西藏高原达则错湖泊铀富集特征

Enriching Characteristics of Uranium in Lake Dagzeco,Tibet

达则错位于班怒构造带的次级盆地中,湖水最深为36 m,平均深度为20.8 m。湖表水体矿化度17.27~20.27 g/L,平均为19.46 g/L,水化学类型为(CO_(3)+HCO_(3))·SO_(4)-Na型,属弱度碳酸盐型咸水湖;在垂向上,由浅及深矿化度略有增加,水化学类型不变。湖表水体铀浓度264~324μg/L,平均铀浓度为286μg/L,8 m、18 m和28 m深度铀浓度平均值分别为288μg/L、290μg/L和300μg/L。湖底沉积物铀含量为2.31~4.08μg/g,平均铀含量为3.16μg/g,略高于我国东海大陆架海底沉积物的铀含量。达则错湖水的铀元素来自于周边岩体和地层,通过河水迁移到湖泊中。在河口混合带,铀酰离子部分吸附于悬浮物上,到湖区以碳酸铀酰的形式存在于水体中,沉淀于湖底的悬浮物铀含量没有明显增加。

Lake Dagzeco is located in the secondary basin of Bangongco-Nujiang suture zone,the maximum depth of lake water is 36 m and the average depth is 20.8 m.The salinity of the surface water is 17.27~20.27 g/L,with an average of 19.46 g/L.The water’s hydrochemical type is(CO_(3)+HCO_(3))·SO_(4)-Na,suggesting the lake is a weakly carbonate-type saline.Vertically,the salinity increases slightly from shallow to deep,and the hydrochemical type unchanged.The uranium concentration in the surface water is 264~324μg/L,and the average is 286μg/L.the average uranium concentration at the depth of 8 m,18 m and 28 m is 288μg/L,290μg/L and 300μg/L,respectively.The uranium content in the sediments is 2.31~4.08μg/g,and the average is 3.16μg/g,which is slightly higher than that of the sediments in the continental shelf of the East China Sea.The uranium in Lake Dazgeco comes from the surrounding rocks and migrated to the lake through the river.Partly uranyl ions are adsorbed on suspended solids,in the estuarine mixing zone,and it exists in the form of uranyl carbonate,in the lake region,there is no obvious increase in uranium content of suspended solids deposited in the lake bottom.