Low-volume air 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 ... 

Low-volume air sampler A low-volume air sampler is an apparatus having a suction capacity of up to 201/min. It is used for one continuous sampling lasting from several days to 1 week. Filter papers having a diameter of 5 cm and an active-carbon cartridge can be attached as a collecting device. 

In a study of residential exposure to Cr-laden wastes in Hudson County, New Jersey, Lioy etal., 1992) collected 3-day and 4-day composite samples using low-volume air samplers equipped with 37-mm Teflon filters. Total Cr in airborne particles was determined using XRF with a detection limit of 2 pg g (shown in Table 11.3), and extractable Cr (not shown) was determined using nitric acid/sulfiiric acid digestion and ICP-AES. The mean ratio of extractable Cr to total Cr was 0.3. 

Collection efficiency is a measure of the amount of material collected by the sampler relative to the amount of material to which the sampler was exposed. Collection efficiencies for many types of samples can be obtained from literature references. If not available in the literature, collection efficiencies can be obtained by comparing the amount collected by the sampler with the amount collected by samplers with known collection efficiency (e.g., nominal 100% for isokinetic samplers). Alternatively, the collection efficiency can be determined by measuring the amount of material collected in a low-speed wind mnnel or spray chamber relative to the release of a known amount of material. Some samplers have collection efficiencies below 100% (e.g., wide collectors sampling small droplets), while others may exceed 100% if they sweep the air of more material than passes a given location based on sampling area alone (e.g., high-volume air samplers). 

Initially, a low volume system was installed at Skua Lake, but this was changed in 1991-1992 to match the high volume air samplers around the station. The data from Skua Lake indicated that the site had become affected by anthropic activities. Thus, it was decided to have a new reference site at Campo Icaro situated about 2000 m S from the main camp and 20 m asl. From the 1994-1995 a high volume air sampler of the same type as all the others was installed there. 

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. 

To verify this hypothesis, low volume samplers have been operated in parallel with the air pollution control district s Km samplers. The samples collected were analyzed optically for elemental carbon and by the Gamma Ray Analysis of Light Elements (GRALE) technique for total carbon. These data were used to assess the concentration of elemental and total carbon aerosols present during the winter months in Los Angeles. It was established that the Km samplers can be calibrated to read elemental carbon concentrations. This calibration can be used to reconstruct historical elemental carbon levels at seven sites in Los Angeles. 

The protocol focuses on the preparation of collected particulate samples and provides guidance in the selection of a suitable collection technique. Particulate collection methods were not specified because the selection and implementation of those methods are source-dependent. Potential air-sampling techniques include the standard high-volume (Hi-Vol) samplers (4), massive-volume samplers (5), medium-volume samplers, low-volume samplers, and ultra-high-volume samplers (6). 

Plugs of the foam may also be deployed in low-volume (63), high volume (61), or multiple air samplers (60). Foam preparation is similar to that of the XAD s, and its commercial availability through local sources is a distinct advantage. 

In air sampling, high-volume samplers are preferable for accuracy, but low-volume techniques are useful for obtaining extensive data [77]. More informative data can be obtained if... 

A very low detection limit, >1 ng/m3 may be achieved using a 24-h sampling period, sampling over 5000 L ambient air. Such a high volume sampler consists... 

The high-volume sampler has become the most widely used tool for monitoring particulate matter air pollution. It is a low-cost, portable, easily maintained, and reasonably precise sampling device. Improvements in sampler performance have resulted from incorporation of automatic timers, flowrate recorders, and size separation devices into the basic system. Although hi-vols are the accepted standard in particulate matter monitoring, they inherently lack the ability to provide realtime particulate matter measurements. 

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