Animal radiocesium

The half-period for decrease of muscle cesium-137 concentration in NTS animals after the cessation of atmospheric nuclear weapons testing in 1959 appears anomalous (Table I and Figure 2). In addition to being considerably greater (2.3 years) than the other half-periods found, its standard deviation was larger than the value. If one considers only the initial rate of decrease of radiocesium in these muscle samples, one finds a half-period of 0.9 year which is quite consistent with other data. Examination of these data, in comparison with data from liver (Figures 2 and 3), indicates that only muscle decreased its rate of decline in 1960. It should also be noted that the values during 1960 were only about twice the standard error of analysis. Thus, analytical error alone is not an improbable cause of these anomalous values. 

Techniques for the analysis of trace amounts of stable cesium include neutron activation analysis (NAA), and optical emission and atomic absorption spectroscopy (Iyengar et al., 1980). Often, the analysis of cesium in biological samples was only developed as a by-product of multielement NAA. Older analytical techniques include precipitation with potassiumiodobis mutha-te(III) or with K3[Fe(CN)6] in the presence of acetic acid. A more modem approach is that of precipitation with NH4Fe[Fe(CN)6] to the CsFe[Fe(CN)6], a reaction which is mainly used to minimize the intestinal absorption of radiocesium in farmed or wild animals (Jander and Blasius, 1989). 

To date, no sign of essentiality for plants, animals, and humans have been reported for cesium neither has any biomagnification by fauna been described, and soil concentrations of cesium are always much higher than that of both plants and animals. Cesium bioconcentration has not been observed in any specialized parts of plants, except for the skin of the hats of certain types of mushrooms, wherein cesium (detected as radiocesium) accumulates to high levels. In this situation it is thought that the cesium is enriched in the color pigments of the hat skin (Kalac, 2001). The potassium content of the mushroom was also found to relate inversely to the cesium content in other words, the higher the potassium content, the lower the cesium content (Marin et al., 1997). 

Haffelder, 1995). Indeed, this heterogeneity is still apparent at 10 years after the Chernobyl accident, as demonstrated by the radiocesium contamination of muscle tissues in game animals living in low- and highly contaminated areas of Bavaria (Table 1-5.1) (Hecht, 2004). 

Radiocesium is an excellent indicator for the behavior of inactive cesium in the biosphere because its radiation can be detected rather quickly, its passage through the compartments of biosystems can be studied much more easily than by direct estimation of the inactive cesium content. Thus, the behavior of radiocesium in ecosystems supplies much information relating to cesium transport in the atmosphere, soil, plants, and animals. 

Most cesium compounds are water-soluble, and this enables plants to absorb almost all radiocesium from the soil (Zhu and Smolders, 2000). The cesium isotopes are transported and stored in plants much in the way that potassium ions are stored, and this results in total radiocesium contamination of the plant tissues that in turn are eaten by animals (Zhu and Shaw,... 

In animals, cesium is absorbed almost totally in the intestine, and then distributed through the whole body via the blood circulation. Based on their analogy to potassium, radiocesium isotopes mainly accumulate in muscle tissues (Whickers and Finder, 2002). By contrast, connective tissues contain much less radiocesium, and fatty tissues are virtually radiocesium-free. 

Incorporated radiocesium mainly is eliminated via kidneys within weeks, and corresponds with potassium excretion. The biological half-lives range from a few days to several weeks, depending on species metabolic activity and the animals age (Hecht,... 

The radiocesium is lost from the cycle only by its own radioactive decay which, in the case of Cs is very slow due to the long physical half-life of this isotope (30.1 years). Thus, the vegetation in forest ecosystems will contain radiocesium for a long time, and this will result in radiocesium contamination of game animals living in cesium-contaminated forests. Indeed, this... 

The contamination of the game is species-dependent (see Table 1-5.1), due mainly to the types of plant eaten by the animals, as different plant species absorb different amounts of radiocesium from the soil (Table 1-5.3). Plant species gro ving vithin the same region also exhibit large variation in cesium uptake and accumulation (Table 1-5.4). Examples of this include mushroom species found in the Bavarian Forest and the Cortinarius species, vhich retain high cesium levels (Haffelder, 1995, Steine et ah, 2002). 

Radiocesium isotopes from the Chernobyl accident transferred easily to grazing farm animals. Both Cs and Cs were rapidly distributed throughout the soft tissues of animals after dietary ingestion and were most highly concentrated in muscle. Radiocesium activity in milk and flesh of Norwegian sheep and goats, for example, increased three- to fivefold 2 years after the accident and coincided with an abundant growth and availability... 

---