AAAR 34th Annual Conference
October 12 - October 16, 2015
Hyatt Regency
Minneapolis, Minnesota, USA
Abstract View
Sharing the Air Space in the Great State of Texas: Aerosol Sources over Agricultural Operations
SARAH D. BROOKS, John Zenker, Gunnar Schade, Geoffrey Roest, Naruki Hiranuma, Texas A&M University
Abstract Number: 484 Working Group: Primary and Secondary Aerosols from Agricultural Operations
Abstract Housing ~10 million cattle in the Southwest United States, open air cattle feedlots represent a significant but poorly constrained source of atmospheric particles. While cattle ranches are much less densely populated than feedlots, many ranches in Texas are now also sites of unconventional oil and gas extraction. Hence, former agricultural-only emissions now coexist with primary and secondary aerosol emissions arising from drilling, fracking, and flaring processes. This presentation will include previous aerosol measurements conducted at concentrated feedlots and ongoing measurements at a ranch in southwest Texas. At the feedlots, 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, and Environmental Scanning Electron Microscopy (ESEM) was used to determine the water uptake by individual particles in our field samples as a function of relative humidity. 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/m3. 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. While the majority of particles were only slightly hygroscopic, a significant fraction of particles took up water and deliquesced at ~75% RH. Our results to date demonstrate that the characteristics of agricultural aerosols are 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.