Ammonia was the main component of PM2.5
, the long time series of ammonia emission characteristics was an important basis for studying the historical causes of PM2.5
pollution. According to the activity data of various anthropogenic ammonia emission sources in Beijing, Tianjin, Hebei, Shanxi, Shandong and Henan provinces and emission factors, an ammonia emission inventory of Beijing-Tianjin-Hebei and surrounding areas was established.
The results showed that ammonia emissions in Beijing-Tianjin-Hebei and its surrounding areas generally showed a downward trend, from 3699.92 kt to 3252.34 kt from 2008 to 2020. Locally, it showed a rising and then falling trend, with an average annual growth rate of 1.61% in ammonia emissions from 2008 to 2012; next few years, the average annual decline rate was 3.69%. Agricultural sources were the main contributors, accounting for 93.37% to 94.52% of total emissions, ranging from 3036.68 to 3616.46 kt; non-agricultural sources ranged from 209.99 to 232.38 kt. In 2020, the largest ammonia emission in Henan Province was 1113.82 kt, accounting for 34.25% of total ammonia emission，followed by Shandong, Hebei and Shanxi Province, with 1024.04 kt, 772.23 kt and 272.25 kt respectively, resulting in 31.49%, 23.74% and 8.37%. Livestock accounted for 58.43% of total ammonia emissions, hen, sheep, beef and goat with annual emissions of 581.73, 264.46, 234.63 and 230.71 kt respectively, accounting for 30.61%, 13.92%, 12.35% and 12.14% of the emissions from livestock. Nitrogen fertilizer application was the second-largest emission source with 32.50% of total ammonia emissions, and urea accounted for 68.81% of the emissions from nitrogen fertilizer application sources, followed by three-element compound fertilizer (18.19%). Ammonia emissions were mainly distributed in Beijing and Tianjin, scattered in other provinces. The high value areas had obvious spatial characteristics, mainly in the central region along the eastern side of the Taihang Mountains.