10 Anthropogenic Sources of High-Fluoride Groundwater

Anthropogenic sources of F can be produced by wastewater discharges and by atmospheric emissions. Such emissions are the largest of the industrial F releases, originating from coal-fired power plants, brick-making plants, ceramic industries, and aluminum smelters (Fuge, 2019). Coal combustion accounts for the largest source of anthropogenic emissions of F and has contaminated soils and crops. No cases of groundwater contamination from this source are known. Shallow groundwater contamination by F immediately below the Tiwai Point aluminum smelter in New Zealand has been reported but observation wells are not sufficient to delineate a plume of F in the groundwater. The smelter is situated on a spit surrounded by seawater at the southern tip of South Island, quite remote from any major residential or agricultural areas. The Kaiser Aluminum-Mead Works Potliner superfund site in the state of Washington, USA, has a documented 2-mile fluoride and cyanide groundwater plume which was discovered in 1978. Recent analyses indicate the main part of the plume to range from 10 to 75 mg F/L (Hydrometrics, 2013).

Most soils have a strong ability to sorb air-borne F and the attenuation of F in soils may be strong enough in many places to prevent much groundwater contamination. Both air and water discharges can contribute F to groundwater although wastewater discharges are likely to be the larger contributor of F. The phosphate industry and the aluminum industry produce wastewater discharges that can have high F concentrations. Cases of fluorosis were found among residents who lived close to the phosphorite mining area of Hahotoe-Kpogame, Togo (Tanouayi et al., 2016). The highest concentrations were found in wastewater discharged to the sea (12-20 mg/L) and in local market produce (up to 2 percent). There is often abundant limestone where phosphorite deposits occur and this rock has a strong capacity to sorb F, inhibiting its transport in groundwater. Several other industries can also produce F in their wastes such as the steel industry, glass-making industries, dye industries, and plastics industries. The effects on groundwater composition are generally of localized concern, whereas geogenic F contamination is much more widespread both in spatial coverage and global occurrences.