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
An indoor chamber facility is described for investigation of atmospheric aerosol chemistry. Two sets of α-pinene ozonolysis experiments were conducted in the presence of dry ammonium sulfate seed particle: ozone limi...An indoor chamber facility is described for investigation of atmospheric aerosol chemistry. Two sets of α-pinene ozonolysis experiments were conducted in the presence of dry ammonium sulfate seed particle: ozone limited experiments and α-pinene limited experiments. The concentration of gas phase and particle phase species was monitored continuously by on-line instruments and recorded automatically by data sampling system. The evolution of size distribution was measured by a scanning mobility particle sizer ...展开更多
To investigate the sensitivity of secondary aerosol formation and oxidation capacity to NOx in homogeneous and heterogeneous reactions, a series of irradiated toluene/NOx/air and ?-pinene/NOx/air experiments were cond...To investigate the sensitivity of secondary aerosol formation and oxidation capacity to NOx in homogeneous and heterogeneous reactions, a series of irradiated toluene/NOx/air and ?-pinene/NOx/air experiments were conducted in smog chambers in the absence or presence of Al2O3 seed particles. Various concentrations of NOx and volatile organic compounds(VOCs) were designed to simulate secondary aerosol formation under different scenarios for NOx. Under "VOC-limited" conditions, the increasing NOx concentration suppressed secondary aerosol formation, while the increasing toluene concentration not only contributed to the increase in secondary aerosol formation, but also led to the elevated oxidation degree for the organic aerosol. Sulfate formation was suppressed with the increasing NOx due to a decreased oxidation capacity of the photooxidation system. Secondary organic aerosol(SOA) formation also decreased with the presence of high concentration of NOx, because organo-peroxy radicals(RO2) react with NOx instead of with peroxy radicals(RO2 or HO2), resulting in the formation of volatile organic products. The increasing concentration of NOx enhanced the formation of sulfate, nitrate and SOA under "NOx-limited" conditions, in which the heterogeneous reactions played an important role. In the presence of Al2O3 seed particles, a synergetic promoting effect of mineral dust and NOx on secondary aerosol formation in heterogeneous reactions was observed in the photooxidation. This synergetic effect strengthened the positive relationship between NOx and secondary aerosol formation under "NOx-limited" conditions but weakened or even overturned the negative relationship between NOx and secondary aerosol formation under "VOC-limited" conditions. Sensitivity of secondary aerosol formation to NOx seemed different in homogeneous and heterogeneous reactions, and should be both taken into account in the sensitivity study. The sensitivity of secondary aerosol formation to NOx was further investigated under "winter-like" and NH3-rich c展开更多
Micron-sized nonspherical polymer particles having different morphologies were synthesized by seeded soap-free emulsion polymerization of styrene （St） and ethyleneglycol dimethacrylate （EGDMA, used as a crosslinker...Micron-sized nonspherical polymer particles having different morphologies were synthesized by seeded soap-free emulsion polymerization of styrene （St） and ethyleneglycol dimethacrylate （EGDMA, used as a crosslinker） on spherical, linear polystyrene （PS） seed particles. The morphology of the resulting PS/poly（St-co-EGDMA） particles was dependent on the crosslinker concentration and polymerization temperature.展开更多
为了采用聚团-磁选的方式回收微细粒级硫化矿物,研究了油酸钠作用下,微细粒硫化矿物与磁铁矿之间的异相聚团机理。结果表明,静电力和疏水力是硫化矿物与磁铁矿颗粒间形成聚团的主要作用力。p H=4.0时,2种矿物动电位均小于20 m V,且油酸...为了采用聚团-磁选的方式回收微细粒级硫化矿物,研究了油酸钠作用下,微细粒硫化矿物与磁铁矿之间的异相聚团机理。结果表明,静电力和疏水力是硫化矿物与磁铁矿颗粒间形成聚团的主要作用力。p H=4.0时,2种矿物动电位均小于20 m V,且油酸钠在两种矿物颗粒表面吸附量最大,矿物颗粒间易发生异相聚团,人工混合矿聚团-磁选回收率达到最大,为87%;p H>7.0时,2种矿物动电位均大于60 m V,由于磁铁矿表面油酸钠吸附量大幅降低,疏水力减小,导致聚团效果变差,硫化矿回收率显著降低。展开更多
采用离散元法DEM(Discrete element method)对包衣锅内冰草种子和粉料在振动状态下的混合均匀度进行了数值模拟研究,同时建立颗粒运动模型,接触模型采用Hertz-Mindin无滑移模型。选取振幅、振动频率和振动方向作为影响因素,分别设立3个...采用离散元法DEM(Discrete element method)对包衣锅内冰草种子和粉料在振动状态下的混合均匀度进行了数值模拟研究,同时建立颗粒运动模型,接触模型采用Hertz-Mindin无滑移模型。选取振幅、振动频率和振动方向作为影响因素,分别设立3个水平,进行种粉混合的正交试验模拟。采用种粉碰撞接触系数q和混合趋于稳定的时间作为试验指标来评价种粉间的混合均匀性,并对3个因素进行极差分析,结果表明:振动方向和振动频率对混合趋于稳定的时间的影响显著,振幅对混合趋于稳定的时间的影响不显著;振动方向和振幅对碰撞接触系数的影响显著,振动频率对碰撞接触系数的影响不显著。综合评估后采用振动方向为Z方向、振幅为8 mm和振动频率为20 Hz能获得最佳的混合效果。研究结果对在振动状态下种粉间的混合提供参考依据。展开更多
Dry rice seeds(Oryza sativa,subspecies indica)were sandwiched between nuclear track detectors,aboard the Chinese spaceship Shenzhou-3 for seven days.The seeds were recovered and the genomic polymorphism in 201 plants ...Dry rice seeds(Oryza sativa,subspecies indica)were sandwiched between nuclear track detectors,aboard the Chinese spaceship Shenzhou-3 for seven days.The seeds were recovered and the genomic polymorphism in 201 plants developed from these seeds was studied using random amplified polymorphism DNA analysis.When compared with plants from ground-based control seeds,the genomic polymorphic bands were amplified in 30.2%of the plants from the seeds exposed in space.The results for sequencing and SNP analyses of the polymorphic bands verified the single nucleotide variations in these plants.Genomic poly-morphisms in the consecutive generations of individual plants of the seeds from space were also discovered.Seven seeds receiving hits of HZE(high atomic number and high energy)particles from space were selected for further analyses and variable genomic polymorphisms were detected in all plants that developed from these seeds.Among them,the embryos of three seeds were hit at least once,and mutants with significant changes in agronomic traits were only found in later generations of these seeds.This result implies that the HZE particles of space are effective in inducing the changes of plant genome of inherited phenotypes.展开更多
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the National Natural ScienceFundation of China (No. 20637001)
文摘An indoor chamber facility is described for investigation of atmospheric aerosol chemistry. Two sets of α-pinene ozonolysis experiments were conducted in the presence of dry ammonium sulfate seed particle: ozone limited experiments and α-pinene limited experiments. The concentration of gas phase and particle phase species was monitored continuously by on-line instruments and recorded automatically by data sampling system. The evolution of size distribution was measured by a scanning mobility particle sizer ...
基金supported by the National Natural Science Foundation of China(21407158)the"Strategic Priority Research Program"of the Chinese Academy of Sciences(XDB05010300,XDB05040100,XDB05010200)
文摘To investigate the sensitivity of secondary aerosol formation and oxidation capacity to NOx in homogeneous and heterogeneous reactions, a series of irradiated toluene/NOx/air and ?-pinene/NOx/air experiments were conducted in smog chambers in the absence or presence of Al2O3 seed particles. Various concentrations of NOx and volatile organic compounds(VOCs) were designed to simulate secondary aerosol formation under different scenarios for NOx. Under "VOC-limited" conditions, the increasing NOx concentration suppressed secondary aerosol formation, while the increasing toluene concentration not only contributed to the increase in secondary aerosol formation, but also led to the elevated oxidation degree for the organic aerosol. Sulfate formation was suppressed with the increasing NOx due to a decreased oxidation capacity of the photooxidation system. Secondary organic aerosol(SOA) formation also decreased with the presence of high concentration of NOx, because organo-peroxy radicals(RO2) react with NOx instead of with peroxy radicals(RO2 or HO2), resulting in the formation of volatile organic products. The increasing concentration of NOx enhanced the formation of sulfate, nitrate and SOA under "NOx-limited" conditions, in which the heterogeneous reactions played an important role. In the presence of Al2O3 seed particles, a synergetic promoting effect of mineral dust and NOx on secondary aerosol formation in heterogeneous reactions was observed in the photooxidation. This synergetic effect strengthened the positive relationship between NOx and secondary aerosol formation under "NOx-limited" conditions but weakened or even overturned the negative relationship between NOx and secondary aerosol formation under "VOC-limited" conditions. Sensitivity of secondary aerosol formation to NOx seemed different in homogeneous and heterogeneous reactions, and should be both taken into account in the sensitivity study. The sensitivity of secondary aerosol formation to NOx was further investigated under "winter-like" and NH3-rich c
基金partially supported by the National Natural Science Foundation of China(No.50943028)Scientific Research Foundation for the Returned Overseas Chinese Scholars,State Education Ministry
文摘Micron-sized nonspherical polymer particles having different morphologies were synthesized by seeded soap-free emulsion polymerization of styrene （St） and ethyleneglycol dimethacrylate （EGDMA, used as a crosslinker） on spherical, linear polystyrene （PS） seed particles. The morphology of the resulting PS/poly（St-co-EGDMA） particles was dependent on the crosslinker concentration and polymerization temperature.
文摘为了采用聚团-磁选的方式回收微细粒级硫化矿物,研究了油酸钠作用下,微细粒硫化矿物与磁铁矿之间的异相聚团机理。结果表明,静电力和疏水力是硫化矿物与磁铁矿颗粒间形成聚团的主要作用力。p H=4.0时,2种矿物动电位均小于20 m V,且油酸钠在两种矿物颗粒表面吸附量最大,矿物颗粒间易发生异相聚团,人工混合矿聚团-磁选回收率达到最大,为87%;p H>7.0时,2种矿物动电位均大于60 m V,由于磁铁矿表面油酸钠吸附量大幅降低,疏水力减小,导致聚团效果变差,硫化矿回收率显著降低。
文摘采用离散元法DEM(Discrete element method)对包衣锅内冰草种子和粉料在振动状态下的混合均匀度进行了数值模拟研究,同时建立颗粒运动模型,接触模型采用Hertz-Mindin无滑移模型。选取振幅、振动频率和振动方向作为影响因素,分别设立3个水平,进行种粉混合的正交试验模拟。采用种粉碰撞接触系数q和混合趋于稳定的时间作为试验指标来评价种粉间的混合均匀性,并对3个因素进行极差分析,结果表明:振动方向和振动频率对混合趋于稳定的时间的影响显著,振幅对混合趋于稳定的时间的影响不显著;振动方向和振幅对碰撞接触系数的影响显著,振动频率对碰撞接触系数的影响不显著。综合评估后采用振动方向为Z方向、振幅为8 mm和振动频率为20 Hz能获得最佳的混合效果。研究结果对在振动状态下种粉间的混合提供参考依据。
基金This study was supported by the grants from The National High-Tech R&D Program of China in Aerospace(No.2002AA744061)the National Natural Sciences Foundation of China(Grant No.30170534).
文摘Dry rice seeds(Oryza sativa,subspecies indica)were sandwiched between nuclear track detectors,aboard the Chinese spaceship Shenzhou-3 for seven days.The seeds were recovered and the genomic polymorphism in 201 plants developed from these seeds was studied using random amplified polymorphism DNA analysis.When compared with plants from ground-based control seeds,the genomic polymorphic bands were amplified in 30.2%of the plants from the seeds exposed in space.The results for sequencing and SNP analyses of the polymorphic bands verified the single nucleotide variations in these plants.Genomic poly-morphisms in the consecutive generations of individual plants of the seeds from space were also discovered.Seven seeds receiving hits of HZE(high atomic number and high energy)particles from space were selected for further analyses and variable genomic polymorphisms were detected in all plants that developed from these seeds.Among them,the embryos of three seeds were hit at least once,and mutants with significant changes in agronomic traits were only found in later generations of these seeds.This result implies that the HZE particles of space are effective in inducing the changes of plant genome of inherited phenotypes.
