Toward a better characterization of the aromatic and alicyclic components of marine dissolved organic matter: development and application of a one-step reduction reaction

确定化合物的化学结构，构成难溶有机物（RDOM）水库将产生新的见解的过程中，控制有机物的积累和去除的水生环境。 斯克里普斯海洋研究所的一位科学家将致力于优化现有的化学还原技术，以使氧化的脂肪族和芳香族溶解有机物（DOM），这两种化合物共同构成RDOM中多达60%的碳，更适合气相色谱（GC）分离。 这将允许这个重要的RDOM组件的特征化。 与拟议研究有关的大量时间和精力将用于确定还原产物的骨架结构。为了帮助进行这种结构表征，该提案还试图调整和修改现有的GC×GC飞行时间质谱技术，以更好地分离还原产物的复杂混合物。除了能够更准确的化合物表征，这种技术还可以更快地确定水生DOM内的结构均匀性。 作为该提案的一部分，还将修改预备GC×GC，以便使用以前的仪器开发的方法可以很容易地应用于分离相关化合物以进行进一步表征（包括同位素测量）。 这项工作还将产生一个脂肪族和芳香族还原产物的MS库，供其他有兴趣从事类似研究的研究人员使用。除了继续进一步发展分析方法外，研究人员还计划应用该方法来验证三个假设，即（1）还原将产生几种芳香族化合物，其中一些类似于降解的木质素;（2）还原将产生一系列脂环族化合物，包括萜烷衍生物;（3）GC×GC分离将证实存在结构相关的芳香族和脂肪族化合物家族。 本研究的样品包括Suwannee河富里酸和天然有机物，从热带太平洋东部和热带大西洋西部分离的超滤DOM，使用Agilent Bondesil PPL从南大洋的绕极深水分离的DOM，以及在北太平洋亚热带环流中收集的一个表层水和一个深层水样本，这些样本是使用反渗透/电渗析技术获得的，参考DOM。 这四种不同DOM样品类型的分析将有助于确定反应和基于GC/MS的分析参数，以优化每种样品类型和化合物类的研究。 科学界将对有待开发的分析方法和还原产物质谱分析库感兴趣。 作为该项目的一部分，将支助和培训一名研究生。 在海洋探索中心的帮助下选择的两名高中暑期实习生也将参加这项研究。 这个项目的学生往往是代表性不足的少数民族。

Identifying the chemical structure of compounds that constitute the refractory dissolved organic matter (RDOM) reservoir will yield new insights into the processes that control the accumulation and removal of organic matter from aquatic environments. A scientist from Scripps Institute of Oceanography will be working to optimize an existing chemical reduction technique to render oxidized aliphatic and aromatic dissolved organic matter (DOM), two compounds which together comprise as much as 60% of the carbon in RDOM, more amenable to gas chromatography (GC) separation. This will allow for the characterization of this important RDOM component. Much of the time and effort associated with the proposed research will be invested in identifying backbone structures of reduction products. To assist with this structural characterization, the proposal also seeks to adapt and modify existing GC×GC time of flight mass spectrometry techniques to better separate the complex mixture of reduction products. In addition to enabling more accurate compound characterization, this technique will also allow a more rapid determination of structural homogeneity within aquatic DOM. As part of this proposal, a preparatory GC×GC will also be modified such that methods developed using the previous instrument can be easily applied to isolate relevant compounds for further characterization (including isotope measurements). This work will also generate an MS library the aliphatic and aromatic reduction products that will be made available to other investigators interested in pursuing a similar avenue of research.Besides continuing to further develop the analytical method, the researcher also plans to apply the method to test three hypothesis, namely (1) that reduction will yield several aromatic compounds, some of which resemble degraded lignin; (2) that reduction will yield a range of alicyclic compounds including terpane derivatives; and (3) that GC×GC separation will confirm the presence of structurally related families of aromatic and aliphatic compounds. Samples for this study include Suwannee River fulvic acids and natural organic matter, ultrafiltered DOM isolated from the eastern tropical Pacific Ocean and western tropical Atlantic Ocean, DOM isolated from Circumpolar Deep Water in the Southern Ocean isolated using Agilent Bondesil PPL, and one surface and one deep water sample collected in the North Pacific subtropical gyre obtained using reverse osmosis/electrodialysis that will serve as an ad-hoc marine, reference DOM. Analyses of these four different DOM sample types will help to determine reaction and GC/MS-based analysis parameters to be optimized for each sample type and compound class under study. The analytical method to be developed and the mass spectrometry library for reduction products would be of interest to the science community. One graduate student would be supported and trained as part of this project. Two high school summer interns chosen with the help of the Ocean Discovery Center would also participate in the study. Students from this program tend to be underrepresented minorities.