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Description:
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An engineering analysis of the fugitive particulate matter emissions from a
feedyard is not simple . The presence of an evening dust peak in concentration
measurements downwind of a feedyard complicates the calculation of an average 24 -h
emission flux for the feedyard . The evening dust peak is a recurring event that occurs
during evening hours when particulate matter concentration measurements increase and
decrease dramatically during a short period of time . The concentrations measured during
the evening can be up to 8 times the concentrations measured throughout the rest of the
day . There is a perception that these concentration increases are due to increases in cattle
activity as the temperature decreases during the evening . The purpose of Objective 1 of
this research was to quantify the changes in concentrations based on changes in
meteorological conditions and /or cattle activity . Using ISCST3 , a Gaussian -based EPAapproved
dispersion model used to predict concentrations downwind of the feedyard , the
results of this work indicate that up to 80 % of the increase in concentrations can be
attributed to changes in meteorological conditions (wind speed , stability class , and
mixing height . )The total fugitive particulate matter emissions on a cattle feedyard are due to two
sources : unpaved roads (vehicle traffic ) and pen surfaces (cattle activity ) . Objective 2 of
this research was to quantify the mass fraction of the concentration measurements that
was due to unpaved road emissions (vehicle traffic ) . A recent finding by Wanjura et al .
(2004 ) reported that as much as 80 % of the concentrations measured after a rain event
were due to unpaved road emissions . An engineering analysis of the potential of the
unpaved road emissions versus the total feedyard emissions using ISCST3 suggests that it
is possible for 70 to 80 % of the concentration measurements to be attributed to unpaved
road emissions .
The purpose of Objective 3 was to demonstrate the science used by ISCST3 to
predict concentrations downwind of an area source . Results from this study indicate that
the ISCST3 model utilizes a form of the Gaussian line source algorithm to predict
concentrations downwind of an area source . |