Abstract:

Deyang, situated in Sichuan Province, is rich in groundwater resources，which serves as the most important source of drinking water for the local people. However, high concentration of iron in groundwater has been found in many places. Laboratory leaching experiments were carried out to examine the factors that may increase the concentration of iron in groundwater, including pH, microorganisms, ammonium nitrogen, redox conditions and organic matter content. The results showed: (1) the leaching solution had higher concentration of ferrous iron in acidic conditions; (2) ferrous iron concentration increased with organic matter content in soil; (3) the ferrous iron concentration in solution decreased when microorganism activities were inhibited; (4) in reducing environment, ammonium content had little influence on ferrous iron concentration; (5) in reducing environment, it was easier for iron in soil to be leached comparing to oxidizing environment. Together with the hydrogeological and geochemical condition in the area, the causes of high concentration of iron in groundwater were the weak acid of shallow groundwater in Deyang, high organic matter content in soil as well as the reducing environment.

Key words: groundwater, iron content, leaching experiment, oxidizing environment, reducing environment, pH, organic matter in soil