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VOL. 70 (4), 961-999, 2004 VANADIUM - AN ELEMENT BOTH ESSENTIAL AND TOXIC

Lowest concentrations were found in limestones, dolomites (10-
45 mg/kg), sandstones (10-60 mg/kg) and syenites, granites and gneis-
ses (30-100 mg/kg). The geochemical characteristics of vanadium are
strongly dependent on the oxidant state (+ 2, + 3, + 4 and + 5) and
on the acidity of the media. Vanadium does not form its own mine-
rals, but rather replaces other metals (Fe, Ti, Al) in crystal structu-
res. During weathering, vanadium is adsorbed or incorporated into
mineral structures of clay or iron oxides.

Highest concentrations of vanadium in soil are reported in soils
of mafic rocks (150-460 mg/kg), while the lowest (5-22 mg/kg) were
found in peat soils. Loamy and silty soils, as well as some ferralitic
soils (Rotliegende), also contain large amounts of vanadium, which
exceed those of the parent materials. The average vanadium content
of soils world-wide has been calculated to vary from 18 to 115 mg/
kg. The geometric mean of vanadium concentration in soils varied
between 60 and 100 mg/kg.

Industrial processing of certain mineral ores (ore smelters, ce-
ment, and phosphate rock plants) and the burning of coal and oil
will increase the deposition of vanadium residues in soils. Combus-
tion of vanadium-rich fuel oils is an especially serious source of
vanadium in soils (71).

Small amounts of vanadium compounds are found in air where
there is no known anthropogenic contamination (0.02-0.08 ng/m3).
About 65000 t of vanadium per year naturally enter the earth’s at-
mosphere (dust, erosion of soil and rocks, marine aerosols). The
vanadium concentration over populated areas is often greater than
over unpopulated regions (130). During cold periods the concentra-
tions of vanadium are usually higher than in warm weather. The
increases in vanadium have been assumed to be due primarily to fly
ash formed during the burning of fossil fuels. Burning these fuels in
the past caused about 110000 t of V/a to enter the atmosphere glo-
bally (96).

The concentration of vanadium in sea water is in the order of
2 µg/L, but it is about 5 times higher in the deep sea compared to
the surface (27). The vanadium concentration in drinking water in
Germany varies with the geological origin of the site, with levels
between 0.18 µ/L (Keuper, slate, phyllite, Bunter) and 1.10 µg/L (Rot-

967