CAREER: Particle dynamics at the free surface: waves, turbulence, and microplastics

塑料污染是一个无处不在的问题，影响着全球海洋生态系统的健康。然而，塑料一旦进入海洋，围绕其命运和运输的关键知识缺口阻碍了补救和预防工作。预测海洋中任何颗粒的迁移都很困难，但微塑料带来了特别的挑战，因为它们的大小和密度不在传统研究的环境颗粒的范围内，如低密度气泡和高密度沉积物。因此，该奖项的目标是(1)观察在受控实验室环境中重建的真实海洋流动中的塑料颗粒，以及(2)利用观察结果建立一个描述塑料在海洋表面垂直混合和运输的模型框架。通过研究颗粒和海洋流动之间的基本相互作用，该奖项将能够更准确地模拟海洋表面的浮力颗粒。调查员将与当地海滩清理组织合作，通过外联活动分享这项工作。该奖项还将支持本科生和研究生的教育活动。海洋表面边界层是由上覆风强迫的多相流动，产生波浪和湍流。这些过程影响物质的运输和混合，从营养物质和污染物到气泡和有机体。微塑料是一种新的环境颗粒，在海洋表面的浓度正在增加；然而，预测微塑料的行为并不容易，因为它依赖于人们很少了解的海洋表面边界层(大多数微塑料居住的地方)中波浪、湍流和颗粒惯性之间的相互作用。为了帮助弥合颗粒流动的这一基础知识空白，并改进微塑料传输模型，该奖项旨在描述浮力颗粒的上升速度如何受波浪和湍流的综合影响、颗粒被带到表面下的过程以及在波浪和湍流中对颗粒扩散率的控制。这项研究将在一个既能产生风又能产生海浪的实验室设施中进行。先进的光学技术将被用来在一系列表面条件下跟踪表面和下面的颗粒，包括破碎波。这些观察结果将被用来开发自由表面边界层中浮力颗粒的传输和混合的波浪相分辨模型，该模型将广泛适用于微塑料和海面上发现的其他颗粒。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。

Plastic pollution is a ubiquitous issue impacting the health of marine ecosystems worldwide. Yet, critical knowledge gaps surrounding the fate and transport of plastic once it enters the ocean impede remediation and prevention efforts. Predicting transport is difficult for any particle in the ocean, but microplastics present a particular challenge because their size and density fall outside the regimes of traditionally studied environmental particles such as low-density bubbles and high-density sediment. Thus, the goal of this award is to (1) observe plastic particles in realistic ocean flows recreated in a controlled laboratory setting, and (2) use the observations to build a modelling framework that describes the vertical mixing and transport of plastic at the ocean surface. By examining fundamental interactions between particles and ocean flows, this award will enable more accurate modelling of buoyant particles at the ocean surface. The investigator will partner with local beach-cleanup organizations to share this work through outreach events. This award will additionally support educational activities for both undergraduate and graduate students.The ocean surface boundary layer is a multiphase flow forced by the overlying wind, which generates waves and turbulence. These processes affect the transport and mixing of materials ranging from nutrients and pollutants to bubbles and organisms. Microplastics are a new environmental particle that is increasing in concentration at the ocean surface; yet, predicting the behavior of microplastics is non-trivial because it depends on poorly understood interactions among waves, turbulence, and particle inertia in the ocean surface boundary layer (where most microplastics reside). To help close this foundational knowledge gap in particle-laden flows and improve microplastics transport modeling, this award seeks to describe how the rise velocity of buoyant particles is modulated by the combined effects of waves and turbulence, the processes by which particles are entrained beneath the surface, and the controls on particle diffusivity in waves and turbulence. The research will be conducted in a laboratory facility that can generate both wind and waves. Advanced optical techniques will be used to track particles both at the surface and beneath it under a range of surface conditions, including breaking waves. These observations will be used to develop a wave phase-resolved model for the transport and mixing of buoyant particles in a free-surface boundary layer, a model which will be broadly applicable to microplastics, and other particles found at the ocean surface.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.