Collaborative Research: Humidity and Temperature Effects on Phase Separation and Particle Morphology in Internally Mixed Organic-Inorganic Aerosol

在NSF化学系环境化学科学项目的支持下，加州大学河滨分校(UCR)的詹姆斯·戴维斯和三一大学的瑞安·戴维斯将研究环境条件下有机-无机混合气溶胶粒子的相态。气溶胶影响气候，因为它们构成了云的基础，并参与了太阳光的散射和吸收。气雾剂还会对空气质量产生负面影响，并为空气传播疾病提供传播途径。与气溶胶有关的具体环境影响取决于气溶胶颗粒的化学成分和物相状态。对有机-无机气溶胶相状态的了解不足，例如环境中发现的气溶胶，是气候和空气质量模型中不确定性的来源。混合的有机-无机颗粒可以根据环境条件形成一系列相态；这些相态包括液体和固体相，以及无定形相，如粘性液体、玻璃和凝胶。该项目将探索气溶胶颗粒中无定形相态的形成，并表征决定其对环境的影响的性质。加州大学河滨分校和三一大学之间的这项合作将促进两个机构的本科生和研究生研究，并寻求在一系列科学学科中更好地了解气溶胶化学。为了增强对环境中气溶胶粒子的知识，该项目是由R1公立大学加州大学河滨分校的团队和以本科为主的文科大学三一大学的詹姆斯·戴维斯研究小组和三一大学的瑞安·戴维斯研究小组共同开展的，他们将研究温度和相对湿度对内部混合的有机-无机气溶胶颗粒相态和相关性质的影响。由于吸湿作用，含有有机和无机化合物混合物的气溶胶粒子在相对湿度(RH)和温度变化时表现出复杂的相行为。气溶胶粒子的相形态影响着它们与光的相互作用，它们由于粘度的变化而对化学处理的反应，以及它们的冰和云成核势。这项建议将研究在受控相对湿度和温度条件下，内部混合的有机-无机气溶胶颗粒的相形态和相关的流变性。主要目标是：(1)系统地表征含有与大气相关的盐和含氧有机物的颗粒的吸湿性和粘度；(2)确定相分离开始的温度和湿度条件，并与分子组成相关；以及(3)探索粘度和相分离对分子扩散速度的影响。为了实现这些目标，将使用电动天平将含氧有机化合物和与大气相关的单价和二价盐的单个颗粒悬浮起来。光学光谱、显微镜和光散射方法将用于识别相分离，而新的和已建立的表征方法将用于测量吸湿生长、粘度和扩散传输。这项研究将有助于激励下一代科学家，让本科生和研究生研究人员接触到气溶胶的物理严谨研究和表征，该项目更广泛地与气候科学研究有关，这是一个当今社会非常感兴趣和重要的领域。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

With support from the Environmental Chemical Sciences Program in the Division of Chemistry at NSF, James Davies of the University of California-Riverside (UCR) and Ryan Davis of Trinity University will study the phase state of mixed organic-inorganic aerosol particles under environmental conditions. Aerosols influence climate as they form the basis of clouds and are engaged in both the scattering and the absorption of sunlight. Aerosols can also negatively affect air quality and provide a vehicle for the spread of airborne disease. The specific environmental impact associated with aerosols depends upon the chemical composition and phase state of the aerosol particles. Inadequate knowledge of the phase state of organic-inorganic aerosols, such as those found in the environment, represents a source of uncertainty in climate and air quality models. Mixed organic-inorganic particles can form a range of phase states depending on environmental conditions; these include liquid and solid phases, and amorphous phases, such as viscous liquids, glasses, and gels. This project will explore the formation of amorphous phase states in aerosol particles and characterizes the properties that determine their impacts in the environment. This collaboration between UC Riverside and Trinity University will facilitate undergraduate and graduate research across both institutions and seeks to provide for an improved understanding of aerosol chemistry across a range of scientific disciplines.To enhance knowledge of aerosol particles in the environment, this project is a collaborative study between teams at an R1 public university, UC-Riverside--the James Davies research group--and at a predominantly undergraduate liberal arts and sciences university, Trinity University--the Ryan Davis research group--will examine the role of temperature and relative humidity on the phase state and associated properties of internally mixed organic-inorganic aerosol particles. Aerosol particles containing mixtures of organic and inorganic compounds exhibit complex phase behavior in response to changes in relative humidity (RH) and temperature due to hygroscopic interactions. The phase morphology of aerosol particles influences their interactions with light, their response to chemical processing due to changes in viscosity, and their ice and cloud nucleating potential. This proposal will investigate the phase morphology and associated rheological properties of internally mixed organic-inorganic aerosol particles exposed to controlled RH and temperature conditions. The main objectives are: (1) systematically characterize the hygroscopicity and viscosity of particles containing atmospherically-relevant salts and oxygenated organics; (2) determine the temperature and humidity conditions for the onset of phase separation and correlate with molecular composition; and (3) explore the consequences of viscosity and phase separation on the rate of molecular diffusion. To achieve these goals, single particles of aqueous oxygenated organic compounds and atmospherically-relevant mono- and divalent salts will be levitated using an electrodynamic balance. Optical spectroscopy, microscopy and light scattering methods will be used to identify phase separation while new and established characterization methods will be applied to measure hygroscopic growth, viscosity, and diffusive transport. The research will help to motivate the next generation of scientists by exposing undergraduate and graduate researchers to the physically rigorous study and characterization of aerosols in a project that relates more generally to climate science research, an area of great societal interest and importance today.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.