CAS-MNP: Evaluating Patterns and Controls on Microplastic Accumulation in Floodplains

环境中的塑料积累是一个普遍存在的全球性问题，对生物、生态系统和人类健康造成严重后果。塑料在环境中的表现就像天然材料一样，它们被降解成更小的颗粒，包括微塑料（长度为5毫米的碎片）。这些塑料颗粒通过传统的地貌过程（包括风和水）运输。塑料的降解和运输导致其在一系列环境中积累，为全球塑料-碳循环提供了基础。然而，塑料-碳循环的一个关键组成部分——即微塑料通过河流和洪泛平原的运输和储存——仍然缺乏限制。了解塑料在河流和洪泛区积聚的位置和原因对于减轻和管理塑料污染至关重要，因为河流将塑料的生产和使用上游连接到海岸和开阔的海洋。该项目将分析土壤样本，量化在不同洪泛平原环境中发现的微塑料的数量和类型，并将塑料积累模式与环境参数联系起来。作为马萨诸塞州林恩市一个环境正义社区的“海滩姐妹”项目的一部分，该团队将共同开发并向高中生提供有关塑料在流域运输的双语教材。该项目将为本科生和研究生提供指导研究机会，并支持早期职业研究人员。洪泛平原是沉积物、碳和污染物的重要汇，但由于塑料的独特材料特性以及调节洪泛平原沉积的复杂动态过程，人们对它们在全球塑料-碳循环中的作用知之甚少。控制洪泛区沉积的相同地貌过程应该在这些环境中调节微塑料的积累，尽管普通塑料的密度（~0.05至1.5 g/cm3）相对于自然沉积物（~1.4至2.9 g/cm3）相对较低，这意味着塑料侵蚀和沉积在洪泛区的模式将是独特的。该项目将实地调查和采样与地球化学分析和水力建模相结合，以测试一系列假设，这些假设描述了洪水淹没、流速、地貌环境以及塑料的物理和化学性质对洪泛平原堆积的相互作用。这项研究将使研究人员能够建立一个全面的模型，研究塑料在何处以及如何在洪泛区的地貌单元中积聚，为量化其他河流-洪泛区走廊沿线的微塑料储存提供基础。更广泛地说，该项目将允许他们在观测环境中测试为不同材料特性的塑料颗粒的自然沉积物开发的沉降速度模型的适用性。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 accumulation in the environment is a pervasive global problem with severe consequences for organisms, ecosystems, and human health. Plastics behave like natural materials in the environment in that they are degraded to form smaller particles including microplastics (fragments 5 mm in length). These plastic particles are transported by conventional geomorphic processes including wind and water. The degradation and transport of plastics has led to its accumulation across a range of environments, providing the basis for a global plastic-carbon cycle. However, a key component of the plastic-carbon cycle — namely the transport and storage of microplastics through rivers and floodplains — remains poorly constrained. Understanding where and why plastics accumulate along rivers and floodplains is critical for mitigating and managing plastic pollution because rivers connect plastics production and use upstream to coasts and the open ocean. This project will analyze soil samples to quantify the amount and types microplastics found in different floodplain environments, and relate patterns of plastic accumulation to environmental parameters. The team will co-develop and deliver bilingual educational materials on plastic transport through watersheds for high school students as part of the Beach Sisters program in Lynn, Massachusetts, an environmental justice community. The project will provide mentored research opportunities for an undergraduate and graduate student and support an early career researcher.Floodplains serve as critical sinks for sediments, carbon, and pollutants, but their role in the global plastic-carbon cycle is poorly understood owing to the unique material properties of plastics, and the complex and dynamic processes that mediate floodplain sedimentation. The same geomorphic processes that control floodplain sedimentation should mediate microplastic accumulation in these environments, although the relatively low density of common plastics (~0.05 to 1.5 g/cm3) relative to natural sediments (~1.4 to 2.9 g/cm3) imply that patterns of plastic erosion and deposition across a floodplain will be unique. This project integrates field-based surveys and sampling with geochemical analyses and hydraulic modeling to test a series of hypotheses describing the interaction of flood inundation, flow velocity, geomorphic setting, and the physical and chemical properties of plastics on their accumulation in floodplains. The study will allow the investigators to build a comprehensive model of where and how plastics accumulate across the geomorphic units of a floodplain, providing a basis to quantify microplastic storage along other river-floodplain corridors. More broadly, the project will allow them to test the suitability of settling velocity models developed for natural sediments on plastic particles with different material properties in an observational setting.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.