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

预测和管理水环境中颗粒物的迁移是处理饮用水和废水、监测沉积物运动、预测污染物迁移和了解全球海洋碳循环对气候变化的影响等战略的关键组成部分。水生环境中细胞外聚合物(EPS)的存在往往会影响颗粒的传输。EPS是由藻类和细菌大量分泌的生物聚合物，已知可以促进颗粒聚集并影响聚集体的物理性质。这个职业项目包括几个实验，以量化EPS对颗粒聚集体的影响。这项研究的结果将通过解释EPS如何影响聚集过程中颗粒对颗粒键的形成，通过展示EPS在定义聚集物理性质中所起的作用，以及通过跟踪这些性质最终如何控制湍流中聚集的破碎和沉淀，来改进对水环境中颗粒传输的预测。综合教育活动将促进本科生和研究生的职业发展机会，并向未被充分代表的高中生群体推广环境科学和工程。在该职业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如何形成包含自然产生的颗粒物、沉积物颗粒和微塑料污染物的聚集体。根据粘聚力特性、流体动力剪切中骨料变形的实验数据以及胶体凝胶和粘弹性液滴的基本原理，将建立一个理论框架来预测EPS骨料的变形能力。最后，三维流动实验将聚集体的凝聚力和变形能力与EPS在湍流中的破碎和沉降特性联系起来。这项研究产生的结果将填补EPS集合体聚集和破坏的几个知识空白，并改变水生EPS集合体的建模方式。这些结果将有助于理解聚集过程，这些过程对于量化海洋碳循环和完善人为污染物的环境协议至关重要。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，并为专注于工程环境研究的教师机会提供综合研究经验。该奖项反映了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。

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.