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

识别构成难溶有机物(RDOM)储藏库的化合物的化学结构将使人们对控制有机物从水环境中积累和去除的过程有新的见解。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)更易于气相色谱(GC)分离，这两种化合物加起来占RDOM中碳的60%。这将允许对这一重要的RDOM组件进行表征。与拟议研究相关的大部分时间和精力将投入到确定减排产品的主干结构上。为了帮助这种结构表征，该提案还寻求调整和修改现有的GC×GC飞行时间质谱学技术，以更好地分离还原产物的复杂混合物。除了实现更准确的化合物表征外，这项技术还将允许更快地确定水生DOM中的结构同质性。作为这项建议的一部分，还将对预备GC×GC进行修改，以便使用以前的仪器开发的方法可以很容易地用于分离相关化合物，以供进一步表征(包括同位素测量)。这项工作还将生成脂族和芳香族还原产物的质谱库，供有兴趣进行类似研究的其他研究人员使用。除了继续开发分析方法外，研究人员还计划应用该方法检验三个假设，即(1)还原将产生几种芳香化合物，其中一些类似于降解的木质素；(2)还原将产生包括萜烷衍生物在内的一系列脂环化合物；(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。本研究的样本包括苏万尼河黄腐酸和天然有机物、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从南大洋绕极深水分离的DOM、以及在北太平洋亚热带环流用反渗透/电渗析获得的一个表层和一个深水样本，作为特别海洋的参考DOM。对这四种不同类型的DOM样品的分析将有助于确定针对所研究的每种样品类型和化合物类别需要优化的反应和基于GC/MS的分析参数。科学界将对将要开发的分析方法和还原产物的质谱库感兴趣。作为该项目的一部分，一名研究生将得到支持和培训。在海洋探索中心的帮助下挑选的两名高中暑期实习生也将参与这项研究。这个项目的学生往往是代表不足的少数族裔。

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.