ‐Al2O3catalyst exhibits the highest catalytic activity as a result of having a high relative Ce3+/Ce4+ratio,optimum reduction behavior,and the largest total acid site concentration.Finally,the CeO2/γ‐Al2O3catalyst also presents excellent H2O+SO2tolerance during the NH3‐SCR process.
基金This work was supported by the National Key R&D Program of China(Grant No.2017YFC0210000)the National Natural Science Foundation of China(Grant Nos.41705113 and 41877312)+1 种基金the Young Talent Project of the Center for Excellence in Regional Atmospheric Environment,Chinese Academy of Sciences(Grant No.CERAE201802)a Beijing Major Science and Technology Project(Grant No.Z181100005418014).
文摘The vertical observation of volatile organic compounds(VOCs)is an important means to clarify the mechanisms of ozone formation.To explore the vertical evolution of VOCs in summer,a field campaign using a tethered balloon during summer photochemical pollution was conducted in Shijiazhuang from 8 June to 3 July 2019.A total of 192 samples were collected,23 vertical profiles were obtained,and the concentrations of 87 VOCs were measured.The range of the total VOC concentration was 41-48 ppbv below 600 m.It then slightly increased above 600 m,and rose to 58±52 ppbv at 1000 m.The proportion of alkanes increased with height,while the proportions of alkenes,halohydrocarbons and acetylene decreased.The proportion of aromatics remained almost unchanged.A comparison with the results of a winter field campaign during 8-16 January 2019 showed that the concentrations of all VOCs in winter except for halohydrocarbons were more than twice those in summer.Alkanes accounted for the same proportion in winter and summer.Alkenes,aromatics,and acetylene accounted for higher proportions in winter,while halohydrocarbons accounted for a higher proportion in summer.There were five VOC sources in the vertical direction.The proportions of gasoline vehicular emissions+industrial sources and coal burning were higher in winter.The proportions of biogenic sources+long-range transport,solvent usage,and diesel vehicular emissions were higher in summer.From the surface to 1000 m,the proportion of gasoline vehicular emissions+industrial sources gradually increased.
基金This research is supported by grants from the National Key Research and Development Program of China(2018YFC0213104)Project supported by the Presidential Foundation of the Hefei Institutes of Physical Science,Chinese Academy Sciences,China-“Spark”(YZJJ2021QN06)+6 种基金National Natural Science Foundation of China(41722501,91544212,51778596,41575021,41977184,and 41875043)National Key Research and Development Program of China(2017YFC0210002,2016YFC0203302,and 2017YFC0212800)Anhui Science and Technology Major Project(18030801111)the Strategic Priority Research Program of the Chinese Academy of Sciences(XDA23020301)the National Key Project for Causes and Control of Heavy Air Pollution(DQGG0102 and DQGG0205)the National High-Resolution Earth Observation Project of China(05-Y30B01-9001-19/20-3)Civil Aerospace Technology Advance Research Project(Y7K00100KJ).From 0-100 and 200-300 m layers,the production of O_(3) changed from predominantly VOCs-limited condition to mainly mixed VOCs-NOx-limited condition.
文摘With the coming of the“14th Five-Year Plan,”the coordinated control of particulate matter with an aerodynamic diameter no greater than 2.5 lm(PM_(2.5))and O_(3) has become a major issue of air pollution prevention and control in China.The stereoscopic monitoring of regional PM_(2.5) and O_(3) and their precursors is crucial to achieve coordinated control.However,current monitoring networks are currently inadequate for monitoring the vertical profiles of both PM_(2.5) and O_(3) simultaneously and support air quality control.The University of Science and Technology of China(USTC)has established a nationwide ground-based hyperspectral stereoscopic remote sensing network based on multi-axis differential optical absorption spectroscopy(MAX-DOAS)since 2015.This monitoring network provides a significant opportunity for the regional coordinated control of PM_(2.5) and O_(3) in China.One-year vertical profiles of aerosol,NO_(2) and HCHO monitored from four MAX-DOAS stations installed in four megacities(Beijing,Shanghai,Shenzhen,and Chongqing)were used to characterize their vertical distribution differences in four key regions,Jing–Jin–Ji(JJJ),Yangtze River Delta(YRD),Pearl River Delta(PRD),and Sichuan Basin(SB),respectively.The normalized and yearly averaged aerosol vertical profiles below 400 m in JJJ and PRD exhibit a box shape and a Gaussian shape,respectively,and both show exponential shapes in YRD and SB.The NO_(2) vertical profiles in four regions all exhibit exponential shapes because of vehicle emissions.The shape of the HCHO vertical profile in JJJ and PRD was Gaussian,whereas an exponential shape was shown in YRD and SB.Moreover,a regional transport event occurred at an altitude of 600–1000 m was monitored in the southwest–northeast pathway of the North China Plain(NCP)by five MAX-DOAS stations(Shijiazhuang(SJZ),Wangdu(WD),Nancheng(NC),Chinese Academy of Meteorological Sciences(CAMS),and University of Chinese Academy of Sciences(UCAS))belonging to the above network.The aerosol optical depths(AOD)in these five stations decreased in the order of SJZ>WD>NC>CAMS>UCAS.The short-distance regional transport of NO2 in the 700–900 m layer was monitored between WD and NC.As an important precursor of secondary aerosol,the peak of NO_(2) air mass in WD and NC all occurred 1 h earlier than that of aerosol.This was also observed for the short-distance regional transport of HCHO in the 700–900 m layer between NC and CAMS,which potentially affected the O_(3) concentration in Beijing.Finally,CAMS was selected as a typical site to determine the O_(3)–NO_(x)–volatile organic compounds(VOCs)sensitivities in vertical space.We found the production of O_(3) changed from predominantly VOCs-limited conditions to mainly mixed VOCs–NO_(x)-limited condition from the 0–100 m layer to the 200–300 m layer.In addition,the downward transport of O_(3) could contribute to the increase of ground surface O_(3) concentration.This ground-based hyperspectral stereoscopic remote sensing network provide a promising strategy to support management of PM_(2.5) and O_(3) and their precursors and conduct attribution of sources.
基金supported by the National Key R&D Program of China (Grant No.2017YFC0209801)the National Natural Science Foundation of China (Grant Nos.41505091,91544221,41675137,41575124 and 41505116)
文摘Three-month wind profiles, 260 m PM_1 concentrations [i.e., particulate matter(PM) with an aerodynamic diameter ≤1μm], and carrier-to-noise ratio data at two Beijing sites 55 km apart(urban and suburban) were collected to analyze the characteristics of low-level nocturnal wind and PM in autumn and winter. Three mountain-plain wind events with wind shear were selected for analysis. The measurements indicated that the maximum wind speeds of the northerly weak low-level jet(LLJ) below 320 m at the suburban site were weaker than those at the urban site, and the LLJ heights and depths at the suburban site were lower than those at the urban site. The nocturnal 140 m mean vertical velocities and the variations in vertical velocity at the urban site were larger than those at the suburban site. A nocturnal breeze with a weak LLJ of ～3 m s^(-1) noticeably offset nocturnal PM transport due to southerly flow and convergence within the northern urban area of Beijing. Characteristics of the nocturnal LLJ, such as start-up time, structure, intensity, and duration, were important factors in determining the decrease in the nocturnal horizontal range and site-based low-level variations in PM.
基金supported by the National Natural Science Foundation of China[grant number 91544221],[grant number41571130024],[grant number 41675137],[grant number41505091]the LAPC Free Exploration Fund
文摘A field experiment of nocturnal mountain wind and corresponding particulate matter （PM） evolution under weak synoptic forcing at five sites within urban Beijing was conducted using a moving Doppler wind lidar and a fixed tower. Clear wind shear and zero-horizontal-wind zones at 40-320 m above the ground with a delay of 1.5 h were found at two sites between 20 km from north to south urban Beijing. The wind speed and height of the low-level jet at the north urban Beijing site were greater than those at the east urban Beijing site. The average horizontal distribution of low-level PM at 240 m was similar to the ground-level PM at night. The PM2.s （aerodynamic diameter ≤2.5 μm） accumulation center showed no abrupt changes with a shift in wind direction until the northerly wind jet arrived.
基金This work was supported by the National Key R&D Program of China(Grant No.2017YFC0210000)the National Natural Science Foundation of China(Grant Nos.41705113,41877312)+1 种基金the National Research Program for Key Issues in Air Pollution Control(Grant No.DGQQ202004)the Beijing Major Science and Technology Project(Grant No.Z181100005418014).
文摘Multiaxis differential absorption spectroscopy(MAX-DOAS)is a newly developed advanced vertical profile detection method,but the vertical nitrogen dioxide(NO_(2))profiles measured by MAX-DOAS have not yet been fully verified.In this study,we perform MAX-DOAS and tower gradient observations to simultaneously acquire tropospheric NO_(2)observations in the Beijing urban area from 1 April to 31 May 2019.The average values of the tropospheric NO_(2)vertical column densities measured by MAX-DOAS and the tropospheric monitoring instrument are 15.8×1015 and 12.4×1015 molecules cm−2,respectively,and the correlation coefficient R reaches 0.87.The MAX-DOAS measurements are highly consistent with the tower-based in situ measurements,and the correlation coefficients R from the ground to the upper air are 0.89(60 m),0.87(160 m),and 0.76(280 m).MAX-DOAS accurately measures the trend of NO_(2)vertical profile changes,although a large underestimation occurs by a factor of two.By analyzing the NO_(2)vertical profile,the NO_(2)concentration reveals an exponential decrease with height.The NO_(2)vertical profile also coincides with the evolution of the boundary layer height.The study shows that the NO_(2)over Beijing mainly originates from local sources and occurs in the boundary layer,and its vertical evolution pattern has an important guiding significance to better understand nitrate production and ozone pollution.
基金This study was supported by The Ministry of Science and Technology of the people's Republic of China:[Grant Numbers 2017YFC0210000 and 2016YFC0202700]the National Natural Science Foundation of China:[Grant Number 41705110].
文摘Based on online observations of fine particulate matter(PM2.5) for five consecutive years from January 2013 to December 2017 in Beijing, combined with simultaneous measurement of gaseous precursors and meteorological parameters, the evolution and meteorological causes of fineparticle explosive growth(FPEG) events were analyzed. During the 5-year observation period,132 FPEG events were observed and these events were further divided into three types(3-, 6-, and 9-h events) according to their evolution duration. The majority of FPEG events were observed in winter under the conditions of higher gas precursor concentrations and unfavorable meteorological conditions. The average concentration of PM2.5 during winter FPEG events changed little from 2013 to 2016, whereas it decreased significantly in 2017, in accordance with the similar variation of gaseous species(SO2, NO2, and CO). In addition, the higher wind speeds and lowest relative humidity observed in 2017 were also conducive to the decrease in PM2.5. The evolutions of FPEG events and normal haze episodes were analyzed, revealing that the rate of increase in NO2 was much greater than that of SO2, suggesting more of a contribution from mobile sources than stationary sources. The polar Plot results suggest that the transportation from the southeast area of Beijing plays a major role in the formation of 3-h events, whereas local emissions is the main contributory factor for 9-h events and normal haze episodes. However, further quantitative analysis regarding the contributions of these factors is still needed.
基金financially supported by the National Key Research and Development(R&D)Program of China(2017YFC0211100)the consulting research project of the Chinese Academy of Engineering(2020-XY-22)the Cultivating Project of Strategic Priority Research Program of Chinese Academy of Sciences(XDPB1901 and RCEES-CYZX-2020).
文摘1.Introduction In recent years,the air quality in China has improved significantly.In many cities,however,the concentration of fine particulate matter(PM_(2.5))remains higher than the secondary-level national ambient air quality standard(NAAQS level-2,35μg·m^(-3),GB3095-2012[1])and much higher than the first-level NAAQS(15μg·m^(-3),GB3095-2012[1])and the World Health Organization(WHO)air quality guidelines(5μg·m^(-3)).
基金supported by National Natural Science Foundation(Grant Nos.41875164 and 92044303)。
文摘In recent years,China has implemented several measures to improve air quality.The Beijing-Tianjin-Hebei(BTH)region is one area that has suffered from the most serious air pollution in China and has undergone huge changes in air quality in the past few years.How to scientifically assess these change processes remain the key issue in further improving the air quality over this region in the future.To evaluate the changes in major air pollutant emissions over this region,this paper employs ensemble Kalman filtering(EnKF)for integrating the national ground monitoring pollutant observation data and the Nested Air Quality Prediction Modeling System(NAQPMS)simulation data to inversely estimate the emission rates of SO_(2),NOX,CO,and primary PM_(2.5)over BTH region in February from 2014 to 2019.The results show that SO_(2),NOX,CO,and primary PM_(2.5)emissions in the BTH region decreased in February from 2014 to 2019 by 83%,37%,41%,and 42%,while decreases in Beijing during this period were 86%,67%,59%,and 65%,respectively.Compared with the prior emission inventory,the inversion emission inventory reduces the uncertainty of multi-pollutant simulation in the BTH region,with simulated root mean square errors of the monthly average concentrations of SO_(2),NOX,PM_(2.5),and CO reduced by 41%,30%,31%,and 22%,respectively.The average uncertainties of SO_(2),NOX,PM_(2.5),and CO inversion emissions in2014-19 are±14.03%yr^(-1),±28.91%yr^(-1),±126.15%yr^(-1),and±43.58%yr^(-1).Compared with the uncertainty of MEIC emission,the uncertainties of all species changed by+2%yr^(-1),-2%yr^(-1),-26%yr^(-1),and-4%yr^(-1),respectively.The spatial distribution results illustrate that air pollutant emissions are mainly distributed over the eastern and southern BTH regions.The spatial gap between the inversion emissions and MEIC emissions was further closed in 2019 compared to 2014.The results of this paper can provide a new reference for assessing changes in air pollution emissions over the BTH region in recent years and validating a bottom-up emission inventory.
基金support by the National Natural Science Foundation of China(91544227,21777166)the National Key R&D Program of China(2016YFC0202202)~~
文摘A series of Co-based oxide catalysts were prepared by calcining hydrotalcite precursors in different atmospheres and studied for HCHO catalytic oxidation. The N2-calcined catalyst exhibits enhanced HCHO oxidation and superior stability. On the basis of H2-TPR, X-ray photoelectron spectroscopy, and Raman characterizations, this can be ascribed to better redox ability, octahedrally coordinated Co2+ ions derived from the CoO phase, and other surface oxygen species, such as O2– or O–. The extra octahedrally coordinated Co2+ ions may reside in a more open framework site than the inactive tetrahedrally coordinated Co2+ ions. This species of Co2+ can easily make contact with oxygen and oxidize. The surface oxygen species, along with the octahedrally coordinated Co2+ ions, and a part of the Co3+ species constitute the Co2+-oxygen species-Co3+ sites, which enhance the catalytic activities. According to DRIFTS, Co2+-oxygen species-Co3+ makes oxidation of HCHO and conversion of DOM to formate easier.
