Particle samples

Note that the relative sampling variance is inversely proportional to the number of particles sampled. Increasing the number of particles in a sample, therefore, improves the sampling variance. 

This short paper describes a demonstration suitable for use in the classroom. Two populations of corks are sampled to determine the concentration of labeled corks. The exercise demonstrates how increasing the number of particles sampled improves the standard deviation due to sampling. 

Cyclone collectors are popularly used both for particle removal and for particle sampling (Fig. 13.1). The separation process of a cyclone relies on the centrifugal accelerations that are produced when particle-laden fluid experi-... 

The particle size analyzer, based on laser light diffraction, consists of a laser source, beam expander, collector lens, and detector (Fig. ] 3.45). The detector contains light diodes arranged to form a radial diode-array detector. The particle sample to be measured can be blown across the laser beam (dry sample), or it can be circulated via a measurement cell in a liquid suspension. In the latter case, the beam is direaed through the transparent cell. 

Figure 7. Guinier plot for a rod-like particle. Sample C40 in O.IM NaCl (6 10 g/L) with calcium (6 10 mol/L)...

Transmission electron microscopy also gave evidence for bridging flocculation at partial coverage. Figure 3 shows electron micrographs of the bare particles and the particles covered partially with adsorbed Vinol 350. The partially covered particles are interconnected with fibrillar links, which are not observed in the bare-particle sample. 

Particle shape plays an important role in particle size determination. The simplest definition of particle size diameter is based on a sphere, which has a unique diameter. In reality, however, many particles are not well represented by this model. Figure 1 illustrates the variety of shapes that may be found in particle samples [1]. As the size of a particle increases, so does its tendency to have an irregular shape [2], complicating statistical analysis. Particle shape coefficients have been derived for different geometries [3], and various equivalent diame-... 

Fig. 3. SEM image and EDS spectrum of aerosol particle (sampling point ME-20).

Zdanowicz, C.M. Banic, C.M. Paktunc, D. Kliza-Petelle, D.A. 2006. Metal emissions from a Cu-smelter, Rouyn-Noranda, Quebec Characterization of particles sampled in air and snow. Geochemistry Exploration, Environment and Analysis, 6, 147-162. 

The purpose of laboratory testing to obtain contaminant-solid phase relationships is not only to obtain some insight into the accumulation and transmission characteristics of the solid materials with specific regard to the contaminants) of interest, but also to obtain physical input for transport modeling and chemodynamic purposes. It is also most important to conduct tests with the actual contaminant leachate or chemical species and also with the solid particle samples representative of the field matrix. 

Although Rs values of high Ks compounds derived from Eq. 3.68 may have been partly influenced by particle sampling, it is unlikely that the equation can accurately predict the summed vapor plus particulate phase concentrations, because transport rates through the boundary layer and through the membrane are different for the vapor-phase fraction and the particle-bound fraction, due to differences in effective diffusion coefficients between molecules and small particles. In addition, it will be difficult to define universally applicable calibration curves for the sampling rate of total (particle -I- vapor) atmospheric contaminants. At this stage of development, results obtained with SPMDs for particle-associated compounds provides valuable information on source identification and temporal... 

Examples of GC-MS data for typical total extracts from rural and urban aerosol particle samples (analyzed as silylated derivatives) (a) total ion current (TIC) trace for Oakridge, OR, rural aerosol (Jan/Feb. 1985) and (b) TIC trace for Pasadena, CA, aerosol (Feb. 1989), DEHP = diethylhexyl phthalate, lA = carbon chain length of -alkanoic acids. 

Figure 6. Enrichment factor vs. particle size curves for Se in aerosol particles sampled upstream of the Plant A cold-...

An upper limit to the absorption efficiency of the elemental carbon particles sampled can be obtained if it is assumed that all aerosol light absorption is due to elemental carbon. In that case the specific absorption from the slope of the line in Figure 5 is about 11.9 0.9 m g. That value is higher than would be... 

The relative contribution of primary and secondary carbon to urban aerosol is discussed in this paper. Some data from the ACKEX study in Los Angeles have been reexamined using new values for the carbon and lead emissions. Data on total carbon, elemental carbon and lead in fine particle samples collected in St. Louis are presented. Lead and elemental carbon have been shown to be useful tracers of primary carbonaceous aerosol. It is concluded that secondary carbon is most likely to be a significant portion of the urban carbonaceous aerosol in the summer and in the middle of the day. Secondary carbon can best be measured with short time resolution sampling (At 6h). 

Thus from the total mass (MT) of the particle sample and its total surface area (ST) (which can be determined experimentally), the surface mean diameter of the particles can be calculated if their density (p) is known. 

Sulfate is a ubiquitous component of particles in the troposphere in both polluted urban areas and remote regions such as the Mauna Loa Observatory (e.g., see Johnson and Kumar, 1991). Indeed, sulfates can sometimes be the major component of tropospheric particles. For example, more than 90% of the total particles sampled in the upper troposphere were observed to... 

FIGURE 9.43 Concentrations of n-alkanes as a function of carbon number from (a) a particle sample collected in Jos, Nigeria (the dashed line represents the estimated concentrations from fossil fuel sources), (b) vegetation wax in the Jos area, and (c) particles collected over the Atlantic Ocean (adapted from Sinioneit et al., 1988). 

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