针对“中国大气复合污染的成因与应对机制的基础研究”的核心科学问题“大气复合污染生成的关键过程”，本项目将采用同位素示踪方法探索华北、长三角等地雾霾发生期间硫酸盐和硝酸盐形成的大气化学机制。在雾霾发生期间，采集白天和黑夜PM2.5样品并同时开展SO2、NOx和O3等痕量气体以及气象参数的观测，测试硫酸根和硝酸根等离子和Fe、Mn等痕量元素含量，采用高温裂解元素分析仪-固相微萃取-稳定同位素比率质谱仪(TC/EA-GB-IRMS)方法测试硫酸根和硝酸根中的Δ17O,构建硫酸盐和硝酸盐箱子模型,采用蒙特卡洛（Monte Carlo）方法模拟,定量区分液相和气相等各种氧化路径的相对比例，获取硫酸盐和硝酸盐的转化速率，了解各种氧化剂所起的相对作用以及发生氧化过程的物理化学条件，为有效控制硫酸盐和硝酸盐的生成提供科学依据。

This study focuses on the atmospheric chemistry mechanism of sulfate and nitrate formation during haze period in the Northern China and Yangzi River Delta regions. This is expected to help understand the key scientific issues “ The key process for atmospheric composite pollution” for the project “The basic research on the cause and response mechanism for the atmospheric composite pollution in China”. We will collect the PM2.5 samples for day and night during haze period, and monitoring the trace gases including SO2、NOx and O3 and meterological parameters. The samples will be analyzed for Δ17O in sulfate and nitrate using TC/EA-GB-IRMs method topgether with ions and trace elements (e.g., Fe, Mn etc). Based upon the results, Monte Carlon box model will be established to quantitatively analysis the oxidation pathways, production rate, the role of oxidant and the physical chemcial conditions for oxdation. This will provide insight to control the transformation of sulfate and nitrate.