Airborne Observations of Ammonia Emissions from North Carolina Swine Facilities

Ammonia (NH₃) is the dominant gas-phase base in the troposphere. As a consequence, NH₃ abundance influences particle formation and composition. Anthropogenic emissions of NH₃ can react with sulfuric acid (H₂SO₄) and nitric acid (HNO₃), photochemical oxidation products of sulfur dioxide (SO₂) and nitrogen oxides (NO_x (NO + NO₂)), to form ammoniated particles that typically account for half or more of measured PM_2.5 mass in the Eastern US. NH₃ emissions are predominantly from agricultural sources, primarily livestock animal waste and crop fertilization. Accurate NH₃ emissions estimates from these sources are necessary for developing effective particle control strategies. Swine facilities in North Carolina are the largest source of NH₃ emissions in the Southeastern US. Airborne measurements of NH₃ and particulate ammonium (NH₄⁺) made aboard the NOAA WP-3D aircraft during the 2013 SENEX field campaign are used to quantify NH₃ emissions from North Carolina swine facilities. The observed NH₃ emissions are compared to swine facility emissions estimates from inventories. In addition, the NH₃ emissions from swine facilities are placed in a broader context of NH₃ sources throughout the Southeastern US and compared to previous airborne NH₃ emissions estimates from other agricultural facilities in the US.