PM2.5 and nitrogen deposition mitigation under agricultural ammonia emission reduction in Beijing-Tianjin-Hebei region, China

Ammonia emissions in China mainly came from agricultural activities. Excess emissions could lead to degraded air quality and excess nitrogen deposition. Therefore, it is essential to improve air quality and nitrogen deposition through agricultural ammonia reduction measures. On the basis of the existing research, this study established an Agricultural Management Technology-Ammonia emission assessment platform with 51 measures of fertilizer application and 53 measures of livestock farming derived from a literature review and adopted the Monte Carlo method to apply this platform to Beijing-Tianjing-Heibei (BTH) region where active agricultural activities occur. An updated agricultural ammonia emission inventory at 3-km resolution in BTH region was used in this study.  We find that ammonia emissions from livestock farming could be reduced by 79-151Gg (30%-57%) and from fertilizer application by 58-163Gg (18%-51%) in BTH region in 2019. We applied two reduction scenarios that could achieve average and maximum ammonia emission reduction based on the Monte Carlo results, and evaluated the resulting improvements of air quality and deposition using the GCHP model with a resolution of 10km × 10km in BTH region. The results show that the baseline of PM2.5 concentration, NHX and NOy deposition in BTH region in 2019 is 27-61 µg/m3, 8-57 Gg N/month and 3-51 Gg N/month. Under two ammonia emission reduction scenarios, PM2.5 concentration and NHx deposition would, respectively, reduce 1.38-3.89 µg/m3, 3-14 Gg N/month while NOy deposition would increase 0.5-2 Gg N/month. Our research shows that agricultural ammonia has great emission reduction potential that would benefit to the reduction of nitrogen pollution.