Particulate sampler

FIGURE 11.56 Schematic of Hi-Vol particulate sampler (adapted from Lawrence Berkeley Laboratory, f979). 

For this reason, particulate samplers designed for particulate removal have to generate the maximum possible particulate mass. Modern examples include impactors based on the high-volume sampler (Hi-Vols), the MOUDI (17) of the University of Minnesota, and the BLPI (16). The Hi-Vols, in particular, collect 330 m3 of air in 4 h, giving 1100 xg of deposit for three size cuts below a particle diameter of 2.5 xm. Table I shows some key parameters for a few widely used ambient air impactors for multiple size cuts. 

Measurement and Characterization of (Wet) Cooling Tower Drift (Including a Particulate Sampler)... 

Air particulate samplers are usually classified as low-volume air samplers or high-volume air samplers. There are, in addition to these classifications, dust samplers that consist of a combination of a low-volume suction pump and a movable filter-paper system. Characteristics of these samplers are as follows ... 

Two problems are of importance radioactive gases and particulates, the airborne particulate monitoring in the critical stage is by air-particulate sampler. Here we shall describe some of them being used at different laboratories. 

The metallic element whose concentration in air is most clearly ascribable to man s activities is lead. The level of lead found varies from about 0.1 iig/vn in sparsely populated areas to about 10 /xg/m in areas where automobile traflBc is at a maximum. In a study conducted at Los Angeles, two sites were monitored on either side of a freeway which had approximately 200,000 cars per day as a traflBc level 21), One site was downind a preponderance of the time. If the concentrations at the downwind site are divided by the concentrations of the site that was usually upwind, one can see, in Table XII, ratios that vary from 1.03 (where the percentage of favorable wind was 28) to 4.3 (where the favorable wind percentage was 68). In Table XIII are shown the results obtained when a massive respirable particulate sampler was field tested. The collector was built for EPA by Battelle Columbus. Particles greater than 20 /xm are eliminated with a cyclone. The first stage collects particles by impaction... 

British suspended particulate sampler In recent years the old British standard method has been super-ceded by European directives such as EN12341 Air Quality - Field test procedure to demonstrate reference equivalence of sampling methods for the PMIO fraction of particulate matter. The determination of smaller size fractions (PM2.5) is also covered by a further directive. The US EPA have similar standard reference methods for particulate material (USEPA 40 CFR part 50). An early method was to simply compare the color of a filter paper through which a volume of air was drawn to an incremental gray scale (16 shades from white to black) this was then converted into an integrated particle loading with reference to the size cut-off offered by the pore size of the filter used. This was known as the black smoke index method. 

This experiment describes the construction of an air sampler using an aquarium pump, a flow meter, a filter holder, and bottles that serve as traps for analytes. Applications include the determinations of SO2, NO2, HCHO, and suspended particulate matter. 

Two simple air samplers are described as well as their use for determining particulates in air. 

Total airborne particulates are determined using a high-volume air sampler equipped with either cellulose fiber or glass fiber filters. Samples taken from urban environments require approximately 1 h of sampling time, but samples from rural environments require substantially longer times. 

Sampling of Particulates. Ambient air suspended particulate concentration was traditionaUy measured gravimetricaUy over a 24-h period with a "Hi-Vol" sampler. However, in 1987 the EPA changed ambient particulate control to the PM q reference method (24). In the PM q method, a... 

Because a filter sample includes particles both larger and smaller than those retained in the human respiratory system (see Chapter 7, Section III), other types of samplers are used which allow measurement of the size ranges of particles retained in the respiratory system. Some of these are called dichotomous samplers because they allow separate measurement of the respirable and nonrespirable fractions of the total. Size-selective samplers rely on impactors, miniature cyclones, and other means. The United States has selected the size fraction below an aerodynamic diameter of 10 /xm (PMiq) for compliance with the air quality standard for airborne particulate matter. 

A second sampling program in Southern California sampled for polychlorinated dioxins and polychlorinated dibenzofurans at seven locations (9). Because of the semivolatile nature of these compounds, a tandem sampler was used with a glass fiber filter to collect the particulate-associated compo-... 

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. 

The particles most likely to cause adverse health effects are the fine particulates, in particular, particles smaller than 10 p and 2.5 mm in aerodynamic diameter, respectively. They are sampled using (a) a high-volume sampler with a size-selective inlet using a quartz filter or (b) a dichotomous sampler that operates at a slower flow rate, separating on a Teflon filter particles smaller than 2.5 mm and sizes between 2.5 mm and 10 mm. No generally accepted conversion method exists between TSP and PM,o, which may constitute between 40% and 70% of TSP. In 1987, the USEPA switched its air quality standards from TSP to PMk,. PM,q standards have also been adopted in, for example, Brazil, Japan, and the Philippines. In light of the emerging evidence on the health impacts of fine particulates, the USEPA has proposed that U.S. ambient standards for airborne particulates be defined in terms of fine particulate matter. 

Particle Sampler an instrument to measure particulate matter in ambient air. Particulate Matter dust, soot, other tiny bits of solid materials that are released into and move around in the air. See also fine particle, PM,o. 

High-volume sampler A device used for extracting particulates from the air for analysis that requires a shorter. sampling period than a low-volume sampler. 

Flg ire 8.29 Apparatus for siunpling airborne organic samples. A, trapping of organic volatiles in air using a sorbent trap B, thermal desorption chamber C, high-volume sampler for air particulates. 

Only one actual comparison of these techniques is available in the literature. Daumas et al. [13] compared the Harvey drum sampler to the Garrett screen, and found greater organic enrichment in both dissolved and particulate matter in the drum samples. The size of the difference between the two samplers suggests that the Garrett screen included 2-3 times as much water as did the Harvey drum. 

One type of point detector, the Aerosol Particle Sizer (APS), inhales air with a high-speed sampler, then counts and sizes the particulates. In the APS the counting and sizing of particles is done with a flow... 

---