延安吴起县地下水中 Cr6+分布规律及来源探讨

摘要

Six-valence chromium is exceeded in Cretaceous Groundwater from Wuqi County. There are many different versions about the sources of Cr6 + ,the six-valence chromium may be sourced from layer,surface water,groundwater and human activities. After carrying out the en-vironmental hydrogeology survey,collecting thesamples ofrock,water and petroleum based on watershed unit,the sources and distribution regularity of six-valence chromium have been sum-marized and analyzed systematically. The results show that the six-valence chromium in ground-water was mainly originated from the soil in Wuqi County,and the content of six-valence chromi-um in Cretaceous groundwater was controlled by special geological structure and hydrogeological condition. The chromium elements were brought into the groundwater by water-rock interaction in the rainfall infiltration processes,and are influenced by the sediment redox environment during the groundwater circulation processes,and then enriched into the different water-bearing sys-tems. These processesresulted that the six-valence chromium is over-standard at different degree in groundwater.%在严重缺水的陕北吴起地区，白垩系地下水中 Cr6+严重超标，其为原生地质环境所致，还是石油开采等污染引起，不能确定，直接影响着该区地下水资源的开发利用。通过专项水文地质调查，系统地采集分析了岩(土)、水样及石油样品，总结分析了该区 Cr6+的来源与富集规律。研究结果表明，吴起地区地下水中 Cr6+主要来源于区内含水层上覆的土层，其白垩系地下水中 Cr6+含量受控于地质结构及地下水循环。大气降水在入渗过程中通过水岩作用将土层中 Cr 元素带入地下水中，在地下水循环过程中受到氧化还原环境影响富集于不同含水系统中，使得地下水中 Cr6+不同程度超标。