基于镭同位素示踪的青海湖金沙湾沿岸地下水排放研究

Estimating groundwater discharge into Jinshawan via, Qinghai Lake Radium isotopic

青海湖作为我国内陆最大的咸水湖,针对其水域的研究具有重要的环境意义。采集青海湖金沙湾沿岸9个间隙水样,2个井水样,1个湖水样以及2个降水样。调查研究了青海湖金沙湾间隙水溶解态镭同位素活度的空间分布情况,发现间隙水中^(223)Ra和^(224)Ra的平均活度为3.5 dpm/100 L和162.6 dpm/100 L,均高于井水和湖水。通过对沿湖岸线水平向和垂直向的间隙水镭同位素活度分布研究发现,金沙湾间隙水镭同位素活度随离岸距离的增大而增大、随深度的加深而减小,这与湖水镭同位素活度随离岸距离的变化规律相反。结合镭同位素活度随盐度的变化,发现湖水与间隙水在离岸30 m左右发生了交换,交换深度在1 m以下。最后,通过水平涡动扩散模型估算了金沙湾沿岸表层地下水的排放通量为0.20 m^3·m^(-2)·d^(-1)。

Qinghai Lake is the largest inland saltwater lake in China.The research of its aqueous environment has important environmental implications.We collected 9 interstitial water samples,2 groundwater samples,1 lake water sample and 2 rainfall samples,and investigated the distributions of dissolved Ra of interstitial water in Jinshawan,Qinghai Lake.The activities of ^223Ra and ^224Ra were respectively 3.5 dpm/100 L and 162.6 dpm/100 L.The radium isotopes activity of interstitial water increases with the offshore distance in Jinshawan,which is in contrary to the case of lake.On the vertical distribution,isotope radium activity of interstitial water decreases with the increasing depth.In Jinshawan,Qinghai Lake,lake water and interstitial water exchange occurred at about 30 m offshore and at the depth below 1 m.By the radium isotopes horizontal eddy diffusion model,we estimated groundwater discharge flux per square meter which is 0.20 m^3·m^-2·d^-1.