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质和固体反应相之间的联系对于预测地下水系统中的营养途径、碳的生物地球化学循环和污染物迁移至关重要。 在许多冲积含水层中，氧化还原敏感金属在终端电子接受过程中发挥着重要作用。 由于这些金属对于含水层能量学和生物地球化学至关重要，因此本研究重点关注受地表-地下水交换影响的浅层冲积含水层中的时空控制和氧化还原敏感金属迁移率。 该研究包括两个研究要素。 研究要素 I 将研究对氧化还原敏感金属迁移率的时间/季节控制。 通过系统的地表-地下水和沉积物采样和分析；含水层特征、水体地球化学和生物功能将在卡拉维拉斯河（新墨西哥州杰梅斯山脉中一个仪器齐全、未受干扰的地点）进行鉴定。 浅层冲积层填充物的特征包括细尺度含水层结构（地层元素）、沉积物地球化学（例如，可提取金属、有机质含量和可提取碳）和水体生物地球化学（溶解气体、有机和无机溶质）。 每两个月对广泛的井网进行采样，将能够测量动态地球化学和生物学对季节性和降水事件的扰动。 在研究期间确保观察到几个完整的周期。 多级水采样仪器将提供必要的高垂直分辨率，以量化沉积物特征（生物可利用的碳和金属）、水体地球化学和微生物功能之间的联系。 研究要素 2 重点关注冲积含水层内的空间异质性，并提出一系列假设和测试，以评估 (a) 沿地下水流路径的位置、(b) 溶解的有机碳物质的螯合和 (b) 螯合对金属流动性的控制。 (c)微生物介导的铁还原反应。 将通过沿流动路径采样地球化学参数（由现有的特定地点水文模型定义）并通过应用地球化学模型（用于水体形态和反应路径建模）来评估水文控制。 将使用沉积物孵化进行受控实验室实验，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。 该提案是为了响应环境地球化学和生物地球化学征集而提交的，该项目得到了地球科学部和海洋科学部（地球科学）的共同支持。