The Distribution Regularity and Sources of Six-valence Chromium in Groundwater from Wuqi County, Yanan City

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 environmental hydrogeology survey,collecting thesamples ofrock, water and petroleum based on watershed unit, the sources and distribution regularity of six-valence chromium have been summarized and analyzed systematically. The results show that the six-valence chromium in groundwater was mainly originated from the soil in Wuqi County, and the content of six-valence chromium 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 systems. These processesresulted that the six-valence chromium is over-standard at different degree in groundwater.