Arsenic pollution of groundwater and its release mechanism in the central part of the Hetao Plain, Inner Mongolia, China

• Published in: Chinese journal of geochemistry Vol. 25; no. B08; pp. 101 - 102
• Main Author: Hanjin LUO Hiroki Hagiwara Kouichi Terasaki Fumio Kanai Takahisa Yoshimura Junji Akai Takeo Ta kano Tadashi Hasegawa Yoh＇ichi Sakai
• Format: Journal Article
• Language: English
• Published: 2006
• Subjects: 内蒙古; 地下水; 水体污染; 环境控制
• ISSN: 1000-9426; 1993-0364

Arsenic pollution of groundwater has become a serious health problem in several regions of the world. Wuyuan County located in the central part of the Hetao Plain, Inner Mongolia, is one of the most severely arsenic polluted areas. Peoples of the county have used groundwater of shallow （12-25 m） tube-well as drinking water. The groundwater is Na-HCO3 and Na-Cl type on the piper plots and aligns with steady Ca ： Mg ratio on cation diagram. The arsenic content in the water is more than 0.2 mg/L and the highest value reaches up to 0.52 mg/L. Drilling data show that Holocene sediments are divided into three zones on the basis of their color appearances; brown, grey and dark gray zones. The strata from 2m to 9-14m under the surface are mainly composed of clay and silt which are impermeable layers. The grey and dark grey zones composed of sand underlie the impermeable bed and the condition of their zones is reductive. At the depth of 30 m near the bottom of drilling, ORP of the groundwater is -300- -400 mV. The dark grey sand changes to yellow in color under the atmosphere. Under reducing environment, the color returns to its original dark grey. The characteristic color is due to amorphous or low-crystalline Fe sulfide coating sand grains. The sediments are of fluvial origin by the Yellow River. The arsenic content in the sediments is rich in fine-grained part and its values are more than 20 mg/kg in clay layer. The highest is 38 mg/kg. X-ray diffraction and macroscopic observation show that the clay layer is made of minerals such as chlorite and illite and contains high quantities of organic matter.