Number size distribution

Shape Density Pore size Numbers Size distribution... 

Covert, D. S., Gras, J. L., Wiedensohler, A., and Stratmann, F. Comparison of directly measured CCN with CCN modeled from the number-size distribution in the marine boundary layer during ACE 1 at Cape Grim, Tasmania, J. Geophys. Res.-A., 103, 16597-16608,1998. 

Figure 3. Cumulative number size distributions of samples from fructose crystallization for Run 5.

FIGURE 9.9 Particle number size distributions measured at Cheeka Peak, Washington, in 1991 (adapted from Quinn et at., 1993). 

For example, as seen in Fig. 14.41, aerosol particle number size distributions in the clean marine boundary layer outside of clouds are often observed to have a bimodal distribution. The larger mode above 0.1 /xm... 

The structure (e.g., number, size, distribution) of fat crystals is difficult to analyze by common microscopy techniques (i.e., electron, polarized light), due to their dense and interconnected microstructure. Images of the internal structures of lipid-based foods can only be obtained by special manipulation of the sample. However, formation of thin sections (polarized light microscopy) or fractured planes (electron microscopy) still typically does not provide adequate resolution of the crystalline phase. Confocal laserscanning microscopy (CLSM), which is based on the detection of fluorescence produced by a dye system when a sample is illuminated with a krypton/argon mixed-gas laser, overcomes these problems. Bulk specimens can be used with CLSM to obtain high-resolution images of lipid crystalline structure in intricate detail. 

Thimmaiah D, Hovorka J, Hopke PK (2009) Source apportionment of winter submicron Prague aerosols from combined particle number size distribution and gaseous composition data. Aerosol Air Qual Res 9 209-236... 

Rodriguez S, Van Dingenen R, Putaud JP, Dell Acqua A, Pey J, Querol X, Alastuey A, Chenery S, Kin-Fai H, Harrison RM, Tardivo R, Scamato B, Gianelle V (2007) A study on the relationship between mass concentration, chemistry and number size distribution of urban fine aerosols in Milan, Barcelona and London. Atmos Chem Phys 7 2217-2232... 

Birmili W, Weinhold K, Nordmann S et al (2009) Atmospheric aerosol measurements in the German ultrafine aerosol network (GUAN). Part 1. Soot and particle number size distributions. Gefahrst Reinhalt Luft 69 137-145... 

Number Size Distributions of Submicron Particles in Europe... 

Abstract The aerosol particle number size distribution is a key component in aerosol indirect climate effects, and is also a key factor on potential nanoparticle health effects. This chapter will give background on particle number size distributions, their monitoring and on potential climate and health effects of submicron aerosol particles. The main interest is on the current variability and concentration levels in European background air. 

The submicron particle number size distribution controls many of the main climate effects of submicron aerosol populations. The data from harmonized particle number size distribution measurements from European field monitoring stations are presented and discussed. The results give a comprehensive overview of the European near surface aerosol particle number concentrations and number size distributions between 30 and 500 nm of dry particle diameter. Spatial and temporal distributions of aerosols in the particle sizes most important for climate applications are presented. Annual, weekly, and diurnal cycles of the aerosol number concentrations are shown and discussed. Emphasis is placed on the usability of results within the aerosol modeling community and several key points of model-measurement comparison of submicron aerosol particles are discussed along with typical concentration levels around European background. 

Keywords Aerosol number concentration, Aerosol number size distribution, Atmospheric aerosols, CCN... 

Measuring the Aerosol Particle Number Size Distributions. 302... 

Spatial Differences and Similarities of Aerosol Number Size Distributions. 305... 

Comparing Measurements of Number Size Distribution with Model Output. 316... 

The climate effects of atmospheric aerosol particles are a matter of continuous interest in the research community. The aerosol-climate effects are divided into two groups The direct effect represents the ability of the particle population to absorb and scatter short-wave radiation - directly affecting the radiation balance. These direct effects depend primarily on the aerosol optical properties and particle number size distribution, as the particle size significantly affects the scattering efficiency of... 

As particle number size distributions can be complex, and the instruments used generate large amount of size distribution data, which can be hard to effectively describe, a common method is to calculate integrated particle number concentrations for specific aerosol particle diameter ranges, depending on which part of the particle number size spectrum is needed for the application. In this chapter, three different ranges are used (Fig. la) ... 

Fig. 1 (a) Typical clean Northern European median number size distribution (measured at SMEAR II station in Hyytiala, Finland). The approximate modal locations and size ranges of different integral properties of the aerosol number size distribution used are shown (b) variance of number concentration as a function of particle diameter (c) variance of (computed) volume concentration in the same station (adapted from Asmi (2012), [11])... 

Number concentrations are dominated by submicron particles, whereas the mass concentrations are strongly influenced by particle concentrations in 0.1-10 pm diameter range [13]. Similarly, the variability of the number-based measurements is strongly dominated by variability in smaller diameter ranges, whereas the variability of mass-based properties, such as PM10, are dominated by variability in the accumulation mode (usually around 500 nm of mass mean diameter) and in the coarse mode. This means the variabilities of these properties are not necessarily similar in shorter timescales, due to sensitivity of variance from very different air masses and thus aerosol types. This is demonstrated in Fig. lb, where the variance of the each size class of particle number concentrations between 3 and 1,000 nm is shown for SMEAR II station in Hyytiala, Finland. The variance has similarities to the particle number size distribution (Fig. la), but there are also significant differences, especially on smaller particles sizes. Even though in the median particle number size distribution the nucleation mode is visible only weakly, it is a major contributor to submicron particle number concentration variability. 

GUAN is a network of multiple German institutes with an interest in submicron aerosol properties, which was established in 2008 [17]. The methodologies of particle number size distribution measurements and data handling procedures in both GUAN and EUSAAR networks are very similar, and the size distribution measurement results are comparable between the two networks. The EUSAAR measurements were available (with some station-to-station variability) for the year 2008-2009 and the GUAN measurements were mostly from 2009. The locations of the stations are shown in Fig. 2. 

Fig. 2 Stations used in measurements of aerosol number size distributions. Black symbols are EUSAAR stations, white GUAN (MPZ was in both networks). Triangles denote high-altitude mountain stations (over 1,000 m from mean sea level). Figure adapted from figure published in [18], which also has more details on the locations and types of the stations...

Levels and Variability of Aerosol Number Concentrations 3.1 General Properties of Number Size Distributions... 

Combining the physical aerosol measurements from a high number of European background stations shows that there are clear similarities between particle number size distributions and concentration levels measured at different locations over wide geographical regions. These similarities are connected to similar emissions, particle loss processes, and meteorological patterns. The main aim of this section is just to provide key factors of each station categorization, more details and complete analysis of individual stations are available in [18] and references therein. 

The particle number size distributions and concentration levels measured at the Central European stations were remarkably similar. The median particle number size distributions did not change significantly from season to season, and the differences between the stations were not very large (N50 from 2,500 to 3,100 cm-3). The variability of nucleation and small Aitken particles was elevated... 

Overall, the results suggest that the particle number size distributions in Central Europe are very similar over very large region, and even though the mean concentrations somewhat vary from station to station, the background air in Europe is homogenous from the aerosol point of view. 

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