Biogeochemical Cycling of Redox-Sensitive Metals During Surface-Subsurface Water Exchange in a Shallow Alluvial Aquifer

浅层冲积含水层地表-地下水交换过程中氧化还原敏感金属的生物地球化学循环

• 批准号: 9630285
• 负责人: Laura Crossey
• 金额: $ 34万
• 依托单位: University of New Mexico
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1996
• 资助国家: 美国
• 起止时间: 1996-08-15 至 1999-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9630285&HistoricalAwards=false
• 关键词: Biogeochemical; Cycling; Redox; Sensitive; Metals

9630285 Crossey Understanding the linkage between dissolved redox-sensitive species and solid reactive phases in an aquifer matrix is crucial to the prediction of nutrient pathways, biogeochemical cycling of carbon, and contaminant transport in ground water systems. In many alluvial aquifers redox-sensitive metals play an important role in terminal electron-accepting processes. Because these metals are critical to aquifer energetics and biogeochemistry, this research focuses on the temporal and spatial controls and redox-sensitive metal mobility in a shallow alluvial aquifer influenced by surface-subsurface water exchange. The study comprises two Research Elements. Research Element I will examine temporal/seasonal controls on redox-sensitive metal mobility. Through systematic surface-subsurface water and sediment sampling and analysis; aquifer characteristics, aqueous geochemistry, and biological functioning will be identified at Rio Calaveras (a heavily-instrumented, unperturbed site in the Jemez Mountains of New Mexico). The shallow alluvial fill will be characterized with respect to fine-scale aquifer structure (stratigraphic elements), sediment geochemistry (e.g., extractable metals, organic matter content, and extractable carbon), and aqueous biogeochemistry (dissolved gases, organic and inorganic solutes). Bi-monthly sampling of an extensive well network will permit measurement of dynamic geochemically, and biologically to seasonal and precipitation event perturbations. Observation of several complete cycles are assured over the time period of the study. Multi-level water sampling instrumentation will allow the high vertical resolution necessary to quantify links among sediment characteristics (bioavailable carbon and metals), aqueous geochemistry, and microbial functioning. Research Element 2 focuses on spatial heterogeneity within the alluvial aquifer, and poses a series of hypotheses and tests to assess the control on metal mobility exerted by (a) position along gro undwater flow paths, (b) chelation by dissolved organic carbon species, and (c) microbially-mediated iron reduction reactions. Hydrologic controls will be assessed through sampling geochemical parameters along flow paths (defined by an existing site-specific hydrologic model) and through application of geochemical models (for aqueous speciation and reaction path modeling). Controlled laboratory experiments will be conducted using sediment incubations to distinguish abiotic (chelation) and biotic (microbial reduction) mechanisms of iron mobilization. Aquifer heterogeneity will be a primary organizing factor in the experimental design. This proposal was submitted in response to the Environmental Geochemistry and Biogeochemistry solicitation, and the project is being jointly supported by the Divisions of Earth Sciences and Divisions of Ocean Sciences (Geosciences).

9630285 Crossey了解含水层基质中溶解的氧化还原敏感物种与固体反应相之间的联系对于预测营养途径，碳的生物地球化学循环以及地下水系统中污染物的运输至关重要。 在许多冲积含水层中，氧化还原敏感的金属在末端电子感受过程中起着重要作用。 由于这些金属对含水层的能量和生物地球化学至关重要，因此该研究的重点是在受表面膨胀水交换影响的浅层冲积含水层中的时间和空间控制以及对氧化还原敏感的金属迁移率。 该研究包括两个研究元素。 研究元素I将检查对氧化还原敏感金属迁移率的时间/季节性控制。 通过系统的表面表面水以及沉积物采样和分析；含水层特征，水性地球化学和生物功能将在里约热内卢（Rio Calaveras）（在新墨西哥州的Jemez山上受到严重启发，不受干扰的地点）进行鉴定。 浅层冲积填充物将在细尺度含水层结构（地层元素），沉积物地球化学（例如，可提取的金属，有机物含量和可提取的碳）以及生物地球化学（溶解的气体，有机和无机溶液）中进行表征。 大量井网的两个月进行一次采样将允许在地球化学以及生物学上对季节性和降水事件的扰动进行测量。 在研究期间，确保了几个完整周期的观察。 多级水采样仪器将允许量化沉积物特性（生物利用碳和金属），水性地球化学和微生物功能所需的高垂直分辨率。 研究元素2着重于冲积含水层内的空间异质性，并提出了一系列假设和测试，以评估（a）沿Gro undwater流动路径施加的金属迁移率的控制，（b）溶解的有机碳种类的螯合作用，以及（c）微生物介导的铁还原反应。 水文控制将通过沿流动路径（由现有位点特异性水文模型定义）的地球化学参数进行采样，并通过应用地球化学模型（用于水性物种形成和反应路径建模）来评估。 将使用沉积物孵育进行对照实验室实验，以区分铁动员的非生物（螯合）和生物（微生物还原）机制。 含水层异质性将是实验设计中的主要组织因素。 该提案是针对环境地球化学和生物地球化学招标提交的，并且该项目由地球科学和海洋科学划分（地球科学）的划分共同支持。