Shang Jing, Xu Wei Wei, Ye Chun Xiang, George Christian, Zhu Tong
State Key Joint Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, Beijing, 100871, People's Republic of China.
Université Lyon 1, CNRS, UMR 5256, IRCELYON, Institut de recherches sur la catalyse et l'environnement de Lyon, 2 avenue Albert Einstein, F-69626, Villeurbanne, France.
Sci Rep. 2017 Apr 25;7(1):1161. doi: 10.1038/s41598-017-01396-x.
The uptake of formaldehyde (HCHO) on mineral dust affects its budget as well as particle properties, yet the process has not yet been fully investigate. Here, TiO and nitrate-doped TiO aerosols were used as proxies for mineral dust, and the uptake of HCHO was explored in a chamber under both dark and illuminated conditions. The uptake loss of HCHO on UV-illuminated aerosols is 2-9 times faster than its gaseous photolysis in our experimental system. The uptake coefficient in the range of 0.43-1.68 × 10 is 1-2 orders of magnitude higher than previous reports on model mineral dust particles. The reaction rate exhibits a Langmuir-Hinshelwood-type dependence on nitrate content and relative humidity, suggesting the competitive role of nitrate salts, water vapor and HCHO on the TiO surface. The reaction produces carbon dioxide as the main product and gaseous formic acid as an important intermediate. The hydroxyl radical produced on illuminated TiO primarily drives the fast oxidation of HCHO. The nitrate radical arising from the TiO-catalyzed photoreaction of nitrate synergistically promotes the oxidation process. This study suggests a novel oxidation route for HCHO in the atmosphere, taking into account high abundance of both mineral dust and anthropogenic TiO aerosols.
矿物尘埃对甲醛（HCHO）的摄取会影响其收支以及颗粒物性质，但该过程尚未得到充分研究。在此，将TiO和硝酸盐掺杂的TiO气溶胶用作矿物尘埃的替代物，并在暗室和光照条件下的腔室内探究了HCHO的摄取情况。在我们的实验系统中，紫外光照气溶胶上HCHO的摄取损失比其气相光解快2至9倍。摄取系数在0.43 - 1.68×10范围内，比先前关于模拟矿物尘埃颗粒的报道高1至2个数量级。反应速率对硝酸盐含量和相对湿度呈现出朗缪尔 - 欣谢尔伍德型依赖性，表明硝酸盐、水蒸气和HCHO在TiO表面存在竞争作用。该反应以二氧化碳作为主要产物，并生成气态甲酸作为重要中间体。光照TiO上产生的羟基自由基主要驱动HCHO的快速氧化。由硝酸盐的TiO催化光反应产生的硝酸根自由基协同促进氧化过程。考虑到矿物尘埃和人为TiO气溶胶的高丰度，本研究提出了大气中HCHO的一条新的氧化途径。
