Collaborative Research: Impacts of surface ocean surfactant sources and transformations on their chemical composition and air-sea relevant properties

表面微层（SML）是海洋和大气交界面上的一层薄薄的水，控制着物质进出海洋的交换。因此，它可以深刻地影响生物地球化学循环和全球气候。表面活性剂分子是在空气-水界面积聚的一类化学物质，它影响空气-水界面的表面张力和物质交换速率。生物和化学生产和降解过程代表了表面活性剂的来源和去除途径，但这些过程在确定表面活性剂数量和分子组成方面的相对重要性尚不清楚。同样，表面活性剂分子组成与空气-水界面表面张力之间的关系尚未建立。因此，它们对界面上物质交换的影响目前还无法预测。这项工作将使用海上测量、实验室实验和高分辨率分析来测量表面活性剂的化学和物理特性及其在海气界面的特性。提高对表面活性剂过程和海洋表面的理解，将通过提高我们对与气候有关的气体和颗粒交换的理解，使社会受益。两位早期职业生涯的私人顾问将推进他们已建立的合作，并获得领导研究项目和指导学生的进一步经验。学生将获得宝贵的实践培训，在海洋领域的收集，最先进的科学分析技术，数据解释和数据传播。这项工作的结果和方法将在乔治亚大学和特拉华大学的课程中出现，并将开发成K-12学生的内容，加强教育基础设施。这项工作包括独特的跨时间和空间尺度的科学测量配对，以评估海洋过程对表面活性剂化学成分和物理海气相关性质的影响。在高生产力和低生产力条件下，将从河口、沿海和开放海域收集SML和地下水，以建立表面活性剂在一定空间、时间和海洋生物活性范围内的分子特征。光的影响将通过每日取样和实验室实验来评估。将对样品进行详细的化学、生物和物理特性分析。预计SML的表面张力与高生物活性期间产生的类脂化合物（低O含量，高H/C比，例如含硫脂类）的丰度呈负相关。假设长时间暴露于光下会导致表面活性剂化合物的光氧化，氧合脂肪化合物的丰度更高，分子量更低，表面张力增加。多元统计方法将用于揭示生物和光化学过程之间联系的机制理解，以及由此产生的表面活性剂和SML化学和物理特性。这一新知识将是朝着改进海气交换气候相关气体模型迈出的第一步，这些模型目前存在很大的不确定性。它将为未来有关挥发性有机物和气溶胶有机物交换的工作提供信息，这些有机物对我们对气候系统的理解具有重大的潜在影响。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The surface microlayer (SML), the thin layer of water at the interface between the ocean and the atmosphere, controls the exchange of materials to and from the ocean. As a result, it can profoundly influence biogeochemical cycles and global climate. One type of chemical species that accumulates at this interface are surfactant molecules, which influence the surface tension of and the rate of material exchange at air-water interfaces. Biological and chemical production and degradation processes represent surfactant sources and removal pathways, but the relative importance of those processes for determining surfactant quantities and molecular composition remains unclear. Similarly, the relationship between surfactant molecule composition and surface tension at the air-water interface has not been established. As a result, their effects on material exchange at the interface cannot currently be predicted. This work will use measurements at sea, laboratory experiments, and high-resolution analyses to measure the chemical and physical characteristics of surfactants and their properties at the air-sea interface. An improved understanding of surfactant processes and surface ocean will benefit society by improving our understanding of the exchange of climate-relevant gases and particles. Two early career PIs will advance their established collaboration and gain further experience leading research projects and mentoring students. Students will receive valuable hands-on training in oceanographic field collections, state-of-the-science analytical techniques, data interpretation, and data dissemination. The results and methodologies from this work will be featured in courses at the University of Georgia and the University of Delaware and will be developed into content for K-12 students, enhancing infrastructure for education. This work includes the unique pairing of state-of-the-science measurements across time and spatial scales to assess the influence of oceanographic processes on surfactant chemical composition and physical air-sea relevant properties. SML and subsurface waters will be collected from estuarine, coastal ocean, and open ocean sites during high and low productivity conditions to establish surfactant molecular characteristics over a range of space, time, and ocean biological activity. The effects of light will be assessed via diurnal sampling efforts and laboratory experiments. Samples will be analyzed for their detailed chemical, biological, and physical characteristics. The surface tension of the SML is expected to be inversely correlated with the abundance of lipid-like compounds (low O content, high H/C ratios, e.g., sulfur-containing lipids) produced during periods of high biological activity. Prolonged exposure to light is hypothesized to result in photo-oxidation of surfactant compounds, higher abundances of oxygenated and lower molecular weight aliphatic compounds, and increased surface tension. Multivariate statistical approaches will be used to reveal a mechanistic understanding of the links between biological and photochemical processes and the resulting surfactant and SML chemical and physical characteristics. This new knowledge will represent a first step toward improved models of the air-sea exchange of climate relevant gases which currently have large uncertainties. It will inform future work on the exchange of volatile and aerosol organics with significant potential impacts for our understanding of the climate system.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.