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

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 (Nr) pollution. Here, we investigated NH3 emissions from an intensive dairy farm, atmospheric NH3/NH4+ deposition, and PM2.5 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 PM2.5 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 PM2.5. 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.