Ground and Airborne Observations of Ammonia in a Naturally Ventilated Swine Farming Area

Ammonia (NH₃) is a key atmospheric pollutant emitted predominantly from agricultural activities, particularly swine farming, where it contributes to odor nuisance and secondary particulate matter formation. In this study, we conducted ground-based and airborne measurements of NH₃ from September 2023 to July 2024 in Gimje, Korea, a region characterized by densely clustered, naturally ventilated swine facilities. Average surface concentrations reached ~81.2 ppb, with consistently higher levels near farms compared to surrounding croplands. Distinct diurnal cycles were observed, with elevated concentrations at night and early morning and reduced levels during the afternoon. Relative humidity exhibited a strong positive correlation with NH₃ (R²> 0.9), while temperature effects were weak, suggesting that high moisture conditions enhance NH₃ volatilization in livestock environments. Airborne measurements revealed substantially lower NH₃ concentrations aloft (5~23 ppb) than at the surface, with seasonal differences linked to boundary layer dynamics. Source apportionment using conditional probability function analysis confirmed that local swine operations dominated NH₃ emissions. These findings highlight the persistence of high NH₃ in swine-farming regions, its sensitivity to meteorological factors, and the need for targeted mitigation strategies to reduce odor and secondary aerosol formation.