Collaborative Research: Secondary Organic Aerosol Production in Real Atmospheric Waters

这一合作项目涉及一种新发现的大气中二次有机气溶胶(SOA)形成的(水)途径。对SOA形成的不了解是影响气候、能见度和健康的大气气溶胶浓度和特性预测的一个主要不确定性来源。目前的模型没有捕捉到测量到的有机气溶胶浓度的大小、分布和动态，烟雾室内实验形成的SOA的含氧量大大低于老化的大气有机气溶胶，因此吸湿性低于老化的大气有机气溶胶。越来越多的证据表明，这些和其他大气观测可以解释，至少部分是由于云、雾和湿气溶胶中涉及水反应的多相SOA形成。当这一过程被包括在模型中时，预测的通过水化学形成的SOA在大小上与美国东北部和全球通过传统途径(例如，气相反应和分配到颗粒有机物)形成的SOA相当。几种类型的大气测量也为这一过程提供了证据。这个项目解决了以下问题：1)在野外可以清楚地观察到水中的SOA形成吗？2)水中的SOA的形成如何影响有机气溶胶的氧碳比？3)观察到的水中有多少可以用已知的机制来解释？哪些前体是重要的？4)SOA的形成在多大程度上依赖于光、液态水和有机物？有多少可以归因于水的形成过程？在意大利Po山谷的PEGASOS运动期间将进行现场测量，那里的条件非常适合通过气溶胶水中的反应形成SOA。与这些实地研究相结合，将在实验室进行受控水溶液光氧化实验，进行详细的化学分析和化学模拟，使用1)从环境空气中去除的水溶性(过滤)化合物混合物，2)收集(过滤)雾水，以及3)根据项目结果确定为潜在水前体的选定化合物。更广泛的影响：这项工作将进一步阐明二次有机气溶胶形成的一条重要途径，并评估这一途径在条件有利于在湿气溶胶和雾中形成SOA的地点的相对重要性。该项目将提供一个测量数据库和一个独特的雾样本档案，供其他调查人员使用。这项研究的目的是最终有助于改进对前体排放造成的气溶胶影响的全球/区域预测。这个项目将促进科学家的教育。计划中的K-12外联活动旨在接触到大量学生，并增加青年对科学发现过程的兴趣和了解。

This collaborative project addresses a newly recognized (aqueous) pathway for the formation of secondary organic aerosol (SOA) in the atmosphere. The poor understanding of SOA formation is a major source of uncertainty in predictions of atmospheric aerosol concentrations and properties that affect climate, visibility and health. Current models do not capture the magnitude, distribution and dynamics of measured organic aerosol concentrations, and smog chamber experiments form SOA that is substantially less oxygenated and, therefore, less hygroscopic than aged atmospheric organic aerosol. There is growing evidence that these and other atmospheric observations can be explained, at least in part, by multiphase SOA formation involving aqueous reactions in clouds, fogs and wet aerosols. When this process is included in models, predicted SOA formed through aqueous chemistry is comparable in magnitude to that formed through the traditional pathway (e.g., gas phase reaction and partitioning to particulate organic matter) in the northeastern United States and globally. Several types of atmospheric measurements also provide evidence for this process. This project addresses the following questions: 1) Is aqueous SOA formation clearly observable in the field? 2) How does aqueous SOA formation influence the oxygen-to-carbon ratio of the organic aerosol? 3) How much of the observed aqueous SOA produced can be explained by known mechanisms? What precursors are important? 4) To what extent does SOA formation depend on light, liquid water, and organic matter? How much can be attributed to aqueous formation processes?Field measurements will be conducted during the PEGASOS campaign in the Po Valley, Italy, where conditions are ideal for SOA formation through reactions in aerosol water. In conjunction with these field studies, controlled aqueous photooxidation experiments will be conducted in the laboratory with detailed chemical analysis and chemical modeling using 1) water-soluble (filtered) mixtures of compounds scrubbed from the ambient air, 2) collected (filtered) fog water, and 3) selected compounds identified as potential aqueous precursors based on project findings. Broader Impacts: This work will further elucidate an important pathway for secondary organic aerosol formation and provide an assessment of the relative importance of this pathway in locations where conditions are favorable to SOA formation in wet aerosols and fogs. This project will provide a measurements database and a unique archive of characterized fog samples for use by other investigators. This research is designed to contribute ultimately to improved global/regional prediction of aerosol effects from precursor emissions. This project will facilitate the education of scientists. The planned K-12 outreach is designed to reach large numbers of students and to increase interest in and understanding of the process of scientific discovery by youth.