1B.3 Quantifying Emissions of NH3 and NOx from Agricultural Sources and Biomass Burning Using SOF

Monday, 8 January 2018: 9:15 AM
Room 18CD (ACC) (Austin, Texas)
N. Kille, Univ. of Colorado Boulder, Boulder, CO; and B. Dix and R. Volkamer

Column measurements of trace gas absorption along the direct solar beam present a powerful yet underused
approach to quantify emission fluxes from area sources. The University of Colorado Solar Occultation Flux
(CU SOF) instrument (Kille et al., 2017, AMT, doi:10.5194/amt-10-373-2017) features a solar tracker that is
self-positioning for use from mobile platforms that are in motion (Baidar et al., 2016, AMT, doi: 10.5194/amt-9-
963-2016). This enables the use from research aircraft, as well as the deployment under broken cloud
conditions, while making efficient use of aircraft time. First airborne SOF measurements have been
demonstrated recently, and we discuss applications to study emissions from biomass burning using aircraft,
and to study primary emissions of ammonia and nitrogen oxides (= NO + NO2) from area sources such as
concentrated animal feeding operations (CAFO). SOF detects gases in the open atmosphere (no inlets), does
not require access to the source, and provides results in units that can be directly compared with emission
inventories. The method of emission quantification is relatively straightforward. During FRAPPE (Front Range
Air Pollution and Photochemistry Experiment) in Colorado in 2014, we measured emission fluxes of NH3, and
NOx from CAFO, quantifying the emissions from 61400 of the 535766 cattle in Weld County, CO (11.4% of the
cattle population). We find that NH3 emissions from dairy and cattle farms are similar after normalization by
the number of cattle, i.e., we find emission factors, EF, of 11.8 ± 2.0 gNH3/h/head for the studied CAFOs;
these EFs are at the upper end of reported values. Results are compared to daytime NEI emissions for case
study days. Furthermore, biologically active soils are found to be a strong source of NOx. The NOx sources
account for ~1.2% of the N-flux (i.e., NH3), and can be competitive with other NOx sources in Weld, CO. The
added NOx is particularly relevant in remote regions, where O3 formation and oxidative capacity is NOx
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