海水对含水层沉积物中镭解吸的模拟实验

本研究采用莱州湾沿岸含水层中的沉积物,通过渗滤实验模拟镭的解吸过程。结果表明,在典型的地下水流速范围内(0.02~0.30 cm/min),镭同位素(223Ra、224Ra、226Ra)的解吸没有显著变化。在海水与淡水的混合过程中,解吸的镭比活度与水的盐度呈显著的线性正相关关系。当盐度超过海水盐度时(如S=80的卤水中),解吸的镭比活度则趋于最值平台。对比模拟估算的地下水中镭的比活度与莱州湾沿岸实测间隙水中镭的比活度,223Ra和224Ra的结果基本一致,而226Ra的实测结果较模拟估算结果偏小。可能由于含水层中226Ra经反复解吸后得不到母体核素及时补充所致。本研究将为更好地理解镭同位素在含水层中的地球化学行为提供科学依据,为合理地选择量化海底地下水排放(submarine groundwater discharge,SGD)模型的镭端元值提供新的参考视角。

Simulating the process of radium desorption from coastal aquifer sediments by seawater

In this paper,leaching experiments were conducted with the aquifer sediments in the coast of Laizhou Bay to simulate the process of radium desorption.Within a typical range of SGD flow rates (0.02~0.30 cm/min),radium desorption (223Ra,224Ra and 226Ra) did not show much variation.Desorbed radium activity had positive linear relationship to salinity in the mixture of seawater and freshwater.However,when salinity was beyond salinity of seawater (e.g.,S=80),desorbed radium activity would approach the maximum platform.Compared the estimated activities of desorbed radium with in-situ measured values of pore water in the coast of Laizhou Bay,the results of 223Ra and 224Ra had good agreement while the results of in-situ measured 226Ra were less than estimate.It is likely because frequent desorption will decrease 226Ra activity before it can be regenerated from parent nuclide.This study should benefit better understanding of geochemical behavior of radium isotopes in aquifer sediments and offer new perspective of choosing SGD end-member.