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Trace Elements in Abiotic and Biotic Environments
be a source of elevated W contents in soils of certain areas. According to Thomas et al.
(2009), the toxicity of W released from discharged shot was assessed against previous
studies, which established a 1% toxic threshold for soil organisms.
In soils, W remains mainly in primary compounds and minerals. Some part of
W is associated with Fe oxides, and with humic acid and fulvic acid. Mobile species
of W, especially in soils at pH > 7, may enter groundwater. In alkaline soils, W is
mainly in monomeric forms, whereas in acidic soils it is present in polymeric forms.
In soil, W metal oxidizes to the W anion, which can be uptaken by some small
organisms, where it may substitute for Mo in several enzymes. Presumably, it plays
an essential role in the biology of microbial organisms, and is present as an active
site in specific microbial enzymes.
52.3 WATERS
Although most of W minerals are slightly soluble, its global mobility is relatively
high (Gaillardet et al. 2003). The median W concentration in seawaters is estimated
to be 0.1  μg/L (Reimann and de Caritat 1998), whereas its content of 0.01  μg/L
is reported for the North Pacific Ocean (Nozaki 2005). In seawaters it is likely to
occur as oxide species, WO 4
2 . Stream and river waters contain W within the range of
0.01–0.05 μg/L. Exposure to water-soluble W compounds is a great threat to human
and animal health.
Tungsten is readily accumulated in ocean bottom sediments, mainly in polymetallic compounds. In Fe–Mn nodules of the Baltic Sea, W contents vary from 0.4 to
284 mg/kg (Szefer 2002).
In rainwaters collected in 1999 in Sweden, the concentrations ranged from 4.2 to
23 ng/L (Eriksson 2001a).
Median W concentrations in bottled water of the European Union countries are
0.0189 μg/L, and is a bit higher than in tap water, estimated to be 0.0113 μg/L (Birke
et al. 2010).
52.4 AIR
The atmosphere above Spitsbergen, Norway, contain W within the range of 0.004–
0.08 ng/m 3 . Its amounts in air from remote and polluted regions vary from 0.005 to
0.02 ng/m 3 , respectively (Reimann and de Caritat 1998). However, the median W
concentration in air was estimated to be 2.5 ng/m 3 , whereas according to the recent
data (ATSDR 2005c), mean W concentration in air is 10 ng/m 3 .
52.5 PLANTS
Tungsten is relatively easily available to plants. A lower uptake from acidic soils suggests that W is absorbed in anionic species, WO 4 . Its great proportion is accumulated
in roots. Plant growing in areas around W ore bodies, may accumulate much higher
W amounts, up to about 2500 μg/kg, without toxicity symptoms. Therefore, W contents in plants have been used in geochemical prospecting. Elevated W contents of
these plants might be associated also with its atmospheric source.