Application of radon and radium isotopes to groundwater flow dynamics: An example from the Dead Sea
Application of radon and radium isotopes to groundwater flow dynamics: An example from the Dead Sea
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DOI：
10.1016/j.chemgeo.2015.06.014
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发表时间：
2015-09
期刊：
影响因子：
3.9
通讯作者：
Y. Kiro;Y. Weinstein;A. Starinsky;Y. Yechieli
中科院分区：
文献类型：
--
作者：
Y. Kiro;Y. Weinstein;A. Starinsky;Y. Yechieli
本文介绍了氡和镭同位素的行为及其在地下水年龄和流动动力学中的应用。该研究是在复杂的死海地下水系统中进行的，该系统包括各种沉积物，地下水盐度，流动机制和地下水年龄。死海周围的地下水含有高浓度的氡（高达数万dpm/L）和镭（高达数百dpm/L）。部分受盐度控制的镭的吸附是不负载222rn的重要来源，可用于估算镭的吸附分配系数。除矿化度外，锰、铁氧化物浓度和含水层非均质性是控制吸附分配系数的重要因素。死海两岸岩石的性质不同，死海西部集水区碳酸盐岩的Th/U比值较低，而死海东部砂岩含水层的Th/U比值较高，这反映在东部地下水的228ra /226Ra活度比值高于西部地下水（平均值分别为0.76和0.15）。死海周围不同的地下水群包含长期或非长期平衡比率，这取决于地下水的年龄（地下水进入含水层的时间）或地下水系统是否处于稳定状态（地下水系统的年龄）。年轻的地下水，如在含水层或淡水泉中循环的死海水，与短寿命同位素相比，长寿命的镭同位素已经耗尽，而年老的地下水含有相对较高的226ra活度（~ 500 dpm/L），并且镭活度比接近长期平衡。死海地下水中所有四种镭同位素的共同长期平衡比表明，在过去8000年里，许多地下水流动路径没有显著变化。
This study presents the behavior of radon and radium isotopes and their application to groundwater age and flow dynamics. The research was conducted in the complex Dead Sea groundwater system, which includes a large variety of sediments, groundwater salinities, flow mechanisms and groundwater ages. Groundwater around the Dead Sea contains high activities of radon (up to tens of thousands dpm/L) and radium (up to hundreds dpm/L). Adsorption of radium, which is partially salinity controlled, is an important source of unsupported222Rn, which is used for estimating the adsorption partition coefficient of radium. In addition to salinity, the concentration of Mn and Fe oxides and aquifer heterogeneity are important factors controlling the adsorption partition coefficient. The different nature of the rocks on both sides of the Dead Sea transform, with lower Th/U ratios in the carbonate rocks on the western catchment of the Dead Sea compared to higher ratios in the sandstone aquifer east of the Dead Sea, is reflected in a higher228Ra/226Ra activity ratio in the eastern compared with the western groundwaters (averages of 0.76 and 0.15, respectively). The different groundwater groups around the Dead Sea contain secular or non-secular equilibrium ratios, which depend on the age of the groundwater (the time since the groundwater entered the aquifer) or whether the groundwater system is in a steady state (the age of the groundwater system). Young groundwater, such as the Dead Sea water that circulates in the aquifer or freshwater springs, is depleted in the long-lived radium isotopes compared to the short-lived isotopes, whereas old groundwater contains relatively high activity of226Ra (∼ 500 dpm/L) and the radium activity ratios are close to secular equilibrium. The common secular equilibrium ratios between all four radium isotopes in the Dead Sea groundwaters suggest that many of the groundwater flow paths did not change significantly during the past 8000 years.