SusChEM: Redox and mineral controls maximizing Phosphorus mobility and bioavailability

了解磷(P)在环境中的行为对社会至关重要，因为磷通常作为肥料在促进生产性农业中起着核心作用。然而，磷在水生环境中也是一种污染物，在水生环境中，人类在水和沉积物中富集磷会促进有害的藻类繁殖。世界范围内磷的储量是有限的，尤其是在美国，维持农业生产将需要磷的回收和循环利用。水资源的保护也是一个越来越重要的关注领域，以促进可持续的清洁饮用水，健康的渔业和经济上至关重要的娱乐资源。这些问题需要更好地理解P是如何在不同的地质和工程环境中被调动的。磷与其他元素，特别是铁、锰和碳的相互作用通常控制着磷的流动性，因此了解这种相互作用是制定更可持续农业和水质战略的关键。这个研究项目？S的目标是制定一个环境条件的概念框架，最大限度地提高磷在沉积物-水系统中的流动性。该项目将与NSF-EPSCoR湖泊水质调查项目相结合。对这些主题的研究将与外联机会相结合，向当地学童和利益攸关方传授负责任的营养管理以及如何更好地保护水资源。磷通常在沉积物-水系统中分为矿物池、溶解池和有机池。确定不同磷物种池对变化的氧化还原条件的响应时间是理解沉积物-水系统中磷迁移和生物利用度驱动因素的主要障碍。描述这些池之间的P分区和迁移的静态模型非常庞大，但没有捕捉到关键因素。沉积物-水界面（SWI）附近的氧化还原条件是浅层淡水和海洋系统中P和相关氧化还原活性元素（特别是Fe， Mn， S， N）反应性的关键控制因素，并且可以在日、季节和更混乱的基于事件的时间尺度上波动。该项目的中心假设是，特定磷池的流动性通过在短时间（几分钟到几小时）内SWI氧化还原条件的变化而最大化，并且这些氧化还原振荡的持续时间和严重程度驱动了SWI附近P（和Fe）物种随时间的分配和行为。为了验证这一点，需要对磷的形成和迁移进行全面的调查，结合现场和实验室的方法来阐明这个复杂系统的驱动因素和动力学。对特定磷池和相关元素的分析将利用先进的技术来检查不同氧化还原条件下不同池中不同形式磷的分配。具体来说，使用环境伏安技术对自然和操纵SWI氧化还原动力学进行高分辨率原位监测，并结合一套有针对性的分析来描述氧化还原驱动的沉积物-水P池演化，包括：1)沉积物磷矿物组成和可提取性；2)磷和铁形态；3)确定有机磷形态的酶消化和核磁共振技术将为建立沉积物-水系统中磷形态和迁移的基于分子和时间约束的模型提供所需的数据。

Understanding phosphorus (P) behavior in the environment is critical to society, as P often plays a central role in promoting productive agriculture as a fertilizer. Yet phosphorus is also a contaminant in aquatic environments, where human-derived enrichment of P in water and sediment can promote harmful algal blooms. Worldwide reserves of P are limited, especially in the U.S., and sustaining agricultural production will require the recovery and recycling of P. The protection of water resources is also an increasingly critical area of concern to promote sustainable clean drinking water, healthy fisheries, and economically vital recreational resources. These issues require improved understanding of how P is, and can be, mobilized in different geological and engineered settings. P interaction with other elements, especially iron, manganese, and carbon, often controls P mobility, and understanding this interaction is therefore key to developing strategies for more sustainable agriculture and water quality. This research program?s goal is to develop a conceptual framework of the environmental conditions that maximize phosphorus mobility in sediment-water systems. The project will integrate with NSF-EPSCoR program investigating lake water quality. Research on these topics will be integrated with outreach opportunities to teach local schoolchildren and stakeholders about responsible nutrient management and how to better protect water resources.Phosphorus is generally partitioned in sediment-water systems between mineral, dissolved, and organic pools. Determining the response times for different pools of P species to changing redox conditions is a major hurdle in understanding the drivers of phosphorus mobility and bioavailability in sediment-water systems. Static models describing P partitioning and mobility between these pools are voluminous but do not capture key factors. The redox conditions near the sediment-water interface (SWI) are a critical control on the reactivity of P and associated redox-active elements (Fe, Mn, S, N especially) in shallow freshwater and marine systems, and can fluctuate on diel, seasonal, and more chaotic event-based timescales. The central hypothesis of this project is that the mobility of specific P pools is maximized by changes in redox conditions at the SWI over short (minutes to hours) time spans, and that the duration and severity of these redox oscillations drives the partitioning and behavior of P (and Fe) species over time near the SWI. To test this requires a comprehensive investigation of P speciation and mobility that couples field and laboratory approaches designed to elucidate the drivers and dynamics of this complex system. Analysis of the specific P pools and related elements will utilize advanced techniques to examine the partitioning of different P forms in different pools under changing redox conditions. Specifically, high-resolution in-situ monitoring of natural and manipulated SWI redox dynamics using environmental voltammetric techniques, combined with a suite of targeted analyses to describe the redox-driven evolution of sediment-water P pools including: 1) sediment P mineralogical composition and extractability, 2) P and Fe speciation, and 3) enzyme digestion and NMR techniques to determine organic P speciation will provide the data needed to develop a molecular-based and temporally constrained model of P speciation and mobility in sediment-water systems.