Atmos. Chem. Phys. Discuss., 11, 14417-14453, 2011
© Author(s) 2011. This work is distributed
under the Creative Commons Attribution 3.0 License.
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This discussion paper has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP.
The unique properties of agricultural aerosols measured at a cattle feeding operation
N. Hiranuma1,*, S. D. Brooks1, J. Gramann1, and B. W. Auvermann2
1Department of Atmospheric Sciences, Texas A&M University, 3150 TAMU, College Station, Texas 77843-3150, USA
2Texas AgriLife Research, 6500 Amarillo Blvd W.,Amarillo, Texas 79106, USA
*now at: Atmospheric Sciences and Global Change Division, Pacific Northwest National Laboratory, 902 Battelle Boulevard, Richland, WA 99352, USA

Abstract. Housing roughly 10 million head of cattle in the United States alone, open air cattle feedlots represent a significant but poorly constrained source of atmospheric particles. Here we present a comprehensive characterization of physical and chemical properties of particles emitted from a large representative cattle feedlot in the Southwest United States. In the summer of 2008, measurements and samplings were conducted at the nominally upwind and downwind edges of the facility. A series of far-field measurements and samplings was also conducted 3.5 km north of the facility. Two instruments, a GRIMM Sequential Mobility Particle Sizer (SMPS) and a GRIMM Portable Aerosol Spectrometer (PAS), were used to measure particle size distributions over the range of 0.01 to 25 μm diameter. Raman microspectroscopy (RM) was used to determine the chemical composition of particles on a single particle basis. Volume size distributions of fugitive dust were dominated by coarse mode particles. Twenty-four hour averaged concentrations of PM10 (particulate matter with a diameter of 10 μm or less) were as high as 1200 μg m−3 during the campaign. The primary constituents of the particulate matter were carbonaceous materials, such as humic acid, water soluble organics, and less soluble fatty acids, including stearic acid and tristearin. A significant percentage of the organic particles, up to 28 %, were composed of internally mixed with salts. Basic characteristics such as size distribution and composition of agricultural aerosols were found to be different than the properties of those found in urban and semi-urban aerosols. Failing to account for such differences will lead to serious errors in estimates of aerosol effects on climate, visibility, and public health.

Citation: Hiranuma, N., Brooks, S. D., Gramann, J., and Auvermann, B. W.: The unique properties of agricultural aerosols measured at a cattle feeding operation, Atmos. Chem. Phys. Discuss., 11, 14417-14453, doi:10.5194/acpd-11-14417-2011, 2011.
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