Extending the Use of Proton-Transfer-Reaction Mass Spectrometer (PTR-MS) for New Measurements of Volatile Organic Compounds and Their Oxidation Products - Phase II

该项目涉及挥发性有机化合物（VOC）的生物源排放，将在加州中部的Blodgett森林进行测量。快速响应质子转移反应质谱仪（PTR-MS）将用于实时原位测量生物源VOC，特别是萜烯的浓度和通量。这些物质通过促进重要的大气自由基和对流层臭氧的循环，并通过二次有机气溶胶的形成，在大气化学中发挥重要作用。在国家科学基金会的早期支持下，通过森林树冠层对垂直浓度分布进行的实地测量显示，存在大量以前未报告的氧化产物，在烟雾室研究中也观察到了这些产物。结果表明，约有一半的生态系统尺度的臭氧通量在Blodgett森林在夏季测量是由于臭氧与萜烯的森林冠层内的化学反应，和萜烯离开森林冠层的流量只代表一小部分的萜类化合物实际排放，而其余的是化学处理的森林冠层内。在下一阶段的研究中，将追求以下目标：1。烟雾室研究将扩大到包括与加州理工学院的Seinfeld教授合作进行的完整的光化学氧化实验，以便在更具代表性的大气条件下识别更多的相关氧化产物; 2.采用涡度相关法测定萜烯氧化产物的垂直通量;将进行新的实地测量，以观察全套萜烯氧化产物，其时间响应足够快，以观察它们在森林冠层中的化学转化; 4.将尝试识别萜烯氧化产物，迄今为止，这些产物仅通过PTR-MS中的质荷比检测到。这项活动的更广泛影响将在研究中为预测二次有机气溶胶的形成和分布的模型提供重要的新约束，估计VOC排放对区域空气质量和全球气候的影响的模型，以及预测生物挥发性有机化合物排放对气候变率和变化的响应的模型。在Blodgett森林的多个合作研究工作将通过这个奖项成为可能或得到加强。本研究将培养一名博士后研究员。本科生也将参与其中。该项目产生的研究方法和成果将被Goldstein教授整合到课堂教学中。

This project addresses biogenic emissions of volatile organic compounds (VOC), which will be measured at the Blodgett Forest site in central California. Fast response Proton-Transfer-Reaction Mass Spectrometers (PTR-MS) will be used for real-time in-situ measurements of concentrations and fluxes of biogenic VOCs, especially terpenes. These play important roles in the chemistry of the atmosphere by contributing to the cycling of important atmospheric radicals and tropospheric ozone, and through secondary organic aerosol formation. With earlier NSF support, field measurements of vertical concentration profiles through the forest canopy revealed the presence of large amounts of previously unreported oxidation products, which were also observed in smog chamber studies. The results suggest that about half the ecosystem scale ozone flux measured at Blodgett Forest in summer is due to chemical reactions of ozone with terpenes within the forest canopy, and that the flux of terpenes leaving the forest canopy represents only a small fraction of the terpenoid compounds actually emitted, while the rest is chemically processed within the forest canopy. In the next phase of this research, the following objectives will be pursued:1. The smog chamber research will be expanded to include full photochemical oxidation experiments in collaboration with Prof. Seinfeld at Caltech in order to identify even more of the relevant oxidation products under more representative atmospheric conditions; 2. The vertical flux of terpene oxidation products out of the forest canopy will be measured using the eddy covariance method; 3. New field measurements will be performed to observe the full suite of terpene oxidation products with a time response fast enough to observe their chemical transformations in the forest canopy; 4. Attempts will be made to identify the terpene oxidation products that have so far only been detected by their mass to charge ratio in the PTR-MS. The Broader Impacts of this activity will be in the research providing important new constraints for models predicting the formation and distribution of secondary organic aerosol, models that estimate the effects of VOC emissions on regional air quality and global climate, as well as models predicting the response of biogenic VOC emissions to climate variability and change. Multiple collaborative research efforts at Blodgett Forest will be made possible or enhanced through this award. A postdoctoral researcher will be trained through this research. Undergraduate students will also be involved. Research methodologies and results generated from this project will be integrated into classroom teaching by Prof. Goldstein.