Collaborative Research: Freshwater flocculation and its impact on sustaining floodplains and deltaic wetlands

合作研究：淡水絮凝及其对维持洪泛区和三角洲湿地的影响

• 批准号: 2136991
• 负责人: Michael Lamb
• 金额: $ 42.11万
• 依托单位: California Institute of Technology
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-06-01 至 2025-05-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2136991&HistoricalAwards=false
• 关键词: Collaborative; Research; Freshwater; flocculation; its

Most sediment transported from continents to the oceans is mud that consists of very fine-grained particles. The fate of muddy sediment is important in many ways. Mud transport governs the fate of riverine pollutants, heavy metals and organic carbon; mud also is a key resource that can restore coastal areas and make flat, low-lying landscapes habitable. Growing evidence indicates that mud and organic matter in rivers are often bound together into large aggregates through a process called flocculation. This project will develop a predictive mathematical model for the transport of flocculated mud in rivers and apply the model to real-world coastal restoration problems in the Mississippi Delta wetlands. The project brings together a team from the California Institute of Technology (Caltech), the University of New Orleans (UNO), and the Water Institute of the Gulf, to solve environmental and societal challenges in the Gulf of Mexico region. The results will be shared with scientists in the Gulf Region from local, state, and federal agencies, academia, and environmental NGOs to influence coastal wetlands management decisions in the Mississippi Delta. The project will engage students from the University of New Orleans, who are directly affected by Mississippi Delta land loss, in a summer research program at Caltech.Compared to sand, far less is known about the basic mechanics of mud transport and deposition in river systems. This is a major knowledge gap because mud adsorbs pollutants, nutrients and organic carbon, and the fate of this material directly impacts environmental quality and the global carbon cycle. Mud also is the primary building block of terrestrial and coastal landscapes: it builds floodplains, coastal wetlands and deltas, affects bank erosion rates and levee stability, and sets the depositional architecture of fluvial strata. In rivers, mud is typically considered as “washload,” particles with settling velocities so small that they act as passive water tracers. However, growing evidence indicates that mud and organic matter in fluvial systems are often flocculated together into aggregates with settling velocities equivalent to sand. This project will develop a mechanistic model for freshwater flocculation using theory and semi-empirical relations from new flume experiments. A database of floc settling velocities from rivers will be compiled by inversion from concentration-depth profiles, to test the freshwater floc model using field data. The mud transport theory will be integrated into numerical models used for wetland restoration in the Mississippi Delta. A series of numerical experiments will evaluate the impact of flocculation on wetland accretion rates for engineered diversions that are needed to rebuild sinking wetlands.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.

从大陆到海洋的大多数沉积物都是由非常细粒的颗粒组成的泥浆，泥浆的运输在很多方面都决定着河流污染物、重金属和有机碳的命运。越来越多的证据表明，河流中的泥浆和有机物经常通过一种称为絮凝的过程结合在一起形成大的聚集体。该项目汇集了来自加州理工学院 (Caltech)、新奥尔良大学 (UNO) 和海湾水研究所，旨在解决墨西哥湾地区的环境和社会挑战。研究结果将与来自当地、州和联邦机构、学术界和环境非政府组织的科学家分享，以影响沿海湿地管理。密西西比三角洲的决定。该项目将让新奥尔良大学的学生参与加州理工学院的夏季研究项目，这些学生直接受到密西西比三角洲土地流失的影响。与沙子相比，人们对河流系统中泥浆输送和沉积的基本机制知之甚少。这是一个重大的知识差距，因为泥浆会吸收污染物、营养物和有机碳，并且这种材料的命运直接影响环境质量和全球碳循环，泥浆也是陆地和沿海景观的主要组成部分：它建造了洪泛区，沿海湿地和三角洲，影响河岸侵蚀率和堤坝稳定性，并决定河流地层的沉积结构，在河流中，泥浆通常被认为是“冲刷物”，其沉降速度如此之小，以至于可以充当被动水示踪剂。表明河流系统中的泥浆和有机物经常絮凝成聚集体，其沉降速度相当于沙子。该项目将利用理论和半经验开发淡水絮凝的机械模型。将通过浓度-深度剖面反演来编制河流絮凝体沉降速度的关系，以利用现场数据测试淡水絮凝体模型，并将泥浆输送理论整合到用于湿地恢复的数值模型中。密西西比三角洲的一系列数值实验将评估絮凝对重建下沉湿地所需的工程改道的湿地增生率的影响。该奖项是 NSF 的法定使命，并被认为值得通过以下方式获得支持：使用基金会的智力价值和更广泛的影响审查标准进行评估。

项目成果

A Mechanistic Model for Mud Flocculation in Freshwater Rivers

淡水河流泥浆絮凝机理模型

• DOI: 10.1029/2021jf006392
• 发表时间: 2022-05-01
• 期刊: Journal of Geophysical Research: Earth Surface
• 作者: J. Nghiem;W. Fischer;Gen K. Li;M. Lamb
• 通讯作者: M. Lamb