Transport and Fate of Microplastics in Freshwater Sediments

微塑料（尺寸小于5毫米）已成为新兴污染物，研究表明它们对公众健康和环境产生有害影响。虽然对海洋环境中的微塑料进行了大量研究，但淡水和淡水沉积物尚未进行如此详细的研究。然而，在世界各地的淡水水体中都发现了微塑料。作为宏观塑料降解的初级颗粒或次级产物，它们可直接引起毒性，或作为吸附污染物的载体。最近的研究表明，微塑料可以进入我们的食物链，并且在微塑料运输过程中，双酚A （BPA）和壬基酚（NP）等内分泌干扰添加剂可以渗入淡水资源。因此，河床沉积物可能是微塑料积聚的潜在热点。该项目的总体研究目的是研究淡水和淡水沉积物中微塑料的运输和积累。本项目旨在回答以下两个基本问题：(i)哪些过程控制不同形状、密度或成分的微塑料的运输和积累，以及潜在的微塑料热点如何在淡水-沉积物界面形成？（ii）：在可变的水动力、生物地球化学和沉积物条件下，如何描述和预测微塑料的运输和积累以及微塑料中添加剂（如双酚a、NP）的释放？为了回答这些问题，提出了以下两个工作包（WP）：WP1将侧重于揭示性质（大小，形状，组成，密度浮力）依赖于微塑料运输的机制，系统研究不同类型的微塑料如何以及在不同的水动力，河床形态和沉积条件下在淡水-沉积物界面积聚。为此，将进行人工河槽实验，模拟不同泥沙、河床形态和水动力条件下具有代表性的初级和次级微塑料的运输和积累。将使用具有代表性河床地形的水槽，并在实验期间研究添加剂的释放。微塑料将使用诸如单颗粒ICP-MS来确定微塑料粒度或FT-IR来确定微塑料聚合物的类型等技术进行表征。在实验过程中，监测水槽沉积物和生物膜中的生物地球化学状况，以及淡水和孔隙水中BPA和NP的浓度，分析形成的富集热点的反应性。WP2将专注于建立和实施一个建模工具，以预测微塑料的命运、运输和添加剂在淡水-沉积物界面的释放。为了克服现有模型的局限性，我们将探索晶格-玻尔兹曼方法作为一种新的建模方法。

Microplastics (<5 mm in size) have become emerging pollutants and research has shown their detrimental effects to public health and the environment. While considerable research exists on microplastics in the marine environment, freshwater and freshwater sediments have not yet been studied with such detail. However, microplastics have been detected in freshwater bodies around the world. As primary particles or secondary products of macroplastics degradation they can cause toxicity directly, or by acting as vectors for sorbed contaminants. Recent studies suggest that microplastics can enter our food chain and that endocrine disrupting additives, such as Bisphenol A (BPA) and Nonylphenol (NP) can leach into freshwater resources during microplastics transport. Hereby, streambed sediments may represent potential hotspots for microplastics accumulation. The overall research aim of this project is to study the transport and accumulation of microplastics in freshwater and freshwater sediments.This project aims to answer the following two fundamental questions:(i) Which processes control the transport and accumulation of microplastics of different shapes, densities or composition and how do potential microplastics hotspots form at the freshwater-sediment interface?(ii): How can transport and accumulation of microplastics as well as the release of additives (such as BPA, NP) from microplastics be described and predicted under variable hydrodynamic, biogeochemical and sediment conditions?To answer these questions the following two work packages (WP) are proposed:WP1 will focus on uncovering the mechanisms of property (size, shape, composition, density buoyancy) dependent microplastics transport, to systematically study how and where different types of microplastics can accumulate at freshwater-sediment interfaces, with respect to varying hydrodynamic, streambed morphological and sediment conditions. For that, artificial river flume experiments will be conducted to simulate transport and accumulation of a representative range of primary and secondary microplastics for variable sediment, streambed morphological and hydrodynamic conditions. Flumes with representative streambed topographies will be used and additive release will be investigated during the experiments. Microplastics will be characterized using techniques such as single particle ICP-MS to determine the microplastics particle size or FT-IR to determine the type of microplastics polymer. During experiments, biogeochemical conditions in the flume sediments and biofilms as well as concentrations of BPA and NP in freshwater and pore water will be monitored to analyze the reactivity of formed accumulation hotspots.WP2 will focus on building and implementing a modeling tool to predict microplastics fate and transport and additive release at the freshwater-sediment interface. To overcome limitations of current models, the Lattice-Boltzmann method will be explored as a new modeling approach.