Emission inventory and distribution characteristics of NH3 from agricultural fertilizers in Hunan, China, from 2012 to 2021

Abstract

Fertilization is the main source of NH₃ emissions from agricultural ecosystems. Based on fertilization activity data and NH₃ emission factors, we aimed to develop an NH₃ emission inventory for fertilization in Hunan Province from 2012 to 2021. Additionally, we analyzed the historical trends in, spatial distributions of, and contributions of various districts and counties to NH₃ emissions in Hunan. The results showed that the highest emissions were estimated to be 112.69 Gg in 2012, which decreased to 84.11 Gg in 2021, with an average annual decline rate of approximately 3.17%. Additionally, NH₃ emissions from paddy fields were greater than those from drylands, and NH₃ emissions from nitrogen fertilizer were greater than those from compound fertilizer. During the study period, the NH₃ emission intensity of fertilization remained below 0.5 t km⁻² in Hunan Province. The areas with greater NH₃ emissions were mainly distributed in the northern, northeastern, and central regions. The cities with high emissions mainly included Changde, Hengyang, Yueyang, and Yongzhou. Zhangjiajie had the lowest NH₃ emissions and emission intensity in Hunan Province. Hanshou and Anxiang counties had substantial contributions to NH₃ emissions in Changde, with contribution rates of 17.86–19.1% and 18.9–19.24%, respectively. Huarong County had the greatest contribution to NH₃ emissions in Yueyang, with a contribution rate of 21.49–24.35%; Hengnan County had the greatest contribution to those in Hengyang, with a contribution rate of 20.38–23.62%; and Nan County had the largest contribution to those in Yiyang, with a contribution rate of 33.58–35.36%.