390
Trace Elements in Abiotic and Biotic Environments
generators, are used in some spacecrafts as reactor fuel, and may be a component of
some nuclear weapons and reactors.
Currently, most of the Pu found in the Earth’s environment results from human
activities, in particular, the testing of nuclear weapons in the atmosphere. There is
an estimation that about 3  t of 239 Pu and 241 Pu was released into the atmosphere,
of which about 80% are in the Northern Hemisphere (United Nations Scientific
Committee on the Effects of Atomic Radiation). Disposal of Pu waste from nuclear
power plants and nuclear weapons is of environmental concern. Earlier aboveground
nuclear tests are still its source in some places.
58.4.2 ENVIRONMENT
Plutonium is discharged from nuclear facilities mainly as PuO 2 , and when in soils,
its behavior is controlled by various soil factors. Its migration down rural soils is
relatively low, and it is likely to accumulate in 10 cm top layer (Roussel-Debet 2005).
In soils of a buffered zone near Denver, Colorado, which was contaminated with
Pu in 1960, about 99% of its radionuclides remain in the top layer (Little et al. vide
Kabata-Pendias 2011).
Elevated concentrations of Pu radionuclides in soils, bottom sediments, and
aquatic plants along the Yenisei river, Siberia, were reported, as an effect of a longterm impact of weapon plants and mining activities (Bolsunovsky and Bondareva
vide Kabata-Pendias 2011). The average fallout of 239+240 Pu on soils in the temperate zone of the United States, was calculated as 7.5 × 10 4  Bq/km 2 and of 238 Pu as
1.9 × 10 3  Bq/km 2 (ATSDR 2002b). The levels of 238 Pu in soils of the United Kingdom
were detected within the range of 0.2–18 nCi/kg and of 239+240 Pu in the range of
0.8–83 nCi/kg (ATSDR 2002b). Soils of Kazakhstan, sampled in 1992, contained
239+240 Pu from 10 to 93 mCi/km 2 (Panin 2004). Soils of Iran contain 239+240 Pu from
80 to 360  mBq/kg (Aliabadi vide Kabata-Pendias 2011). Meadow soils around
Heidelberg, Germany, contain both Pu isotopes within the range of 290–450 mCi/km 2
(Jakubick vide Kabata-Pendias 2011).
Plutonium is known to bind to soil particles very strongly, especially it is adsorbed
by hematite in larger amounts than by silica and montmorillonite. It is easily complexed by fulvic and humic acids, and is fixed by mineral particles in organic forms.
Low pH value, low clay minerals and OM contents, as well as microbial activity may
enhance Pu mobility. However, it may also be accumulated in some microorganisms.
Its nitrate compound, Pu(NO 3 ) 4 , is mobile, and thus may migrate in soils and is available to plants. Mobile Pu species (organic and nitrate compounds) are easily available to
plants. However, Pu is more likely to be fixed to the root surface than to be transported
into plant tops. Observed absorption of Pu on the plant surface indicates predomination
of its aerial sources.
PuO 2
2+ is tightly bound in soils, whereas Pu(NO 3 ) 4 is easily mobile and thus
available to plants. Also Pu complexes with organic compounds are phytoavailable.
However, even in areas where soils contained elevated amounts of Pu (53 mCi/m 2 ), its
concentrations in plants were relatively low (Little et al. vide Kabata-Pendias 2011).
Radionuclides, 239+240 Pu, were present in waters of the southern Baltic Sea, during
the period 1980–1991, at the level about 0.0035 MBq/L, and have not changed after the