Spatiotemporal patterns and drivers of agricultural ammonia emissions in China (1990–2020)

Agricultural ammonia (NH 3 ) is an important precursor for the formation of atmospheric fine particulate matter (PM 2.5 ) in China. However, the long-term evolution and driving mechanisms of its emissions remain poorly understood, particularly at fine spatial scales. Based on the bottom-up emission factor approach, this study developed a county-level agricultural NH 3 emission inventory of China for 1990–2020. The logarithmic mean Divisia index (LMDI) method was applied to quantitatively decompose the drivers of changes in agricultural NH 3 emissions. From 1990 to 2020, total emissions rose from 6.15 Tg to 8.69 Tg. NH 3 emissions from livestock production increased from 3.08 Tg to 4.90 Tg and gradually became the dominant emission source. Meanwhile, NH 3 emissions from fertilizer application increased from 3.07 Tg to 3.79 Tg. Spatially, NH 3 emission hotspots were concentrated in major agricultural regions, including the North China Plain, the Northeast China Plain, and the Sichuan Basin, with relatively high emissions also observed along basin margins in Northwest China. Driving factor decomposition results indicated that agricultural structural adjustments, technological and management improvements, and emission control policies exerted significant mitigating effects on agricultural NH 3 emissions during different periods. For livestock production, promoting the development of intensive production systems is important. Regarding fertilizer application, sustained efforts are required to optimize fertilization practices. These findings provide scientific support for further exploiting the substantial potential for NH 3 emission reduction in China.