MRI: Acquisition of a Chemical Ionization Mass Spectrometer and a High-Resolution Time of Flight Aerosol Mass Spectrometer for Organic Aerosol Oxidation Studies

“这项奖励是根据2009年美国复苏和再投资法案（公法111-5）资助的。”[09:22643 . donahuer卡内基梅隆大学大气粒子研究中心（CAPS）的研究人员将获得两台仪器，以探测气相有机氧化化学和有机颗粒物（PM）演化之间复杂的相互作用。一种仪器是化学电离质谱仪（CIMS），设计用于灵活，高灵敏度的测量临界自由基（OH， HO2和RO2），硫酸蒸气或氨。自由基水平控制着大气中有机化合物的氧化速率和氧化机制；氨和硫酸盐以及有机物是新粒子形成和在大气中生长的关键因素。另一台仪器是高分辨率飞行时间气溶胶质谱仪（HR-AMS），质量分辨率为5000 （_0.02 amu）。HR-AMS将测量颗粒组成中与尺寸相关的非难熔组分在50到700 nm之间，明确地分辨出颗粒中的C:H:O:N:S。通过一个光散射模块来检测单个颗粒，HR-AMS将能够检测单个颗粒，从而使实验能够解决来自不同来源的气溶胶不断变化的混合状态。这些仪器加在一起，将使大气化学的前沿研究成为可能。有机气溶胶是一个动态系统，结合了气体和颗粒相之间的相分配和氧化化学，这使得与大气颗粒相关的有机物质的挥发性分布在大气中大约一周的停留时间内不断演变。同时，冷凝相测量的最新技术正在迅速发展，因此现在可以测量在有机质谱中观察到的大多数片段的分子式。因此，HR-AMS将能够测量由于气相氧化反应而演变的有机颗粒物质的氧化状态。

"This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5)."0922643DonahueResearchers in the Carnegie Mellon University Center for Atmospheric Particle Studies (CAPS) will acquire two instruments in order to probe the complex interactions between gas-phase organic oxidation chemistry and the evolution of organic particulate matter (PM). One instrument is a Chemical Ionization Mass PSpectrometer (CIMS) designed for flexible, highly sensitive measurement of critical radicals (OH, HO2, and RO2), sulfuric acid vapor, or ammonia. The radical levels control the rate as well as the mechanisms for oxidation of organic compounds in the atmosphere; ammonia and sulfate, along with organics, are critical players in new-particle formation and grown in the atmosphere. The other instrument is a High-Resolution Time of Flight Aerosol Mass Spectrometer (HR-AMS), with a mass resolution of 5000 (_0.02 amu). The HR-AMS will measure the size-dependent non-refractory fraction of particle composition between 50 and 700 nm, explicitly resolving C:H:O:N:S in the particles. With a light-scattering module to detect individual particles, the HR-AMS will be able to detect single particles, enabling experiments addressing the evolving mixing state of aerosols from different sources.Taken together, these instruments will permit research at the forefront of atmospheric chemistry. Organic aerosols are a dynamic system, combining phase partitioning between the gas and particulate phases with oxidation chemistry, which causes the volatility distribution of organic material associated with atmospheric particles to evolve continuously over their roughly week-long residence time in the atmosphere. Concurrently, the state-of-the-art in condensed-phase measurements is evolving rapidly, so that it is now possible to measure the molecular formula of most fragments observed in an organic mass spectrum. The HR-AMS will thus enable measurements of the oxidation state of organic particulate matter as it evolves due to gas-phase oxidation reactions.