长三角地区有机胺和有机酸的检测和源解析

Organic acid (OA) and amine can lead to faster nucleation rate and enhance secondary organic aerosol formation. Many sources of OA and amines have been reported although systematic field observations and quantitative analyses are still limited. The chemical structure and reactivity of these OA and amines vary significantly from place to place due to various formation mechanisms. Despite the potential impacts of amines and OA on the atmospheric chemistry-related processes, little is known about their chemical speciation, ambient concentration, spatial and temporal distributions, source profiles, and source distributions. In this work, we propose to systematically conduct field measurements of amines and OA in the Yangzi River Delta area using a high-resolution time-of-flight chemical ionization mass spectrometer (HTOF-CIMS) equipped with a bipolar proton-transfer reaction ion source. By conducting seasonal, long-term field observations of OA and amines at representative locations (e.g., urban site, suburban site, and industrial site) and performing statistical analyses (e.g., Positive Matrix Factorization) with the assistance of other trace gas measurements (e.g., O3, NOx, and CO) and meteorological observations, we will identify the major amine and OA species, quantify their ambient concentrations, investigate their spatial and temporal variations, and categorize individual source profile and source distributions. The data sets obtained from this work will be used to establish OA and amine emission inventories for model simulations so that the model can accurately capture the chemical evolutions of OA and amines and SOA formations in the atmosphere.

有机酸和有机胺可显著加快大气颗粒物成核速率和促进二次有机颗粒物的生长。已知有机酸和有机胺潜在来源多种多样，但缺乏系统的观测和定量分析。在不同地域其产生机制各异，因而其化学结构、反应活性也大不相同。尽管有机胺和有机酸对气溶胶大气理化过程有着重大影响，其在大气中的种类、浓度、时空分布和源谱及源分布确知之甚少。本研究将采用高分辨率飞行质谱和正/负质子交换化学电离方法，对长三角地区的有机胺和有机酸进行系统的观测。通过选择代表性的站点（如城区、郊区和工业区），进行季节性中长期观测、积累数据，并利用辅助观测资料（如臭氧、氮氧化物、一氧化碳等标准污染物和气象参数）进行统计学模式分析（PMF）以取得其化学种类、时空分布和特征区域源谱及分布。为大气化学模式模拟有机胺和有机酸化学过程和二次有机气溶胶形成提供源排放清单。

我国第一大经济区的长江三角洲地区（YRD）是我国重要的工业带，人口密集，空气质量却显著低于我国平均水平，灰霾污染治理已刻不容缓。有机胺是大气中浓度较低但又无处不在的一种含氮挥发性有机物（pptv量级）。尽管有机胺的典型大气浓度远低于氨气，但有机胺具有更强的碱性和更高的分子量，其在大气化学过程中的作用，尤其对大气颗粒物的形成、演化过程的影响已越来越引起人们的关注。与无机氨盐相比，有机胺盐的热稳定性更高，因此有机胺气体可以从无机氨盐中置换出氨气生成更加稳定的有机胺盐并可在低湿度下吸湿增长，促进灰霾发生。基于此，本项目在国内首次研发出有机胺和有机酸的在线测量技术（化学电离质谱，CIMS）并在南京、上海等长三角代表性区域开展外场观测研究。已初步掌握长三角地区有机胺、有机酸的主要化学种类，气／粒分配特征。研究发现：1）工业锅炉脱硫脱硝过程是潜在的重要氨和有机胺的排放源并估算了其排放因子（Emission Ratio, ER）；2）有机胺和有机酸气／粒分配特征为：i）颗粒态浓度显著高于气态；即有机胺和大分子有机酸的饱和蒸气压较低，易于转换到颗粒态，因此可对二次颗粒物的生成有重要贡献；ii）有机胺的氧化产物酰胺在日间出现峰值，印证了有机胺的高光化学反应活性；iii）颗粒态有机胺和有机酸的时间变化规律十分相似，很可能在颗粒物中相互结合。综上所述，本项目的研究结果对评价我国长三角地区有机胺和有机酸对灰霾污染形成的贡献具有重要意义。尤其对研究长江流域高湿度下的二次颗粒物形成机制有重大促进作用。