Suspended particle sampler

Construction of the suspended particle sampler (SPS). (Reproduced from Liess, M., Schulz, R., and Neumann, M., Chemospkere, 32(10), 1963, 1996. With permission.)... 

Pan et al. (1999) reported detailed observations of PAH decay in aerosols under UV light of 253.7 nm. The study used a high volume sampler to collect the total suspended particles in air with quartz filters as the supporter. The results showed that the photo degradation of PAHs under UV radiation took place immediately, and was a first-order reaction. The photodegradation rate constant (k) is related to the oxidation half-wave potential (Ei/2) and the structure of the PAHs. 

The sampling method most widely used for ambient particles is the high volume sampler . This instrument has been standardized in many countries (FRG VDI 1972 USA US EPA 1971) and collects total suspended particles with sampling rates of 40 to lOOm h k During a sampling interval of 24 h, around 0.01-0.5 g of particles are retained which are evaluated gravimetrically and can be subjected to trace metal analysis. 

Suspended atmospheric particles vary in size and composition. " Smaller particles (<0.08 pm) arise from condensation from the vapor phase while the larger particles (>2.5 pm) are produced by processes such as the weathering of soils, volcanic activity, and so on. Composition of the particles will vary with location and total carbon comprises 10-20% of the total suspended particles (TSP)." The average urban TSP load has been reported to be 98 pg m of air." The vapor-particle distribution under held conditions is evaluated using a device" in which air is drawn through the sampler such that particles will be trapped hrst on a hlter while compounds in the vapor phase will be absorbed on the absorbent plug. Each phase... 

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. 

Water for the analysis of suspended particles may be collected with any clean water sampler used for oceanographic work, e.g., Niskin bottles, Go-Flo bottles, Nansen bottles. Hydrobios water samplers (see also Chapter 1). The sample volume will depend on the expected concentration of POM. In nearshore and/or biologically productive water, 0.5-2 L usually is an adequate sample volume. Ten litres may be required in particle-poor open ocean waters such as the Sargasso Sea. For sampling large volumes of water, 30 L Niskin bottles are recommended. Even larger volumes may be sampled with in situ pumps. (See Chapters 1,2 and 13). 

Exposure water or air flow rate exposure cage geometry air samplers wind direction location (coordinates, and preferably a digital picture) start and end date and time physical appearance after exposure (description, and preferably a digital picture) temperature pH (when organic acids or bases are flie target analytes) suspended matter, and POC and DOC levels (water) or particle (air) levels other observations relevant to QC... 

It should be noted that the sampler used in the study, (a stacked filter unit), collected only particles less than 15pm aerodynamic diameter, i.e. particles of respirable size. State standards for TSP are based on High Volume samplers which have no inlet cutoff. Hence, particles as large as 100 microns can be captured by these instruments. Therefore, measurements made in this study may not indicate whether particulate standards have been violated, since a significant portion of the total suspended particulate mass is not measured by the stacked filter unit (SFU). 

There are two types of Mastersizer instruments the Mastersizer Micro and the Mastersizer E, which are low cost instruments for repetitive analyses and the modular series of Mastersizer S and Mastersizer X, the ultimate in resolution and dynamic size range, which are required when samples in the form of aerosols, suspensions and dry powders need to be measured. Mastersizer X provides a selection of small size ranges using a variety of interchangeable lenses whereas the Mastersizer S provides a wider dynamic size range covered in a single measurement. For powders which are to be suspended in a solvent, emulsions, suspensions and particles in liquids there are small volume cells which require as little as 15 ml of dispersant. Where a material is either valuable or toxic the Malvern Small Volume Flow Cell, with a sample volume of 50-80 ml and full sample recovery, can be used. The X-Y sampler is a 40-sample accessory... 

Figure 2 Representative example of a mass distribution of ambient particulate matter as a function of particle diameter. Mass distribution per particle size interval is shown as Amass/A(logDa) (in Rgni ) plotted against particle size (ZJa) in micrometers. Tbe figure also shows the range of aerosol sizes included in various methods of aerosol measurement wide range aerosol classifiers (WRAC), total suspended particulate (TSP) samplers, PMjo and PM25 samplers (source Lippman and Schlesinger, 2000) (reproduced by permission of Annual Reviews from Annual Review of Public Health 2000, 21, 309-333).

The choice of the system to be used for collecting particulate matter depends on the water volume to be sampled and the expected particle concentration therein. Borosilicate glass microfiber filters proved to be appropriate to separate the suspended material from the aqueous solution for a sample size up to 300 L [14]. A limiting factor may be represented by filter plugging, as demonstrated in a validation study conducted by Uza and coworkers to test the efficiency of an automated preconcentration water sampler (APS) for PCDDs and PCDFs [21]. The APS system is composed of a two-stage particulate filtering unit with coarse and fine filters, and an Amberlite XAD-2 resin column to trap dissolved hydrophobic compoimds. Various filter combinations were tested and, in all runs, filter plugging was observed. 

The method commonly used for determining the quantity of total suspended particulate matter in the atmosphere draws air over filters that remove the particles. This device, called a Hi-Vol sampler (Figure 18.18), is essentially a glorified vacuum cleaner that draws air through a filter. The samplers are usually placed under a shelter that excludes precipitation and particles larger than about 0.1 mm... 

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