Understanding interactions that determine the fate of microplastics in riverbed environments

微塑料（MP）是一种日益受到关注的新兴污染物，在淡水和海洋生态系统中无处不在。河流被认为是MP的基本运输途径;将陆地塑料源连接到海洋生态系统，以及可能发生高水平生物活动和修饰的区域。然而，很少有人考虑这些淡水生态系统中塑料的来源和命运。河流受到点源（即污水系统）和扩散源（即农业和城市径流）的塑料污染。预计河床沉积物可作为微塑料碎片的汇（1）。然而，河床与MP相互作用的程度及其截留率将受到许多物理，生物和化学因素的影响。微生物生物膜对塑料碎片的定殖研究表明，会导致浮力聚合物下沉（2，3）。同样，河床沉积物上的微生物生物膜也会影响MP的入渗和沉降速率。然而，这些过程的相对重要性在很大程度上仍然不清楚，迫切需要经验数据来参数化模型。在这个项目中，您将研究河床动力学和MP之间的相互作用和反馈。的主要目的是确定的关键变量，有助于截留和再悬浮的MP在这个淡水生态交错带。将使用我们新开发的方法来考虑和分析具有不同密度的不同类型的塑料颗粒，以使用基于荧光的技术和创新方法来跟踪MP在我们基于实验室的系统（4）中的运动。MP的释放速率和来源对于更全面地了解和评估这些污染物造成的危害至关重要。因此，该项目提供的新见解有可能直接促进与水管理和环境保护有关的新政策。方法学：我们将使用我们的新的围隔系统，调查和隔离不同的机制过程中，河床和MP之间的相互作用。我们将测试不同的塑料聚合物，具有一系列的密度和尺寸，跨越一系列具有独特特征（即孔径，生物膜涂层，床形形状）的河床系统。此外，我们将采用我们新开发的方法，并将MP结果与传统的监管批准的荧光溶质示踪技术进行比较。重要的是将我们的理解应用到现实世界的环境中。因此，我们还将使用当地的河流和伦敦各地的场地作为“活实验室”，从河床收集沉积物芯，并进行监管批准的跟踪测试。使用傅里叶变换红外显微光谱（FTIR）在沃林福德生态与水文中心（CEH），您将确定沉积物中MP的类型和分布，并将其与收集的环境/季节和生成的中生态系统数据相关联。

Microplastics (MPs) are an emerging contaminant of increasing concern that are ubiquitous within freshwater and marine ecosystems. Rivers are recognised as a fundamental transport pathway for MPs; connecting terrestrial plastic sources to marine ecosystems, as well as an area where high levels of biological activity and modification can occur. However, there is little consideration as to the sources and fate of plastics within these freshwater ecosystems. Rivers are subject to plastic pollution from both point (i.e. sewage systems) and diffuse (i.e. agricultural and urban runoff) sources. It is expected that riverbed sediments act as a sink for microplastic debris (1). However, the extent to which riverbeds interact with MPs and their entrapment rates will be governed by many physical, biological and chemical factors. Colonisation studies of plastic debris by microbial biofilms have shown to cause buoyant polymers to sink (2,3). Equally, microbial biofilms over riverbed sediment will influence MP infiltration and settling rates. Nevertheless, the relative importance of these processes remains largely unclear with empirical data urgently needed to parametrise models. In this project you will investigate the interactions and feedbacks between riverbed dynamics and MPs. The main aim will be to determine the key variables which contribute to the entrapment and resuspension of MPs within this freshwater ecotone. Different types of plastic particles with different densities will be considered and analysed using our newly developed method to track the movement of MPs within our laboratory-based system (4) using fluorescence-based technology and innovative methods. The release rate and sources of MPs is vital for a more complete understanding and assessment of the hazards posed by these contaminants. As such, the new insights offered by the project have the potential to contribute directly towards new policies relating to water management and environmental conservation. Methodology: We will use our novel mesocosm systems to investigate and isolate the different mechanistic processes governing the interaction between the riverbed and MPs. We will test different plastic polymers, with a range of densities and sizes, across a range of riverbed systems with unique characteristics (i.e. pore size, biofilm coated, bedform shape). In addition, we will adopt our newly developed method and baseline the MPs results against traditional regulatory approved fluorometric solute tracing techniques. It is important to apply our understanding to the real-world environment. As such, we will also use local rivers and sites across London as a 'living laboratory' to collect sediment cores from the river bed & perform regulatory approved tracing tests. Using FTIR (Fourier-transform infrared microspectroscopy) at the Centre for Ecology & Hydrology (CEH) in Wallingford, you will identify the types and distribution of MPs within sediments and relate this to the environment/season in which it was collected and mesocosm data generated.