Collaborative Research: RUI: IRES - Track I: Brown Carbon Aerosol Formation by Photooxidation of Phenolic Compounds in Nanodroplets

该IRES项目为来自圣地亚哥大学和哈维穆德学院的4-6名本科生研究人员提供了经验，他们将花费8-10周的时间研究大气中酚类化合物水溶液光氧化形成的棕色碳。为期四周的研究将在大学现场进行。巴黎东部？在那里，本科生研究人员队列将与他们的国际导师密切合作，利用先进的光谱方法进行一系列CESAM气雾室实验。从法国回来后，本科生研究团队将专注于室内数据的整理、解释和演示，同时继续通过视频会议与国际导师互动。每个参与者将在之前至少一个学期和之后的两个学期参与该项目，然后前往他们的美国校园进行培训和进一步的实验。总共有15名3年以上的本科生将参与这一国际项目，并将在法国科学家的指导下获得先进研究工具的实践经验。该IRES项目侧重于大气化学，将有助于更好地了解清洁空气和全球变暖。酚类化合物是生物质燃烧过程中产生的，是人为芳香前体氧化产生的，被认为是在云滴中氧化时棕色碳气溶胶的重要来源，特别是在存在铁(来自粉尘)或氮氧化物(来自燃烧污染)的情况下。然而，酚类化合物的多相反应主要是在大块水溶液中进行的，而不是在更真实的纳米液滴中进行的，在纳米液滴中，光漂白可以变成光褐化，反应活性经常被加速，特别是对于表面活性齐聚物种。因此，研究人员将在巴黎CESAM实验室的纳米液滴“云模拟”光氧化实验中研究酚类前体物种形成棕色二次有机气溶胶(SOA)，表征云事件之前、期间和之后气溶胶颗粒的化学和光学变化。当反应物在压力、温度和相对湿度控制的室内与种子气溶胶、水滴和模拟阳光相互作用时，将通过CAPS-SSA和水溶性OA的UV/可见光光谱来监测颗粒褐变。颗粒相化学将通过气溶胶质谱仪(ACSM-TOF)监测，颗粒吸收和放气将通过高分辨率PTR-MS和气相物质的长程FTIR监测进行检测。该项目将在一个最先进的云室设施为15名不同的美国本科生提供国际研究经验，作为每个参与者为期3个学期的研究体验的中心。项目活动将增加对棕色SOA的重要来源的了解，这反过来将使这种污染物及其对人类健康和气候的不利影响以更具成本效益的方式降至最低。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

This IRES project provides experiences for 4-6 undergraduate researchers from the University of San Diego and Harvey Mudd College to spend 8-10 weeks researching brown carbon formation by aqueous photooxidation of atmospheric phenolic compounds. Four weeks of research will be conducted onsite at Universit? Paris Est ? Cr?teil (UPEC), where the cohort of undergraduate researchers will closely collaborate with their international mentors on a series of CESAM aerosol chamber experiments utilizing advance spectroscopic methods. After returning from France, the undergraduate research team will focus on the workup, interpretation, and presentation of chamber data, while continuing to interact with international mentors via video conferencing. Each participant will be involved in the project for at least one semester prior and two semesters subsequent to travel for training and further experimentation at their U.S. campuses. In total, 15 undergraduates over 3 years will participate in this international project and will be mentored by French scientists while gaining hands-on experience with advanced research tools. This IRES project is focused on atmospheric chemistry and will contribute to the better understanding of clean air and global warming.Phenolic compounds, which are produced during biomass burning and from the oxidation of anthropogenic aromatic precursors, are believed to be significant sources of brown carbon aerosol when oxidized in cloud droplets, especially in the presence of iron (from dust) or nitrogen oxides (from combustion pollution). However, multi-phase reactions of phenolic compounds have been studied mainly in bulk aqueous solutions rather than in more realistic nanodroplets, where photobleaching can become photobrowning and where reactivity is often accelerated, especially for surface-active oligomerizing species. The researchers will therefore study brown secondary organic aerosol (SOA) formation by phenolic precursor species in nanodroplet "cloud simulation" photooxidation experiments at the CESAM chamber in Paris, characterizing chemical and optical changes in aerosol particles before, during, and after cloud events. Particle browning will be monitored by CAPS-ssa and UV/visible spectroscopy of water-soluble OA as the reactants interact with seed aerosol, water droplets, and simulated sunlight in the pressure, temperature, and RH-controlled chamber. Particle-phase chemistry will be monitored by aerosol mass spectrometry (ACSM-TOF), and particle uptake and outgassing will be detected by high-resolution PTR-MS and long-path FTIR monitoring of gas- phase species. This project will provide 15 diverse U.S. undergraduates with international research experiences at a state-of-the-art cloud chamber facility as the center of a 3-semester research experience for each participant. Project activities will increase understanding of important sources of brown SOA, which will in turn allow this pollutant, and the adverse effects on human health and climate that it causes, to be minimized in a more cost-effective manner.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.