Formation of photo-oxidants and processing of organic species in aerosol liquid water

该项目的目标是提高对大气中高度反应的凝聚态物质如何影响大气颗粒的化学和组成的理解。微粒和液滴中的许多反应是由高活性的光氧化剂驱动的，这些光氧化剂是在某些有机和无机分子吸收阳光时形成的凝聚态。本研究结果将有助于阐明这些物种在颗粒有机物的形成、转化和损失中的作用，并有助于减少颗粒物质空气污染的监管工作。该项目的目标是：(1)测量吸收光的有机化合物（3C*）、单线态分子氧（1O2*）和羟基自由基（•OH）的浓度和动力学（即形成速率和寿命），这些化合物是在加利福尼亚州戴维斯收集的一年中相对稀释的细颗粒水提取物中形成的；(2)开发新的方法来量化在大气中存在的非常浓的气溶胶液态水条件下的光氧化剂浓度；(3)探索3C*和1O2*在转化颗粒中有机物质的重要性；(4)整合研究结果，提高学界对颗粒和滴状光氧化剂的认识。主要研究人员计划与合作者合作，模拟生物质燃烧羽流中的颗粒和气相化学，并探索凝聚相光氧化剂在有机气溶胶形成和演化中的作用。这项工作包括指导一名博士后、研究生和本科生，并与初高中学生一起开展活动，以提高他们对空气污染颗粒物的认识。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The goal of this project is to improve the understanding of how highly reactive, condensed phase species in the atmosphere influence the chemistry and composition of atmospheric particles. Many reactions in particles and droplets are driven by highly reactive photo-oxidants that are formed within the condensed phase when certain organic and inorganic molecules absorb sunlight. The results of this research will help to elucidate the role of these species in the formation, transformation, and loss of particulate organics and assist with regulatory efforts to reduce particulate matter air pollution.The objectives of the project are to: (1) Measure the concentrations and kinetics (i.e., formation rates and lifetimes) of the triplet states of light-absorbing organic compounds (3C*), singlet molecular oxygen (1O2*), and hydroxyl radical (•OH) in relatively dilute water extracts of fine particles collected over the course of a year in Davis, California; (2) Develop new methods to quantify photo-oxidant concentrations under the very concentrated aerosol liquid water conditions present in the ambient atmosphere; (3) Explore the importance of 3C* and 1O2* in transforming organic species in particles; and (4) Integrate the results to improve the community’s understanding of photo-oxidants in particles and drops. The principal investigators plan to work with a collaborator to model the particle- and gas-phase chemistry in biomass-burning plumes and explore the role of condensed phase photo-oxidants in the formation and evolution of organic aerosols.This effort includes the mentoring of a postdoctoral fellow and both graduate and undergraduate students, and activities with middle and high school students to improve their understanding of particulate matter air pollution.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.