Collaborative Research: Defining the Structural Basis of the Optical Properties of Chromophoric Dissolved Organic Matter

有色溶解有机物(CDOM)是一种广泛存在于水生生物系统中的复杂有机物质，它不仅通过影响水生光场、影响卫星海洋颜色传感器对浮游植物生物量的遥感，而且通过其光化学反应在水生生物中起着核心作用。尽管五十多年来人们对CDOM的光学吸收和发射特性已经有了广泛的了解和研究，但对于这些材料的长波吸收和发射行为还没有提供令人满意的解释。马里兰大学和伍兹霍尔海洋研究所的研究人员联合提出，这种行为是由于可溶木质素前体部分氧化形成的羟基-芳香族供体和奎宁受体之间的分子内电荷转移相互作用造成的。他们将通过将波长选择性单色(激光)和多色光漂白研究与超高分辨率电喷雾电离质谱学相结合来验证这一假设，以获得关于特定被波长选择性照射破坏或产生的物种的结构信息。将使用吸收光谱和荧光光谱、凝胶渗透层析和木质素酚分析来提供补充的结构信息。将研究腐植酸和木质素的模型系统，然后是在特拉华湾/大西洋中部海湾地区进行的一系列实地研究中收集的CDOM样本。这些实地研究将通过检查从广泛的海洋环境和季节收集的CDOM的光学性质与木质素苯酚含量、分子尺寸和质谱图之间的关系来进一步验证这一假说。这项工作将从根本上限制CDOM的来源和形成方式，以及它的光化学性质。

ABSTRACTOCE-0443263Chromophoric dissolved organic matter (CDOM) is a complex organic material found ubiquitously in aquatic systems where it plays a central role, not only through its impact on the aquatic light field and on the remote sensing of phytoplankton biomass by satellite ocean color sensors, but also through its photochemical reactions. Although the optical absorption and emission properties of CDOM have been known and studied extensively for over fifty years, no satisfactory explanation has yet been provided that can account for the long-wavelength absorption and emission behavior of these materials. Researchers at the University of Maryland and at Woods Hole Oceanographic Institution have teamed up to propose that this behavior results from intramolecular charge transfer interactions between hydroxy-aromatic donors and quinoid acceptors formed by the partial oxidation of soluble lignin precursors. They will test this hypothesis by combining wavelength-selective monochromatic (laser) and polychromatic photobleaching studies with ultrahigh resolution electrospray ionization mass spectrometry to acquire structural information on the species that are specifically destroyed or produced by the wavelength-selective irradiations. Absorption and fluorescence spectroscopy, gel permeation chromatography and lignin phenol analyses will be employed to provide complementary structural information. Both model humic and lignin systems will be examined, followed by CDOM samples collected during a series of field studies in the Delaware Bay/Mid-Atlantic Bight region. These field studies will provide further tests of this hypothesis through an examination of the relationships among the optical properties and the lignin phenol content, molecular size and mass spectra of CDOM collected across a wide range of oceanic environments and seasons. This work will place fundamental constraints on the origins and modes of formation of CDOM, as well as on its photochemical properties.