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，因为磷作为肥料通常在促进生产性农业中发挥着核心作用。然而，磷也是水生环境中的一种污染物，人类在水和沉积物中富集的磷会促进有害藻类的繁殖。 全球磷储量有限，尤其是在美国，维持农业生产需要磷的回收和循环利用。为了促进可持续清洁饮用水、健康渔业和经济重要的休闲资源，水资源保护也是一个日益重要的关注领域。这些问题需要更好地了解 P 在不同的地质和工程环境中如何以及如何被调动。磷与其他元素（尤其是铁、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对于制定更可持续的农业和水质战略至关重要。该研究计划的目标是开发一个环境条件的概念框架，最大限度地提高沉积物-水系统中磷的迁移率。 该项目将与 NSF-EPSCoR 湖泊水质调查计划相结合。这些主题的研究将与外展机会相结合，向当地学童和利益相关者传授负责任的养分管理以及如何更好地保护水资源。磷通常在沉积物-水系统中分为矿物质池、溶解池和有机池。确定不同磷物种对氧化还原条件变化的响应时间是了解沉积物-水系统中磷迁移率和生物利用度驱动因素的主要障碍。描述这些池之间的 P 划分和流动性的静态模型数量庞大，但没有捕获关键因素。 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（尤其是 Fe、Mn、S、N）反应性的关键控制因素，并且可能在昼夜、季节性和基于更混沌事件的时间尺度上波动。该项目的中心假设是，特定磷库的流动性通过短时间（分钟到小时）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随着时间的推移驱动 SWI 附近 P（和 Fe）物种的分配和行为。 为了测试这一点，需要对磷的形态和迁移率进行全面的研究，将现场和实验室方法结合起来，旨在阐明这个复杂系统的驱动因素和动力学。 对特定磷库和相关元素的分析将利用先进技术来检查在变化的氧化还原条件下不同磷库中不同磷形式的分配。 具体而言，使用环境伏安技术对自然和操纵的 SWI 氧化还原动力学进行高分辨率原位监测，并结合一系列有针对性的分析来描述沉积物 - 水磷库的氧化还原驱动的演化，包括：1）沉积物磷矿物学组成和可提取性，2）磷和铁形态，以及 3）确定有机磷形态的酶消化和核磁共振技术，将提供开发基于分子和时间约束的磷形态和模型所需的数据。沉积物-水系统中的流动性。

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.