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91.
Amines have many atmospheric sources and their clusters play an important role in aerosol nucleation processes. Clusters of a typical amine, dimethylamine (DMA), of different sizes were measured with matrix isolation IR (infrared) and NIR (near infrared) spectroscopy. The NIR vibrations are more separated and therefore it is easier to distinguish different sizes of clusters in this region. The DMA clusters, up to DMA tetramer, have been optimized using density functional methods, and the geometries, binding energies and thermodynamic properties of DMA clusters were obtained. The computed frequencies and intensities of NH-stretching vibrations in the DMA clusters were used to interpret the experimental spectra. We have identified the fundamental transitions of the bonded NH-stretching vibration and the first overtone transitions of the bonded and free NH-stretching vibration in the DMA clusters. Based on the changes in vibrational intensities during the annealing processes, the growth of clusters was clearly observed. The results of annealing processes indicate that DMA molecules tend to form larger clusters with lower energies under matrix temperatures, which is also supported by the calculated reaction energies of cluster formation. 相似文献
92.
气动雾化含有酚、甲醛的标样产生气溶胶,因其微粒中金属元素在炬焰中原子化效率的提高,结果ICP-AES法的检测能力提高了1~2个数量级。 相似文献
93.
94.
利用气象站点能见距的历史资料和NASA的MOD1S卫星遥感手段获取10km*10km分辨率的气溶胶光学厚度资料,建立二者之间的季节平均关系。得到了上海地区季节变化的气溶胶标高,并利用标高数据和气溶胶光学厚度的季节分布。反演出上海地区季节变化的区域能见距分布,研究近地层大气气溶胶与地面能见距的关系,分析上海市能见度时空分布特征,结果显示:上海城区在冬春季平均能见距较差,市区中心能见距在lOkm以下;低能见距中心分布明显。且主要分布在杨浦、桃浦、吴淞等工业区范围。 相似文献
95.
Jiraporn Chomanee Kunchira Thongboon Surajit Tekasakul Masami Furuuchi Racha Dejchanchaiwong Perapong Tekasakul 《环境科学学报(英文版)》2020,32(8):72-80
Transboundary haze from biomass burning is one of the most important air pollutions in Southeast Asia. The most recent serious haze episode occurred in 2015. Southern Thailand was affected by the haze during September to October when the particulate matter concentration hit a record high. We investigated physical and chemical characteristics of aerosols, including concentration and aerosol size distribution down to sub-micron sizes during haze episodes in 2013 and 2015 and, for reference, an insignificant haze period in 2017. The highest total suspended particulates and PM10 levels in Hat Yai city were 340.1 and 322.5 µg/m3. The mass fractions were nanoparticles (< 100 nm) 3.1%-14.8% and fine particles (< 1 µm) 54.6%-59.1%. Polycyclic aromatic hydrocarbon size distributions in haze periods peaked at 0.75 µm and the concentrations are 2-30 times higher than the normal period. High molecular weight (4-6 ring) PAHs during the haze episode contribute to about 56.7%-88.0% for nanoparticles. The average values of benzo(a)pyrene toxic equivalency quotient were 3.34±2.54ng/m3 in the 2015 haze period but only 0.89±0.17 ng/m3 in 2017. It is clear that particles smaller than 1 µm, were highly toxic. Nanoparticles contributed 19.4%-26.0% of total BaP-TEQ, whereas the mass fraction is 13.1%-14.8%. Thus the nanoparticles were more carcinogenic and can cause greater health effect than larger particles. The fraction of BaP-TEQ for nanoparticles during 2017 non-haze period was nearly the same, while the mass fraction was lower. This indicates that nanoparticles are the significant source of carcinogenic aerosols both during haze and non-haze periods. 相似文献
96.
Two different aerosol mass spectrometers, Aerodyne Aerosol Mass Spectrometer(AMS) and Single Particle Aerosol Mass Spectrometer(SPAMS) were deployed to identify the aerosol pollutants over Xiamen, representing the coastal urban area. Five obvious processes were classified during the whole observation period. Organics and sulfate were the dominant components in ambient aerosols over Xiamen. Most of the particles were in the size range of 0.2–1.0 μm, accounting for over 97% of the total particles measured by both instruments.Organics, as well as sulfate, measured by AMS were in good correlation with measured by SPAMS. However, high concentration of NH4+was obtained by AMS, while extremely low value of NH4+was detected by SPAMS. Contrarily, high particle number counts of NO3-and Clwere given by SPAMS while low concentrations of NO3-and Cl-were measured by AMS. The variations of POA and SOA obtained from SPAMS during event 1 and event 2 were in accordance with the analysis of HOA and OOA given by AMS, suggesting that both of AMS and SPAMS can well identify the organic clusters of aerosol particles. Overestimate or underestimate of the aerosol sources and acidity would be present in some circumstances when the measurement results were used to analyze the aerosol properties, because of the detection loss of some species for both instruments. 相似文献
97.
98.
Combustible liquids in the form of aerosols are important for many industrial processes. Therefore the problem of explosion hazards posed by the aerosols becomes increasingly more prominent. To correctly assess the explosion risk and fulfil the requirements of the ATEX directive, it is necessary to obtain information regarding the flammable and explosive properties of the aerosols. Unlike in the case of gases and dusts, no standard procedures aimed at obtaining quantitative information of this type exist. Factors that influence the explosion dynamics of aerosols include: concentration, droplet size, temperature etc. Some of these factors are strongly dependent on the aerosol generation methods. A prototype apparatus was designed and constructed to address that dependence. The apparatus was used in an attempt to determine the basic explosion parameters of liquid flammable aerosols. The device consisted of a 5-L spherical vessel equipped with a pump-injection system that generated aerosols as well as a spark ignition source. A wide variety of injection settings were tested to select the most suitable conditions over a broad range of concentrations and fluid properties. A measurement procedure was developed for operating the device. Prototype tests were carried out with fluids commonly used in industry: isopropanol and kerosene. The tests demonstrated the significant influence of the vessel wall temperature on the result accuracy. Correct temperature control made it possible to obtain relationships between the aerosol concentration and the following explosion parameters: maximum explosion pressure and maximum rate of pressure rise. 相似文献
99.
In 2004, airborne particulate matter (PM) was collected for several aerosol episodes occurring in the southern region of Taiwan.
The particulate samples were taken using both a MOUDI (Micro-orifice Uniform Deposit Impactor) and a nano-MOUDI sampler. These
particulate samples were analyzed for major water-soluble ionic species with an emphasis to characterize the mass concentrations
and distributions of these ions in the ambient ultrafine (PM0.1, diameter <0.1 μm) and nano mode (PMnano, diameter <0.056 μm) particles. Particles collected at the sampling site (the Da-Liao station) on the whole exhibited a typical
tri-modal size distribution on mass concentration. The mass concentration ratios of PMnano/PM2.5, PM0.1/PM2.5, and PM1/PM2.5 on average were 1.8, 2.9, and 71.0%, respectively. The peak mass concentration appeared in the submicron particle mode (0.1 μm < diameter <1.0 μm).
Mass fractions (percentages) of the three major water-soluble ions (nitrate, sulfate, and ammonium) as a group in PMnano, PM0.1, PM1, and PM2.5 were 18.4, 21.7, 50.0, and 50.7%, respectively. Overall, results from this study supported the notion that secondary aerosols
played a significant role in the formation of ambient submicron particulates (PM0.1−1). Particles smaller than 0.1 μm were essentially basic, whereas those greater than 2.5 μm were neutral or slightly acidic.
The neutralization ratio (NR) was close to unity for airborne particles with diameters ranging from 0.18 to 1 μm. The NRs
of these airborne particles were found strongly correlated with their sizes, at least for samples taken during the aerosol
episodes under study. Insofar as this study is exploratory in nature, as only a small number of particulate samples were used,
there appears to be a need for further research into the chemical composition, source contribution, and formation of the nano
and ultrafine mode airborne particulates. 相似文献
100.
Karsten Suhre Vincent Crassier Cline Mari Robert Rosset Doug W. Johnson Simon Osborne Robert Wood Meinrat O. Andreae Brian Bandy Timothy S. Bates Steven Businger Christian Gerbig Frank Raes Jochen Rudolph 《Atmospheric environment (Oxford, England : 1994)》2000,34(29-30)
Three Lagrangian experiments were conducted during IGAC's second aerosol characterization experiment (ACE-2) in the area between Portugal, Tenerife and Madeira in June/July 1997. During each Lagrangian experiment, a boundary layer air mass was followed for about 30 h, and the temporal evolution of its chemical and aerosol composition was documented by a series of vertical profiles and horizontal box pattern flown by the Meteorological Research Flight research aircraft Hercules C130. The wealth of observational data that has been collected during these three Lagrangian experiments is the basis for the development and testing of a one-dimensional Lagrangian boundary layer model with coupled gas, aqueous, and aerosol phase chemistry. The focus of this paper is on current model limitations and strengths. We show that the model is able to represent the dynamical and chemical evolution of the marine boundary layer, in some cases requiring adjustments of the subsidence velocity and of the surface heat fluxes. Entrainment of a layer rich in ozone and carbon monoxide from a residual continental boundary layer into the marine boundary layer as well as in-cloud oxidation of sulphur dioxide by hydrogen peroxide are simulated, and coherent results are obtained, concerning the evolution of the small, presumably sulphate–ammonia aerosol mode. 相似文献