Photooxidation of Biogenically Produced Alkenes: Impacts on HOx, NOx, and Aerosol

该项目将采用最先进的仪器来研究生物烯烃及其氧化产物的光氧化，作为加州内华达山脉森林环境中一个多研究员实地项目的一部分，这是一种化学制度，有机过氧自由基与过氧化氢在相对较低水平的氮氧化物（NOx）条件下发生反应。目前，这一机制的特征很差；以前的实地观测表明，目前光化学模型中使用的机制与观测到的氮氧化物水平不一致。三重四极杆质谱仪将与定制的选择离子化学电离入口耦合，用于实时分析许多短寿命活性化合物，包括有机过氧化物，迄今为止，这些化合物的定量很差。在实地活动期间，将使用第二台化学电离质谱仪通过涡流相关方差测量氰化氢、过氧化氢和硝酸的通量。这些结果将改善对以下机制的限制：1)臭氧的产生和损失，2)有机硝酸盐的产生和命运，以及3)地球大气中二次有机气溶胶的形成，从而大大提高了对控制世界许多地区臭氧和气溶胶负担的有机化学性质的理解。这项工作将涉及与广泛的科学家合作，包括其他大气化学家、气象学家和生态学家，他们研究导致树木形成和释放生物烯烃的生物化学过程。这些合作将使参与这项工作的研究生和博士后学者接触到地球科学的广度。

This project will employ state-of-the-art instrumentation to investigate the photo-oxidation of biogenic alkenes and their oxidation products as part of a multi-investigator field program in the forested environment of California's Sierra Nevada, a chemical regime where organic peroxy radicals react with hydrogen peroxide under conditions with relatively low levels of nitrogen oxides (NOx). This regime is currently poorly characterized; previous field observations have suggested that the mechanisms currently used in photochemical models are inconsistent with observed levels of NOX. A triple quadrupole mass spectrometer will be coupled to a custom, selected-ion chemical ionization inlet for real-time analysis of many short-lived, reactive compounds including the organic peroxides that have, to date, been poorly quantified. During the field campaign, a second chemical ionization mass spectrometer will be used to measure, via eddy covariance, the fluxes of hydrogen cyanide, hydrogen peroxide and nitric acid.The results will improve constraints on the mechanisms responsible for 1) production and loss of ozone, 2) the production and fate of organic nitrates, and 3) formation of secondary organic aerosol in Earth's atmosphere, thus providing substantially improved understanding of the nature of the organic chemistry that controls the burden of ozone and aerosol in many regions of the world. The work will involve collaborations with a broad spectrum of scientists, including other atmospheric chemists, meteorologists, and ecologists studying the biochemistry leading to the formation and release of biogenic alkenes from trees. These collaborations will expose graduate students and post-doctoral scholars involved in the work to the breadth of earth science.