Location: Grain Quality and Structure ResearchTitle: Measuring cattle feedlot dust using laser diffraction analysis Author
Submitted to: Transactions of the ASABE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/29/2011
Publication Date: 1/1/2012
Citation: Gonzales, H.B., Maghirang, R.G., Wilson, J.D., Razote, E.B. and Guo, L. 2012. Measuring cattle feedlot dust using laser diffraction analysis. Transactions of the ASABE. 49(1):98-105. Interpretive Summary: Open beef cattle feed lots can emit considerable amounts of particulate matter. The combined effects of warm temperature, low humidity and high wind speed can promote rapid water evaporation from the pen surface, making particulates susceptible to air suspension. Emitted particles have human health and environmental effects such as vascular inflammation, atherosclerosis, an increased incidence of asthma and other respiratory problems. Rapid and accurate determination of particulate size distribution of this air borne dust is crucial in developing management policy for improved both human and livestock health in these large feed lots. These studies compares and contrasts laser diffraction analysis to a standard cascade impactor as well as determine meteorological factors and sampling period on dust particle size distribution. This study took place in a large commercial feedlot in Kansas over two years. The laser diffraction analysis and the cascade impactor did not differ significantly of the geometric mean diameter of the dust particles, consequently could be used interchangeably. Wind speed and period of sampling (day vs. night) significantly affected the measured geometric mean diameter of the particles, while increasing pen surface water content decreased large (<10µm ) to small (<2.5 µm) fractions.
Technical Abstract: Considerable amounts of particulate matter (PM), including total suspended particulates (TSP), particulates with equivalent aerodynamic diameter less than or equal to 10 um (PM10), and particulates with equivalent aerodynamic diameter less than or equal to 2.5 um (PM2.5), are emitted from large beef cattle feedlots. Particle size distribution and concentrations of TSP, PM10, and PM2.5 at a commercial cattle feedlot in Kansas were measured over a 2-yr period. The feedlot had a capacity of 30,000 head with a total pen area of 50 ha and was equipped with a sprinkler system for dust control. Collocated low-volume samplers for TSP, PM10, and PM2.5 were used to measure concentrations of TSP, PM10, and PM2.5 at the upwind and downwind edges of the feedlot. A laser diffraction (LD) analyzer (Beckman Coulter LS 13 320) was utilized to determine particle size distribution of dust samples collected by TSP samplers. A micro-orifice uniform deposit impactor (MOUDI) was also used to measure particle size distribution at the downwind edge of the feedlot. The LD analyzer and MOUDI did not differ significantly in mean geometric mean diameter (GMD) (13.7 vs. 13.0 um) but differed in mean geometric standard deviation (2.9 vs. 2.3). Wind speed and period of sampling significantly affected the mean GMD of the particles. The PM10 and PM2.5 concentrations that were calculated from the LD method and TSP data were not significantly different from those measured by low-volume PM10 and PM2.5 samplers (122 vs. 131 ug/m3 for PM10; 26 vs. 35 ug/m3 for PM2.5). Both PM10 and PM2.5 fractions decreased as pen surface water content increased, but the PM2.5/PM10 ratio showed little change as pen surface water content increased.