OH自由基是大气中最重要的氧化剂之一，导致二次污染物的形成，增强大气的氧化能力，驱动灰霾的形成。亚硝酸（HONO）作为OH自由基的重要前体物，由于缺少能够准确检测相关含氮物种的在线仪器，其主要来源还不清楚，导致无法准确估计大气氧化性。HONO、HNO3和NH3活性高，粘性大并且容易与多种表面发生反应，目前难以准确测量。本项目拟研发新型高精度HONO、HNO3和NH3同时在线检测方法，并通过一系列实验室模拟、对比测试来优化仪器，最终将其应用于外场观测研究。拟在北京城区进行综合观测，获取HONO、HNO3和NH3三者准确的浓度，同时结合OH自由基、NO、NO2、硝酸盐、铵盐的浓度及颗粒物粒径分布等关键参数，对北京城区HONO的不同来源进行分析和量化，为控制我国大气氧化性提供检测保障，为灰霾的治理提供科学指导。

OH radical is one of the most important oxidants in the atmosphere, which leads to the formation of secondary pollutants, enhances the ability of atmospheric oxidation and drives the formation of haze. Due to the lack of on-line instruments for accurate detection of related nitrogen-containing species, the main HONO sources are unclear, which results in the inability to accurately estimate the atmospheric oxidation. HONO, HNO3 and NH3, the key nitrogen species, are high-activity, sticky, easy to react with various surfaces, and can’t be accurately measured at present. This project intends to develop a new instrument for simultaneously on-line detecting HONO, HNO3 and NH3 with high precision, and optimize this new instrument through a series of laboratory simulations and comparative tests. Finally, it will be applied to the field observation. The accurate concentrations of HONO, HNO3 and NH3 and other key parameters, such as the concentrations of OH radical, nitrate, ammonium and particle size distribution, will be obtained by comprehensive observation in urban area of Beijing to analyze and quantify the sources of HONO in urban area of Beijing. This result will provide a scientific guide for controlling atmospheric oxidation and haze in China.