CAREER: The Impact of Extracellular Polymeric Substances on Particle Transport in Aquatic Environments

预测和管理水生环境中颗粒的运输是处理饮用水和废水、监测沉积物运动、预测污染物运输以及了解全球海洋碳循环对气候变化的影响的战略的关键组成部分。在水生环境中，颗粒的运输经常受到细胞外聚合物质（EPS）存在的影响。EPS是藻类和细菌大量分泌的生物聚合物，已知可促进颗粒聚集并影响聚集体的物理性质。这个CAREER项目包括几个实验来量化EPS对颗粒聚集体的影响。研究结果将通过解释EPS在聚集过程中如何影响颗粒对颗粒键的形成，通过展示EPS在定义聚集体物理特性中的作用，以及通过跟踪这些特性最终如何控制聚集体在湍流中破碎和沉降，来改善水生环境中颗粒运输的预测。综合教育活动将为本科生和研究生提供加强职业发展的机会，并向代表性不足的高中学生群体推广环境科学和工程。在CAREER奖下进行的实验将测量来自水生藻类和细菌的EPS的化学组成、表面能和相互作用能，以确定EPS如何形成聚集体，包括自然发生的颗粒物、沉积物颗粒和微塑料污染物。本文将根据聚苯乙烯聚集体的黏聚特性、流体动力剪切作用下聚集体变形的实验数据以及胶凝胶和粘弹性液滴的基本原理，建立预测聚苯乙烯聚集体变形能力的理论框架。最后，三维流动实验将把聚集体的内聚力和变形能力与EPS在湍流中的破碎和沉降特性联系起来。本研究的结果将填补EPS聚集体聚集和破坏的几个知识空白，并改变水生EPS聚集体的建模方式。研究结果将有助于理解对量化海洋碳循环和完善人为污染物环境协议至关重要的聚集过程。该项目将为不同的本科生和研究生提供合作的职业发展机会，并为教师提供专注于工程环境研究的综合研究经验机会。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。

Predicting and managing the transport of particles in aquatic environments are critical components of strategies to treat drinking and wastewater, to monitor sediment movement, to predict pollutant transport, and to understand effects of the global ocean carbon cycle on climate change. The transport of particles is often affected by the presence of extracellular polymeric substances (EPS) in aquatic environments. EPS are biopolymers that are secreted in high quantities from algae and bacteria and are known to promote aggregation of particles and influence the physical properties of the aggregates. This CAREER project comprises several experiments to quantify the influence of EPS on particle aggregates. The results of the research will improve predictions of particle transport through aquatic environments by explaining how EPS influence the formation of particle-to-particle bonds during aggregation, by demonstrating the roles EPS play in defining aggregate physical properties, and by tracking how these properties ultimately govern aggregate breakup and settling in turbulent fluid flows. Integrated educational activities will advance career-strengthening opportunities for undergraduate and graduate students as well as promote environmental science and engineering to underrepresented high school student groups.Experiments conducted under this CAREER award will measure the chemical makeup, surface energy, and interaction energy of EPS from aquatic algae and bacteria to determine how EPS form aggregates that incorporate naturally occurring particulate matter, sediment particles, and microplastic pollutants. A theoretical framework will be formulated to predict the deformability of EPS aggregates based on cohesion properties, experimental data for aggregate deformation in hydrodynamic shear, and fundamental principles for colloidal gels and viscoelastic droplets. Finally, three-dimensional flow experiments will link aggregate cohesion and deformability to breakup and settling characteristics of EPS in turbulence. The results generated in this research will fill several knowledge gaps for aggregation and disruption of EPS aggregates and transform the way aquatic EPS aggregates are modeled. The results will help understand aggregation processes that are crucial to quantifying the ocean carbon cycle and refining environmental protocols for anthropogenic pollutants. The project will provide collaborative career-development opportunities for diverse undergraduate and graduate students and an integrated Research Experience for a Teacher opportunity that focuses on environmental research in engineering.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.