Abstract
Large commercial cattle feedlots are significant sources of particulate matter (PM) emissions. This research compared WindTrax and the flux-gradient technique in estimating emissions of PM with aerodynamic diameter 10) from cattle feedlots. Meteorological conditions were measured and PM10 concentrations were profiled vertically (i.e., 2.0 to 7.62 m) at a large commercial beef cattle feedlot in Kansas from May through September 2011. Results show that between the two methods evaluated, WindTrax was least sensitive to changes in heights and number of heights used in the emission estimation, with calculated PM10 emission rates varying by up to 18% only. On the other hand, PM10 emission rates produced by the flux-gradient technique varied by almost 56% when changing either heights and/or number of heights in emission calculation. Both methods were sensitive to height settings, with their respective PM10 emission rates higher when the lowest height setting (2.0 m) was included. Calculating PM10 emission rates with the 7.62-m height led to lower estimates for the flux-gradient technique but no significant change in estimates was observed for WindTrax. As demonstrated in this study, for the flux-gradient technique, settings for the lowest and highest heights were the most critical in emission estimation; exclusion of other heights in between showed only to 2% to 6% change in calculated PM10 emission rates. In general, the higher PM10 emission rates were obtained with the flux-gradient technique. However, eliminating the lowest height (2.0 m) in the calculation and, at the same time, using a specific set of formulations for the flux-gradient technique made its calculated PM10 emission rates slightly lower (but not significantly different) than those from WindTrax.
Highlights
Air pollutant emissions from concentrated animal feeding operations (CAFOs), such as large commercial cattle feedlots, are a major air quality concern because of their harmful effects on human health and the environment
The lowest PM with aerodynamic diameter < 10 μm (PM10) emission rates were calculated using data sets 2, 4, and 7, with overall median values ranging from 29.1 to 30.5 μg/m2∙s. These results indicate that use of the 2.0-m height, which was the lowest sampling height, in determining hourly PM10 emission rates with WindTrax led to emission estimates higher by almost 27%
Using PM10 concentration measurements at several heights and measured meteorological conditions at a Kansas cattle feedlot, the two emission estimation methods were compared using different concentration data sets, which varied in terms of heights and number of heights included, and several formulations for the flux-gradient technique’s nondimensional correction parameter φm
Summary
Air pollutant emissions from concentrated animal feeding operations (CAFOs), such as large commercial cattle feedlots, are a major air quality concern because of their harmful effects on human health and the environment. In large beef and dairy cattle feedlots, the animals are typically confined in open dirt lots For these CAFOs, emission estimation is challenging because direct measurement of emission rates is often not feasible. The authors of the present study were involved in a large air quality project that included estimation of PM emission rates from a large commercial beef cattle feedlot in Kansas. The PM emission rates for the cattle feedlot studied were determined using several estimation methods, which included AERMOD, WindTrax and the flux-gradient technique, and estimates were already presented in published companion studies [8] [17] [18]. PM10 emission rates determined by WindTrax and the flux-gradient technique were compared using the same set of concentration and meteorological measurements employed in companion studies [8] [17]. Similar to the previous study, the possibility of development of conversion factors between these two methods was explored
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