Particle Growth Mechanisms During Ambient New Particle Formation

从芬兰偏远的北方森林到墨西哥城等受污染的大城市，全球各地都观察到大气中的新粒子形成（NPF）。尽管NPF无处不在，但人们对它的了解还不够透彻，这主要是因为它的化学复杂性，包括从气相物质到分子簇，再到“大块”纳米颗粒物质的一切。该项目将采用一种独特的纳米气溶胶质谱仪（NAMS）在两次多研究员实地考察中测量单个尺寸选择颗粒（10-30纳米尺寸范围）的元素组成，一次是2012年在宾夕法尼亚州匹兹堡，另一次是2013年在俄克拉荷马州北部的能源部大气辐射测量（ARM）计划南部大平原地点。结果将允许在NPF期间由硫酸盐对有机物和其他无机物种的颗粒生长进行量化。测量的生长速率将与基于气相浓度的预测生长速率进行比较，并用于辅助颗粒生长模型的开发。NAMS还将提供关键信息，帮助确定除中和无机酸所需的阳离子氮外，纳米颗粒中存在多少阳离子氮。该结果将对胺对颗粒生长的影响提供更定量的测量。此外，NAMS将量化环境颗粒组成的变化与吸湿性/挥发性的变化之间的关系。结果将提供一个独立的评估，即基于吸湿性/挥发性实验室研究的化学成分的间接测量在多大程度上表明了真实的环境成分。科学影响将来自对NPF及其与云凝结核（CCN）浓度的联系的更好理解，而CCN浓度反过来又对降水模式和地球能量平衡产生重要影响。更广泛的教育影响将包括通过支持两名研究生促进教与学。外联工作将包括通过一年一度的“海岸日”活动吸引更广泛的社区，在此期间，首席研究员将介绍工作的某些方面。

New particle formation (NPF) in the atmosphere has been observed all over the globe, from remote boreal forests in Finland to polluted megacities such as Mexico City. Although it is pervasive, NPF is not that well understood owing in large part to its chemical complexity, which encompasses everything from gas phase species, to molecular clusters, to "bulk" nanoparticulate matter. This project will employ a unique Nano Aerosol Mass Spectrometer (NAMS) to measure the elemental composition of individual size-selected particles (10-30 nm size range) during two multi-investigator field campaigns, one in Pittsburgh, Pennsylvania in 2012 and another at the Department of Energy's Atmospheric Radiation Measurement (ARM) program Southern Great Plains site in northern Oklahoma in 2013. The results will allow particle growth by sulfate vs. organics and other inorganic species during NPF to be quantified. Measured growth rates will be compared to predicted growth rates based on gas phase concentrations and used to assist development of models for particle growth. The NAMS will also provide key information to help determine how much cationic nitrogen exists in nanoparticles beyond that needed to neutralize inorganic acids. The results will give a more quantitative measure of the impact of amines on particle growth. In addition, the NAMS will quantify how changes in ambient particle composition correlate with changes in hygroscopicity/volatility. The results will provide an independent assessment of how well indirect measurements of chemical composition based on laboratory studies of hygroscopicity/volatility give an indication of the true ambient composition.Scientific impacts will derive from better understanding of NPF and their linakge to cloud condensation nucleus (CCN) concentrations which, in turn, have important impacts on precipitation patterns and Earth's energy balance. Educational broader impacts will include promotion of teaching and learning through the support of two graduate students. Outreach efforts will include engaging the broader community via an annual "Coast Day" event during which the principal investigator will present some aspects of the work.