Hydrochemical characteristics of natural water and selenium-rich water resources in the Northern Daba Mountains, China

The Northern Daba Mountains (NDM) of Shaanxi Province, China, are a well-known selenium (Se)-rich area, and the area is also known for endemic fluorine (F) and arsenic (As) poisoning. In order to study the hydrochemical characteristics and trace element contents of the natural waters of this region, 62 water samples were collected from Lan'gao area in the NDM. The hydrochemical composition was principally characterized by Ca center dot Mg-HCO3 center dot SO4. F and As concentrations ranged from 0.01 to 0.67 mg/L and from 0.33 to 6.29 mu g/L, respectively, lower than Chinese national standard and international guidelines for drinking water quality. One year of monitoring proved that F and As in natural water were not the sources of the local fluorosis and arseniasis in the NDM. The average Se concentration in fissure water was 5.20 mu g/L. The average Se content of river water was 2.82 mu g/L, 14 times that of the world's surface level (0.2 mu g/L). The Se content in eight samples reached the Chinese national standards for mineral drinking water quality (> 10 mu g/L). Contrasting the water samples of May, July, and September in 2015 shows that the Se content is relatively stable and the increase of humidity might be beneficial to increase the content of selenium and strontium in water.