Aerosol properties

The condensed phases also are important to the physical processes of the atmosphere however, their role in climate poses an almost entirely open set of scientific questions. The highest sensitivity of physical processes to atmospheric composition lies within the process of cloud nucleation. In turn, the albedo (or reflectivity for solar light) of clouds is sensitive to the number population and properties of CCN (Twomey, 1977). At this time, it appears impossible to predict how much the temperature of the Earth might be expected to increase (or decrease in some places) due to known changes in the concentrations of gases because aerosol and cloud effects cannot yet be predicted. In addition, since secular trends in the appropriate aerosol properties are not monitored very extensively there is no way to know... 

Theoretical unattached fractions of RaA using average aerosol concentrations and count median diameters as found in track and trackless Canadian uranium mine are presented in Table III. The reported uranium mine aerosol properties are N 120,000 particles/cm3 and CMD = 0.069 ym for a trackless mine and N =... 

A different approach which also starts from the characteristics of the emissions is able to deal with some of these difficulties. Aerosol properties can be described by means of distribution functions with respect to particle size and chemical composition. The distribution functions change with time and space as a result of various atmospheric processes, and the dynamics of the aerosol can be described mathematically by certain equations which take into account particle growth, coagulation and sedimentation (1, Chap. 10). These equations can be solved if the wind field, particle deposition velocity and rates of gas-to-particle conversion are known, to predict the properties of the aerosol downwind from emission sources. This approach is known as dispersion modeling. 

At the receptor, the mass concentration of aerosol property i, C , will be... 

These conditions cannot be completely met in practice, and by limiting the model to only one tracer property per source type, valuable information contained in the other aerosol properties is being discarded. Thus, solutions to the set of equations like Equation 1 have been developed to make use of the additional information provided by more than one unique chemical property of a source type, and even that of properties which are not so unique. 

Ambient aerosol property measurements are quite sophisticated source measurements are not as well developed. Certain aerosol property measurements have been made on emissions of many sources. Unfortunately these tests seldom provide a full accounting of samples, sometimes do not report confidence Intervals on the measurements, and often do not fully describe the operating parameters of the source at the time of the test. 

The future development of the chemical mass balance receptor model should include 1) more chemical components measured in different size ranges at both source and receptor 2) study of other mathematical methods of solving the chemical mass balance equations 3) validated and documented computer routines for calculations and error estimates and 4) extension of the chemical mass balance to an "aerosol properties balance" to apportion other aerosol indices such as light extinction. 

The microscopic receptor model can include many more aerosol properties than have been used in the chemical mass balance and multivariate models. The data inputs required for this model are the ambient properties measurements and the source properties measurements. To estimate the confidence Interval of the calculated source contributions the uncertainties of the source and receptor measurements are also required. Microscopists generally agree that a list of likely source contributors, their location with respect to the receptor, and windflow during sampling are helpful in confirming their source assignments. 

Existing data on characteristics of particles from various types of sources are inadequate for general use, though they have been used in specific studies with some success. Most of the source tests have been made for purposes other than receptor modeling and complete chemical and microscopical analyses have not been performed. Source operating parameters which might affect the aerosol properties of emissions have not been identified nor measured in ambient sampling and no provision is made for likely transformations of the source material when it comes into equilibrium under ambient conditions. 

Develop standard reference materials representing different ambient and source particulate matter matrices. Characterize them in terms of relevant aerosol properties. 

Next, the applications have to be validated and placed into standardized forms. Validation should consist of two steps. First, simulated data sets of aerosol properties should be generated from pre-selected source contributions as did Watson in his simulation studies of the chemical mass balance method. These data should be perturbed with the types of uncertainties expected under field conditions. The types of sources and their contributions predicted by the receptor model application should be compared with the known source model values and the extent of perturbation tolerable should be assessed. 

The combustion products then pass through a series of convective heat exchangers which cool them to normal flue gas temperature. Samples extracted from the cool (400-500°K) combustion products are analyzed for major gaseous products and aerosol properties. 

Hegg, D. A., P. V. Hobbs, R. J. Ferek, and A. P. Waggoner, Measurements of Some Aerosol Properties Relevant to Radiative Forcing on the East Coast of the United States, J. Appl. Meteorol., 34, 2306-2315 (1995). 

Torres, 0 P. K. Bhartia, J. R. Herman, Z. Ahmad, and J. Gleason, Derivation of Aerosol Properties from Satellite Measurements of Backscattered Ultraviolet Radiation Theoretical Basis, J. Geophys. Res., 103, 17099-17110(1998). 

TABLE 14.8 Some Cloud and Subcloud Aerosol Properties Measured in Polluted and Clean Air Masses near the Azoresu... 

Davison, B., C. N. Hewitt, C. D. O Dowd, J. A. Lowe, M. H. Smith, M. Schwikowski, U. Baltensperger, and R. M. Harrison, Dimethyl Sulfide, Methane Sulfonic Acid, and Physicochemical Aerosol Properties in Atlantic Air from the United Kingdom to Halley Bay, J. Geophys. Res., 101, 22855-22867 (1996). 

Linear polarization ratios have also been measured remotely. For example, results are given by Ward et al. (1973) and by Reagan et al. (1980). The sensitivity of scattering diagrams (Fig. 13.8), especially polarization (Fig. 13.9), to particle shape signals caution in inferring aerosol properties such as k from bistatic remote sensing. 

Hunt, A. J., and D. R. Huffman, 1975. A polarization-modulated instrument for determining liquid aerosol properties, Jpn. J. Appl. Phys., 14 (Suppl. 14-1), 435-440. 

Torres, O., Bhartia, P.K., Herman, J.R., Ahmad, Z and Gleason, J. (1998) Derivation of aerosol properties from satellite measurements of backscattered ultraviolet radiation Theoretical basis, J. Geophys. Res., 103, pp. 17,099-17,110. 

Toledano C, Cachorro VE, Gausa M, Stebel K, Aaltonen V, Berjon A, Ortiz de Galisteo JP, de Frutos AM, Bennouna Y, Blindheim S, Myhre CL, Zibordi G, Wehrli C, Kratzer S, Hakansson B, Carlund T, de Leeuw G, Herber A, Torres B (2012) Overview of sun photometer measurements of aerosol properties in Scandinavia and Svalbard. Atmos Environ 52 18-28... 

Several European intensive short-term ( campaign-type ) projects have provided important information on the atmospheric aerosol properties in Europe, usually by concentrating on specific aerosol properties or interactions. However, these kinds of campaign-type measurements do not necessarily represent the seasonal or annual variations of the aerosol concentrations and can overestimate some properties of the aerosol populations. Long-term measurements, especially with intercalibrated instruments and common data handling and calibration protocols make the data comparison between stations much more reliable and provide the end users (e.g., atmospheric modelers) good datasets to compare with. 

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. 

McFiggans G et al (2006) The effect of physical and chemical aerosol properties on warm cloud droplet activation. Atmos Chem Phys 6 2593-2649... 

Heintzenberg J et al (1998) Mass-related aerosol properties over the Leipzig basin. J Geophys Res D 103 13125-13135... 

It is difficult to extract precise Qd values from ambient air sampling data. Plots of Equation (11) are constructed by measuring Kp on days when temperatures vary (Bidleman et al., 1986 Foreman and Bidleman, 1990 Gustafson and Dickhut, 1997 Pankow, 1991 Yamasaki et al., 1982). Unfortunately, these experimental Kp estimates also reflect the day-to-day variations in relative humidity and aerosol properties. As a result, confidence intervals around Qd are typically large (Bidleman et al., 1986 Pankow, 1991). Moreover, differences in the rates at which gases equilibrate with particles on hot and cold days (Kamens... 

Hansen et al. (1998) noted that the most reliable estimate of total RF due to aerosol constitutes — 0.4 0.3Wm 2 instead of the earlier estimate 0.54, though in any case such an estimate is still very uncertain due to unreliable input data on aerosol properties. 

Kondratyev K.Ya. Ivlev L.S. Krapivin V.F. and Varotsos C.A. (2006a). Atmospheric Aerosol Properties Formation, Processes and Impacts. Springer/Praxis, Chichester, U.K., 572 pp. 

To characterize adequately the dynamic properties of a chemically reactive aerosol, a very large amount of information is required. However, aerosol properties generally are determined in only a limited way because of limitations of available techniques. With air pollution monitoring and the driving force of progress in the development of theory, heavy emphasis has been placed on the size distribution and its moments, as well as the chemical composition of particles and the suspending gas. 

In general, the methods are difficult to interpret quantitatively in terms of aerosol properties because of ambiguities in the size distribution-concentration-distance profiles and variations in chemical properties contributing to the index of refraction. Nevertheless, remote sensing continues to be important for the surveillance of aerosol behavior in planetary atmospheres. 

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