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首页> 外文期刊>Marine Chemistry >Estimating submarine groundwater discharge in a South Pacific coral reef lagoon using different radioisotope and geophysical approaches
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Estimating submarine groundwater discharge in a South Pacific coral reef lagoon using different radioisotope and geophysical approaches

机译：使用不同的放射性同位素和地球物理方法估算南太平洋珊瑚礁泻湖中的海底地下水排放量

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摘要

The multi-scale and temporally variable nature of submarine groundwater discharge (SGD) has led to various ways of characterizing SGD fluxes. In this study, qualitative and quantitative methods were applied to describe SGD in a South Pacific coral reef lagoon arid to determine the limitations and advantages of these ways of characterizing SGD fluxes. Synoptic and continuous monitoring of ~(222)Rn and salinity were used over nested spatial and temporal scales and, electrical resistivity (ER) imaging was used to infer surface and groundwater salinity distributions throughout the lagoon. Moored deployments were used to estimate the lagoon residence time using ratios between radium isotopes. Spatial surveys indicated between a five and ten-fold decrease in ~(222)Rn away from the beach face. The magnitude of the decrease was dependent on the survey scale. However, only a high resolution medium scale survey was able to detect a zone of higher ~(222)Rn water towards the reef crest The high ~(222)Rn concentrations towards the reef crest corresponded to areas of higher ER and lower temperatures which indicated a point source SGD approximately 350 m off the beach. Concentrations of ~(222)Rn and salinity during the spatial surveys and time series at each location were affected by the level of seawater recharge, the terrestrial hydraulic gradient, point source SGD, and the concentration of 222Rn laden creek water. Radioisotope measurements were used in a steady-state model, a non-steady state model and an exit point model to calculate SGD rates into the lagoon. The steady-state model resulted in the lowest estimate of 7835 ㎥·day~(-1). The non-steady state model, using the near-shore and mid-lagoon 24 hour time series ~(222)Rn concentrations, gave SGD volumes of 58422 m~3day~(-1) and 28259 m~3day~(-1), respectively. The exit point model indicated a rate of 31278 m~3day~(-1). The areal-averaged SGD fluxes from the three models ranged between 0.2 and 1.8 an day~(-1). The suitability of each model for quantifying fluxes rates depended on a range of factors including the presence or absence of a dominant or local seepage zone, temporal variability, spatial heterogeneity, and the degree of mixing of low ~(222)Rn offshore water. This study highlighted the need to employ different methods and sampling strategies to qualitatively and quantitatively characterise SGD fluxes occurring over multiple spatial and temporal scales.
机译：海底地下水排放（SGD）的多尺度和随时间变化的性质导致了表征SGD通量的各种方法。在这项研究中，采用定性和定量方法描述南太平洋珊瑚礁泻湖和干旱地区的SGD，以确定这些表征SGD通量的方法的局限性和优势。对嵌套空间和时间尺度上的〜（222）Rn和盐度进行天气和连续监测，并使用电阻率（ER）成像来推断整个泻湖的地表和地下水盐度分布。系泊部署用于通过镭同位素之间的比率估算泻湖停留时间。空间调查显示，远离海滩面孔的〜（222）Rn减少了五到十倍。减少的幅度取决于调查规模。但是，只有高分辨率的中等规模的调查才能检测到朝向礁顶的〜（222）Rn水较高的区域。朝向礁顶的〜（222）Rn高浓度对应于较高ER和较低温度的区域，这表明距海滩约350 m的点光源SGD。在每个地点的空间调查和时间序列中，〜（222）Rn和盐度的浓度受海水补给水平，陆地水力梯度，点源SGD和含222Rn的小溪水浓度的影响。在稳态模型，非稳态模型和出口点模型中使用放射性同位素测量来计算进入泻湖的SGD率。稳态模型的最低估计值为7835㎥·day〜（-1）。使用近岸和泻湖中部24小时时间序列〜（222）Rn浓度的非稳态模型得出的SGD量为58422 m〜3day〜（-1）和28259 m〜3day〜（-1） ， 分别。出口点模型显示的速率为31278 m〜3day〜（-1）。这三个模型的面积平均SGD通量范围为每天0.2至1.8〜（-1）。每个模型对通量率进行量化的适用性取决于一系列因素，包括是否存在显性或局部渗漏区，时间变化性，空间异质性以及低〜（222）Rn海上水的混合程度。这项研究强调了需要采用不同的方法和采样策略来定性和定量地表征发生在多个时空尺度上的SGD通量。

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  • 来源
    《Marine Chemistry》 |2013年第20期|49-60|共12页
  • 作者

    Douglas R. Tait; Isaac R. Santos; Dirk V. Erler; Kevin M. Befus; M. Bayani Cardenas; Bradley D. Eyre;

  • 作者单位

    Centre for Coastal Biogeochemistry, School of Environmental Science and Management, Southern Cross University, PO Box 157, Lismore, NSW, 2480, Australia;

    Centre for Coastal Biogeochemistry, School of Environmental Science and Management, Southern Cross University, PO Box 157, Lismore, NSW, 2480, Australia;

    Centre for Coastal Biogeochemistry, School of Environmental Science and Management, Southern Cross University, PO Box 157, Lismore, NSW, 2480, Australia;

    Department of Geological Sciences, University of Texas at Austin, Austin, TX, 78712, USA;

    Department of Geological Sciences, University of Texas at Austin, Austin, TX, 78712, USA;

    Centre for Coastal Biogeochemistry, School of Environmental Science and Management, Southern Cross University, PO Box 157, Lismore, NSW, 2480, Australia;

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  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

    Submarine groundwater discharge; Radon; Permeable sediments; Electrical resistivity; Coral reef lagoon;

    机译：海底地下水排放;氡;渗透性沉积物;电阻率;珊瑚礁泻湖;

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