Fluoride distribution and transport along rivers in the French Alps.

Fluoride concentrations in water, sediments, and plants were determined at 26 locations along five rivers in the French Alps where aluminum factories have been discharging fluoride into the surrounding environment since the end of the last century. Despite a wide range of biological and constructional damages caused by fluoride contamination in the past, there was no alarming level of fluoride found in the water, sediments, or plants. Fluoride concentration in water ranged from 0.11 ppm (considered to be natural background level) to 0.62 ppm (moderate contamination). The highest fluoride concentration was 360 ppm in sediments and 207 ppm in plants. The increase of fluoride concentration along the rivers was gradual from upstream to downstream. This gradual increase suggested that the fluoride pathway was from factory to stack, to air, to the entire valley, and to the river. The amount of fluoride transported from the Maurienne valley by the Arc river was estimated to be 680 tons per year. Of this 97.8% tons (665 tons) was transported by the flowing water and the rest (2.2% or 15 tons) by sediments moving downstream.