Abstract:

Ammonia is an important precursor for secondary generation of PM_2.5, which is widely present in the atmospheric environment. Agricultural activities are the main sources of ammonia emissions; thus, establishing a city-scale and county-level agricultural ammonia emission inventory has great significance for improving the accuracy of air quality models and fine-tuning emission reduction measures. Using field investigations and statistical data, a comprehensive ammonia emission inventory of agricultural sources from 2013 to 2021 in Yancheng was established based on the emission factor method. Furthermore, the annual variation, distribution characteristics, and reduction contribution of ammonia emissions from all sources were analyzed. The spatial allocation method for livestock and poultry was improved by integrating detailed activity level data, such as the registration information of industrial and commercial enterprises, as well as land-use datasets. This study showed that 1) the total ammonia emissions from agricultural sources were 87.58 kt in 2021, with nitrogen fertilizer application and livestock and poultry accounting for 63.1% and 31.6%, respectively. In addition, urea and poultry were the dominant emission sources, with proportions of 86.2% and 69.8%, respectively. 2) From 2013 to 2021, the total agricultural ammonia emissions in Yancheng decreased by an annual average rate of 2.8%, which was consistent and slightly higher than the average for Jiangsu Province (where Yancheng is located). The emission intensity per unit area decreased 24.1% from 6.52 t·km⁻² to 4.94 t·km⁻². Compared with typical cities in key provinces, the agricultural ammonia emission intensity in Yancheng was at an average level but was relatively higher than that in cities in the Yangtze River Delta region. 3) Substantial regional differences in agricultural ammonia emissions exist between districts and counties. Dongtai, Dafeng, Sheyang, Binhai, and Funing contributed 75.2% of the total emissions from Yancheng. The emission intensities of Funing, Jianhu, Dongtai, and Binhai were higher than citywide averages. 4) From the perspective of emission reduction, among all types of ammonia emission sources, livestock, poultry, and nitrogen fertilizer application had the highest cumulative emission reduction contributions (69.0% and 31.6%, respectively). Since 2016, ammonia emissions from livestock and poultry have decreased by more than 6.0% over five consecutive years. To a certain extent, this was an important reason for the trend in total ammonia emissions from agricultural sources in Yancheng, turning from constant to downward. Future studies should focus on Dongtai, Binhai, and Funing. Ammonia emission control should focus on poultry, urea, and other high-emission sources, as well as fecal storage and treatment, breeding enclosures, and other key agricultural practices.

Key words: ammonia emission, emission inventory, agricultural source, nitrogen fertilizer, livestock and poultry, emission reduction, city-scale

摘要：

氨是广泛存在于大气环境中的一种碱性气体，是PM_2.5二次生成的重要前体物之一。农业活动是氨排放的主要来源，建立城市尺度分区县农业源氨排放清单对提升空气质量模型准确度、制定精细化减排措施具有重要意义。根据调研与统计数据，基于排放因子法，建立了盐城市2013—2021年农业源氨排放清单，分析了各类排放源的年际变化、分布特征及减排贡献。综合利用企业工商注册信息、土地利用等精细化活动水平数据，改进了畜禽养殖的空间分配方法。结果表明，1）2021年盐城市农业源氨排放总量为87.58 kt，氮肥施用、畜禽养殖分别占63.1%和31.6%。氮肥施用中尿素排放占86.2%，畜禽养殖中家禽排放占69.8%。2）2013—2021年间，盐城市农业源氨排放总量年均下降2.8%，总体趋势与江苏省平均水平基本一致，降幅略高；排放强度由6.52 t·km⁻²持续下降至4.94 t·km⁻²，降幅达24.1%。盐城市排放强度在全国重点省份典型城市中处于中等水平，在长三角区域中处于相对高位。3）各区县排放地域差异明显，东台、大丰、射阳、滨海和阜宁等5个区县贡献了盐城市75.2%的氨排放，阜宁、建湖、东台和滨海等4个区县的排放强度高于全市平均。4）各类氨排放源中累计减排贡献率最高的为畜禽养殖和氮肥施用，分别为69.0%和31.6%。2016年起畜禽养殖氨排放量连续5年保持6.0%以上降幅，是盐城市农业源氨排放总量从平台期进入下降通道的重要原因。建议进一步关注东台、滨海、阜宁等区县，重点针对家禽、尿素等高排放源类，以及粪水贮存处理、养殖圈舍等关键环节，持续开展氨排放治理。

关键词: 氨排放, 排放清单, 农业源, 氮肥施用, 畜禽养殖, 减排, 城市尺度