Postdoctoral Fellowship: OCE-PRF: Influence of Environmentally-Induced Changes on the Transport and Fate of Microplastics at a Regional Scale

由于环境条件的风化作用，海洋中的塑料会分解成被称为微塑料的小块。微塑料越来越普遍，危害着沿海地区的生态健康，因此了解它们在哪里以及它们是如何被沿海水流输送的非常重要。由于微塑料暴露在不同的环境条件下（例如，光、氧和沉积物磨损），它们会破碎成更小的碎片，并促进有机物的生长。这些变化会影响微塑料在水柱中悬浮的容易程度。然而，目前尚不清楚这些转变如何影响区域尺度上的微塑料运输。该项目将调查何时、何地以及有多少微塑料暴露在导致其密度、大小和形状变化的条件下。此外，该项目将量化暴露在不同环境条件下如何影响区域范围内微塑料的分散和命运。该项目将增加对微塑料运输的了解，这将有助于为政策决策和清理工作提供信息。在项目过程中，PI还将参与到当地学校和大学生的辅导中。该项目的目的是更好地了解微塑性转化如何影响其在区域尺度上的运输。首先，PI将使用代表微塑料的拉格朗日示踪剂和现有模型输出来量化微塑料暴露于导致风化或生物污染的条件下。具体来说，利用现有的墨西哥湾北部水动力-沉积物运输-生物地球化学模型的输出，将用于估计微塑料暴露于光、沉积物磨损和其他环境条件下的情况。其次，微塑料将作为沉积物类别添加到上述数值模型中，并将使用新的模型运行来分析环境产生的微塑料特性变化如何影响其扩散和命运。为了表示微塑性输运，它们的沉降速度和侵蚀的临界剪应力将作为它们暴露于不同环境条件的函数参数化。对于项目的两个部分，将进行敏感性测试，以评估模型结果的不确定性。总的来说，这种方法将使我们更好地了解区域尺度上的微塑料运输如何受到环境条件下颗粒转化的影响，这对于未来的微塑料管理工作以及保护为社会提供食物、娱乐和旅游的沿海生态系统非常重要。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Plastic in the ocean breaks down into small pieces known as microplastics due to weathering by environmental conditions. Microplastics are increasingly pervasive and harm the ecological health of coastal areas, so it is important to understand where they are and how they are transported by coastal flows. As microplastics are exposed to varying environmental conditions (e.g., light, oxygen, and sediment abrasion), they fragment into smaller pieces and facilitate the growth of organic matter. These transformations affect how easily microplastics remain suspended in the water column. Yet, it is not known how these transformations impact microplastic transport at regional scales. This project will investigate when, where, and how much microplastics are exposed to conditions that lead to changes in their density, size, and shape. Additionally, this project will quantify how exposures to varying environmental conditions impact the dispersion and fate of microplastics at a regional scale. The increased understanding of microplastic transport that will result from this project will be useful for informing policy decisions and cleanup efforts. Over the course of the project, the PI will also engage in outreach to local schools and mentoring of university students. The objective of this project is to better understand how microplastic transformations impact their transport on regional scales. First, the PI will use Lagrangian tracers representing microplastics and existing model output to quantify the exposure of microplastics to conditions that cause weathering or biofouling. Specifically, use of output from an existing hydrodynamic-sediment transport-biogeochemical model for the northern Gulf of Mexico will be used to estimate microplastic exposure to light, sediment abrasion, and other environmental conditions. Second, microplastics will be added to the numerical model described above as a sediment class, and new model runs will be used to analyze how environmentally produced changes in microplastic properties impact their dispersal and fate. To represent microplastic transport, their settling velocities and critical shear stresses for erosion will be parameterized as a function of their exposure to different environmental conditions. For both parts of the project, sensitivity tests will be performed to evaluate the uncertainty of model results. Overall, this approach will allow us to better understand how microplastic transport on regional scales is influenced by particle transformations due to environmental conditions, which is important for future microplastic management efforts and therefore for preserving coastal ecosystems that provide food, recreation, and tourism for society.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.