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首页> 外文学位 >Characterization of the Spatial and Temporal Variations of Submarine Groundwater Discharge Using Electrical Resistivity and Seepage Measurements.
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Characterization of the Spatial and Temporal Variations of Submarine Groundwater Discharge Using Electrical Resistivity and Seepage Measurements.

机译：利用电阻率和渗流测量法表征海底地下水排放的时空变化。

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摘要

Submarine groundwater discharge (SGD) encompasses all fluids crossing the sediment/ocean interface, regardless of their origin, composition or driving forces. SGD provides a pathway for terrestrial contaminants that can significantly impact coastal ecosystems. Overexploitation of groundwater resources can decrease SGD which favors seawater intrusion at depth. Understanding SGD is therefore crucial for water quality and resource management. Quantifying SGD is challenging due to its diffuse and heterogeneous nature, in addition to significant spatio-temporal variations at multiple scales.;In this thesis, an integrated approach combining electrical resistivity (ER) surveys, conductivity and temperature point measurements, seepage rates using manual and ultrasonic seepage meters, and pore fluid salinities was used to characterize SGD spatio-temporal variations and their implications for contaminant transport at several locations on Long Island, NY.;The influence of surficial sediments on SGD distribution was investigated in Stony Brook Harbor. A low-permeability mud layer, actively depositing in the harbor, limits SGD at the shoreline, prevents mixing with seawater and channels a significant volume of freshwater offshore. SGD measured at locations without mud is high and indicates significant mixing between porewater and seawater. A 2D steady-state density-difference numerical model of the harbor was developed using SEAWAT and was validated by our field observations.;Temporal variations of SGD due to semi-diurnal tidal forcing were studied in West Neck Bay, Shelter Island, using a 12-hr time-lapse ER survey together with continuous salinity and seepage measurements in the intertidal zone. The observed dynamic patterns of groundwater flux and salinity distribution disagree with published standard transient state numerical models, suggesting the need for developing more specific models of non-homogeneous anisotropic aquifers.;SGD distribution and composition were characterized in Forge River, a tidal river that experiences chronic hypoxia due to nitrogen contamination. We found that nitrogen speciation and concentration are linked to different SGD regimes. Near shore sandy zones with high SGD show little nitrate reduction and constitute the major source of nitrogen input to surface waters. Offshore areas rich in silt and organic matter exhibit low SGD and higher denitrification. Dredging activities have altered the sediment distribution and subsequently have created preferential flow paths focusing freshwater discharge into the center of the river.
机译：海底地下水排放（SGD）涵盖了所有穿过沉积物/海洋界面的流体，无论其来源，组成或驱动力如何。 SGD为可能严重影响沿海生态系统的陆地污染物提供了途径。过度开采地下水资源可以降低SGD，从而有利于深层海水入侵。因此，了解SGD对于水质和资源管理至关重要。由于SGD的弥散性和异质性，以及在多个尺度上的显着时空变化，因此量化SGD仍具有挑战性。用超声渗漏仪和孔隙水盐度来表征SGD时空变化及其对纽约长岛几个位置污染物迁移的影响。;在斯托尼布鲁克港研究了表面沉积物对SGD分布的影响。低渗透性泥浆层活跃地沉积在港口中，限制了海岸线上的SGD，阻止了与海水的混合，并向海上输送了大量淡水。在没有泥浆的位置测得的SGD高，表明孔隙水和海水之间存在明显的混合。使用SEAWAT建立了港口的二维稳态密度差数值模型，并通过我们的现场观测得到了验证。;在Shelter Island的西内克湾，研究了半日潮汐强迫引起的SGD的时空变化，使用12时延ER调查以及潮间带连续的盐度和渗流测量。观测到的地下水通量和盐分分布的动态模式与已发布的标准瞬态数值模型不符，这表明需要开发更具体的非均质各向异性含水层模型。由于氮污染导致的慢性缺氧。我们发现氮的形态和浓度与不同的SGD方案有关。 SGD较高的近岸沙质区几乎没有硝酸盐还原，是向地表​​水输入氮的主要来源。富含泥沙和有机质的近海区域显示出较低的SGD和较高的反硝化作用。疏activities活动改变了沉积物的分布，并随后形成了优先的流动路径，使淡水集中到河流中心。

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  • 作者

    Durand, Josephine Miryam Kalyanie.;

  • 作者单位

    State University of New York at Stony Brook.;

  • 授予单位 State University of New York at Stony Brook.;
  • 学科 Hydrology.;Geophysics.
  • 学位 Ph.D.
  • 年度 2014
  • 页码 182 p.
  • 总页数 182
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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