Formation and Evolution of Atmospheric Brown Carbon from Nitrate Radical Initiated Oxidation of Heterocyclic Volatile Organic Compounds

生物质燃烧羽流中的棕色碳(BRC)粒子通过与辐射和地球能量收支的相互作用来影响气候，但对其形成和辐射特性却知之甚少。在这个多PI项目中，利用先进的分析工具，在系统的实验室实验中研究了BRC颗粒的大气形成和转化过程。由此产生的新的机械信息将有助于对实地观测的解释，并为预测气候模型提供信息。该项目旨在增进对作为棕碳(BRC)二次有机气溶胶(SOA)来源的杂环挥发性有机碳(VOCs)大气氧化机理的了解。将进行系统的实验室和流动反应器实验，模拟夜间条件，在该条件下，相关的VOCs最初用硝酸根(NO3)氧化，然后用NO3和羟基(OH)自由基日老化。将使用一套在线和离线最先进的仪器来表征粒子的物理和化学性质，包括尺寸、光学参数、分子组成和官能团。此外，还将利用从成分测量获得的数据建立多相动力学模型。这项工作的结果将有助于解释复杂的真实生物质燃烧系统中的观测结果，并提供可纳入更大规模气候模型的基本机制信息。三名研究生将执行大部分实验室工作，并将从PIS校园现有的项目中招募一些来自代表性不足人群的本科生。外展活动包括与当地高中的接触。这一奖项反映了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。

Brown carbon (BrC) particles in biomass burning plumes affect climate through their interaction with radiation and Earth’s energy budget, yet, little is known about their formation and radiative characteristics. In this multi-PI project, atmospheric formation and transformation processes of BrC particles are studied in systematic laboratory experiments using sophisticated analytical tools. Resulting new mechanistic information will aid in the interpretation of field observations and inform predictive climate models. The project aims at increasing understanding of mechanisms of atmospheric oxidation of heterocyclic volatile organic carbons (VOCs) as sources of brown carbon (BrC) secondary organic aerosols (SOA). Systematic laboratory chamber and flow reactor experiments will be carried out that mimic nighttime conditions in which relevant VOCs are oxidized initially with nitrate radical (NO3) and subsequently aged diurnally with NO3 and hydroxyl (OH) radicals. A suite of on- and off-line state-of-the-art instruments will be employed to characterize particles’ physical and chemical properties, including size, optical parameters, molecular composition, and functional groups. In addition, a multiphase kinetic model will be developed with the data obtained from compositional measurements. The outcome of this work will aid in the interpretation of observations made in complex real biomass burning systems and provide fundamental mechanistic information that can be incorporated into larger scale climate models. Three graduate students will carry out the bulk of the laboratory work, and a number of undergraduate students from underrepresented populations will be recruited from existing programs on the PIs campus. Outreach activities include engagement with local high schools.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.