Collaborative Research: Quantifying Geologic and Temporal Controls on Water and Chemical Exchange between Groundwater and Surface Water in Coastal Estuarine Systems

合作研究：量化沿海河口系统中水和地下水与地表水之间化学交换的地质和时间控制

• 批准号: 0910756
• 负责人: Holly Michael
• 金额: $ 45万
• 依托单位: University of Delaware
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-10-01 至 2013-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0910756&HistoricalAwards=false
• 关键词: Collaborative; Research; Quantifying; Geologic; Temporal

Collaborative Research: Quantifying Temporal and Geologic Controls on Water and Chemical Exchange between Groundwater and Surface Water in Coastal Estuarine SystemsH. Michael, J. Bratton, D. Krantz, L. Konikow, and A.S. AndresEstuarine ecosystems are increasingly threatened by excess nutrient loading. Groundwater is an important nutrient source, but the spatial and temporal heterogeneity of groundwater discharge makes quantifying fluxes and transformations of nutrient species prior to discharge challenging. A multi-disciplinary investigation in the well characterized and representative estuary of Indian River Bay in Delaware will improve understanding of the interaction of physical and chemical processes critical to evaluation of the role of groundwater discharge in nitrogen loading to coastal waters.The primary goal of the research is to characterize the controls of geologic heterogeneity and temporally-variable hydraulic forcing on fluid and nitrogen fluxes between aquifers and coastal surface waters. We hypothesize that: (1) mixing between fresh and saline water, driven by transient forcing and geologic heterogeneity, enhances denitrification of freshwater-derived nitrate before discharge, and (2) saline exchange flux, driven by hydraulic forcing and dispersion-induced subsurface density gradients, transports ammonium derived from decay of sedimentary organic matter into coastal waters. The project will include numerical modeling, hydrologic and geochemical monitoring, and geophysical investigations conducted within and surrounding Indian River Bay, DE. Variable-density numerical models will be developed over multiple spatial and temporal scales to quantify fluxes, evaluate system controls, synthesize data, and guide data collection. Direct measurements of groundwater discharge, hydraulic gradients, and salinities will be obtained over tidal to annual cycles. The complex subsurface salinity distribution will be mapped using continuous resistivity profiling, and high-resolution geochemical sampling will be conducted along flowpaths to determine both source and fate of solutes and to quantify denitrification. Analyses will include nitrogen species and isotopes, noble gases to enable calculations of excess N2, and organic matter in saline recharge zone sediments as a source of ammonium. Geologic features such as paleochannels will be imaged using CHIRP seismic surveys, and hydrogeologic properties will be characterized, guided in part by the data needs of the models. The proposed work will have educational impacts, and results will provide insight to managers who regulate nitrogen loading to improve coastal ecosystem health. The project will be carried out in coordination with investigations of carbon-mineral interactions along a salinity gradient proposed as part of a Critical Zone Observatory in the Christina River Basin of Delaware and Pennsylvania.

合作研究：量化沿海河口系统中地下水和地表水之间的水以及化学交换的时间和地质控制。 Michael，J。Bratton，D。Krantz，L。Konikow和A.S. Andresestuarine生态系统越来越受到过多营养负荷的威胁。地下水是一个重要的营养来源，但是地下水排放的空间和时间异质性使量化的通量和转化在排出具有挑战性之前。 A multi-disciplinary investigation in the well characterized and representative estuary of Indian River Bay in Delaware will improve understanding of the interaction of physical and chemical processes critical to evaluation of the role of groundwater discharge in nitrogen loading to coastal waters.The primary goal of the research is to characterize the controls of geologic heterogeneity and temporally-variable hydraulic forcing on fluid and nitrogen fluxes between aquifers and coastal地表水。我们假设是：（1）在瞬时强迫和地质异质性的驱动下，在排出前的淡水衍生硝酸盐的硝化和（2）盐水交换驱动，由水力强迫和分散诱导的地下密度梯度驱动ammon驱动Ammon，decay decay demand demane venteral demane demane demane demane vernife，（2）盐水交换量。该项目将包括数值建模，水文和地球化学监测，以及在印度河湾和周围进行的地球物理研究。可变密度的数值模型将在多个空间和时间尺度上开发，以量化磁通量，评估系统控制，合成数据和指南数据收集。直接测量地下水排放，液压梯度和盐度将在潮汐中获得年度周期。复杂的地下盐度分布将使用连续的电阻率分析绘制，并将沿流道进行高分辨率地球化学采样，以确定溶质的来源和命运并量化非硝化作用。分析将包括氮种和同位素，贵重气体以实现过量N2的计算以及盐水补给区沉积物中的有机物作为铵的来源。地质特征将使用Chirp地震调查进行成像，并且水文地质特性将被表征，部分地是由模型的数据需求引导的。拟议的工作将产生教育影响，结果将为调节氮气负荷以改善沿海生态系统健康的经理提供洞察力。该项目将与对特拉华州和宾夕法尼亚州克里斯蒂娜河盆地关键区天文台的盐度梯度沿盐度梯度进行协调进行协调。