CAREER: Photochemical Aging of Atmospheric Organic Aerosol: Chamber Studies of the Chemical Evolution of Oxidized Organic Species

本项目通过实验室研究氧化有机物的光化学老化来研究有机气溶胶（OA）的化学演变。 光化学老化被定义为颗粒在大气氧化的几天内经历的质量和组成的变化，在OA形成的实验室研究中通常无法准确模拟。 这在很大程度上是由于实验时间尺度的限制或将实验条件外推到大气层条件。 在该项目中，老化研究将在环境室中进行，允许气体-颗粒分离和其他关键过程以与大气中相似的程度发生，但具有升高和持续的氧化剂浓度，以便可以获得更长的氧化剂暴露。计划实验的重点是低挥发性，多功能，氧化物种的化学，这构成了OA的大部分。 由这种氧化的有机物（单一模型化合物或更复杂的混合物）组成的颗粒将被引入到腔室中并暴露于高浓度的羟基（OH）自由基。 三种不同的途径，有机气溶胶可能是光化学老化将进行研究：非均相氧化的凝聚相有机物，气相氧化的半挥发性物种，和水相氧化的水溶性物种。 作为OH暴露的函数的粒度和组成的测量将允许确定OA的质量和氧化程度的变化，以及这些反应的动力学。 从这些研究的结果可以用来直接通知模型，旨在模拟大气OA的变化后oxidative ageing.Broader影响：这项研究的结果将告知气溶胶气候和气溶胶/健康相互作用的政策。 此外，该项目的教育部分旨在通过在当地公立学校实施新的教育方案、让本科生参与实验室研究和培养研究生，促进各级学生的科学发展。 将在罗克斯伯里（波士顿经济落后的社区）的一所K-8学校为6 - 8年级学生制定和实施一个以“天气和污染”为重点的外联方案。 这将建立在现有的成功的中学生推广计划，其中主要研究者（PI）小组的成员开发和运行学校的第一个科学博览会计划，以及课后科学俱乐部。 该计划最初将作为一个单一的学校试点计划实施，目标是通过教师培训扩展到波士顿公立学校系统的其他学校。 这项工作还将促进本科和研究生教育。 本科生将直接参与研究，通过麻省理工学院的本科生研究机会计划（针对麻省理工学院的学生）和麻省理工学院的夏季研究计划（针对来自其他学院传统上代表性不足的群体的学生），PI是导师。 这项研究将占研究生博士学位的很大一部分。培训，研究生也将获得教育经验，发挥在推广计划的主要作用，并建议本科生（S）。 研究结果将纳入PI的本科和研究生课堂教学。

This project addresses the chemical evolution of organic aerosol (OA) through laboratory studies of the photochemical aging of oxidized organics. Photochemical aging, defined as the changes in mass and composition that particles undergo over several days of atmospheric oxidation, is generally not simulated accurately in laboratory studies of OA formation. This is largely due to limitations in experimental timescales or extrapolation of experimental conditions to those of the atmosphere. In this project, aging studies will be carried out in an environmental chamber, allowing for gas-particle partitioning and other key processes to occur to a similar extent as in the atmosphere, but with elevated and sustained oxidant concentrations, so that longer oxidant exposures can be accessed. The focus of the planned experiments is the chemistry of low-volatility, multifunctional, oxidized species, which make up a large fraction of OA. Particles made up of such oxidized organics (either single model compounds or more complex mixtures) will be introduced into the chamber and exposed to high concentrations of hydroxyl (OH) radicals. Three different pathways by which organic aerosol may be photochemically aged will be investigated: heterogeneous oxidation of condensed-phase organics, gas-phase oxidation of semivolatile species, and aqueous-phase oxidation of water-soluble species. Measurements of particle size and composition as a function of OH exposure will allow for the determination of the changes to mass and degree of oxidation of the OA, as well as of the kinetics of these reactions. Results from such studies can be used to directly inform models aimed at simulating changes to atmospheric OA upon oxidative aging.Broader Impacts: The results of this research will inform policy on aerosol-climate and aerosol/health interactions. Additionally, the educational component of this project aims to promote the scientific development of students spanning a range of levels, by implementation of a new education program at a local public school, the engagement of undergraduates in laboratory research, and the training of graduate students. An outreach program focused on "Weather and Pollution" for 6th-8th graders will be developed and implemented at a K-8 school in Roxbury (an economically disadvantaged neighborhood of Boston). This will build upon an existing successful outreach program to middle school students, in which members of the Principal Investigator's (PI) group developed and ran the school's first science fair program, as well as an after-school science club. This program will originally be implemented as a single-school pilot program, with the goal of expansion to other schools in the Boston Public School system via teacher training. This work will also promote education at the undergraduate and graduate level. Undergraduate students will be directly involved in the research, via MIT's Undergraduate Research Opportunity Program (for MIT students) and MIT's Summer Research Program (aimed at students from traditionally underrepresented groups from other colleges), for which the PI is a mentor. The proposed research will represent a large fraction of a graduate student's Ph.D. training, and the graduate student will also gain educational experience by playing a major role in the outreach program and advising the undergraduate student(s). Results from the research will be incorporated into the PI's undergraduate- and graduate-level classroom teaching.