Plants cesium uptake

Clinoptilolite amendments to soil have greatly reduced cesium uptake by plants (e.g. on Bikini AtoU) and clinoptilolite from the Belli Plest deposit in Bulgaria was dropped by air to help control the Chernobyl accident. Finally, both zeolite A and a chabazite played key roles in the Three Mile Island clean-up program, again to scavenge Cs radioisotopes. 

The bioavailability of cesium for plants depends on the pH-value of the soil (Wytten-bach et al., 1991), and is high on soils with low pH-values, as are found on moors and in forests. The bioavailability is markedly lower in soils with higher pH-values such as in farmed soils (e.g., meadows or pastures) and other agricultural soils where the pH-value is maintained at 6-8 by fertilizing. A high potassium concentration in the soil has also been shown to lead to a decrease in cesium uptake by plants (Shaw and Bell, 1991). 

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). 

Higher phytoextraction coefficients indicate higher metal uptake. The effectiveness of phytoextraction can be limited by the sorption of metals to soil particles and the low solubility of the metals however, metals can be solubilized through the addition of acids or chelating agents and so allow uptake of the contaminant by the plant. Ethylene diamine tetra-acetic acid (EDTA), citric acid, and ammonium nitrate have been reported to help in the solubilization of lead, uranium, and cesium... 

Plant roots take up cesium readily because of its similarity with the essential nutrient, potassium. Plants differ in their accumulation of cesium (Broadley and Willey, 1997 Lasat et al., 1998 Broadley et al., 1999a,b). This may be due to differences in rooting pattern, root uptake, or translocation within the plant, but the cause is not clearly identified. Cesium is mobile within plants and has similar trends in the translocation within plants to K (Broadley and Willey, 1997 Zhu and Smolders, 2000). Rather little is known about differences between species in their capacity to discriminate between Cs and K. There appears to be a threshold below which Cs uptake by roots increases with decreasing K concentration. The value of this threshold has been reported to be 1 mmol L , 250 Itmol L , or 20 Itmol (Shaw and Bell, 1989, 1991 Shaw et al., 1992 Buysse et al., 1996 Smolders et al., 1996 Zhu, 2001). This inhibition may be due in part to increased efflux of absorbed Cs (Zhu et al., 1999). Model prediction of Cs uptake often overpredict uptake and are improved if account is take of soil-solution potassium concentration below 1 mM (Smolders et al., 1997 Absolom et al., 1999 Roca-Jove and Vallejo-Calzada, 2000), Cs uptake is found to be enhanced by potassium starvation (Jones et al., 1998 Broadley et al., 1999b Zhu et al., 2000), but the effect is short-lived (Willey and Martin, 1997 Staunton et al., 2003). 

Kodaira K, Tsumura A, Kobayashi H. 1973. Uptake of radioactive strontium and cesium in rice plants (1) Accumulation of Sr and Cs in rice grains through roots. J Radiat Res 14 31-39. 

Fuhrmann M, Lasat MM, Ebbs SD, Kocliian LV, Cornish J (2002) Uptake of cesium-137 and strontium-90 from contaminated soil by three plant species application to phytoremediation. J Environ Qual 31 904-909... 

Berreck, M., Haselwandter, K., 2001. Effect of the arbuscular mycorrhizal symbiosis upon uptake of cesium and other cations by plants. Mycorrhiza 10, 275-280. 

Deposited cesium penetrates slowly from the soil surface into deeper soil layers [3] depending strongly on the soil type [2]. Sorption processes can further retard the Cs migration rate. The relative abundance of clay and mica minerals, particularly illite, results in the rapid and nearly irreversible cesium immobilization in the topsoil layer [4]. Meanwhile, cesium, as well as the other radionuclides that behave like cations, can be moved upward by plant uptake. This process depends on various factors plant... 

Certain plant species are known as cesium pollution indicators, but the uptake by each individual plant can be very different. In the first place, it depends on the presence of free cesium in the species root system zone and competitive effects of potassium [5-10]. Different soil types show differences in the ratio of sorbed to fixed cesium, in soil size fractions, in pH value, and content of organic matter, as well as in Cs vertical distribution profiles and, consequently, in cesium transfer from soil to plants [11-18]. 

Alternatively, plants and the bees that visit them can provide a means of detecting and monitoring radionuchde pollution over large areas. Depending on the honey bee pasture types and the plant uptake factors mentioned previously, Cs appears in measurable levels in various types of honey [19-21], Heather plants, Calluna vulgaris especially, are species well-known as indicators of cesium pollution [22,23],... 

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