生物源挥发性有机物生成烷基硝酸酯的观测与模拟

Alkyl nitrates (RONO2), formed by complex photochemical reactions between volatile organic compounds (VOCs) and nitrogen oxides (NOx), are major components of reactive odd nitrogen (NOy) and reservoir NOy species that undergo atmospheric transport. The formation mechanisms of RONO2 from biogenic VOC (BVOC) are still not well understood with a myriad of unknown products RONO2 to be identified. The present project, by use of online measurement techniques like Thermal Dissociation-Laser Induced Fluorescence (TD-LIF) and Proton Transfer Reaction-Time of Flight-Mass Spectrometry (PTR-ToF-MS) and a series of offline analytical tools, will firstly be targeted on isoprene and alpha-pinene, the two BVOC with the largest emissions, to conduct smog chamber simulation for their photochemical evolution under high-/low-NOx conditions to form RONO2: exploring RONO2 formation mechanisms and resolving unknown RONO2 species. Total NONO2 and speciated BVOC-derived RONO2 will then be measured both offline and online at two representative sites in the Pearl River Delta, one in a forest and another in urban Guangzhou, to study their variation in ambient air and factors influencing their occurrence and abundance. Finally the chamber simulation and field measurement results will be used to compare with the MCM modeled results and thereafter to calibrate and gradually improve the domain of RONO2 chemistry in the MCM. The study of this project will not only improve the understanding of the composition and formation mechanisms of RONO2, but also have scientific significance in regional NOx cyclying and atmospheric nitrogen chemistry.

挥发性有机物（VOCs）和氮氧化物（NOx）经复杂大气化学过程形成的烷基硝酸酯（RONO2）是反应性奇氮化合物（NOy）的重要组成和大气输送的重要载体。生物源挥发性有机物（BVOC）生成RONO2的机制尚不完全清楚，很多未知产物有待进一步鉴定。本申请项目拟利用TD-LIF、PTR-ToF-MS等在线观测手段和离线分析表征方法，针对BVOC中排放量最大的异戊二烯和alpha-蒎烯，通过高/低NOx条件下烟雾箱模拟，鉴定BVOC生成的未知RONO2组成，探讨其生成演变的过程机制；在珠江三角洲选择代表性的森林和城区站点，对比观测环境空气中RONO2总量及BVOC生成RONO2组分的变化特征与影响因素；通过与烟雾箱模拟和外场观测结果的映证校验，逐步完善和改进MCM机制中与RONO2相关的化学机制模块。项目研究可深入揭示大气RONO2组成和形成机制，拓展对区域NOx循环演化和大气氮化学的科学认识。

挥发性有机物（VOCs）和氮氧化物（NOx）经复杂大气化学过程形成的烷基硝酸酯（RONO2）是反应性奇氮化合物（NOy）的重要组成和大气输送的重要载体。生物源挥发性有机物（BVOC）生成RONO2的机制尚不完全清楚，很多未知产物有待进一步鉴定。本项目开发和表征了热解离-激光诱导荧光（TD-LIF）、PTR-ToF-MS等先进的高分辨率在线测定方法；对包括异戊二烯、α-蒎烯、β-蒎烯的“BVOC+NOx+SO2”体系进行烟雾箱模拟，并率先对其氧化过程中生成的气相和颗粒相的含N含O化合物进行了鉴定；对涵盖了我国东、西、南、北、中部和西藏高原地区的九个典型森林生态系统同步开展了野外观测，获得全国森林大气中RONO2的浓度水平、时空分布、形成途径和来源判识；对珠三角城市地区大气中过氧乙酰基硝酸酯（PAN）进行了长期观测，探讨了PAN的浓度水平、季节变化特征和形成机制；结合烟雾箱模拟参数和野外观测结果对化学机制模式MCM进行了本地化，并模拟了RONO2的生成过程和机制，判识了RONO2在典型城区生成的敏感性。该研究有助于系统认识典型地区大气中RONO2组成和形成机制，并拓展对区域NOx循环演化和大气氮化学的科学认识。