The submicroparticles of β-sitosterol were produced by using an aerosol solvent extraction system （ASES） and characterized by scanning electronic microscope （SEM）, X-ray diffraction （XRD）, and Fourier transform...The submicroparticles of β-sitosterol were produced by using an aerosol solvent extraction system （ASES） and characterized by scanning electronic microscope （SEM）, X-ray diffraction （XRD）, and Fourier transform infrared （FT-IR） analysis. The effects of operational parameters including pressure, temperature, solution concentration, and ratio of flow rate （CO2/solution, r） on particle size （PS）, yield, and morphology were investigated. The results showed that microparticles of β-sitosterol （less than 1000 nm size and larger than 70% yield） could be obtained at 10-15 MPa, 35 50℃, 15 mg·ml^-1, 10/1（r）; β-sitosterol particles were found to occur as three mophologies： flakes, rods, and spheres by varying ratio of flow rate or solution concentration. In contrast, the crystallinity of β-sitosterol decreased, whereas its molecular structure remained almost unchanged after being ASES-treated. Therefore, ASES was an effective method to produce submicroparticles of β-sitosterol.展开更多
The paper calculates and analyzes physical and chemical characteristics of total suspended particles （TSP）, including mass concentration, absorption coefficient, optical refraction index imaginary unit and chemical ...The paper calculates and analyzes physical and chemical characteristics of total suspended particles （TSP）, including mass concentration, absorption coefficient, optical refraction index imaginary unit and chemical composition based on observational data of atmosphere aerosol in Xi＇an and Nanjing from 1997 to 1999. Enrichment characteristic of TSP elements and sources of pollution are discussed via statistical treatment of enrichment factor of elements and correlation analysis. The result shows that aerosol particles exist remarkable differences in physical and chemical. The highest enrichment in TSP is Pb, Zn, S and As, which comes from different kinds of pollution.展开更多
Ozone(O3) and secondary organic aerosol(SOA) are considered to be the most serious secondary air pollutants of concern in most metropolitan areas,as well as for Beijing.In this study,O3 and SOA for-mation potential of...Ozone(O3) and secondary organic aerosol(SOA) are considered to be the most serious secondary air pollutants of concern in most metropolitan areas,as well as for Beijing.In this study,O3 and SOA for-mation potential of α-pinene,the most abundant biogenic VOCs,is investigated at Tsinghua Indoor Chamber Facility.The experiments were conducted under atmospheric relevant HCs/NOx ratios in both presence and absence of ammonia sulfate seed aerosol.A Scanning Mobility Particle Sizer system(3936,TSI) and a Condensation Particle Counter(3010,TSI) were used to study the SOA formation and a gas chromatograph(GC) equipped with a DB-5 column and a flame ionization detector(FID) was used to measure α-pinene simultaneously.The results show that the presence of ammonia sulfate seed aerosol did not change the formation trend of O3,but significantly contribute to SOA formation.A strong linear relationship(r2 = 0.90) between SOA yield enhancement(△Y*) and surface concentration of seed aerosol(PMi,s)has been found,denoting that the PMi,s is the control factor for SOA yield en-hancement.And the possible reason for the enhancement is acid-catalyzed heterogeneous reactions.展开更多
Submicron aerosols （PMt） in Beijing were studied using an Aerodyne aerosol mass spectrometer （AMS） from January to Oc tober 2008. This paper presents seasonal variations of different chemical components （sulfate,...Submicron aerosols （PMt） in Beijing were studied using an Aerodyne aerosol mass spectrometer （AMS） from January to Oc tober 2008. This paper presents seasonal variations of different chemical components （sulfate, nitrate, ammonium, chloride and organics） and size distributions of PM1. Results show that mass concentration of PMI was highest in summer, and lowest in autumn. Organics represented the dominant species in all seasons, accounting for 36%58% of PML, and their concentrations were highest in winter. Concentrations of inorganic components, sulfate, nitrate, and ammonium were highest in summer. Based on principal component analysis, organics were deconvolved and quantified as hydrocarbonlike and oxygenated organ ic aerosol （HOA and OOA, respectively）. HOA was highest in winter, accounting for about 70% of organics. However, OOA was highest in summer, and had lower values in autumn and winter. A similar diurnal pattern of various components was ob served, which is higher at nighttime and lower during daytime. HOA increased more dramatically than other species between 17：00 and 21：00 and peaked at noon, which could be related to cooking emissions. OOA, sulfate, nitrate, ammonium and chlo ride varied with the same trend. Their concentrations increased with solar radiation from 9：00 to 13：00, and declined with weakening solar radiation. Size distributions of all species showed apparent peaks in the range 500600 nm. Size distributions of organics were much broader than other species, particularly in autumn and winter. Distributions of sulfate, nitrate and am monium had similar patterns, broadening in winter. Contributions of different species were sizedependent; the finer the parti cle, the greater the contribution of organics. Organics represented more than 60% of particles smaller than 200 nm, contrib uting 50% to PM1 in winter. In spring and summer, HOA was the dominant organic fraction for particles smaller than 200 nm, while OOA contributed more to particles larger than 300 nm. In winter, HOA contributed more than OOA to all PM1 particles.展开更多
基金Supported by Shanghai Special Foundation on Nanomaterials(0243nm305)the National High Technology Research and Development Program of China(2007AA10Z350)
文摘The submicroparticles of β-sitosterol were produced by using an aerosol solvent extraction system （ASES） and characterized by scanning electronic microscope （SEM）, X-ray diffraction （XRD）, and Fourier transform infrared （FT-IR） analysis. The effects of operational parameters including pressure, temperature, solution concentration, and ratio of flow rate （CO2/solution, r） on particle size （PS）, yield, and morphology were investigated. The results showed that microparticles of β-sitosterol （less than 1000 nm size and larger than 70% yield） could be obtained at 10-15 MPa, 35 50℃, 15 mg·ml^-1, 10/1（r）; β-sitosterol particles were found to occur as three mophologies： flakes, rods, and spheres by varying ratio of flow rate or solution concentration. In contrast, the crystallinity of β-sitosterol decreased, whereas its molecular structure remained almost unchanged after being ASES-treated. Therefore, ASES was an effective method to produce submicroparticles of β-sitosterol.
文摘The paper calculates and analyzes physical and chemical characteristics of total suspended particles （TSP）, including mass concentration, absorption coefficient, optical refraction index imaginary unit and chemical composition based on observational data of atmosphere aerosol in Xi＇an and Nanjing from 1997 to 1999. Enrichment characteristic of TSP elements and sources of pollution are discussed via statistical treatment of enrichment factor of elements and correlation analysis. The result shows that aerosol particles exist remarkable differences in physical and chemical. The highest enrichment in TSP is Pb, Zn, S and As, which comes from different kinds of pollution.
基金Toyota Central R&D Labs., Inc.(as part of "Study of Photochemical Reaction under High PM Contaminated Condition to Improve Air Quality of Beijing")the National Natural Science Foundation of China (Grant No.20637001)
文摘Ozone(O3) and secondary organic aerosol(SOA) are considered to be the most serious secondary air pollutants of concern in most metropolitan areas,as well as for Beijing.In this study,O3 and SOA for-mation potential of α-pinene,the most abundant biogenic VOCs,is investigated at Tsinghua Indoor Chamber Facility.The experiments were conducted under atmospheric relevant HCs/NOx ratios in both presence and absence of ammonia sulfate seed aerosol.A Scanning Mobility Particle Sizer system(3936,TSI) and a Condensation Particle Counter(3010,TSI) were used to study the SOA formation and a gas chromatograph(GC) equipped with a DB-5 column and a flame ionization detector(FID) was used to measure α-pinene simultaneously.The results show that the presence of ammonia sulfate seed aerosol did not change the formation trend of O3,but significantly contribute to SOA formation.A strong linear relationship(r2 = 0.90) between SOA yield enhancement(△Y*) and surface concentration of seed aerosol(PMi,s)has been found,denoting that the PMi,s is the control factor for SOA yield en-hancement.And the possible reason for the enhancement is acid-catalyzed heterogeneous reactions.
基金supported by National Natural Science Foundation of China (Grant No.41175113)National Basic Research Program of China(Grant No.2011CB403401)+1 种基金China International Science and Technology Cooperation Project(Grant No.2009DFA22800)Chinese Academy of Meteorological Sciences Group Project(Grant No.2010Z002)
文摘Submicron aerosols （PMt） in Beijing were studied using an Aerodyne aerosol mass spectrometer （AMS） from January to Oc tober 2008. This paper presents seasonal variations of different chemical components （sulfate, nitrate, ammonium, chloride and organics） and size distributions of PM1. Results show that mass concentration of PMI was highest in summer, and lowest in autumn. Organics represented the dominant species in all seasons, accounting for 36%58% of PML, and their concentrations were highest in winter. Concentrations of inorganic components, sulfate, nitrate, and ammonium were highest in summer. Based on principal component analysis, organics were deconvolved and quantified as hydrocarbonlike and oxygenated organ ic aerosol （HOA and OOA, respectively）. HOA was highest in winter, accounting for about 70% of organics. However, OOA was highest in summer, and had lower values in autumn and winter. A similar diurnal pattern of various components was ob served, which is higher at nighttime and lower during daytime. HOA increased more dramatically than other species between 17：00 and 21：00 and peaked at noon, which could be related to cooking emissions. OOA, sulfate, nitrate, ammonium and chlo ride varied with the same trend. Their concentrations increased with solar radiation from 9：00 to 13：00, and declined with weakening solar radiation. Size distributions of all species showed apparent peaks in the range 500600 nm. Size distributions of organics were much broader than other species, particularly in autumn and winter. Distributions of sulfate, nitrate and am monium had similar patterns, broadening in winter. Contributions of different species were sizedependent; the finer the parti cle, the greater the contribution of organics. Organics represented more than 60% of particles smaller than 200 nm, contrib uting 50% to PM1 in winter. In spring and summer, HOA was the dominant organic fraction for particles smaller than 200 nm, while OOA contributed more to particles larger than 300 nm. In winter, HOA contributed more than OOA to all PM1 particles.
