SGER: Exploration of Three-Dimensional Structure in Sedimentary Organic Matter

SGER：沉积有机质三维结构探索

• 批准号: 0648684
• 负责人: Cindy Lee
• 金额: $ 4万
• 依托单位: SUNY at Stony Brook
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-01-01 至 2007-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0648684&HistoricalAwards=false
• 关键词: SGER; Exploration; Three; Dimensional; Structure

Soils and intertidal sediments are often subjected to wet-dry cycles. Most surface soils are wetted in summer and dried in winter. Salt marsh and intertidal sediments can have daily wet-dry cycles due to the rising and falling tide. Under dry conditions, dehydration can alter the three dimensional (3D) structure of soils and sediments; thus dried sediments may behave differently than never-dried sediments. For example, water repellency (or hydrophobicity) is often seen in many types of soils as a result of drying. Furthermore, dried soil organic matter is more easily degraded than non-dried soil. Similarly, the organic matrix of fruits and vegetables can collapse irreversibly after dehydration. With support from this Small Grant for Exploratory Research (SGER), researchers at the State University of New York at Stony Brook will investigate the role play by the structure of organic matter in its decompositional reactivity. They hypothesize that the three-dimensional structure and the polarity of organic matter are important factors controlling decomposition in salt marsh sediment. Hydrophobic groups of organic matter coating mineral surfaces or existing as detritus are exposed to seawater, and have a highly hydrated 3D structure. The organic molecules in the 3D structures are hydrophilic and polar, allowing other polar organic compounds to be absorbed by or partitioned into its 3D structure via electrostatic forces. During the drying process, polar functional groups of organic molecules are forced to interact with each other or with mineral surfaces, thus causing the polar moieties to turn inside out and expose more hydrophobic groups. The drying process makes organic matter change its conformation, shrink its volume, and become more hydrophobic. Rewetted organic matter is more hydrophobic than never-dried material and thus has a stronger sorption capacity for nonpolar organic compounds than the original organic matter. In environments with wet and dry cycles, the distribution of hydrophobic or hydrophilic compounds between solution and particulate phases could thus be influenced by the 3D structure and polarity of organic matter. This should greatly affect the rate of remineralization of the organic matter. The investigators will further explore some preliminary findings that the three-dimensional architecture of organic matter is critically important to sorption behavior of coastal sediments. Specifically, they will investigate (1) the importance of terrestrial versus marine organic matter in this 3D structure, and (2) the importance of the 3D nature to remineralization rates of organic matter. As a clear broader impact, this project has societal implications by contributing to a better mechanistic understanding of organic matter remineralization and thus the global carbon cycle. If a more sophisticated understanding of the ocean's response to increased levels of carbon dioxide can be developed, then more reasonable choices between political alternatives are possible. Coastal sediments contain much of the sedimentary organic carbon in the world oceans.

土壤和潮间沉积物通常受到湿干的周期。大多数表面土壤在夏季都被润湿，并在冬季干燥。由于潮汐的上升和下降，盐沼和潮间沉积物可能每天都有湿干的周期。在干燥条件下，脱水可以改变土壤和沉积物的三维（3D）结构。因此，干燥的沉积物的行为可能与从未干燥的沉积物不同。例如，由于干燥的结果，在许多类型的土壤中经常看到驱水剂（或疏水性）。此外，与非干燥的土壤相比，干土壤有机物更容易降解。同样，脱水后的水果和蔬菜的有机基质会不可逆转地塌陷。在这项小型探索性研究（SGER）的支持下，纽约州立大学Stony Brook的研究人员将调查有机物结构的作用在其分解反应性中。 他们假设三维结构和有机物的极性是控制盐沼泽沉积物分解的重要因素。有机物涂料矿物表面或作为碎屑存在的疏水组暴露于海水，并具有高度水合的3D结构。 3D结构中的有机分子是亲水性和极性的，可以通过静电力将其他极性有机化合物被吸收或分隔为3D结构。在干燥过程中，有机分子的极性官能团被迫相互相互作用或与矿物质相互作用，从而导致极性部分转动内部并暴露更多疏水基团。干燥过程使有机物改变其构象，收缩体积并变得更加疏水。重新燃烧的有机物比从未干燥的材料更疏水，因此，非极性有机化合物的吸附能力强于原始有机物。在具有潮湿和干燥循环的环境中，溶液和颗粒相之间疏水或亲水化合物的分布可能会受到有机物的3D结构和极性的影响。这应该极大地影响有机物的回忆率。研究人员将进一步探讨一些初步发现，即有机物的三维结构对于沿海沉积物的吸附行为至关重要。 具体而言，他们将研究（1）在该3D结构中陆地有机物与海洋有机物的重要性，以及（2）3D性质对有机物质的回忆率的重要性。为了明显的影响，该项目通过对有机物的更好理解以及全球碳循环的更好理解，从而具有社会意义。如果可以发展对海洋对二氧化碳含量增加的反应的更复杂的理解，那么政治替代方案之间的更合理选择是可能的。沿海沉积物在世界海洋中包含许多沉积有机碳。