CAREER: Predicting Biofilm-Bound Sediment Dynamics Through Multiscale Experiments

泥沙输运是控制海岸和河流侵蚀的关键过程，每年花费美国数十亿美元。大多数自然沉积物，如泥和细沙，不可避免地含有微生物生物膜。生物膜已被证明可以改变沉积物迁移的阈值和速率达40倍。然而，预测泥沙输运方程，占生物膜的影响是缺乏的。建立这种预测方程的一个关键挑战是，宏观尺度（1 m）的沉积物输运受微观尺度（10^-6至10^-3 m）至中尺度（10^-3至10^-1 m）的生物膜控制。本研究旨在将联合收割机中尺度流动池和成像技术与大尺度水槽试验相结合，量化中尺度生物膜对大尺度泥沙输移的影响。将开发生物膜结合沉积物输运的预测方程。这项研究的结果将有助于改善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生物膜结合颗粒污染物的传播。此外，基于拟议研究的多规模实践教育活动将被开发并融入教学，辅导，K12教育和公共宣传。这些活动将向各种各样的年轻学习者，包括女性和美洲原住民学生介绍研究的本质。拟议研究的目标是：（1）量化沉积物粒径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-沉积物聚集体的宏观输运;（3）预测中尺度生物膜垫覆盖的沉积物推移质输运的开始。将在微流控流动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上微至中尺度生物膜的发展和生物膜沉积物聚集体的形成。水槽实验结合数字成像，拉伸试验，流变仪测量，水动力测量，地形测量将进行量化的影响，生物膜的形态和流变特性不同的宏观泥沙输运。从微流体和水槽实验的结果将被用来开发悬浮生物膜沉积物聚集体和生物膜垫覆盖bedload.This奖项反映了NSF的法定使命的运输预测方程，并已被认为是值得通过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的支持。

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.