A Targeted Approach to Delineating the Source(s) and Optical Properties of CDOM

描述 CDOM 来源和光学特性的有针对性的方法

• 批准号: 1924595
• 负责人: Neil Blough
• 金额: $ 23万
• 依托单位: University of Maryland, College Park
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-01-01 至 2023-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1924595&HistoricalAwards=false
• 关键词: Targeted; Approach; Delineating; Source; Optical

A Targeted Approach to Delineating the Source(s) and Optical Properties of Chromophoric Dissolved Organic MatterThe colored components of dissolved organic matter (DOM) absorb light to varying degrees in all natural waters. This material, known as colored or chromophoric dissolved organic matter (CDOM), plays an essential role in determining the color of natural waters and influences the amount of ultraviolet and visible light that penetrates into water bodies. Because CDOM absorbs strongly in the ultraviolet, it can protect aquatic organisms from damaging radiation, whereas its absorption in the visible can reduce the amount of light available for photosynthesis, thus potentially affecting aquatic ecosystems. The absorption of light by CDOM also initiates a series of photochemical reactions, which produce reactive oxygen species that can transform CDOM and other compounds, and affect the availability of essential trace metals to aquatic organisms. Despite its established importance in aquatic chemistry, the compounds and structures that give rise to light absorption and emission and produce the photochemical reactions are still poorly understood. This work will use a series of laboratory tests to identify chemical groups within the CDOM that influence its optical and photochemical properties and how these vary with source.These tests (and the information they can provide) include: 1) the effect of sodium borohydride reduction on the optical absorption and emission properties (contribution of ketones/aldehydes to optical properties); 2) pH dependence of the spectral absorption and emission before and after borohydride reduction (identify contributions of carboxylic acids and phenols and possible electronic interactions between these groups and ketones/aldehydes); 3) the effect of anoxic dithionite reduction on the optical properties (content and impact of quinones to optical properties); 4) molecular size dependence of the optical properties of CDOM from differing sources/locales and how this may be affected by borohydride reduction and pH. This work will focus on laboratory studies of humic substances and of archived samples of CDOM acquired in past field work from diverse oceanic and freshwaters sites, but will be augmented by samples collected from the Chesapeake Bay through a complementary collaboration with a NASA project that aims to examine water quality in shellfish beds through direct sampling and optical remote sensing.This proposal will further support plans to initiate a program for talented and gifted students at Kenmoor Middle School in the Prince George’s County Public Schools in Maryland. Plans for this program include presentations/demonstrations to the students and faculty at the middle school that are related to the goals of this project, followed by a visit of an interested, select group of students to the PI’s laboratory where they will be allowed to see and operate some of the scientific instruments employed in this project and be involved in additional hands-on demonstrations.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

色相溶解有机物的来源和光学性质的定位方法在所有天然水体中，色相溶解有机物（DOM）都不同程度地吸收光。这种物质被称为有色或显色性溶解有机物（CDOM），它在决定天然水体的颜色方面起着至关重要的作用，并影响渗透到水体中的紫外线和可见光的数量。由于CDOM强烈吸收紫外线，它可以保护水生生物免受有害辐射，而它在可见光中的吸收会减少光合作用可用的光量，从而潜在地影响水生生态系统。CDOM对光的吸收还引发一系列光化学反应，产生活性氧，使CDOM等化合物转化，影响水生生物必需微量金属的可得性。尽管它在水生化学中具有重要意义，但引起光吸收和发射并产生光化学反应的化合物和结构仍然知之甚少。这项工作将使用一系列实验室测试来确定CDOM中影响其光学和光化学性质的化学基团，以及这些基团如何随来源而变化。这些测试（以及它们可以提供的信息）包括：1)硼氢化钠还原对光学吸收和发射特性的影响（酮类/醛类对光学特性的贡献）；2)硼氢化物还原前后光谱吸收和发射的pH依赖性（确定羧酸和酚的贡献以及这些基团与酮/醛之间可能的电子相互作用）；3)缺氧二亚硝酸盐还原对光学性能的影响（醌类的含量及对光学性能的影响）；4)来自不同来源/地点的CDOM光学性质的分子大小依赖性，以及它如何受到硼氢化物还原和ph值的影响。这项工作将侧重于腐殖质物质的实验室研究，以及过去从不同海洋和淡水地点实地工作中获得的CDOM存档样本。但通过与美国宇航局的一个项目的补充合作，从切萨皮克湾收集的样本将得到加强，该项目旨在通过直接采样和光学遥感来检查贝类床的水质。这项提案将进一步支持在马里兰州乔治王子县公立学校的肯摩尔中学为有才能和有天赋的学生启动一个项目的计划。这个项目的计划包括向中学的学生和教师介绍/演示与这个项目的目标相关的内容，然后选择一组感兴趣的学生参观PI的实验室，在那里他们将被允许看到和操作这个项目中使用的一些科学仪器，并参与额外的实际演示。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。