实时在线测量烟幕气溶胶质量浓度的新方法

为了探索一种实时在线测量烟幕气溶胶质量浓度的新方法,利用电子低压冲击仪对不同烟剂装填量、压力及施放时间条件下形成的烟幕气溶胶质量浓度进行测试分析。结果表明:利用电子低压冲击仪可以实时在线测量烟幕气溶胶质量浓度,当施放压力、烟剂装填量及施放时间改变时,对气溶胶粒子数浓度和质量浓度分布均有不同影响。烟剂装填量增大,粒子数浓度和质量浓度均相应增大;施放压力增大时,粒子数浓度略有增大。     

激光散射法测量烟幕质量浓度的试验研究

为实现实时测量烟幕粒子数浓度、质量浓度和烟幕粒子的粒径分布,开发一种烟幕质量浓度测量装置,该装置采用激光前向散射原理和消光法测量原理相结合的方法。通过测试数据,可以计算出某一时刻的烟幕粒子数浓度和质量浓度的平均值。结果表明:烟幕质量浓度测量装置运行正常,粒径及粒径分布测量值准确。     

两种方法测量大气气溶胶折射率的对比分析

针对气溶胶折射率在分析大气气溶胶光学特性中的重要性,介绍两种综合利用黑碳仪、浊度计、光学粒子计数器和微脉冲激光雷达测量大气气溶胶折射率的新方法。两种方法都是根据球形粒子的Mie散射理论计算大气气溶胶的折射率,使用以上两种方法对厦门地区气溶胶折射率进行了计算和对比分析,证明了它们的合理性,分析了它们的测量精度和误差来源。     

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。     

空气动力学粒径的光学修正

针对空气动力学粒径和光学等效粒径之间存在的差异,本文提出对空气动力学粒径进行光学修正的方法.该方法根据黑碳仪(AE)、浊度计(IN)和光学粒子计数器(OPC)的测量结果,对气溶胶折射率进行反演,再利用反演的折射率结合黑碳仪和浊度计的测量结果对厦门地区空气动力学粒度仪(3321)测量的空气动力学粒径数据进行光学修正,与光学粒子计数器测量结果对比表明修正的结果是合理的.最后还对引起空气动力学粒径和光学等效粒径之间差异的原因进行了分析.     

深圳市环境空气中黑碳气溶胶的污染特征研究

为了解深圳市环境空气中黑碳气溶胶(BC)的污染状况及变化规律,2009年利用黑碳仪(aethalometer)对黑碳气溶胶组分进行了在线观测及来源分析研究.结果表明:大气环境中黑碳气溶胶质量浓度为5.72μg·m-3,占PM25的14.8％,且黑碳气溶胶浓度呈现冬高夏低、占PM25比例呈现夏高秋低的变化趋势.各季节BC浓度均具有显著的日变化,风向分析表明:静风时BC浓度较高,说明BC主要来自本地污染源;而区域污染传输发生时,东北方向的传输更易影响深圳市BC污染水平.     

两类PM_(2.5)监测仪及其计量检测方法的差异

监测PM_(2.5)的的仪器种类繁多,根据其是否带粒径切割器,可分为两类:一类利用切割器将小颗粒与大颗粒分离后再利用粉尘仪原理进行浓度检测,其计量指标主要有切割器的切割性能和质量浓度误差;另一类是基于尘埃粒子计数器改装的,通过光散射强度对颗粒物进行区分,其计量指标主要有粒径分布误差和质量浓度误差。两类仪器的粒径分离原理不同,导致其一系列特征和计量检测方法不同。     

华东乡村站点气溶胶吸收特性的观测研究

利用2014—2015年安徽淮南观测站的黑碳仪观测数据,分析华东乡村代表性地区气溶胶吸收特性的变化特征及其影响因子。研究表明,观测期间520 nm波段的气溶胶吸收系数平均为(24.6±18.4)Mm-1,且存在显著的波长依赖性,吸收波长指数平均为1.3±0.2,这与该地区较高的生物质燃烧排放有关。利用吸收系数与波长的关系,分离获得生物质燃烧排放的除黑碳以外的其他气溶胶的吸收波长指数,平均为2.7±0.7,在此基础上,进一步对吸收系数进行分离,发现每年5—6月、10月到次年1月是该地区受生物质燃烧影响较为严重的时期,以2014年6月为例,本地秸秆焚烧和江浙一带污染物的区域输送过程,是导致淮南地区污染加重的主要原因。     

标准粒子发生器系统的粒子发生规律

为了给激光尘埃粒子计数器提供可靠的校准、标定依据,研究0.296、0.498、1.019、2.995μm这4种标准粒子在不同稀释液喷射流量和粒子数下的分布规律,分析粒子发生系统中粒子数随工作时间的变化关系,探讨粒子计数器校准中的2种测量方法。结果表明,随粒子粒径的增加,测量粒子数所占总粒子数分数逐渐下降;前3种标准粒子具有稳定分布,后一种分布不稳定,且测量粒子数所占总粒子数分数与稀释液的喷射流量和浓度无关;粒子发生系统的稳定时间约为10 min;不同流量计数器比较校准时,前3种标准粒子适用于双管同时测量的方法,后一种适用于单管分时测量的方法。     

光散射法PM_(2.5)颗粒物监测仪(霾表)存在的问题和计量困境

光散射法PM2. 5/PM10颗粒物监测仪,作为一种特殊的粉尘仪和粒子计数器,其测量结果不仅受仪器自身结构,如散射角度、粒径识别通道等因素影响,还受颗粒物材质(密度、颜色等)、粒径分布和环境湿度的影响。其最主要的两个性能指标,浓度示值误差可通过其他方法比对、校准和修正,而粒径识别误差却是无法修正的。由于粒径识别误差在仪器设计、生产和后续管理中,没有检测技术和参考方法,导致无法监管,合格率低,还存在虚拟检测等情况。因此,光散射法颗粒物监测仪只能用于PM2. 5浓度变化趋势的监测,而不能用于浓度示值误差的测量。     

Multicomponent aerosol mass efficiency with various mixture types for polydispersed aerosol

Based on the filter-sampled chemical composition data the seasonal variation of the optical properties of polydispersed aerosols, extinction, scattering, and absorption coefficient, are estimated for various types of aerosol mixtures. The mixtures considered in this study are the internal mixture, elemental carbon (EC)/non-EC external mixture, and fully external mixture. This study also evaluated the sensitivity of the aerosol optical properties for different size distributions. The results show that the extinction coefficient can be mostly accounted for scattering and generally shows a good agreement with each mixture type in this case study. However, the absorption coefficient shows a different tendency for internal and external mixtures. This study also shows that the aerosol optical properties vary as a function of particle diameter at the same composition and mass concentration. This means that mass extinction, scattering, and absorption efficiencies, which were considered as constants in general, should be reassessed and more specifically described as a function of particle size.     

Light scattering and absorption by soot in the presence of sulfate aerosols

The radiative properties of aerosol-soot mixtures, both internal and external, are determined in the visible and near-infrared bands by use of exact indirect mode-matching solutions to electromagnetic-wave scattering from a sphere with an eccentric spherical inclusion and from a cluster of spheres. Spherical sulfate droplets are assumed to represent aerosol particles. Soot particles are represented by volume-equivalent carbon spheres, the size distribution of which is obtained from the number distribution of the primary carbon particles that aggregate into soot grains. The mean gram-specific absorption cross section and the mean albedo of aerosol-soot mixtures are obtained by integration of the corresponding characteristics of composite sulfate-carbon particles over the size range of carbon spheres. Enhanced absorption of light by soot in aerosol-soot mixtures, a result of lensing by sulfate droplets, is highlighted by maps of the electromagnetic field in a sulfate-carbon particle.     

CARBONACEOUS AEROSOLS-SINGLE SCATTERING ALBEDO AND EFFECT ON WEATHER HEATING

An experimental setup for the measurement of single scattering albedo of aerosol particles was described. The setup consisted of a nephelometer to measure aerosol light scattering coefficient, a photoacoustic spectrometer to measure aerosol light absorption coefficient, a Single Particle Aerodynamic Relaxation Time (SPART) Analyzer to measure aerosol aerodynamic size distribution, and an aethalometer to measure aerosol mass concentration. Simultaneous measurements of these parameters of a test carbonaceous aerosol were used to determine its single scattering albedo.

At the other hand, a theoretical model based on a “two-stream approximation” was developed and used to calculate the effect of an atmospheric aerosol layer on either global or regional weather heating. It appears that carbonaceous particles in atmosphere may contribute to global temperature rise.

Finally a method of measuring single scattering albedo of single particle by the use of an electrodynamic trap was suggested for studying the effect of different physical states and shapes of particles.     

非理想聚焦引起的激光粒度仪系统误差的数值模拟

因机械因素产生的非理想聚焦对激光粒度测量精度会产生影响,对此建立了相应的散射光强数学模型。模型的数值积分模拟表明,散焦降低了系统的分辨率,并且对于大颗粒的测量有着显著影响,使得测量结果中大颗粒数量减少,粒度分布向小粒径方向展宽。系统误差可以通过计算积分式光能分布系数矩阵校正。     

Case study of modeled aerosol optical properties during the SAFARI 2000 campaign

We present modeled aerosol optical properties (single scattering albedo, asymmetry parameter, and lidar ratio) in two layers with different aerosol loadings and particle sizes, observed during the Southern African Regional Science Initiative 2,000 (SAFARI 2,000) campaign. The optical properties were calculated from aerosol size distributions retrieved from aerosol layer optical thickness spectra, measured using the NASA Ames airborne tracking 14-channel sunphotometer (AATS-14) and the refractive index based on the available information on aerosol chemical composition. The study focuses on sensitivity of modeled optical properties in the 0.3-1.5 microm wavelength range to assumptions regarding the mixing scenario. We considered two models for the mixture of absorbing and nonabsorbing aerosol components commonly used to model optical properties of biomass burning aerosol: a layered sphere with absorbing core and nonabsorbing shell and the Maxwell-Garnett effective medium model. In addition, comparisons of modeled optical properties with the measurements are discussed. We also estimated the radiative effect of the difference in aerosol absorption implied by the large difference between the single scattering albedo values (approximately 0.1 at midvisible wavelengths) obtained from different measurement methods for the case with a high amount of biomass burning particles. For that purpose, the volume fraction of black carbon was varied to obtain a range of single scattering albedo values (0.81-0.91 at lambda=0.50 microm). The difference in absorption resulted in a significant difference in the instantaneous radiative forcing at the surface and the top of the atmosphere (TOA) and can result in a change of the sign of the aerosol forcing at TOA from negative to positive.     

耦合水雾的声团聚消除火灾烟雾的实验研究

对声波耦合水雾消除火灾烟雾的声团聚技术进行了实验研究,并且深入探究了声团聚的作用机理及微观团聚体结构的样貌,通过改变声波频率、声功率、水雾浓度和初始烟雾浓度等参数比较其对消烟效果的影响.结果 表明,声波耦合水雾技术提高了气溶胶分散性,并且水雾产生的液桥力保证了团聚体结构的稳定性,团聚效率得到提高.在初始烟雾浓度为50 ...     

Measurement of 100 nm and 60 nm Particle Standards by Differential Mobility Analysis

The peak particle size and expanded uncertainties (95 % confidence interval) for two new particle calibration standards are measured as 101.8 nm ± 1.1 nm and 60.39 nm ± 0.63 nm. The particle samples are polystyrene spheres suspended in filtered, deionized water at a mass fraction of about 0.5 %. The size distribution measurements of aerosolized particles are made using a differential mobility analyzer (DMA) system calibrated using SRM^® 1963 (100.7 nm polystyrene spheres). An electrospray aerosol generator was used for generating the 60 nm aerosol to almost eliminate the generation of multiply charged dimers and trimers and to minimize the effect of non-volatile contaminants increasing the particle size. The testing for the homogeneity of the samples and for the presence of multimers using dynamic light scattering is described. The use of the transfer function integral in the calibration of the DMA is shown to reduce the uncertainty in the measurement of the peak particle size compared to the approach based on the peak in the concentration vs. voltage distribution. A modified aerosol/sheath inlet, recirculating sheath flow, a high ratio of sheath flow to the aerosol flow, and accurate pressure, temperature, and voltage measurements have increased the resolution and accuracy of the measurements. A significant consideration in the uncertainty analysis was the correlation between the slip correction of the calibration particle and the measured particle. Including the correlation reduced the expanded uncertainty from approximately 1.8 % of the particle size to about 1.0 %. The effect of non-volatile contaminants in the polystyrene suspensions on the peak particle size and the uncertainty in the size is determined. The full size distributions for both the 60 nm and 100 nm spheres are tabulated and selected mean sizes including the number mean diameter and the dynamic light scattering mean diameter are computed. The use of these particles for calibrating DMAs and for making deposition standards to be used with surface scanning inspection systems is discussed.     

Light absorption from particulate impurities in snow and ice determined by spectrophotometric analysis of filters

Light absorption by particulate impurities in snow and ice can affect the surface albedo and is important for the climate. The absorption properties of these particles can be determined by collecting and melting snow samples and extracting the particulate material by filtration of the meltwater. This paper describes the optical design and testing of a new instrument to measure the absorption spectrum from 400 to 750 nm wavelength of the particles collected on filters using an "integrating-sandwich" configuration. The measured absorption is shown to be unaffected by scattering of light from the deposited particulates. A set of calibration standards is used to derive an upper limit for the concentration of black carbon (BC) in the snow. The wavelength dependence of the absorption spectra from 450 to 600 nm is used to calculate an absorption ?ngstrom exponent for the aerosol. This exponent is used to estimate the actual BC concentration in the snow samples as well as the relative contributions of BC and non-BC constituents to the absorption of solar radiation integrated over the wavelength band 300 to 750 nm.     

Optical properties of dispersed aerosols in the near ultraviolet (355 nm): measurement approach and initial data

An aerosol albedometer combining cavity ring-down spectroscopy (CRDS) with integrating sphere nephelometry was developed for use at λ = 355 nm. The instrument measures extinction and scattering coefficients of dispersed particulate matter in the near ultraviolet (UV) spectral region. Several samples have been analyzed, including: ammonium sulfate, secondary organic aerosols (SOA) resulting from the ozonolysis of α-pinene and photooxidation of toluene, redispersed soil dust samples, biomass burning aerosols, and ambient aerosols. When particle size and number density were experimentally controlled, extinction coefficients and scattering coefficients were found to have a linear relationship with particle number concentration, in good agreement with light scattering theory. For ammonium sulfate and pinene samples, extinction cross sections for size-selected (D(p) = 300 nm) samples were within the range of 1.65-2.60 × 10(-9) cm(2) with the largest value corresponding to ammonium sulfate and the lowest value for pinene SOA. The scattering cross sections of pinene and ammonium sulfate aerosols were indistinguishable from the extinction cross sections, indicating that these particle types had minimal light absorption at 355 nm. However, soil dusts and biomass burning aerosols showed significant absorption with single scatter albedo (SSA) between 0.74 and 0.84. Ambient aerosols also had transient absorption at 355 nm that correlated well with a particle-soot absorption photometer (PSAP) measuring visible light absorption.