Distribution of fluorine in the surface dust of Wuda coal base, Inner Mongolia of Northern China

Wuda coalfield in Inner Mongolia is one of China's typical old coal bases and has a coal fire history of over 50 years. Many studies have been carried out on fluorine pollution caused by high-temperature processing industries such as those related to the production of steel, aluminum, glass, brick, and tile. However, few studies have focused on fluorine pollution caused by coal-fired industrial parks or coal fires. For the present study, 224 dust samples were collected from Wuda district in Inner Mongolia and its surrounding zones, covering a total area of ~270 km2. Subsequently, fluorine concentrations in the samples were analyzed using the combustion-hydrolysis/fluoride-ion selective electrode method. Results showed that the average fluorine concentration of dust is 848 μg·g−1 (430-1504 μg·g−1) in Wuda coalfield and 1016 μg·g−1 (237-2830 μg·g−1) in industrial parks, which are more than four times the background value. The average fluorine concentration in the adjoining downwind urban area of Wuda is 488 μg·g−1, which is twice the background value. The results indicate that long-term fluorine release from the coal fire and industrial parks leads to significantly elevated fluorine concentration levels in the dust around the study area. The scenario of urban areas in close proximity to coal seam fires and industrial parks is not particular to Wuda; it is relatively common in northern China and elsewhere. Thus, the influence of coal seam fire and industrial parks on other cities merits further investigation.