Biogeochemical processes and Air-sea exchange in the Sea-Surface microlayer (BASS): Chemical and photochemical transformation of organic matter

海表微层（BASS）中的生物地球化学过程和气海交换：有机物的化学和光化学转化

• 批准号: 496355888
• 负责人: Professor Dr. Gernot Friedrichs
• 金额: --
• 依托单位: Leibniz-Institut für Troposphärenforschung e.V. (TROPOS)
• 依托单位国家: 德国
• 项目类别: Research Units
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/496355888?language=en
• 关键词: Biogeochemical; processes; Air; sea; exchange

The sea-surface microlayer (SML), a ubiquitous feature of the ocean surface with usually < 1mm thickness, forms the boundary layer between atmosphere and ocean. Direct exposure to UV radiation and to oxidizing species from the atmosphere as well as the increased concentrations of photosensitizers and reactants compared to the underlying bulk water trigger SML-specific reactions. However, neither their roles in overall organic matter transformation or emission of volatile organic compounds to the atmosphere nor their implementation in air-sea interaction models are sufficiently well constrained or understood until now. In this project, which will be closely interlinked with other interdisciplinary project proposals within the research unit “Biogeochemical processes and Air-sea exchange in the Sea-Surface microlayer (BASS)”, we will address molecular details of abiotic SML-specific photochemical, heterogeneous oxidation, and radical-driven reactions. We aim to quantitatively describe the interfacial product formation and to better quantify differences in chemical conversion turnover and selectivity between underlying bulk water and SML. Combining the expertise of three research groups, advanced photochemical, laser-based kinetic and spectroscopic, analytical, and molecular modeling techniques will be combined to improve our molecular-level and mechanistic understanding of such processes in the complex marine SML reaction environment. In particular, the planned research benefits from a wide variety of methods, including state-of-the art vibrational sum-frequency spectroscopy, ultra-performance liquid chromatography mass spectrometry, laser flash photolysis-laser long path absorption, as well as molecular dynamics simulations and quantum-chemistry calculations. Planned work packages focus on the oxidation kinetics of SML bulk and monolayer proxies (e.g., halogen/hydroxyl radical reactions, ozonolysis of surface-active fatty acids), the photochemical reactivity of SML proxies with natural and model photosensitizers (e.g., enhanced radical formation and organic monolayer decomposition), and the analysis of ambient samples (e.g., by targeting surfactant formation and photolysis products during a bloom event). All this will be complemented by method developments, comprising refined measurement protocols for quantitative analysis of organic compounds (e.g., carbonyls and carbohydrates), the development of surface-active photosensitizers (e.g., benzoylbenzoic acid derived lipids), and the implementation of multilevel modeling schemes as needed to get a full theoretical understanding of structure-reactivity trends of fatty acid ozonolysis (e.g., calculation of rate constants by considering steric and electronic effects of the organic matrix).

海表微层（SML）是海洋表面的一个普遍特征，通常厚度小于1 mm，形成大气和海洋之间的边界层。直接暴露于UV辐射和来自大气的氧化物质以及与底层本体水相比增加的光敏剂和反应物浓度触发SML特异性反应。然而，无论是他们的整体有机物质的转化或挥发性有机化合物排放到大气中的作用，也没有足够好的约束或理解，直到现在他们在海气相互作用模型的实施。在这个项目中，这将是密切相关的研究单位内的其他跨学科的项目提案“生物地球化学过程和海-气交换在海面微层（BASS）”，我们将解决非生物SML特定的光化学，非均相氧化和自由基驱动的反应的分子细节。我们的目标是定量描述界面产物的形成，并更好地量化底层本体水和SML之间化学转化周转率和选择性的差异。 结合三个研究小组的专业知识，先进的光化学，基于激光的动力学和光谱，分析和分子建模技术将被结合起来，以提高我们对复杂的海洋SML反应环境中这些过程的分子水平和机理理解。特别是，计划中的研究受益于各种各样的方法，包括最先进的振动和频光谱，超高效液相色谱质谱，激光闪光光解-激光长路径吸收，以及分子动力学模拟和量子化学计算。计划的工作包侧重于SML散装和单层代理的氧化动力学（例如，卤素/羟基自由基反应，表面活性脂肪酸的臭氧分解），SML代用品与天然和模型光敏剂的光化学反应性（例如，增强的自由基形成和有机单层分解），以及环境样品的分析（例如，通过在水华事件期间瞄准表面活性剂形成和光解产物）。所有这些都将通过方法开发得到补充，包括用于有机化合物定量分析的精确测量协议（例如，羰基和碳水化合物），表面活性光敏剂的开发（例如，苯甲酰基苯甲酸衍生的脂质），并根据需要实施多级建模方案以获得对脂肪酸臭氧分解的结构-反应性趋势的全面理论理解（例如，通过考虑有机基质的空间和电子效应计算速率常数）。