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，将在加利福尼亚州中部的Blodgett森林站点进行测量。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性挥发性有机化合物的浓度和通量，特别是萜烯。它们通过促进重要的大气自由基和对流层臭氧的循环，以及通过二次有机气溶胶的形成，在大气化学中发挥重要作用。在早期美国国家科学基金会的支持下，通过森林冠层进行的垂直浓度分布的现场测量显示，存在大量以前未报道的氧化产物，这也在烟雾室研究中观察到。结果表明，在Blodgett森林夏季测量的生态系统尺度臭氧通量中，约有一半是由于臭氧与森林冠层内萜烯的化学反应，而离开森林冠层的萜烯通量仅代表实际排放的萜类化合物的一小部分，而其余部分则在森林冠层内进行化学处理。在本研究的下一阶段，将追求以下目标：1。烟雾室的研究将扩大到包括与加州理工学院的Seinfeld教授合作的完整光化学氧化实验，以便在更有代表性的大气条件下识别更多相关的氧化产物；2. 利用涡动相关法测量森林冠层外萜烯氧化产物的垂直通量；3. 将进行新的实地测量，以观察一整套萜烯氧化产物，其时间响应足够快，可以观察它们在森林冠层中的化学转化；4. 将尝试鉴定萜烯氧化产物，迄今为止，只有通过其质量电荷比在PTR-MS检测。这一活动的更广泛影响将在研究中为预测二次有机气溶胶形成和分布的模式、估计VOC排放对区域空气质量和全球气候的影响的模式以及预测生物源性VOC排放对气候变率和变化的响应的模式提供重要的新约束。该奖项将使布洛杰特森林的多项合作研究工作成为可能或得到加强。通过这项研究将培养一名博士后研究员。本科生也将参与其中。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.