The behaviour of polymer colloids in freshwater flow environment

对环境（水、土壤、生物）中微塑料存在的监测已经取得了相当大的进展，有大量优秀的举措。最近的一个例子是，加州水资源控制委员会已经批准了测试饮用水的程序。塑料颗粒的存在可以进入所有生物的食物链，并可能产生负面影响。在这个项目中，我们将研究直径在20纳米- 5微米范围内的颗粒，因此比5毫米的上限要小得多，换句话说，重点是亚微米范围内的塑料纳米颗粒。在自然界中，它们以天然聚合物乳胶的形式存在（橡胶树、蒲公英）。自20世纪30年代以来，以聚合物分散体形式的人造聚合物纳米颗粒被大量生产，用于涂料/粘合剂、纸张生产、医疗诊断测试等。这些通常太小，无法用明光显微镜跟踪。我们的目标是制造一组模型聚合物分散体，其中颗粒在大小，形状，分子量和化学成分以及胶体稳定性方面具有不同的特征。第二个重点是制造不易降解的颗粒，以及可堆肥/可水解的颗粒。为此，我们将采用最新的聚合物分散体生产技术，如（微）乳液聚合和突变相反转乳化来制备人造乳胶。然后，我们将研究控制颗粒运动行为（流动流体动力学、分散和扩散）、停留和积累行为（粘附、拥挤、凝固、成膜、解体/分解）的潜在物理机制，包括滞池、河流和湿地等模型水生系统。该项目将首次更好地了解这些小颗粒如何在水生区域内表现，它们将驻留在哪里，以及它们如何可能被降解为无害的取代基。该项目提供的新见解将有助于理解微和纳米塑料在具有挑战性的湍流系统中的运输和命运动力学。因此，该项目将通过了解和量化塑料纳米颗粒的运输和命运，为环境保护和综合流域管理提供一个步骤。该项目将结合非均相聚合物化学、胶体科学和流体动力学。聚合物纳米塑料将通过非均相自由基聚合技术制备，其中（微）乳液聚合与可逆失活自由基聚合相结合，以调整摩尔质量分布，化学成分，胶体稳定性以及颗粒形状和结构。将通过暗场和荧光显微镜（Cyclops传感器）、拉曼光谱、离线分析方法（如流体动力分选）和元素分析技术（原子吸收、XRF、ICP-MS）的结合，开发水和模型土壤中颗粒的跟踪方法。将使用开源计算流体动力学建模包（OpenFOAM）研究不同水生流域的粒子运动行为的模型开发。将在本项目中开发的算法将与现有的多相流模型相结合，以模拟各种水文条件下的污染物输送。粒子降解将通过动力学建模（ode和蒙特卡罗方法）进行研究。

The monitoring of the presence of microplastics in the environment (water, soil, organisms) has gained considerable traction, with a plethora of excellent initiatives. A recent example is that Californian state water resources control board has approved procedures for testing drinking water. The presence of plastic particles can enter the food chain for all living species, and potentially have a negative impact. In this project we will look at particles in the diameter range of 20 nm - 5 micrometer, so considerably smaller than the 5 mm upper threshold, in other words a focus on the sub-micron range, plastic nanoparticles. In nature these exist in the form of a natural polymer latex (rubber trees, dandelions). Manmade polymer nanoparticles, in the form of polymer dispersions are produced in vast quantities since the 1930s for coatings/adhesives, paper production, medical diagnostic tests, to name but a few. These are often too small to be tracked with brightfield light microscopy.We aim to fabricate a collection of model polymer dispersions in which the particles have varied characteristics in size, shape, molecular weight and chemical composition, and colloidal stability. A secondary focus is to make particles that will not degrade easily, and particles that are compostable/hydrolysable. For this we will use the latest polymer dispersion production techniques, such as (mini-) emulsion polymerization, and catastrophic phase inversion emulsification to prepare artificial latexes. We then will study the underlying physical mechanisms that govern the particles' motility behavior (flow hydrodynamics, dispersion and diffusion), residence and accumulation behavior (adhesion, crowding, coagulation, film formation, disintegration/decomposition) in model aquatic systems including stagnant pond, river, and wetland. This project, for the first time, will provide a better understanding of how such small particles will behave across aquatic domains, where they will reside, and how they potentially can be degraded into harmless substituents. The new insights offered by this project will enable understanding the dynamics of micro- and nanoplastics transport and fate in challenging turbulent flow systems. Hence, this project will provide a step change in environmental protection and integrated catchment management by understanding and quantifying the transport and fate of plastic nanoparticles.The project will combine heterogeneous polymer chemistry, colloid science, and fluid dynamics. Polymer nanoplastics will be prepared by heterogeneous radical polymerization techniques, where (mini-) emulsion polymerization is combined with reversible deactivation radical polymerization developments, to tune molar mass distribution, chemical composition, colloidal stability, and particle shape and architecture. Tracking methods of the particles in water and model soils will be developed through combination of darkfield and fluorescence microscopy (Cyclops sensors), Raman spectroscopy, and off-line analysis methods, such as hydrodynamic fractionation, and elemental analysis techniques (atomic absorption, XRF, ICP-MS). Model development of particle motility behavior across different aquatic flow domains will be studied using open-source computational fluid dynamic modelling packages (OpenFOAM). The algorithms which will be developed within this project will be coupled with existing multi-phase flow models in order to simulate pollutant transport under various hydrologic conditions. Particle degradation will be studied by kinetic modelling (ODEs and Monte Carlo approaches).