Gallium [Ga, 31]
121
Rainwater, sampled in Norway, contained Ga at the range of 0.03–0.04  μg/L
(Reimann and de Caritat 1998), and those sampled in Sweden, in 1999, had Ga
between 0.002 and 0.011 μg/L (Eriksson 2001a).
Median Ga concentration in bottled water of the EU countries is 0.002 μg/L,
and is lower than those in tap water, 0.07 μg/L (Birke et al. 2010). Water containing
GaCl 3 at the concentration 3.5 mg/L may be toxic to some animals.
16.4 AIR
The atmosphere from remote regions contains Ga at amounts below 0.14 ng/m 3
(Table 16.1).
Gallium concentrations in moss samples collected in Norway during 1999 was
1.1 mg/kg, and in samples collected during 2000 was 0.09 mg/kg, which clearly indicates its lower emission (Berg and Steinnes 1997). Mean Ga contents of two moss
species from mountains in Poland (0.05–0.1 mg/kg) are quite similar to the same
moss species from Alaska (0.09–0.1 mg/kg). This may suggest that atmospheric Ga
concentrations in both regions are quite close (Migaszewski et al. 2009).
16.5 PLANTS
Gallium is commonly present in plants, and the higher Ga/Al ratio in plants than in
soils, in which plants grown can indicate its selective uptake by plants. There is no
evidence for the necessity or toxicity of Ga in plants, although there are some suggestions for its beneficial role in the growth of microorganisms, and some fungi (e.g.,
Aspergillus). Ectomycorrhizal beech roots and organic soil horizon from unpolluted
regions of Sweden contain Ga at amounts 0.06 and 0.41 mg/kg, respectively (Tyler
2005).
Gallium contents of wheat and barley from Sweden average at about 0.001 mg/kg
(Eriksson 2001a). Its much higher concentrations (0.02–5.5 mg/kg) are reported to
be in some herbage. Also in lichens and bryophytes from various regions, Ga concentrations are relatively high, 2.2–60 and 2.7–30 mg/kg, respectively (Kabata-Pendias
2011). Moss sampled in Norway contained Ga up to 16 mg/kg (Berg and Steinnes
1997).
16.6 HUMANS
Persons with a mass of 70 kg contain less than 1  mg of Ga in the body (Emsley
2011). Data on natural Ga levels in humans are scanty. Gallium concentrations are
always below the μg/kg level. Its distribution in several human brain areas, evaluated by radiochemical neutron activation analysis, was found to be dishomogeneous
(Speziali et al. 1989).
Gallium is an element of increasing biological interest: it is involved in problems
related to environmental pollution (Ga compounds are used in electronics industry)
and to clinical treatments. Moreover, as its chemical behavior is similar to that of Al,
it could play a role in the health effects attributed to this element. However, it has no
proven benefit from its function in the body.