Measurements of Tropospheric OH and HO2 Radicals in Forest Environments

该项目的总体目标是利用一种基于激光诱导荧光技术的新型仪器，通过测量森林环境中OH（羟基）和HO2（羟基）自由基的浓度和化学性质，提高对生物源排放对大气化学的影响的认识。这项研究将集中在密歇根州北部的PROPHET（氧化剂研究计划：光化学、排放和运输）塔和印第安纳州中部的AmeriFlux塔的森林冠层顶部和附近不同高度的OH和HO2测量。这些测量将有助于确定未知的活性生物源排放物是否是白天和夜间森林冠层内HOx （OH + HO2）自由基的重要来源。除了拟议的现场测量外，还将对各种生物源性挥发性有机化合物（VOCs）及其氧化产物进行实验室实验，以更好地了解其氧化机制。该项目的更广泛的科学成果将是提高对大气中生物排放对臭氧和气溶胶形成的贡献的理解，从而导致对这些污染物更有效的控制策略。该项目还将为博士后、研究生和本科生提供研究和教育机会，包括那些来自代表性不足群体的人。HOx仪器最终可能用于本科生和研究生的大气化学实验室课程，使学生能够获得和分析痕量气体的环境测量值，并通过发现体验科学的兴奋。

The overall goal of this project is to improve understanding of the influence of biogenic emissions on atmospheric chemistry through measurements of the concentrations and chemistry of OH (hydroxyl) and HO2 (hydroperoxyl) radicals in forested environments using a newly constructed instrument based on the technique of laser-induced fluorescence. The research will focus on measurements of OH and HO2 at various heights in and near the top of the forest canopy at both the PROPHET (Program for Research on Oxidants: PHotochemistry, Emissions and Transport) tower site in northern Michigan, as well as the AmeriFlux tower site in central Indiana. These measurements will help to determine whether unknown reactive biogenic emissions are a significant source of HOx (OH + HO2) radicals inside a forest canopy both during the day and at night. In addition to the proposed field measurements, laboratory experiments will be performed on various biogenic volatile organic compounds (VOCs) and their oxygenated products in order to better understand their oxidation mechanisms. The broader scientific results of this project will be an improved understanding of the contribution of biogenic emissions to ozone and aerosol formation in the atmosphere, leading to more effective control strategies for these pollutants. This project will also provide research and educational opportunities for postdoctoral associates, graduate students and undergraduates, including those from underrepresented groups. The HOx instrument may eventually be used in undergraduate and graduate laboratory-based atmospheric chemistry courses, allowing students to obtain and analyze ambient measurements of trace gases, and to experience the excitement of science through discovery.