Increased nitrogen deposition and airborne particulate matter pollution in the vicinity of intensive animal farms caused by ammonia emissions

Abstract

Intensive animal farms emit large amounts of ammonia (NH₃) into the atmosphere. NH₃ can cause the formation of NH₄⁺ particles in the atmosphere and their return to the land surface via NH₃/NH₄⁺ deposition, imposing the risks of particulate matter and reactive nitrogen (N_r) pollution. Here, we investigated NH₃ emissions from an intensive dairy farm, atmospheric NH₃/NH₄⁺ deposition, and PM_2.5 concentration in the vicinity of the dairy farm in central South China, with the aim of determining the effects of high NH₃ emissions from dairy farms on atmospheric N deposition and aerosol pollution. NH₃ deposition at a distance of 500 m from the edge of the dairy farm accounted for 10.2 % of annual NH₃ emissions from the dairy farm. The measured annual PM_2.5 concentration at the dairy farm showed 1.8 times higher than that reported at the neighboring city sites, with aerosol NH₄⁺ contributing to a large part of PM_2.5. Total N deposition within 500 m of the dairy farm was as high as 78.4 kg N ha⁻¹ yr⁻¹ (NH₃/NH₄⁺ deposition accounting for 64.4 %), which was 2.1 times higher than the N deposition in the neighboring region without dairy farms. Our study indicates that intensive animal farms cause high N deposition and severe airborne particulate matter pollution, and it is important to mitigate NH₃ emissions from intensive dairy farms.