Passive Particulate Sampling to Determine Air Quality

RJ Lee Group is involved in the commercialization of an innovative passive particulate sampler developed at the University of North Carolina (UNC). The UNC passive aerosol sampler is a cost-effective technology and is useful in acquiring particulate concentration and composition data regarding air quality in indoor as well as outdoor environments. The sampler can be utilized virtually anywhere to evaluate the spatial distribution particulate matter as it does not require power. It can be deployed easily by fixing it to readily available objects. The UNC passive aerosol sampler fixed to an EBAM continuous PM_10-2.5 sampler is shown in figure 1.

Photograph and schematic view of the UNC passive aerosol sampler

Development

The UNC passive aerosol sampler is a patented technology, which was originally designed as a personal particulate monitor for use in industrial hygiene (IH) applications. The sampler’s ability to provide particulate concentration data (µg/m³) comparable to that of established IH samplers makes it to be used in applications involving measurement of PM₁₀, PM_2.5, and PM_10-2.5 concentrations in ambient environments. Besides providing data on the characteristics of the particulate matter including elemental composition and size, the sampler presents estimates to be made with respect to ambient concentration as µg/m³ by analyzing the sample utilizing computer-controlled scanning electron microscopy (CCSEM) techniques.

Working Principle

The UNC passive aerosol sampler features a standard scanning electron microscope (SEM) stub and a protective mesh cap. Photograph and schematic view of the UNC passive aerosol sampler is shown in figure 2.

The UNC passive aerosol sampler can be deployed on any stationary structure and does not require an energy source. In this photograph, the UNC passive aerosol sampler is attached to an EBAM continuous PM_10-2.5 sampler.

The sampler is put inside a rain shield for ambient sampling. During sampling, the particles are moved by gravity and diffusion and then deposited on a horizontal substrate placed on the sampler stub. Sampling of ambient particles is normally performed over time periods ranging between two weeks and a month. Once sampling is done, the mesh cap of the sampler is detached in the laboratory. Then, the CCSEM is used for analyzing the particles after placing the stub in an SEM.

Evaluation of UNC Passive Aerosol Sampler

In a study carried out in Phoenix, Arizona, the UNC passive aerosol samplers were assessed against Federal Reference Method (FRM) PM_{10-2 5}. The UNC passive samplers provided results that compare well to data provided by the FRM samplers as shown in figure 3.

Phoenix PM_10-2.5 Results

Following the success of the UNC passive aerosol sampler in the estimation of PM_{10-2 5} concentration data, the U.S. Environmental Protection Agency has used the sampler in a number of studies to estimate the spatial distribution related to coarse particulate matter (PM_10-2.5).

Conclusion

The UNC passive aerosol sampler is useful in providing particulate concentration data in studies in which the use of active samplers is not feasible. Moreover, it can support FRM particulate samplers by delivering spatial distribution data related to coarse PM_10-2.5 particles.

This information has been sourced, reviewed and adapted from materials provided by RJ Lee Group.

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