Singlet Oxygen's Role in the Photochemical-Biochemical Degradation of Dissolved Organic Carbon

单线态氧在溶解有机碳光化学生化降解中的作用

• 批准号: 0527196
• 负责人: Kristopher McNeill
• 金额: --
• 依托单位: University of Minnesota-Twin Cities
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-09-15 至 2009-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0527196&HistoricalAwards=false
• 关键词: Singlet; Oxygen; Role; Photochemical; Biochemical

ABSTRACTOCE-0527196Dissolved organic matter (DOM) is the largest pool of organic carbon in aquatic ecosystems and constitutes a vital link in the global carbon cycle. Despite a large flux (ca. 2 x 1014g) of terrigenous DOM into the oceans every year, little of this material accumulates suggesting that it is rapidly decomposed. While the two main losses, photochemical and biochemical degradation, have been well studied, little work has examined the mechanisms responsible for degradation and chemical transformations, especially regarding photochemical processes.In this research project, researchers at the University of Minnesota - Twin Cities will investigate the effects of a reactive oxygen species (ROS), singlet oxygen (1O2), on the chemical composition, reactivity and bioavailability of organic matter in natural waters. This project will use Lake Superior as a study site and the goals are: (1) To characterize the changes to the chemical and optical properties of DOM when exposed to 1O2; (2) To determine the changes in lability and nutritive quality of DOM following reaction with 1O2; (3) To examine the differential microbial utilization of 1O2-reactive amino acids-histidine, tryptophan, methionine, cysteine, and tyrosine-and their 1O2 reaction products, and (4) To quantify 1O2 production rates in Lake Superior.To achieve these goals, DOM from two sources (soil and phytoplankton) and along a temporal-spatial gradient (river and offshore) will be exposed to a number of treatments including sunlight and well-defined sources of 1O2 with and without quenchers present. This study features the use of non-photochemical 1O2 sources that will enable examination of effects of 1O2 independent of sunlight. Effects on lability and chemical structure of DOM will be observed via bioassays and chemical analyses. The hypothesis that decreased microbial growth efficiency is observed in the presence of oxidized DOM, due to the reaction of 1O2 with specific amino acids present in DOM will be tested. This study is expected to be the first to demonstrate whether or not singlet oxygen is responsible for many of the changes in DOM bioavailability when it is exposed to sunlight. It will also produce some of the first measurements of singlet oxygen concentrations in large aquatic systems.In terms of broader impacts, it ic certain that microbes and photochemical processes play a central role in environmental biogeochemistry. The processes examined in this project will facilitate understanding of global dynamics such as the carbon cycle, nutrient limitation and eutrophication. This project will support a young investigator (McNeill) and is collaboration between an ecologist and a chemist. In addition, several activities in the proposed project will promote teaching and training goals including: training and education of undergraduate students and graduate students and K-12 teachers. The PIs will participate in summer undergraduate research programs directed toward minority students (through the College of Biological Sciences LSSURP Program). The PIs will also participate in a K-12 teacher-training program focused on freshwater ecology. Additionally, this project will link with the NSF-RSEC program at the University of Minnesota by fostering an existing collaboration between one of the investigators and a faculty member at a Principally Undergraduate Institution.

ABSTRACTOCE-0527196溶解有机物（DOM）是水生生态系统中最大的有机碳库，构成全球碳循环的重要环节。 尽管每年都有大量（约 2 x 1014 克）的陆源 DOM 流入海洋，但这种物质的积累很少，表明它正在迅速分解。 虽然光化学和生化降解这两种主要损失已经得到了充分研究，但很少有人研究造成降解和化学转化的机制，特别是在光化学过程方面。在这个研究项目中，明尼苏达大学双城分校的研究人员将调查活性氧 (ROS)、单线态氧 (1O2) 对天然水中有机物的化学成分、反应性和生物利用度的影响。 该项目将以苏必利尔湖为研究地点，目标是：（1）表征DOM暴露于1O2时化学和光学性质的变化； (2)测定DOM与1O2反应后的不稳定性和营养品质的变化； (3) 检查微生物对 1O2 反应性氨基酸（组氨酸、色氨酸、蛋氨酸、半胱氨酸和酪氨酸）及其 1O2 反应产物的差异利用，以及 (4) 量化苏必利尔湖中 1O2 的生产率。实现这些目标，来自两个来源（土壤和浮游植物）并沿着时空梯度（河流和近海）的 DOM 将受到多种处理包括阳光和明确的 1O2 源（存在或不存在猝灭剂）。 这项研究的特点是使用非光化学 1O2 源，这将能够检查 1O2 的影响，不受阳光的影响。 将通过生物测定和化学分析来观察对 DOM 的不稳定性和化学结构的影响。 将测试以下假设：由于 1O2 与 DOM 中存在的特定氨基酸发生反应，在氧化 DOM 存在的情况下观察到微生物生长效率降低。 这项研究预计将首次证明单线态氧是否会导致 DOM 暴露在阳光下时生物利用度的许多变化。 它还将首次测量大型水生系统中的单线态氧浓度。就更广泛的影响而言，可以肯定的是，微生物和光化学过程在环境生物地球化学中发挥着核心作用。 该项目研究的过程将有助于了解碳循环、营养限制和富营养化等全球动态。 该项目将支持一名年轻的调查员（麦克尼尔），并且是生态学家和化学家之间的合作。 此外，拟议项目中的几项活动将促进教学和培训目标，包括：本科生、研究生以及 K-12 教师的培训和教育。 PI 将参加针对少数族裔学生的夏季本科生研究项目（通过生物科学学院 LSSURP 项目）。 PI 还将参加以淡水生态学为重点的 K-12 教师培训计划。 此外，该项目将与明尼苏达大学的 NSF-RSEC 项目联系起来，促进一名研究人员与主要本科机构的一名教职人员之间的现有合作。