Titanium [Ti, 22]
337
whereas in waters of the drainage basin its amounts are from 1.2 to 29 μg/L
(Szefer 2002). Its mean amount in the North Pacific Ocean is reported to be up to
0.007 μg/L (Nozaki 2005).
Aquatic biota, especially seaweeds, accumulate Ti within the range of 22–60 mg/kg
(Szefer 2002). Increased Ti levels in some algae may introduce larger amounts of
the metal into the food chain, which results in high concentrations of the metal, up
to 400 mg/kg, in the hard tissues of some sea animals, which should be of environmental concern.
Rainwaters collected in Sweden, during 1999, contained Ti at an average value of
0.44 μg/L (Eriksson 2001a).
Median Ti concentrations in bottled water of the European Union (EU) countries
are 0.052 μg/L, and is a bit lower than that in tap water, estimated to be 0.087 μg/L
(Birke et  al. 2010). Ti in drinking waters of the United States is in the range of
0.5–15 μg/L, at a mean value of 2.1 μg/L.
51.4 AIR
Titanium concentration in the atmosphere is mainly of terrestrial origin. However,
anthropogenic sources of Ti are also of great importance, which is clearly demonstrated by its highly elevated amounts in air of urban and industrial regions (Table 51.1).
Concentration of Ti in air of the United States range from 10 to 100  ng/m 3 , but is
reported to be elevated in some industrial region up to about 1000  ng/m 3 (KabataPendias and Mukherjee 2007).
Lichens and mosses from Norway contain Ti within the range of 12–310 mg/kg,
which is a clear evidence of Ti aerial pollution (Berg and Steinnes 1997).
51.5 PLANTS
There is no clear evidence about the biochemical role of Ti in plants. Possibly, it
may have some functions in the nitrogen fixation by symbiotic microorganisms and
in photooxidation of nitrogen compounds by higher plants. Thus, although it is not
accepted as an essential element to plants, there are some reports on its beneficial
effects on the yield of some crops. However, there are also described toxicity symptoms (necrotic and chlorotic spots on leaves) at Ti content of 200 mg/kg in bush bean
(Wallace et al. vide Kabata-Pendias 2011). It is considered to be relatively unavailable to plants and not readily mobile in them. Concentrations of Ti decrease with
age, and may be reduced by one-third in older plants, as compared to plants in early
growth.
Contents of Ti in plants seem to be highly controlled by soil properties. The highest Ti contents, up to 100 mg/kg, are in plants grown on loess soils and some weathered in situ soils, whereas its lowest amounts (about 1 mg/kg) are in plants grown on
histosols. In general, its phytoavailability is low.
Levels of Ti in plants vary considerable within the range of 0.15–80  mg/kg,
and in food plants it ranges from about 0.1–7.0 mg/kg. The lowest contents are in
cereal grains and fruits, and the highest in lettuce, radish, and corn. Cereal grains