Identifying the role of dissolved organic matter composition in complete and partial photooxidation in diverse lakes

确定溶解有机物成分在不同湖泊完全和部分光氧化中的作用

• 批准号: 2104716
• 负责人: Christina Remucal
• 金额: $ 32.64万
• 依托单位: University of Wisconsin-Madison
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-08-01 至 2024-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2104716&HistoricalAwards=false
• 关键词: Identifying; role; dissolved; organic; matter

This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117-2).Inland waters, such as lakes and rivers, cover a small percentage of the Earth's surface yet play a central role in the carbon cycle. Dissolved organic matter (DOM), which is made up of chemicals from plants and microorganisms, is a critical component of the carbon cycle within lakes. For example, natural processing of DOM by microorganisms or by reaction with sunlight can produce carbon dioxide, a key greenhouse gas. As a result, lakes are hotspots of carbon cycling and emission in the landscape. However, the reaction of DOM with sunlight is frequently ignored in carbon cycling models and little is known about how the type of DOM, which varies in different lakes, influences its reactivity. This project will study DOM from eleven lakes in the North Temperate Lakes-Long Term Ecological Research (NTL-LTER) program, along with two well-studied DOM isolates. The DOM will be evaluated for its photochemical reactivity using multiple approaches. Importantly, the DOM will be thoroughly analyzed using state-of-the-art techniques, including high-resolution mass spectrometry, before and after reaction with simulated sunlight to identify how sunlight reacts with this complex material. This project will yield important insights into the properties that determine the reactivity of DOM in inland waters by isolating the impact of photochemical reactions, which could ultimately be used to model carbon dioxide production from lakes. A better understanding of the carbon cycle, particularly in sensitive hydrologic environments, is critical for predicting and ultimately adapting to a changing climate.The composition of dissolved organic matter (DOM) is critical to its reactivity. One example of DOM reactivity is its susceptibility to complete and partial photooxidation in sunlit waters, such as lakes. This process is increasingly recognized as an important component of the global carbon cycle. However, a mechanistic understanding of how DOM composition influences its photochemical reactivity is lacking. This research will fully characterize waters collected from the eleven core lakes of the North Temperate Lakes-Long Term Ecological Research (NTL-LTER) program, along with two well-studied DOM isolates. These lakes include dystrophic, oligotrophic, mesotrophic, and eutrophic systems that range widely in DOM composition. Photochemical reactivity will be assessed by quantifying photomineralization rates, measuring quantum yields and steady-state concentrations of photochemically produced reactive intermediates (triplet DOM, singlet oxygen, hydroxyl radical, and carbonate radical anion), and using quencher experiments to distinguish between direct and indirect photolysis of DOM. The DOM samples will be characterized before and after photolysis using UV-visible spectroscopy, fluorescence spectroscopy, antioxidant measurements, and Fourier transform-ion cyclotron resonance mass spectrometry. Multivariate statistics, including multiple linear regressions, hierarchical cluster analysis, and principal component analysis, will be used to identify how DOM is altered during photooxidation, derive new measurements of partial photooxidation, and identify the roles of direct and indirect photolysis in complete and partial photooxidation. The work will yield important insights into the fundamental properties that govern the reactivity of DOM in inland waters by isolating the impact of photochemical reactions. This knowledge can be used to develop relationships between DOM composition and reactivity that could ultimately be used to model the potential for carbon dioxide production from lakes.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.

该奖项的全部或部分资金来自《2021年美国救援计划法案》(公法117-2)。内陆水域，如湖泊和河流，覆盖了地球表面的一小部分，但在碳循环中发挥着核心作用。溶解有机物(DOM)由植物和微生物中的化学物质组成，是湖泊碳循环的关键组成部分。例如，微生物或通过与阳光反应对DOM进行自然处理会产生二氧化碳，这是一种关键的温室气体。因此，湖泊是景观中碳循环和排放的热点。然而，在碳循环模型中，DOM与阳光的反应经常被忽视，而且人们对不同湖泊中DOM的类型如何影响其反应活性知之甚少。该项目将从北温带湖泊-长期生态研究(NTL-LTER)计划的11个湖泊中研究DOM，以及两个研究得很好的DOM分离株。将使用多种方法评估DOM的光化学反应活性。重要的是，将使用最先进的技术，包括高分辨率质谱仪，在与模拟阳光反应之前和之后对DOM进行彻底分析，以确定阳光如何与这种复杂材料反应。该项目将通过隔离光化学反应的影响，对决定DOM在内陆水域的反应性的性质产生重要的见解，最终可用于模拟湖泊二氧化碳的产生。更好地了解碳循环，特别是在敏感的水文环境中，对于预测并最终适应不断变化的气候至关重要。溶解有机物(DOM)的组成对其反应活性至关重要。DOM反应性的一个例子是它在阳光充足的水域，如湖泊中，对完全和部分光氧化的敏感性。这一过程日益被认为是全球碳循环的重要组成部分。然而，对于DOM的组成如何影响其光化学反应的机理还缺乏了解。这项研究将充分描述从北温带湖泊-长期生态研究(NTL-LTER)计划的11个核心湖泊收集的水域，以及两个经过充分研究的DOM分离株。这些湖泊包括营养不良、营养不足、中营养和富营养系统，DOM组成范围很广。光化学反应性将通过量化光矿化速率、测量光化学产生的活性中间体(三重态DOM、单重态氧、羟基自由基和碳酸盐自由基阴离子)的量子产率和稳态浓度，以及使用猝灭实验区分DOM的直接和间接光解来评估。用紫外-可见光谱、荧光光谱、抗氧化剂测量和傅里叶变换离子回旋共振质谱仪对DOM样品光解前后的特性进行了表征。多元统计，包括多元线性回归、层次聚类分析和主成分分析，将被用来确定DOM在光氧化过程中是如何改变的，得出部分光氧化的新测量，并确定直接和间接光解在完全和部分光氧化中的作用。这项工作将通过隔离光化学反应的影响，对支配内陆水域DOM反应性的基本性质产生重要的见解。这些知识可以用来开发DOM组成和反应性之间的关系，最终可以用来模拟湖泊产生二氧化碳的潜力。这一奖项反映了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。