高盐度地下水^(14)C测年样品采集技术探讨

COLLECTION OF SAMPLES FROM UNDERGROUND-HIGH SALINITY BRINE FOR ^(14)C DATING

高盐度地下水 (卤水 ) 14 C样品采集是同位素水文地质界的一个难题。罗布泊钾矿区卤水的化学组成特征是 :平均矿化度为 35 3.5 g/L ,SO2 -4的质量浓度 4 4 .0 3g/L ,HCO-3 的质量浓度为0 .2 71g/L。为此 ,文中借鉴一般地下水 (淡水或微咸水 ) 14 C样品的采集原理 ,设计出一套真空取样装置。其操作步骤是 ,首先通过调节卤水的 pH值 ,使得水中的无机碳以CO2 气体的形式溢出 ,然后 ,导入装有NaOH与BaCl2 混合溶液的样品瓶中 ,在野外获得高盐度卤水14 C测年样品。罗布泊卤水测试结果表明 ,这一流程有效地解决了硫酸盐干扰问题 ,卤水14 C样品质量可靠。该技术可为高盐度地下水测年提供有效手段 ,对低盐度地下水14 C取样也具有重要的推广使用价值。

C dating of the high salinity brine is one of hydrogeological problems. In Lop Nur playa of Xinjiang, the chemical characteristics of underground brine are: the average salinity is 353.5 g/L, SO 2- 4 content is 44.03 g/L, HCO - 3 is 0.271 g/L. Based on the principle of 14 C dating sample collection of common groundwater, the authors designed a vacuum set of collecting samples from high salinity brine. Its working stages in the field are: first of all, adjusting pH values of brine; secondly, making inorganic carbon in brine transformed into carbon dioxide gas; then letting the gas into the solution of NaOH and BaCl 2, thus, 14 C dating sample may be collected. The measurement results of 14 C ages of brine show that the set disposes of the sulfate perturbation effectively and ensures the quality of 14 C dating samples. In summary, the set is not only applicable to brine of high salinity, but also to the groundwater with low salinity for 14 C dating.