Particulate sample

Nonvolatile compounds are normally present either as solid particulates or bound to solid particulates. Samples are collected by pulling large volumes of gas through a filtering unit where the particulates are collected on glass fiber filters. 

The major purpose of ambient particulate sampling is to obtain mass concentration and chemical composition data, preferably as a function of particle diameter. This information is valuable for a variety of problems effects on human health, identification of particulate matter sources, understanding of atmospheric haze, and particle removal processes. 

The chemical composition of particulate pollutants is determined in two forms specific elements, or specific compounds or ions. Knowledge of their chemical composition is useful in determining the sources of airborne particles and in understanding the fate of particles in the atmosphere. Elemental analysis yields results in terms of the individual elements present in a sample such as a given quantity of sulfur, S. From elemental analysis techniques we do not obtain direct information about the chemical form of S in a sample such as sulfate (SO/ ) or sulfide. Two nondestructive techniques used for direct elemental analysis of particulate samples are X-ray fluorescence spectroscopy (XRF) and neutron activation analysis (NAA). 

If the probe velocity is less than the stack velocity, particles will be picked up by the probe, which should have been carried past it by the gas streamlines. The inertia of the particles allows them to continue on their path and be intercepted. If the probe velocity exceeds the stack velocity, the inertia of the particles carries them around the probe tip even though the carrying gases are collected. Adjustment of particulate samples taken anisokinetically to the correct stack values is possible if all of the variables of the stack gas and particulate can be accounted for in the appropriate mathematical equations. 

Modern transducers and microprocessors have been used successfully to automate particulate sampling trains in order to eliminate the operating curves and manual adjustments (7). The automated samplers adjust continuously to maintain isokinetic conditions. In addition, the microprocessor continuously calculates and displays both instantaneous sampling conditions and the total sample volume collected at any given moment. The use of the automated system with the microprocessor, therefore, eliminates both operator and calculation errors. 

Several separating systems are used for particulate sampling. All rely on some principle of separating the aerosol from the gas stream. Many of the actual systems use more than one type of particulate collection device in series. If a size analysis is to be made on the collected material, it must be remembered that multiple collection devices in series will collect different size fractions. Therefore, size analyses must be made at each device and mathematically combined to obtain the size of the actual particulate in the effluent stream. In any system the probe itself removes some particulate before the carrying gas reaches the first separating device, so the probe must be cleaned and the weight of material added to that collected in the remainder of the train. 

A very important analytical tool that is overlooked by many sourcetesting personnel is the microscope. Microscopic analysis of a particulate sample can tell a great deal about the type of material collected as well as its size distribution. This analysis is necessary if the sample was collected to aid in the selechon of a piece of control equipment. All of the efficiency curves for particulate control devices are based on fractional sizes. One would not try to remove a submicron-size aerosol with a cyclone collector, but unless a size analysis is made on the sampled material, one is merely guessing at the actual size range. Figure 32-8 is a photomicrograph of material collected during a source test. 

Maintain integrity of particulate sample (mass, size, chemical composition)... 

Boubel, R. W., Hirsch, J. W., and Sadri, B., Particulate sampling has gone automatic. Proceedings of the 68th Annual Meeting of the Air Pollution Control Association, Pittsburgh, 1975. 

A particulate sample was found to weigh 0.0216 gm. The sample volume from which it was collected was 0.60 at 60°C, 760 mm Hg absolute, and 90% relative humidity. What was the stack loading in milligrams per standard cubic meter ... 

A particulate sample was found to contain 350 mg m . The COj during the sampling period averaged 7.2%. If the exhaust gas flow was 2000 m min, what would be the particulate loading in both milligrams per cubic meter and kilograms per hour, corrected to 12% C O A... 

At Site I, personnel and equipment decontamination procedures were not monitored for their effectiveness in accordance with HAZ-WOPER requirements. The Site I subcontractor did not have provisions for particulate sampling, evaluating exposure to pesticides and herbicides, or evaluating the effectiveness of site zone boundaries and personnel decontamination procedures. Additionally, monitoring had not been conducted to verify that decontamination was not necessary for employees who leave the exclusion zone and enter a clean zone without undergoing decontamination. 

In the measurement of emission gas mass concentration at sources, a gas sample is extracted via an automatic isokinetic particulate-sampling instrument. The monitoring system generates a direct, real-time emission particulate mass... 

Recent Uses of Solid-Surface Luminescence Analysis in Environmental Analysis. Vo-Dinh and coworkers have shown very effectively how solid-surface luminescence techniques can be used for environmentally important samples (17-22). RTF has been used for the screening of ambient air particulate samples (17,18). In addition, RTF has been employed in conjunction with a ranking index to characterize polynuclear aromatic pollutants in environmental samples (19). A unique application of RTF reported recently is a personal dosimeter badge based on molecular diffusion and direct detection by RTF of polynuclear aromatic pollutants (20). The dosimeter is a pen-size device that does not require sample extraction prior to analysis. 

A wide range of azaarenes including acridines and benzacridines, 4-azafluorene, and 10-azabenzo[fl]pyrene (Figure 1.32) has been identified in particulate samples of urban air, and some of them have been recovered from contaminated sediments (Yamauchi and Handa 1987). 

FIGURE 1.32 Azaarenes identified in particulate samples of urban air. 

Phytoplankton are easily sampled with fine-mesh nets. However, samples require considerable processing before analysis to remove zooplankton, detritus, or other particulates. Sampling would not measnrably affect target popnlations, even in the smallest lakes. 

Scott DR, Hemphill DC, Hoiboke LE, et al. 1976. Atomic absorption and optical emission analysis of NASN atmospheric particulate samples for lead. Environ Sci Technol 9 877-880. 

Equation 3.2 was proposed by Roach (1968) almost 40 years ago to model the overlap of coal particulates sampled from air onto a flat surface. The equation was verified by studying the clustering of randomly distributed circles in a square representing the reduced space of a 2D separation (Oros and Davis, 1992). It then was modified (Rowe and Davis, 1995) to study the clustering of inhomogeneous random distributions of circles (Rowe et al., 1995 Davis, 2004), in which more circles are found in parts of the reduced square than in others, and to address the clustering of ellipses and reduction of clustering that occurs near the reduced-square boundaries (Davis, 2005). For simplicity, only Equation 3.2 is used in this chapter. 

Figure 13 Chromatogram of an airborne particulate sample. Peaks 1 = 1,6-dinitropyr-ene 2 = 1,8-dinitropyrene 3 = 1,3-dinitropyrene 4 = 2-fluoro-7-nitrofluorene 5 = 1-nitropyrene. (From Ref. 60.)...

REFERENCE MATERIALS CURRENTLY AVAILABLE FOR THE ANALYSIS OF SEDIMENT AND PARTICULATE SAMPLES... 

Thaulow, N. and White, E.W. (1971) General method for dispersing and disaggregating particulate samples for quantitative S EM and optical microscope studies. Technical Report 5 (US Department of Commerce Technical Report AD733457), Office of Naval Research, Metallurgical Program. 

An Intercomparison study of trace element determinations In simulated and real air particulate samples has been published by Camp, Van Lehn, Rhodes, and Pradzynskl ( ). This Involved twenty-two different laboratories reporting up to thirteen elements per sample. The simulated samples consisted of dried solution deposits of ten elements on Mllllpore cellulose membrane filters. In our data analysis a set of energy dispersive X-ray emission results restricted to eight laboratories reporting six elements (V, Cr, Mn, Fe, Zn, Cd) was... 

In the atmosphere, the vapor pressure of the isomeric cresols, 0.11+0.30 mmHg at 25.5 °C (Chao et al. 1983 Daubert and Danner 1985), suggests that these compounds will exist predominantly in the vapor phase (Eisenreich et al. 1981). This is consistent with experimental studies that found all three isomers in the gas phase of urban air samples, but they were not present in the particulate samples collected at the same time (Cautreels and Vancauwenbergh 1978). The relatively high water solubility of the cresol isomers, 21,520- 25,950 ppm (Yalkowsky et al. 1987), indicates that wet deposition may remove them from the atmosphere. This is confirmed by the detection of cresols in rainwater (Section 5.4.2). The short atmospheric residence time expected for the cresols (Section 5.3.2.1) suggests that cresols will not be transported long distances from their initial point of release. 

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