Previous studies have demonstrated that EPA approved federal reference method
(FRM) samplers can substantially misrepresent the fractions of particles being emitted
from agricultural operations due to the relationship between the performance
characteristics of these samplers and existing ambient conditions. Controlled testing in a
wind tunnel is needed to obtain a clearer understanding and quantification of the
performance shifts of these samplers under varying aerosol concentrations, wind speeds
and dust types.
In this study, sampler performance was tested in a controlled environment wind
tunnel meeting EPA requirements for particulate matter (PM) sampler evaluation. The
samplers evaluated included two low-volume PM10 and Total Suspended Particulate
(TSP) pre-separators. The masses and particle size distributions (PSDs) obtained from
the filters of tested samplers were compared to those of a collocated isokinetic sampler.
Sampler performance was documented using two parameters: cut-point (d_50) and slope.
The cut-point is the particle diameter corresponding to 50% collection efficiency of the
pre-separator while the slope is the ratio of particle sizes corresponding to cumulative
collection efficiencies of 84.1% and 50% (d_84.1/d_50) or 50% and 15.9% (d_50/d_15.9) or the square root of 84.1% and 15.9% (d_84.1/d_ 15.9). The test variables included three levels of
wind speeds (2-, 8-, and 24-km/h), five aerosol concentrations varying from 150 to 1,500
mu g/m3 and three aerosols with different PSDs (ultrafine Arizona Road Dust (ARD), fine
ARD and cornstarch).
No differences were detected between the performance of the flat and louvered
FRM PM10 samplers (a = 0.05). The mean cut-point of both the PM10 samplers was
12.23 mu m while the mean slope was 2.46. The mean cut-point and slope values were
statistically different from the upper limit of EPA-specified performance criteria of 10.5
mu m for the cut-point and 1.6 for the slope. The PM10 samplers over-sampled cornstarch
but under-sampled ultrafine and fine ARD. The performance of the dome-top TSP
sampler was close to the isokinetic sampler, and thus it can be used as a reference
sampler in field sampling campaigns to determine true PM concentrations. There were
large variations in the performance of the cone-top TSP samplers as compared to the
isokinetic sampler. Dust type and wind speed along with their interaction had an impact
on sampler performance. Cut-points of PM10 samplers were found to increase with
increasing wind speeds. Aerosol concentration did not impact the cut-points and slopes
of the tested samplers even though their interaction with dust types and wind speeds had
an impact on sampler performance.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/ETD-TAMU-2009-05-793 |
| Date | 2009 May 1900 |
| Creators | Guha, Abhinav |
| Contributors | Shaw, Bryan W. |
| Source Sets | Texas A and M University |
| Language | English |
| Detected Language | English |
| Type | Book, Thesis, Electronic Thesis, text |
| Format | application/pdf |
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