河北地区秋季大气气溶胶物理特征分析

利用2005年10月20日在河北省石家庄和邯郸地区进行的一次飞机探测资料,初步分析了石家庄和邯郸上空的气溶胶粒子数浓度、粒径、粒子谱垂直分布特征,对石家庄与邯郸之间的水平飞行气溶胶粒子数浓度资料进行分析,并对石家庄、邯郸的气溶胶粒子谱进行函数拟合。结果表明:各高度层气溶胶粒子数浓度基本上都是石家庄高于邯郸,各高度层粒子平均直径基本上都是石家庄低于邯郸。两地气溶胶粒子数浓度、粒子平均直径随高度的分布有不同特点。石家庄、邯郸气溶胶粒子谱谱型,低层相似,基本都是单调下降,高层粒子谱谱型为多峰型。3100m高度层粒子数浓度在水平方向上分布不均匀,城市附近上空气溶胶粒子数浓度相对较大,郊县气溶胶粒子数浓度相对较小。随着高度增加,粒子数浓度减小,水平方向的绝对变化越来越小。利用幂函数N(D)=AD-B可以对不同高度气溶胶粒子谱进行较好的拟合。     

地面气溶胶集成观测系统

介绍一种地面气溶胶集成观测系统的设计思路和集成方法,采用浊度仪、吸收光度计、粒子计数器、粒径谱仪、碳黑仪等仪器观测气溶胶的散射和吸收特性、黑碳浓度、粒径分布和粒子数浓度等。结果表明,测量吸收特性和粒子数浓度的仪器位于测量散射特性的仪器之后,仪器之间可以互相对比验证;将测量气溶胶吸收特性的仪器和黑碳仪"并联",可以观测到更多气溶胶特性信息;测量气溶胶粒径分布及粒子数浓度的仪器可以结合使用,也可以单独分开或"并联"综合观测;仪器综合集成观测的前提是保证仪器流量分配正确,切割头流量达到要求的范围,保证切割效率。     

大气气溶胶对混合相对流云影响的模拟研究

利用二维面对称分档云模式,讨论了气溶胶类型及浓度对混合相对流云及其降水的影响。结果表明:海洋性气溶胶谱分布在一定程度上更有利于降水的形成,随着气溶胶浓度的增加,尤其是在污染大陆性云中,暖云和冷云降水量均大幅减少。海洋性云中的大粒子和较高的过饱和度,加速了暖雨的碰撞过程和冰粒子的凝华增长;初始气溶胶浓度的增加最显著的效应是云滴数浓度和云水含量增加,云滴有效半径减小,云滴的冷却蒸发抑制对流的发展。     

石墨气溶胶粒度分布及远红外消光因子研究

在烟幕试验箱中测试了不同湿度条件下超细石墨气溶胶的粒子分布及其随时间变化的规律。根据Mie散射理论计算了石墨气溶胶粒子对8～14μm远红外的消光因子。分析表明,石墨气溶胶的粒度随着分散时间延长和空气相对湿度减小而变小。小尺度的石墨气溶胶粒子对8～14μm红外的消光效率因子非常小,但随着气溶胶粒子直径的增加,消光效率因子显著变大并趋于稳定。直径大于2.5μm的石墨气溶胶粒子均能够对8～14μm远红外产生良好的消光效果。     

渤海海域上空大气衰减光学厚度的研究

利用太阳光度计和臭氧监测仪的测量数据,对渤海海域上空8月中下旬的大气衰减进行了分析,结果发现：对大气衰减贡献最大的是气溶胶散射,约占86％;从时间和空间上看,气溶胶的浑浊度因子α和Augstrom指数β的变化都很大。在所测量的海域和时间内,α主要分布范围为2～9,β的主要分布范围为-1．4～-1．2;由于α和β日变化较大,观测气溶胶的时间尺度不应大干1天。从海域位置上讲,黄河口附近海域的气溶胶散射光学厚度比其它海域都要大。以上研究结果对于有效地获取我国近岸二类水体海域上空的大气校正所需的资料具有重要意义。     

合肥地区气溶胶光学特性的地基观测研究

利用自主研制的DTF-5型太阳辐射计观测合肥地区2008年10月—2010年5月的太阳直接辐射消光,反演合肥地区气溶胶光学厚度、Angstrom参数和沙尘天气过程中的粒子谱分布,并对结果进行分析。结果表明:合肥地区气溶胶光学厚度季节变化除气候因素外,受人为因素影响明显,季节变化规律复杂。总体上秋季较小,冬春季节持续增大,夏季较平稳。而Angstrom参数与气溶胶光学厚度大致呈反相关,秋冬上升,春季骤降,夏季平稳值较大。气溶胶光学厚度日变化大致可分为4种类型:日变化相对稳定;整体呈上升趋势;整体呈下降趋势;一日内出现一到多个峰值。其中第四种类型出现几率最大。沙尘天气过程中,气溶胶光学厚度和Angstrom参数分别呈现出"谷-峰-谷"、"峰-谷-峰"的变化规律,其中Angstrom参数在沙尘影响严重时甚至出现负值。半径为0.2~1.0μm的大粒子和大于1.0μm的巨粒子浓度在沙尘天气过程中大幅增加。     

气溶胶力学的研究进展

气溶胶力学是一门新兴的交叉学科，具有广泛的应用前景。自Ｆｕｃｈｓ建立了气溶胶力学以后，该学科已从孤粒子动力学阶段发展到多粒子相互作用下的动力学阶段。本文总结该学科的发展历程，重点对许多工业生产中有重要应用价值的气溶胶粒子的沉降与气溶胶粒子的碰并（即聚集、团聚、聚沉、凝并）进行讨论。     

西北戈壁地区气溶胶的浓度及粒度分布特征

为了获取西北戈壁地区气溶胶随着粒径变化的概率分布函数,对该地区的2次现场取样进行调查。结果表明,采样点气溶胶的质量浓度为0.03~0.1 mg/m3;气溶胶的粒径分布遵循双峰分布的规律,第1个峰值出现在约0.5μm处,第2个峰值出现在约3μm处,其差异主要表现在第2个峰值的面积大小;大多数采样点气溶胶粒子数量中位粒径小于1μm,质量中位粒径位于2~5μm之间。     

星载遥感器的可见和近红外波段的绝对定标

在洁净海洋上空,卫星遥感器在可我谱区中接收到的信号主要来自于大气分子 射,根据大气辐射传输机理利用观测海洋的方法,对星载遥感器的可见和近红外通道进行绝对辐射定标。为了克服大气气溶胶散射对辐射定标 影响,利用组合可见和近红外通道同时观测高亮云层和洁净海面对ＮＯＡＡ－１４ ＡＶＨＲＲ作出了精确的辐射定标。     

安全壳内水池气泡破碎后夹带液滴的粒径分布

针对安全壳内气溶胶再夹带问题,设计液池表面气泡破碎特性研究可视化试验装置,进行典型试验条件下的气溶胶再夹带试验,验证高速摄影拍摄法对百微米级含气溶胶液滴进行测量的可行性;通过对液滴进行拍摄和分析,研究液池中气溶胶种类、质量浓度、水温对气泡破碎后液滴粒径分布的影响。结果表明:气溶胶种类、质量浓度、水温均对液滴粒径分布产生影响;升高温度和提高气溶胶悬浊液质量浓度,均使得液滴粒径分布变小; BaSO_4悬浊液较TiO_2悬浊液更不易生成夹带液滴;不同试验条件下的液滴粒径分布公式拟合结果较好。     

PENETRATION OF POLYDISPERSE AEROSOLS THROUGH SCREEN DIFFUSION BATTERY

As an alternative data reduction scheme for diffusion battery measurements, penetration of polydisperse aerosol particles in a screen type diffusion battery has been calculated employing Brownian diffusion and interception as the applicable deposition mechanisms. The influences of the mean particle size and the geometric standard deviation of the aerosol on penetrations of the total particle number, radius, surface area, and the total particle volume have been examined. It is quantitatively shown that depending upon the type of aerosol instrument in use as a particle counting means and depending upon the size distribution of the measured aerosols, penetration characteristics can become markedly different. For a highly dispersed aerosol having a small mean particle size, the total radius, the surface area and the total volume of aerosol particles are shown to penetrate a diffusion battery more slowly in that order than the total number of particles. However, when the mean size of the aerosol increases, such a monotomic increase in penetration becomes no longer valid due to increasing importance of the interceptional deposition. Experimental measurements have been performed to demonstrate applications of the calculated results.     

Containment aerosol characterization during nuclear power plant severe accident

ABSTRACT

The aerosol size distribution and concentration during a postulated severe accident scenario were simulated using a numerical code NAUA to characterize the aerosols dispersed in the containment under various conditions. The model-predicted aerosol concentration and particle size distribution were in general agreement with the measured data reported in previous studies. A large set of sensitivity tests were conducted to examine the effects of input parameters. The main particle removal mechanism in containment was gravitational sedimentation when wall temperature was assumed to be the same as the air temperature, whereas diffusiophoresis became a more important particle removal mechanism when the difference between the wall temperature and air temperature was significant. The operation of a containment filtered venting system (CFVS) resulted in reduced particle concentration, mass median diameter (MMD), and geometric standard deviation (GSD) because aged larger particles were removed by the CFVS. The particle concentration and GSD of the containment aerosol decreased with increasing emitted particle size owing to the effect of gravitational sedimentation that removes large particles selectively. Non-sphericity of particles reduced the particle removal rate due to gravitational sedimentation, leading to higher particle concentration, MMD, and GSD.     

Effect of Air Flow and Acceleration on Particle Size of Dry Powder Aerosols determined by Time-of-Flight Aerosol Beam Spectrometry

The effect of air flow and acceleration on the particle size distributions of two Turbuhalers containing drug loads of 0.5 and 1.3 mg per dose was determined with a time-of-flight aerosol beam spectrometer (Aerosizer®). While the particle size of both inhalers decreased with increasing flow and acceleration, the distributions became narrower and variability was reduced. Simultaneously, a decrease in the number and mass of particles measured was observed which was more pronounced for the 1.3 mg dose. Additionally the count rate for the 1.3 mg dose was lower than for 0.5 mg. These observations were accompanied by a remarkably fine particle size distribution for the high dose Turbuhaler®. It was concluded that the quantity of particles in the DPI aerosols exceeded the resolution of the Aerosizer, erroneously shifting the size distributions towards smaller diameters.

In addition, the DPI aerosols were analyzed with a Four Stage Impinger to evaluate the results. The particle size estimates obtained using the impinger were in the same range as those obtained at an acceleration of 5 L/s2 using the Aerosizer to study the 0.5 mg Turbuhaler. The Aerosizer produced significantly smaller particle sizes than the impinger in all cases evaluating the 1.3 mg Turbuhaler, supporting the theory of distorted particle size distributions due to particle overload.     

Effect of ionizing radiation field on CsI aerosols formed by condensation of supersaturated vapor

The effect of the ionizing radiation field on the behavior of CsI aerosols formed by condensation of supersaturated vapor was examined. Supersaturated CsI vapor was formed by evaporation from a metal surface ohmically heated to high temperatures. A study of the size distribution function of CsI particles showed that, both in the field of ⁶⁰Co γ-radiation and in a stationary electron beam, three modes of particle size are observed with the mean sizes of 0.13, 0.57, and 0.76 μm. The amount of particles of size 0.13 μm is larger by a factor of ～10–20 than the amount of particles of sizes 0.57 and 0.76 μm. Comparison of the distribution functions of CsI aerosol particles formed by supersaturated vapor condensation in an ionizing radiation field and without it showed that the ionizing radiation affected not only the size but also the amount of particles.     

Effect of Air Flow and Acceleration on Particle Size of Dry Powder Aerosols determined by Time-of-Flight Aerosol Beam Spectrometry

ABSTRACT

The effect of air flow and acceleration on the particle size distributions of two Turbuhalers containing drug loads of 0.5 and 1.3 mg per dose was determined with a time-of-flight aerosol beam spectrometer (Aerosizer®). While the particle size of both inhalers decreased with increasing flow and acceleration, the distributions became narrower and variability was reduced. Simultaneously, a decrease in the number and mass of particles measured was observed which was more pronounced for the 1.3 mg dose. Additionally the count rate for the 1.3 mg dose was lower than for 0.5 mg. These observations were accompanied by a remarkably fine particle size distribution for the high dose Turbuhaler®. It was concluded that the quantity of particles in the DPI aerosols exceeded the resolution of the Aerosizer, erroneously shifting the size distributions towards smaller diameters.

In addition, the DPI aerosols were analyzed with a Four Stage Impinger to evaluate the results. The particle size estimates obtained using the impinger were in the same range as those obtained at an acceleration of 5 L/s2 using the Aerosizer to study the 0.5 mg Turbuhaler. The Aerosizer produced significantly smaller particle sizes than the impinger in all cases evaluating the 1.3 mg Turbuhaler, supporting the theory of distorted particle size distributions due to particle overload.     

Optimizing the primary particle size distributions of pressurized metered dose inhalers by using inkjet spray drying for targeting desired regions of the lungs

Conventional suspension pressurized metered dose inhalers (pMDIs) suffer not only from delivering small amounts of a drug to the lungs, but also the inhaled dose scatters all over the lung regions. This results in much less of the desired dose being delivered to regions of the lungs. This study aimed to improve the aerosol performance of suspension pMDIs by producing primary particles with narrow size distributions. Inkjet spray drying was used to produce respirable particles of salbutamol sulfate. The Next Generation Impactor (NGI) was used to determine the aerosol particle size distribution and fine particle fraction (FPF). Furthermore, oropharyngeal models were used with the NGI to compare the aerosol performances of a pMDI with monodisperse primary particles and a conventional pMDI. Monodisperse primary particles in pMDIs showed significantly narrower aerosol particle size distributions than pMDIs containing polydisperse primary particles. Monodisperse pMDIs showed aerosol deposition on a single stage of the NGI as high as 41.75?±?5.76%, while this was 29.37?±?6.79% for a polydisperse pMDI. Narrow size distribution was crucial to achieve a high FPF (49.31?±?8.16%) for primary particles greater than 2?µm. Only small polydisperse primary particles with sizes such as 0.65?±?0.28?µm achieved a high FPF with (68.94?±?6.22%) or without (53.95?±?4.59%) a spacer. Oropharyngeal models also indicated a narrower aerosol particle size distribution for a pMDI containing monodisperse primary particles compared to a conventional pMDI. It is concluded that, pMDIs formulated with monodisperse primary particles show higher FPFs that may target desired regions of the lungs more effectively than polydisperse pMDIs.     

Inversion of multiwavelength Raman lidar data for retrieval of bimodal aerosol size distribution

We report on the feasibility of deriving microphysical parameters of bimodal particle size distributions from Mie-Raman lidar based on a triple Nd:YAG laser. Such an instrument provides backscatter coefficients at 355, 532, and 1064 nm and extinction coefficients at 355 and 532 nm. The inversion method employed is Tikhonov's inversion with regularization. Special attention has been paid to extend the particle size range for which this inversion scheme works to approximately 10 microm, which makes this algorithm applicable to large particles, e.g., investigations concerning the hygroscopic growth of aerosols. Simulations showed that surface area, volume concentration, and effective radius are derived to an accuracy of approximately 50% for a variety of bimodal particle size distributions. For particle size distributions with an effective radius of < 1 microm the real part of the complex refractive index was retrieved to an accuracy of +/- 0.05, the imaginary part was retrieved to 50% uncertainty. Simulations dealing with a mode-dependent complex refractive index showed that an average complex refractive index is derived that lies between the values for the two individual modes. Thus it becomes possible to investigate external mixtures of particle size distributions, which, for example, might be present along continental rims along which anthropogenic pollution mixes with marine aerosols. Measurement cases obtained from the Institute for Tropospheric Research six-wavelength aerosol lidar observations during the Indian Ocean Experiment were used to test the capabilities of the algorithm for experimental data sets. A benchmark test was attempted for the case representing anthropogenic aerosols between a broken cloud deck. A strong contribution of particle volume in the coarse mode of the particle size distribution was found.     

Optical Properties of Polydispersed Atmospheric Aerosols Following Wet Removal

It is well known that size distributions of aerosols influence their optical properties. Many previous studies have focused on the optical properties of aerosols with particular weather conditions, such as haze, fog, or pollution. However, few studies have investigated the influence of precipitation on the optical properties of aerosols. In this study, the optical properties of polydispersed atmospheric aerosols following a wet removal process were investigated. For these calculations, a lognormal distribution was used to represent the raindrop size distribution and the tri-modal aerosol size distributions. Variations in aerosol size distributions and the corresponding changes an extinction coefficient caused by the wet scavenging process were quantified with different compositions of aerosols as a function of rain intensity. The results showed that the extinction coefficient decreased and the corresponding visibility was enhanced with the precipitation duration because of the precipitation scavenging. It was also shown that the rain intensity and the refractive index and size distribution of aerosols influenced the calculations of extinction coefficient of aerosols.     

沙尘和灰霾天气下毛乌素沙漠地区大气气溶胶的光学特征

利用AERONET榆林站点的数据比较分析了在沙尘和灰霾两种不同天气条件下毛乌素沙漠边缘地区大气气溶胶的光学和物理特性。分析的主要内容包括:气溶胶光学厚度、单次散射反照率、复折射指数、不对称因子、气溶胶粒子的粒度分布、Angstrom波长指数、体积浓度、气溶胶粒子半径等光学和物理参数。分析结果表明,榆林地区大气气溶胶光学特性主要是受到沙尘和人为气溶胶的共同影响。在沙尘天气和灰霾天气下,大气气溶胶的光学特性有显著的差异。