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特大城市，全球各地都观察到了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是很好，这在很大程度上是因为它的化学复杂性，它涵盖了从气相物种到分子簇，再到“大宗”纳米颗粒物质的一切。该项目将使用独特的纳米气溶胶质谱仪(NAMS)在两个多调查员现场活动中测量单个尺寸选定的颗粒(10-30 nm尺寸范围)的元素组成，一个将于2012年在宾夕法尼亚州匹兹堡进行，另一个将于2013年在能源部的大气辐射测量(ARM)计划在俄克拉荷马州北部的南大平原现场进行。这一结果将使NPF过程中硫酸盐与有机物和其他无机物之间的颗粒生长得以量化。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，并用于辅助开发颗粒生长模型。NAMS还将提供关键信息，帮助确定纳米颗粒中存在多少阳离子氮，而不是中和无机酸所需的阳离子氮。这一结果将更定量地衡量胺对颗粒生长的影响。此外，NAMS还将量化周围颗粒物组成的变化与吸湿性/挥发性变化的关系。这些结果将提供一个独立的评估，以评估基于实验室吸湿性/挥发性研究的间接化学成分测量在多大程度上指示了真实的环境成分。更好地了解NPF及其与云凝结核(CCN)浓度的关系将产生科学影响，这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两名研究生的支持来促进教和学。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参与，在活动期间，首席调查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.