Quantifying ammonia (NH3) emissions from concentrated animal feeding operations (CAFOs) in northeastern Colorado during the summer of 2021

Phase one of the Transportation and Transformation of Ammonia (TRANS2Am) field campaign took place in Northeastern Colorado during the summer of 2021. TRANS2Am was designed to measure and track ammonia (NH3) and methane (CH4) emissions from concentrated animal feeding operations (CAFOs), calculate the ammonium (NHx = NH3 + NH4+) loss through N deposition in the near field, and investigate the timescale and factors that influence the partitioning of NH3 in plumes originating from CAFOs when they mix with other urban pollutants (i.e., nitric acid (HNO3)). Most of these CAFOs are collocated within oil and gas (O&G) development in the Denver-Julesburg Basin, an important source of CH4 and ethane (C2H6) in the region. Phase one of TRANS2Am had a total of 15 research flights; 12 were dedicated to near-source sampling and 3 to upslope events. We calculated NH3 emissions ratios with respect to CH4, using mean normalized excess mixing ratios (NEMRs) from visually identified transects at a maximum distance of 4 km from a specific CAFO. In order to correct for CH4 from O&G, we ran multivariate regression models (MVR) for each facility and flight. We present estimates of NH3 NEMRs with and without this correction for more than 20 CAFOs. The data shows larger emissions ratios than previously reported in the literature ranging from 0.2 - 3.1 ppb ppb-1. Similar to previous studies, NH3 emission ratios increase exponentially with temperature. We also present estimates of NH3 fluxes from 5 optimally sampled facilities. Finally, we present the evolution of NH3 in plumes that were sampled more than 10 km downwind and calculate the total lifetime of NH3 in these cases.