海洋表面二次有机气溶胶光化学形成机制研究

The exchange between ocean and atmosphere is a key factor to drive global weather and climate change, which is focused on as the academic frontier in the field of atmosphere chemistry. This project will focus on the key question about the formation of second organic aerosol (SOA), and carry out simulated studies on photochemical process on the surface of ocean. Depending on the xenon lamp-quartz photochemical reactor, coupling with PTR-Tof-MS and SPME/GC-MS techniques, to measure accurately the key photochemical reaction rates and transformation efficiencies, to identify intermediate and final products of the reactions quantitatively, to determine the distribution coefficients of the kay species between air and liquid, and to speculate the mechanism of the photochemical reactions. On this basis, to simulate the formation of second organic particles using a new type of photochemical chamber, coupling with SMPS and STXM-NEXAFS, to uncover light-induced transformation process of gas to particle on the surface of ocean, and to explore the contribution of the photochemistry on sea surface films to organic aerosols of marine atmosphere. The smooth implementation of this project will be helpful to develop the mechanisms of multi-phase reactions in the atmosphere, to make for improving atmosphere modeling accuracy, and to supply theoretical support for the control of air pollution on the coastal regions of China.

海-气交换是全球天气和气候变化的关键驱动因子，是大气化学的热点和前沿课题。本项目围绕二次有机气溶胶（SOA）生成这一关键科学问题，开展海洋表面光化学过程的模拟研究。基于氙灯-石英光反应器，结合质子转移反应飞行时间质谱（PTR-Tof-MS)、固相微萃取-气相色谱/质谱（SPME/GC-MS) 等技术，准确测量海洋表面关键光反应速率和转换效率，定量鉴别反应中间产物及最终产物和关键物种的气、液分配，推测光化学反应微观机制；在此基础上，利用新型气-液光化学烟雾箱（Chamber），结合扫描电迁移率粒径谱仪（SMPS）、近边x射线精细结构能谱（NEXAFS）等技术，模拟二次有机新粒子生成现象，阐明海洋表面关键光化学反应诱导的气-粒转换过程，探索海面微表层光化学对海洋大气有机气溶胶的贡献。本项目的实施将丰富大气多相反应机制，有助于提高当前大气模式模拟精度，并为我国近海沿岸大气污染防治提供理论支撑。

海洋表面有机微层的光化学反应可能对海洋大气有机气溶胶有重要的贡献。本项目通过实验室模拟和外场观测相结合，基于PTR-MS、LOPAP等先进仪器，研究了典型脂肪酸光敏化过程，阐明了气-液表面关键光化学反应机制。研究表明，辛醇、壬酸等典型脂肪酸在咪挫类光敏剂作用下，可以产生C5-C9等活性挥发性有机物，在大气氧化剂作用下，有进一步生成二次有机气溶胶的潜势；光解脂肪酸覆盖的硝酸盐溶液，产生气相的亚硝酸（HONO）和NO2以及液相的HNO2。表面脂肪酸对硝酸根离子的富集作用，极大的提高了硝酸盐的光解；液滴中的卤素离子（Cl/Br/I)可进一步富集体相中的硝酸盐至气-液界面，并促进气相产物NO2向HONO的转换；东海航测研究了东海近岸气相HONO及水溶性含氮物种的分布特征，发现HONO与硝酸盐光解有一定相关性。本项目进展顺利，基本完成预期目标，研究结果丰富了海洋大气界面化学知识，为我国沿海城市大气污染防控提供了理论依据。