Actinides
385
in munitions is controversial, because of questions about potential long-term health
effects. Tank armor and other removable vehicle armor are hardened with DU plates.
Most DU arises as a by-product of the production of U for the use in nuclear reactors
and nuclear weapons.
The first use of munitions with DU was in Sarajevo war in 1992, and the second
time in Iraq war in 2003. DU distributed with munitions and various war vehicles
remains a long time in the environment and is taken by people with water, plants, and
aerial dust. some amounts of DU in food are still noticed in Bosna and Hercegovina
(Cubadda et al. 2009). Since 2008, the addition of DU to munitions has been forbidden.
DU is also applied as a shielding material in some containers used to store and
transport radioactive materials. Uranium density is about 70% higher than that of Pb,
but less dense than that of Au and W. Although the metal itself is radioactive, its high
density makes it more effective than Pb in halting radiation from strong sources,
such as Ra. Other uses of DU include counterweights for aircraft control surfaces,
as ballast for missiles, and as a shielding material. It is also used as a colorant in
U-glass, producing orange-red to lemon yellow hues.
58.3.2 SOILS
The worldwide uncontaminated soils contain U within the range of <0.4–96.0 mg/kg.
The lowest U contents (mean 0.6 mg/kg) are reported for sand dunes and peat soils of
Japan, whereas agricultural soils contain median U, within the range of 1.4–2.4 mg/kg
(Takeda et al. 2004). Uranium contents of soils in Spitsbergen, Norway, are within the
range of 0.0032–0.0765 mg/kg (Gulińska et al. 2003), whereas in soils around Sankt
Petersburg (Russia) its amounts vary from 0.5 to 5.5 mg/kg (Shtangeeva 2010). Various
U mean contents of soils are reported for several countries: the lowest is for Poland,
0.79 mg/kg, and the highest for the United States, 3.70 mg/kg (Kabata-Pendias 2011).
Elevated U contents of soils are from various sources, mainly from fossil fuel
power plants, nuclear wastes, and also P fertilizer works (Paulo and Pratas 2008).
Extremely high levels of U are in P fertilizers, within the range of 80–1300 mg/kg,
depending upon the kind of phosphate rocks. Thus, these fertilizers are the important
source of U, which is likely to accumulate in the upper layer of soils, up to about
200 mg/m 2 , after 61 years of cultivation period (Takeda et al. 2006). Some amounts
of U in soils may also be from other fertilizers; its content is 0.22 mg/kg in slurry
from dairy cows and 10 mg/kg in sludge (Eriksson 2001a). Uranium may be fixed by
OM, and thus it is slightly mobile in peat soils. Changing the oxidation state from U 6+
to U 4+ by some bacteria reduces its mobility, as well as adding calcite materials, for
example, apatite. Also melanin produced by various bacteria enhanced U immobilization in soils (Turick et al. 2008).
Soils of the United States show a relatively small variation in U concentration
among soil types, with the exception of radionuclide 238 U, which is likely to be concentrated in soils close to aquatic systems (Meriwether vide Kabata-Pendias 2011).
Uranium in seepage pore water of contaminated soil occurs mainly as sulfate species
UO 2 SO 4(aq) (Baumann et al. 2012). Variable parameters (pH and Eh) of groundwater
may control the reactivity of U species. The range of U concentration in groundwaters is 2–12 μg/L, and it is higher in soils in areas of hot and dry climates.