中原地区城市大气氨变化特征及对细颗粒形成影响研究

As the only alkaline gas in the atmosphere, ammonia (NH3) is one of the important precursors of fine particulate matter (PM2.5) formation, which has significant impacts on air quality, human health and climate changes. At present, in China, the secondary air pollution in urban area is serious with the increasing proportion of nitrate aerosol. The ammonia emissions and concentrations in atmospheric impact the component of secondary inorganic aerosol (sulfate, nitrate and ammonium). Compared to SO2 and NOx, a thorough understanding of the characteristic of atmospheric ammonia is still limited. Studying its impact on PM2.5 formation is the scientific problems that must be tackled on the study of As the only alkaline gas in the atmosphere, ammonia (NH3) is one of the important precursors of fine particulate matter (PM2.5) formation, which has significant impacts on air quality, human health and climate changes. At present, in China, the secondary air pollution in urban area is serious with the increasing proportion of nitrate aerosol. The ammonia emissions and concentrations in atmospheric impact the component of secondary inorganic aerosol (sulfate, nitrate and ammonium). Compared to SO2 and NOx, a thorough understanding of the characteristic of atmospheric ammonia is still limited. Identifying the ammonia rich and poor conditions and studying its impact on PM2.5 formation is the scientific problems that must be tackled on the study of PM2.5 robust control strategy developments in China. Therefore, in this project, focused on atmospheric ammonia in urban area, the major objective will be conducted based on the field passive sampling, particulate matter collection, laboratory analysis and emission inventory development. Special attention is paid to refine the ammonia emission inventory at city level. Atmospheric ammonia concentration in urban and suburban areas will be observed to identify its characteristics. Meanwhile, the size-segregated atmosphere ammonia-poor and ammonia-rich conditions, seasonal and episodic characterizations will be studies based on seasonal particles samples collections and water-soluble ion components chemical analysis. Finally, the impacts of ammonia on the formation of PM2.5 will be explored further. We also chose the city under potential ammonia emission with serious air pollution as object in central China to produce regional featured results hopefully. These results will be expected to provide scientific support for further fine management of air quality.

氨作为大气中唯一碱性气体，是细颗粒物形成的重要前体物，对大气环境、人体健康和气候变化具有重要影响。目前我国城市地区大气二次污染严重，硝酸盐气溶胶占比升高，氨的排放及在大气中浓度水平影响二次无机气溶胶（硫酸盐、硝酸盐和铵盐）构成。相比SO2和NOx，现阶段大气氨的特征识别较为缺少，如何识别大气贫富氨状况研究其对细颗粒物影响，是我国广受关注的PM2.5污染须解决的科学问题。因此，本项目拟以城市地区大气氨为重点，基于现场被动采样、颗粒物采样、实验室分析和清单编制等手段，优化城市地区氨的排放来源，开展分功能区（城区/郊区）大气氨浓度观测进而识别其特征规律，基于四季典型月份PM2.5中铵和相关水溶性离子组分浓度，量化分粒径、分污染程度大气贫富氨环境的季节变化及差异，研究氨对二次无机气溶胶形成影响。并以中原潜在氨排放量大污染严峻的城市为对象，有望作出区域特色成果，为空气质量精细化管理提供科学支撑。

氨作为大气中唯一碱性气体，是细颗粒物形成的重要前体物，对大气环境、人体健康和气候变化具有重要影响。项目以中原地区典型城市郑州市为研究区域，综合“清单编制-氨被动采样-颗粒物采样-实验室分析”手段，在氨排放量化、大气环境氨浓度变化及其对颗粒物形成影响等方面开展了相关工作。. 项目执行期间，建立了郑州市分区县基准年大气氨排放清单和历史趋势清单，识别了8类大源的排放量、源贡献结构、区县排放差异和趋势变化，相比传统农业源对氨排放贡献占绝对贡献，对于城区而言，道路移动源贡献可达27.6%。采用能反映源排放属性的高精度空间地理信息数据和气象、产量等信息，实现了对各类氨排放的1 km*1 km网格分布和月度变化分析。基于在郑州市3类功能区典型站点（交通站、城市站、郊区站）四季典型月份，以及城市站连续12个月大气氨被动采样与分析，量化了观测期间大气氨浓度水平，识别了不同功能区站点大气氨浓度的季节变化和差异，相比其他地区，郑州市城市大气氨处于高位水平（86~32.2 µg/m3），年均达17.9 µg/m3，特别是掌握了不同站点的差异，交通站浓度最高，夏季可达38.1µg/m3，进一步印证了非农业源（汽车尾气）对城市交通街谷环境氨的重要影响；在城市站强化进行全年逐月氨被动采样、颗粒物采样和水溶性离子分析，揭示了分季节、分粒径颗粒物及SIA组分特征及时间变化，研究了分粒径颗粒物形成过程大气贫富氨环境及季节变化，结果显示，采样期间春夏季细颗粒物基本处于贫氨状态，而秋冬季多处于富氨状态。. 项目最终形成了郑州市2007～2020年城市尺度分区县氨排放数据、1 km*1 km网格分辨率及各类源月度排放信息、分功能区3类站点大气氨浓度水平、季节及月度变化信息，以及城市站粗细颗粒物大气贫富氨环境变化等关键数据，弥补了中原地区在城市尺度高分辨率氨排放清单及大气环境氨监测的不足与缺失，探讨了氨在颗粒物形成过程发挥的作用，做出了具有区域特色成果，为空气质量预报和大气污染防治提供了科学支撑。