Aerosol characterization mass concentration

Receptor models are powerful tools for source apportionment of particulates because a vast amount of particulate species characterization data have been collected at many sampling sites worldwide, and because many aerosol species are primary pollutants. Most of the information available is for elemental concentrations, eg, lead, nickel, and alurninum, although more recent measurements have provided data on concentrations of ionic species and carbonaceous compounds. At a sampling (or receptor) site, the aerosol mass concentration of each species i is... 

Aerosol Dynamics. Inclusion of a description of aerosol dynamics within air quaUty models is of primary importance because of the health effects associated with fine particles in the atmosphere, visibiUty deterioration, and the acid deposition problem. Aerosol dynamics differ markedly from gaseous pollutant dynamics in that particles come in a continuous distribution of sizes and can coagulate, evaporate, grow in size by condensation, be formed by nucleation, or be deposited by sedimentation. Furthermore, the species mass concentration alone does not fliUy characterize the aerosol. The particle size distribution, which changes as a function of time, and size-dependent composition determine the fate of particulate air pollutants and their... 

Besides mass concentration, atmospheric particles are often characterized by their size distribution. Aerosols are typically sized in terms of the aerodynamic equivalent diameter (dae) of the particle, usually expressed in micrometer (pm) or nanometer (nm) (Mark, 1998). Atmospheric particles are usually nonspherical and with unknown density. Therefore, the r/ae of a particle is usually defined as the diameter of an equivalent unit density sphere (p = 1 gctrf3) having the same terminal velocity as the particle in question (Mark, 1998 Seinfeld and Pandis, 1998). 

After the collection of particles, it is useful to determine the chemical characteristics of the material. This can be accomplished in terms of analysis of a whole sample corresponding to the total mass concentration, or it can be done on a size-fractionated basis. In some cases, individual particles can also be examined. Chemical characterization is very important when one is considering a heterogeneous collection of aerosol particles such as those found in the ambient air or in the workplace. These include whole sample microscopic analysis by collected batch, as well as continuous measurement. 

A particle sampling and measuring system was set up to characterize the suspended particles in the biomass combustion Fig. ). The system was capable of on-line measuring of the concentration number and particle size distribution in the micron and submicron range. In addition, mass concentration, particle morphology and chemical composition were obtained. The aerosol is first extracted from the duct and then led to the sampling station through an isokinetic probe equipped with an automatic control unit. 

Aerosol concentrations are defined in different ways depending on the application. For example, particle riumber concentrations (particles per unit volume of gas) are used to characterize dean rooms and atmospheric cloud condensation nuclei federal air pollution standards both for the atmosphere and for industrial emissions are usually stated in terms of aerosol mass per unit volume of gas. Effects of particles on viscosity depend on the ratio of the volume of particulate matter per unit volume of gas. For aerosols composed of particles all the same size, it is easy to relate the different methods of characterizing the concentration. For aerosols of mixed sizes, concentration measures are easily related only in certain cases as discussed below. 

We can characterize the particle concentration of an aerosol in two different ways. Firstly, the number concentration can be employed which is the number of the particles in a unit gas volume. Secondly, like the concentration of trace gases, the particle mass in a unit volume (mass concentration) can be given as we have seen in Chapter 3. In this subsection we will always use the number concentration of all particles which is practically equivalent to the number of Aitken size particles (see... 

Ro C-U, Hwang HJ, Kim HK, Chun YS, Van Grieken R (2005) Single-paiticle characterization of four asian dust samples collected in korea, using low-Z particle electron probe X-ray microanalysis. Environ Sci Technol 39 1409-1419 Salma I, Weidinger T, Maenhaut W (2007) Time-resolved mass concentration, composition and sources of aerosol particles in a metropolitan underground railway station. Atmos Environ 41 8391-8405... 

Aerosols in rural areas are mainly of natural origin but with a moderate influence of anthropogenic sources (Hobbs et al., 1985). The number distribution is characterized by two modes at diameters about 0.02 and 0.08 /xm, respectively (Jaenicke, 1993), while the mass distribution is dominated by the coarse mode centered at around 7 /xm (Figure 7.17). The mass distribution of continental aerosol not influenced by local sources has a small accumulation mode and no nuclei mode. The PM lo concentration of rural aerosols is around 20 /xg m . 

The highest concentrations are usually foimd in urban areas, reaching up to 10 and 10 particles per cm, with particle size ranging from around 100 /an to a few nanometer. Size is normally used to classify aerosol because it is the most readily measured property and other properties can be inferred from size information [7]. The highest mass fraction of particles in an aerosol is characterized by particles having a diameter in the range of 8 to 80 /an [8]. 

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