Estimating groundwater discharge into the northeastern Gulf of Mexico using radon-222
Estimating groundwater discharge into the northeastern Gulf of Mexico using radon-222
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DOI：
10.1016/s0012-821x(96)00173-2
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发表时间：
1996-11
影响因子：
5.3
通讯作者：
J. Cable;W. Burnett;J. Chanton;G. Weatherly
中科院分区：
文献类型：
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作者：
J. Cable;W. Burnett;J. Chanton;G. Weatherly
海底地下水排放（SGD）可以提供重要的化学成分的海洋，但这一过程的分散性使得定位和量化其输入极其困难。由于地下水中的氡含量比海水高3-4个数量级，如果能对所有其他氡到底层沃茨的来源进行评估，222 Rn可能是这一过程的有用示踪剂。我们报告了基于墨西哥湾东北部沿海地区氡库存的新元追踪工具的开发情况。我们评估了影响水柱中氡浓度的因素（即，生产衰减，水平运输，并通过密度跃层损失）使用一个连接的海底交换水平运输模式。用原位箱测量的222 Rn底栖通量总量（≥2420 dpm m−2day−1）达到了支持所测量的次密质辉石222 Rn存量所需的量级，而分子扩散的估计表明，这一输入量相对较小（≤230 dpm m−2day−1）。使用这种模型方法，结合氡存量的测量，我们估计了进入620 km 2研究区域的区域地下流体流量，范围为180至710 m3 sec-1。这种排放相当于在整个研究区域中分散的约2-10 cm day-1的向上平流速度，相当于约20个一等泉。
Submarine groundwater discharge (SGD) may provide important chemical constituents to the ocean, but the dispersed nature of this process makes locating and quantifying its input extremely difficult. Since groundwater contains 3–4 orders of magnitude greater radon than seawater,222Rn may be a useful tracer of this process if all other sources of radon to bottom waters can be evaluated. We report development of a SGD tracing tool based on radon inventories in a coastal area of the northeastern Gulf of Mexico. We evaluated factors that influence the concentration of radon in the water column (i.e., production-decay, horizontal transport, and loss across the pycnocline) using a linked benthic exchange-horizontal transport model. Total222Rn benthic fluxes (≥2420 dpm m−2day−1) measured with in situ chambers are of the magnitude required to support measured sub-pycnocline222Rn inventories, while estimates of molecular diffusion show that this input is relatively small (≤230 dpm m−2day−1). Using this model approach, together with measurements of the radon inventory, we estimated a regional subsurface fluid flow ranging from 180 to 710 m3sec−1into the 620 km2study area. This discharge, equivalent to an upward advective velocity of approximately 2–10 cm day−1dispersed over this entire study area, is equivalent to approximately 20 first magnitude springs.