Studies on geological background and source of fluorine in drinking water in the North China Plate fluorosis areas

Abstract

Endemic fluorosis in northern China is usually produced by high fluorine (F) content in drinking water. Thirty-one samples of drinking waters, mainly well waters and nearly 200 samples of rocks, loess, and coal were analyzed for F content using the combustion hydrolysis–fluoride-ion selective electrode (ISE) method. The geologic cross sections of two well-known fluorosis basins were studied. The solubility of F in different rock types collected from fluorosis areas was determined. Results showed that areas of endemic fluorosis in northern China are located in coal-bearing basins which are comprised of three stratagraphic portions. The lowest portion is Precambrian granitic rocks or Cambrian–Ordovician carbonates. The middle portion consists of Permo-Carboniferous or Jurassic coal-bearing sequences. The upper portion is 0–400 m Pleistocene loess. Flourine content in the Precambrian granite-gneiss contained (a) 1090–1460 ppm, in the Cambrian-Ordovician limestone and dolomite, (b) 52–133 ppm, in black shales and coal gob of Permo-Carboniferous coal-bearing strata, (c) 200–700 ppm, and (d) Pleistocene loess 454–542 ppm. The solubility of F in black shales of coal-bearing sequences was higher than in Precambrian granitic rocks, and both were more soluble than loess. F solubility from Precambrian granitic rocks was moderate, but Precambrian granitic rocks have high F content and thus contribute an appreciable amount of ion to the shallow groundwater (well water). Varying F content in shallow groundwater is controlled by geological conditions. The sources of F in the shallow groundwater from fluorosis areas in northern China are mainly derived from black shales of coal-bearing sequences and Precambrian granitic basement in the basins of northern China.

Keywords:

• Fluorosis
• fluorine in drinking waters
• coal
• black shales
• granitic rocks
• northern China

Acknowledgements

We thank Bingren Wei, Biyu Wang, Bolin Gao, Xiangyou Zhao, the staff at Xiangshan and Magouqu Coal Mines, and the staff at the Coal Power Group Company for their valuable help. This work is supported by the National High-Tech R & D Program (863 Program) (Grant No. 2004AA601080 and 2006AA06Z380) and Key Project of National Natural Science Foundation of China (90202017).

Notes

Note

1.  Determination of F in coal. Direction for GB/T4633–1997. Beijing: China Criterion Publishing House, 1997