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Trace Elements in Abiotic and Biotic Environments
15.3 WATERS
The median F concentration in the world ocean water is estimated at 1.3  mg/L,
within the range of 0.03–1.35 mg/L. Nozaki (2005) calculated its average concentration in the North Pacific Ocean as 2.8 mg/kg. Most of the fluorides in the oceans are
received from rivers; lesser amounts come from atmospheric deposition.
River water contains F from 0.05 to 2.7 mg/L (Table 15.1), but its median value
for stream water in Finland is 0.0008 mg/L (Reimann and Caritat 1998). In some spa
water, F concentration can reach 12 mg/L. Its content in groundwater is associated
with both geological and anthropogenic sources. Excess F is reported for calcareous bedrocks and anthropogenic factors. Increased F concentrations are in arid and
semiarid regions, where it is of a great health concern (Jacks et al. 2005). Riverine
flux of F for some industrial regions is of environmental risk.
Fluorine is easily evaporated from water basins to the atmosphere, but also is
deposited into water. In natural water, below pH 5, F ions form strong complexes
with Al, and thus concentration of free F is low. At higher pH, dominate Al–OH
complexes and thus free F level increases. Both Ca carbonates and phosphates fix F,
and remove from the solution.
Fluorides are accumulated in some marine aquatic organisms. Toxic effects due
to fluorosis were observed in some species of mussel, mullet, crab, and shrimp in an
estuary where wastes from an aluminum plant were released.
Rainwater and snow-melt water in regions of the Kola Peninsula contain about
0.05 mg F/L. Rainwater sampled (during 1998–2001) around Italian volcanoes contains F within the broad range of 0.005–450 mg/L (Bellomo vide Kabata-Pendias
and Mukherjee 2007).
Fluorine concentration in drinking water is of a special concern, as it is the main
source of this element in the nutrition. Its level in water of the most countries varies
between <0.1 and 3 mg/L, but in some countries (mainly in dry and hot climates) it
can reach up to >5 mg/L.
Median F concentration in bottled water of the EU countries is 0.21 mg/L, and in
tap water is 0.09 mg/L (Birke et al. 2010). In the United States, bottled water and tap
water contain this element within the range of 0.05–0.34 mg/L, and 0.05–1.0 mg/L,
respectively (ATSDR 2002b). Threshold F concentration for drinking water is established at 1.5 mg/L, by the WHO Guideline (WHO 2011a), whereas by the European
Economic Community it is established for bottled water at 5 mg/L (Diduch et al.
2011). Addition of F to drinking water, relatively common in the last century, is now
definitely stopped (Limeback 2001).
15.4 AIR
Concentrations of F in the atmosphere are highly variable, due to its differentiated
sources: (1) marine aerosols, (2) volcanic eruptions, and (3) industrial emissions,
especially from coal burning. In the air, gaseous HF is absorbed by atmospheric
water (rain, clouds, fog, and snow), forming an aerosol or fog of aqueous hydrofluoric acid. F particulates fall down on land or surface water, by wet and dry
deposition.