Cesium [Cs, 55]
67
Common Cs range in plants is estimated at <0.1–3  mg/kg. Tea leaves contain Cs
within the range 0.5–1.0 mg/kg AW (Aidiniyan vide Kabata-Pendias 2011). Roots
contain more Cs than tops of plants, as well as older plants have more Cs than
younger ones. Cesium distribution in plants is similar to K, which suggests that it
may compete with K in uptake processes and binding sites in cells (Isaure et  al.
2005). Its toxicity may be related to these interactions. According to White et  al.
(2003), the transport of Cs and K to xylem is different, and thus, the Cs/K concentration ratio differs among plants.
Cesium is easily absorbed from the atmosphere by mosses; mosses collected in
Norway during 1990–1995 contained cesium in the range 0.02–3.1 mg/kg (Berg and
Steinnes 1997). Its deposition in the United Kingdom in 1972–1981 was 0.6–1.2 g/ha
(Cawse 1987). The highest Cs content is reported in mosses from Germany (Reimann
and de Caritat 1998).
10.6 CESIUM ISOTOPES
10.6.1 INTRODUCTION
Concerns with radiocesium (two radioisotopes 134 Cs and 137 Cs) in soils and food
chain began since the accident in the Chernobyl nuclear power plant, in 1986. Some
amounts of these two radioisotopes have been released into the environment during
nearly all nuclear weapon tests, and some nuclear accidents. Also, ash from coal
burning and municipal waste incinerations may be a source of 137 Cs. However, there
is much less concern about 134 Cs, because it was released in small quantity and has
short half-life (t 1/2 is 2.1 years) compared to great emission of 137 Cs (t 1/2 is 30 years).
Deposition of both radionuclides was not only in surroundings of the reactor but also
in other European countries, and in other continents.
10.6.2 SOILS
The behavior of 137 Cs in soils is very similar to those of the stable Cs. Thus, when
deposited in soils, it is absorbed by clay fractions and SOM, and, therefore, migrates
slowly. Especially SOM, of a higher molecular weight, is likely to accumulate a high
proportion of this radionuclide. Also Fe and Mn sesquioxides decreased its mobility
in soils. These processes are also noticed in fresh alluvial sediments (Kaplan et al.
2005). Although clay minerals, in general, immobilize 137 Cs, hydromicas increase its
mobility in soils (Korobova and Chizhikova 2006).
All soils contain a certain amounts of 137 Cs. Levels of this radionuclide in agricultural soils of Japan are 1–37 Bq/kg (Tsukada and Nakamura 1999); in wetland of
South Carolina, United States, 0.2–10.1 Bq/g (Kaplan et al. 2005); in soils of Bulgaria,
0.9–21.2 kBq/m 2 (Zhiyanski et al. 2006); in soils of Kazakhstan, 82–120 mCi/km 2
(Panin 2004); in soils of France, >10 kBq/m 2 (Renaud et al. 2003); in soils of Belarus,
103–1500 kBq/m 2 (Kagan et al. 1996). The impact of industrial pollution on levels
of 137 Cs, within the range 15–25  kBq/m 2 , in forest soils of Finland has also been
reported (Outola et al. 2003).