Collaborative Research: Inferring Marine Particle Properties from Polarized Volume Scattering Functions

合作研究：从偏振体散射函数推断海洋颗粒特性

• 批准号: 1917337
• 负责人: Xiaodong Zhang
• 金额: $ 25.59万
• 依托单位: University of Southern Mississippi
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2018
• 资助国家: 美国
• 起止时间: 2018-12-20 至 2021-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1917337&HistoricalAwards=false
• 关键词: Collaborative; Research; Inferring; Marine; Particle

Understanding biogeochemical cycles and their interaction with the climate system requires quantifying the various forms of materials in the global ocean. In particular, the chemical composition and size distribution of living and non-living particles in the ocean have an enormous impact on marine ecosystems, including the dynamics of marine food chains, the vertical transmission of solar energy, and the transport of organic matter and trace elements. These particle characteristics not only affect but reflect changes in many biogeochemical processes in the ocean. In this project, a team of scientists will launch a set of technical and numerical modeling innovations that will allow them to determine key biogeochemical quantities from optical observations of the angular distribution of scattered light. The project will involve an interdisciplinary team of experts, who will theoretically model the optics of marine particles, develop an innovative advanced mathematical modeling scheme, and then laboratory- and field-test and validate the approach for observing marine particle properties. When perfected, the technique should see a broader application, as it will be designed to be amenable to operation on ship-borne and autonomous platforms with the potential to provide estimates of the particle size distribution and composition at high temporal and spatial resolutions. It should thus benefit different fields requiring detailed knowledge of aquatic particles (biogeochemistry, biology, optics). The project will also provide for the training and support of graduate and undergraduate students as well as public educational outreach, including a special effort to reach Native Americans in North Dakota.The goal of this project is to derive water-column quantitative particle size and composition information from in situ unobtrusive volume scattering function (VSF) measurements to characterize marine biogeochemical particulate stocks. The angular patterns of the scattered intensity and polarization state of the scattered light by particles can be described in terms of a 4x4 Mueller matrix (S) that is intrinsically determined by the sizes, shapes, composition, and structures of the particles. The particle properties can be, therefore, potentially inferred from measurements of S. Unfortunately, the complete Mueller matrix of oceanic waters has been seldom measured. Even the most commonly measured component, the volume scattering function (element S11) representing the angular distribution of unpolarized light, was scarcely measured until recently, followed by development of an inversion technique to derive size distributions and composition of particles from the VSF. Recently, a commercial product, LISST-VSF, became available for measuring the Mueller matrix components S11 (VSF), S12 (linear polarization), and S22 (cross-polarization), potentially providing an avenue to obtain a much more detailed characterization of particles. This project will incorporate the additional information provided by S12 and S22 using recent advances in scattering modeling to further constrain the inversion with the following: (i) better knowledge in particle shapes using S22 (spherical vs. non-spherical); (ii) reduced uncertainty using both S11 and S12; and (iii) further improved capability to characterize particles in the size range of 0.02 to 200 um. The study should greatly enhance our ability to quantify size distributions and refractive indices (closely linked to particle densities) for particle groups such as phytoplankton cells, detrital particles, organic particles, mineral particles, bubbles, and emulsified oil (if present).

了解生物地球化学循环及其与气候系统的相互作用需要量化全球海洋中各种形式的物质。 特别是海洋中生物和非生物颗粒的化学成分和尺寸分布对海洋生态系统产生巨大影响，包括海洋食物链的动态、太阳能的垂直传输以及有机物和微量元素的运输。元素。 这些颗粒特征不仅影响而且反映了海洋中许多生物地球化学过程的变化。 在该项目中，一组科学家将推出一系列技术和数值建模创新，使他们能够通过对散射光角分布的光学观察来确定关键的生物地球化学量。 该项目将涉及一个跨学科的专家团队，他们将从理论上对海洋颗粒的光学进行建模，开发创新的高级数学建模方案，然后在实验室和现场测试并验证观察海洋颗粒特性的方法。一旦完善，该技术应该会得到更广泛的应用，因为它将被设计为适合在船载和自主平台上运行，并有可能以高时间和空间分辨率提供颗粒尺寸分布和成分的估计。 因此，它应该有益于需要详细了解水生颗粒知识的不同领域（生物地球化学、生物学、光学）。 该项目还将为研究生和本科生提供培训和支持，以及公共教育推广，包括为北达科他州的美洲原住民做出特别努力。该项目的目标是获得水柱定量颗粒尺寸和成分来自原位不引人注目的体积散射函数 (VSF) 测量的信息，用于表征海洋生物地球化学颗粒库存。 颗粒散射光的散射强度和偏振态的角度模式可以用 4x4 穆勒矩阵 (S) 来描述，该矩阵本质上由颗粒的尺寸、形状、组成和结构决定。因此，可以通过 S 的测量来推断颗粒特性。不幸的是，很少测量完整的海水穆勒矩阵。即使是最常测量的成分，即表示非偏振光角分布的体积散射函数（元素 S11），直到最近才进行测量，随后开发了一种反演技术，可以从 VSF 中得出颗粒的尺寸分布和成分。 最近，一种商业产品 LISST-VSF 可用于测量 Mueller 矩阵分量 S11 (VSF)、S12（线性偏振）和 S22（交叉偏振），这可能提供一种获得更详细的颗粒表征的途径。 该项目将结合 S12 和 S22 提供的附加信息，利用散射建模的最新进展，通过以下内容进一步约束反演：(i) 使用 S22 更好地了解颗粒形状（球形与非球形）； (ii) 使用 S11 和 S12 减少不确定性； (iii) 进一步提高表征 0.02 至 200 微米尺寸范围内颗粒的能力。这项研究将大大增强我们量化浮游植物细胞、碎屑颗粒、有机颗粒、矿物颗粒、气泡和乳化油（如果存在）等颗粒群的尺寸分布和折射率（与颗粒密度密切相关）的能力。