High fluoride groundwater with high salinity and fluorite in aquifer sediments in Inner Mongolia, China

• Published in: Chinese journal of geochemistry 2006, Vol.25 (B08), p.103-103
• Main Author: Liuchun ZHENG Hanjin LUO Kazurou Bandou Fumio Kanai Kouichi Terasaki Takahisa Yoshimura Yoh＇ichi Sakai Sumie Kimura Hiroki Hagiwara
• Format: Article
• Language: English
• Subjects: 内蒙古; 含水层; 地下水; 氟化物; 水文化学; 沉积物; 溶解度
• ISSN: 1000-9426; 1993-0364

Fluoride poisoning is the most widespread and serious endemic disease in the inland river basins of northem China, where igneous rocks containing F-rich minerals of the Yanshan stage （Jurassic-Cretaceous） are extensively exposed in mountainous area. In Inner Mongolia, many residents have been confronted with severe health problem caused by high-fluoride groundwater for drinking. Arid and semi-arid climate in Inner Mongolia provides a favorable condition for the fluoride accumulation in groundwater. But the complicated distribution of high-fluoride shallow groundwater requires different contributing factors such as the type of F-bearing minerals and rocks, geochemical parameters of groundwater for the dissolution of fluoride, interaction period between groundwater and host rocks. The authors carried out investigations on high-fluoride groundwater in Zhenglanqi County of Inner Mongolia. Wells of polluted groundwater are sporadically distributed in the county. In Baiyintalahot and Sugaituhot, the depths of dug and tube wells are 2.6-4.6 m. The fluoride content of the groundwater ranges from 2.3 to 9.8 mg/L. The morbidity of fluorosis is as high as 87%. The groundwater in polluted areas is plotted on CaNa-HCO3Cl type of the Piper classification, whereas in not so polluted one it on Ca-HCO3. The average of sodium content in the polluted water is 302 mg/L, higher than that in not so polluted one. Other characteristic feature of the groundwater is rich in nitrogen in the form of nitrate and nitrite caused by excreta of livestock. The high fluoride groundwater is observed in aquifer of the Holocene sand bed which unconformably overlies the Tertiary clay formation at a depth of 5 m. The detrital sands are derived from surrounding mountains where Jurassic and Cretaceous rhyolitic welded tuff, pyroclastic rocks and intrusives are widely exposed. On the basis of separation of heavy minerals from Holocene sand, the authors found fluorite crystals as detrital grains. It is well known that the solubility of fluorite increases with increasing salinity of water. Recently, Grand and Mucci （2004） measured the solubility of fluorite in various salt solutions.