CAREER: Predicting Biofilm-Bound Sediment Dynamics Through Multiscale Experiments

泥沙输送是控制海岸和河流侵蚀的关键过程，每年给美国造成数十亿美元的损失。大多数自然沉积物，如泥沙和细沙，不可避免地含有微生物生物膜。已经证明，生物膜可以将泥沙输送的门槛和速率改变多达40倍。然而，目前还缺乏能够解释生物膜影响的沉积物迁移预测方程。建立这种预测方程的一个关键挑战是，泥沙在宏观尺度(1m)的输移是由微尺度(10^-6到10^-3m)到中尺度(10^-3到10^-1m)的生物膜控制的。本研究旨在将微中尺度流体池和成像技术与大尺度水槽实验相结合，量化微中尺度生物膜对大尺度泥沙运动的影响。将开发生物膜结合泥沙运移的预测方程。这项研究的结果将有助于改进对沿海和河流侵蚀的预测，这将指导未来的沿海和河流恢复项目，并支持更好地预测和控制与生物膜结合的颗粒污染物的传播。此外，还将开展以拟议研究为基础的多规模实践教育活动，并将其纳入教学、辅导、K12教育和公共宣传。这些活动将向不同范围的年轻学习者介绍研究的精髓，包括女性和美洲原住民学生。拟议研究的目标是(1)量化沉积物尺寸和水动力条件对沉积物表面微-中尺度生物膜特性的影响；(2)预测悬浮微尺度生物膜-沉积物集合体的宏观输运；(3)预测覆盖中尺度生物膜垫的沉积物的推移质输运开始。将在微流体池中进行亚微米分辨率共聚焦显微成像的系统控制实验，以可视化和量化沉积物表面微到中尺度生物膜的发展和生物膜-沉积物聚集体的形成。水槽实验将结合数字成像、拉伸试验、流变仪测量、水动力测量和地形测量，以量化不同形态和流变性的生物膜对大尺度泥沙运动的影响。微流控和水槽实验的结果将被用来建立悬浮生物膜-沉积物集合体和生物膜覆盖的推移负荷的预测方程。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Sediment transport is a key process controlling coastal and riverine erosion, which costs the U.S. billions of dollars per year. Most natural sediment, such as mud and fine sand, inevitably harbors microbial biofilms. Biofilms have been shown to alter the threshold and rate of sediment transport by up to 40-fold. However, predictive sediment transport equations that account for the impacts of biofilms are lacking. A key challenge in developing such predictive equations is that the transport of sediment at macroscale ( 1 m) is controlled by biofilms at micro (10^-6 to 10^-3 m) to mesoscale (10^-3 to 10^-1 m). This study aims to combine micro- to mesoscale flow-cell and imaging technology with macroscale flume experiments to quantify the impacts of micro- to mesoscale biofilms on macroscale sediment transport. Predictive equations for biofilm-bound sediment transport will be developed. The results of this study will help improve predictions of coastal and riverine erosion, which will guide future coastal and riverine restoration projects, and support better predictions and control of the spread of biofilm-bound particulate contaminants. In addition, multiscale hands-on educational activities based on the proposed research will be developed and integrated into teaching, mentoring, K12 education, and public outreach. These activities will introduce the essence of the research to a diverse range of young learners, including female and Native American students. The goal of the proposed research is to (1) quantify the impacts of sediment size and hydrodynamic conditions on the properties of micro- to mesoscale biofilms on sediment surfaces; (2) predict the macroscale transport of suspended microscale biofilm-sediment aggregates; (3) predict the onset of bedload transport for sediment covered with mesoscale biofilm mats. Systematically controlled experiments with submicron resolution confocal microscopic imaging will be conducted in microfluidic flow cells to visualize and quantify the development of micro- to mesoscale biofilms on sediment surfaces and the formation of biofilm-sediment aggregates. Flume experiments combined with digital imaging, tensile tests, rheometer measurements, hydrodynamic measurements, and topographic measurements will be conducted to quantify the impacts of biofilms with varying morphological and rheological properties on macroscale sediment transport. The results from both microfluidic and flume experiments will be used to develop predictive equations for the transport of suspended biofilm-sediment aggregates and biofilm mat-covered bedload.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.