Summertime Airborne Measurements of Ammonia Emissions From Cattle Feedlots and Dairies in Northeastern Colorado

Phase One of the Transportation and Transformation of Ammonia (TRANS2Am) field campaign took place in northeastern Colorado during the summer of 2021. One of the goals of TRANS2Am was to measure ammonia (NH3) emissions from cattle feedlots and dairies. Most of these animal husbandry facilities are co-located within oil and gas development, an important source of methane (CH4) and ethane (C2H6) in the region. Phase One of TRANS2Am included 12 near-source research flights. We present estimates of NH3 emissions ratios with respect to CH4 (NH3 EmR), with and without correction of CH4 from oil and gas, for 29 feedlots and dairies in the region. The data shows larger emissions ratios than previously reported in the literature with a large range of values (i.e., 0.1-2.6 ppbv ppbv-1). Facilities housing cattle and dairy had a mean (std) of 1.20 (0.63) and 0.29 (0.08) ppbv ppbv-1, respectively. We also found that only 15% of the total ammonia (NHx) is in the particle phase (i.e., NH4+ ${\text{NH}}_{4}<^>{+}$) near major sources during the warm summertime months. We examined the evolution of NH3 in one plume that was sampled at different distances and altitudes up to 25 km downwind and estimated the NH3 lifetime against deposition and partitioning to the particle phase to be 87-120 min. Finally, we calculated estimates of NH3 emission rates from four optimally sampled facilities. These ranged from 4 to 29 g NH3 center dot h-1 center dot hd-1. Animal husbandry operations are significant emitters of gases that impact climate change and the health of humans and ecosystems. Northeastern Colorado has a large number of animal husbandry facilities. Many of these facilities are located nearby oil and gas operations, which emit some of the same gases as animal husbandry facilities. During the summer of 2021, as part of the Transportation and Transformation of Ammonia field camping, we deployed instruments to measure methane, ammonia, ethane, and water-soluble aerosol components in northeastern Colorado using the University of Wyoming King Air research aircraft. In this manuscript, we quantify ammonia emissions from 29 animal husbandry facilities and study their relationship with ambient temperature, relative humidity, time of day, and distance from the facility. We report ammonia emission rates and emission ratios with respect to methane for beef cattle feedlots and dairies in ColoradoThe NH3 EmR estimates are generally larger than prior estimates. NH3 EmR estimates for feedlots are four times larger than those for dairiesNH3 inferred emission rates for cattle feedlots range from 4 to 29 g NH3 center dot h-1 center dot hd-1 for sampling temperatures between 19 and 27 degrees C