Using the RO/ED Method to Isolate Low-Ash Dissolved Organic Matter in High Yield along a Salinity Gradient

溶解有机物(DOM)的化学特性有望通过一系列沿盐度梯度的生物地球化学过程(源、汇、转化)来改变，例如河流-河口-海洋系统。为了量化DOM在质量和数量上的这种变化，科学家依赖于固相萃取(SPE)和超滤(UF)等分离方法，对于这些方法，DOM的产量通常会沿着盐度梯度大幅下降。观察到的DOM分离样品沿盐度梯度的化学变化是生物地球化学处理和DOM依赖于盐度的分馏的综合结果，因为个别化合物的保留特性因盐度的增加而改变。大多数以前的工作仅从生物地球化学的角度解释了测量到的成分变化。在这个项目中，佐治亚理工学院的研究人员将进行实验室实验，以优化耦合反渗透/电渗析(RO/ED)方法，以最大限度地提高DOM的产量，并将无机溶质的共浓度降至最低。沿佐治亚州东南部萨蒂拉河和阿尔塔马哈河全盐度梯度的现场试验将为改进的反渗透/反渗透方法的设计和优化提供反馈。将在各种盐度范围内收集高质量、低灰分的DOM样品，并对其进行化学和光谱表征(元素分析(CHON)、酸碱滴定、13C核磁共振和FTICR光谱分析)。建议研究的目标是：(1)扩大RO/ED方法适用的水化学范围，(2)开发去除残留无机物的新能力，以获得低灰分的海洋DOM样品，(3)沿着几个完整的河流-河口-海洋盐度梯度高产量地分离DOM，并检验RO/ED分离方法不会显著分离DOM的假设。更广泛的影响：该项目将为一名研究生的博士研究提供资金支持。在项目期间获得的知识将通过同行评议文献中的出版物和国内和国际会议上的演示文稿正式分享，并直接与当前的合作者和其他科学家分享，这些合作伙伴和其他科学家已请求Pio？S正式支持使用RO/ED方法从各种自然水域中分离DOM。

The chemical characteristics of dissolved organic matter (DOM) are expected to be modified by an array of biogeochemical processes (sources, sinks, transformations) along a salinity gradient such as the river-estuary-ocean system. To quantify such changes in the quality and quantity of DOM, scientists have relied upon methods of isolation such as solid-phase extractions (SPE) and ultrafiltration (UF), for which yields of DOM typically decline substantially along the salinity gradient. Observed changes in the chemistry of isolated samples of DOM along a salinity gradient are the integrated result of biogeochemical processing and salinity-dependent fractionation of DOM as the retention characteristics of individual compounds are modified by increased salinity. Most prior work has interpreted measured compositional changes solely in terms of biogeochemistry. In this project, researchers at the Georgia Institute of Technology will conduct laboratory experiments to optimize a coupled reverse osmosis/electrodialysis (RO/ED) method to maximize the yield of DOM and minimize co-concentration of inorganic solutes. Field experiments along the full salinity gradients of the Satilla and Altamaha rivers in southeast Georgia will provide feedback to the design and optimization of the modified RO/ED method. High-quality, low-ash samples of DOM will be collected across a range of salinities and characterized chemically and spectroscopically (elemental analyses (CHONS), acid-base titrations, 13C NMR and FTICR spectrometry). The goals of the proposed research are: (1) to extend the range of water chemistries over which the RO/ED method can be applied, (2) to develop new capabilities for removing residual inorganic materials to obtain low-ash samples of marine DOM, and (3) to isolate DOM in high yield along several complete river-estuary-ocean salinity gradients and to test the hypothesis that DOM is not significantly fractionated by the RO/ED isolation method.. Broader Impacts: The project will provide financial support for the doctoral research of one graduate student. Knowledge gained during the project will be shared formally through publications in the peer-reviewed literature and presentations at national and international meetings and directly with current collaborators and other scientists who have requested the PI?s formal support in using the RO/ED method to isolate DOM from a variety of natural waters.