CAREER: Towards a Better Understanding of Ambient Semi-volatile Organic Aerosol: Investigation of Thermodynamic Properties of Multi-component Organic Aerosols

该项目的目标是获得用于化学输送模型的多组分有机气溶胶热力学性质的经验参数。主要假设是，混合物中有机化合物的挥发性是该化合物以及混合物的碳数和极性的函数；并且可以使用包含关于混合物中每种化合物的碳数和极性的入库数据的简化矩阵来预测整个混合物的挥发性。对环境中半挥发性有机气溶胶的预测仍然存在很大问题，空气质量模型往往与观测结果不符。对半挥发性化合物在气体和复杂气溶胶基质之间的分配缺乏了解是造成这种差异的主要原因之一。在这项研究中，将在受控的实验室条件下和现场研究多组分气溶胶的平衡热力学性质。在实验室实验中，将测试有机化合物的模型混合物以及改进的环境气雾剂。环境气溶胶将通过添加已知数量的已知热力学性质和可变分子量和极性的不同有机物质来以受控方式进行修改。在与环境条件相关的温度范围内，将使用由首席研究员(PI)实验室开发的积分体积法(IVM)来研究气体/气溶胶的平衡分配。研究结果将被用于计算作为碳数和极性函数的测试化合物的平衡蒸汽压和活度系数，并确定在这些维度上能够充分代表环境气溶胶挥发度的最小箱数。该项目将提高对环境气溶胶主要成分的理解、预测和控制，环境气溶胶与公众健康和全球气候变化有关。教育和宣传部分将面向广大受众，以帮助公众了解目前与空气污染有关的环境问题，并帮助吸引学生学习环境科学和工程。将特别注意吸引和留住代表性不足的群体，如妇女和少数群体。该项目将包括为中学生提供实践经验的教育推广部分；将向北卡罗来纳科学与数学学院的学生、杜克大学和北卡罗来纳中央大学(NCCU)的研究生和本科生提供暑期研究项目，北卡罗来纳中央大学(NCCU)是一所历史悠久的黑人大学。研究成果将通过会议和同行评议的出版物传播。为了接触到更广泛的受众，PI计划利用社交媒体工具的力量，如Facebook小组，分享研究成果，并直接与社区互动。

The goal of this project is to obtain empirical parameterizations of thermodynamic properties of multi-component organic aerosol to be used in chemical transport models. The main hypothesis is that volatility of an organic compound in a mixture is a function of the carbon number and the polarity of this compound, as well as those of the mixture; and that volatility of the total mixture can be predicted using a simplified matrix containing binned data on the carbon number and polarity of each of the compounds in the mixture. Prediction of ambient semi-volatile organic aerosol remains highly problematic and air quality models often do not agree with observations. The lack of understanding of the partitioning of semi-volatile compounds between the gas and the complex aerosol matrix is one of the main reasons for this discrepancy.In this study the equilibrium thermodynamic properties of multi-component aerosols will be investigated under controlled laboratory conditions as well as in the field. In the laboratory experiments model mixtures of organic compounds as well as modified ambient aerosols will be tested. The ambient aerosols will be modified in a controlled way by adding known amounts of different organic substances of known thermodynamic properties and variable molecular weight and polarity. The equilibrium gas/aerosol partitioning in a temperature range relevant to ambient conditions will be investigated using the Integrated Volume Method (IVM), developed in the principal investigator's (PI) laboratory. The results will be used to derive equilibrium vapor pressures and activity coefficients of test compounds as a function of their carbon number and polarity and to determine the minimum number of bins along these dimensions that will adequately represent ambient aerosol volatility.This project will improve the understanding, predictions and control of the major fraction of ambient aerosol, which is relevant for public health and global climate change. The educational and outreach component will be directed at a wide audience in order to help educate the public about the current environmental problems related to air pollution and help attract students to environmental science and engineering. Special attention will be given to attracting and retaining under-represented groups, such as women and minorities. The project will include an educational outreach component with hands-on experience for middle school students; summer research projects will be offered to students from the North Carolina School of Science and Math, for graduate and undergraduate students at Duke University and North Carolina Central University (NCCU), an Historically Black University. The research results will be disseminated via conferences and peer-reviewed publications. To reach a wider audience the PI plans to utilize the power of social media tools, such as Facebook groups, to share the research results and engage the community directly.