Rhizospheric Mobilization of Radiocesium in Soils

Abstract

Though soil-plant transfer is the first step by which radiocesium enters the food chain, it has been scarcely studied in the rhizosphere. Forty-seven soil horizons from 17 pedons with widely varying properties were contaminated with carrier-free 137 Cs + and placed into close contact with an active macroscopic rhizosphere of ryegrass for 4 days. The 137 Cs rhizospheric mobilization was strongly correlated with the sodium tetraphenylboron-extractable 137 Cs (r ) 0.94), supporting that K depletion in the rhizosphere is a capital driving force in 137 Cs uptake. The 137 Cs soilplant transfer factor varied from 0.02 to 3.69 g g -1 between soil materials and was strongly negatively correlated to the radiocesium interception potential (RIP) (r ) -0.88), a common Cs binding characteristic in soil. RIP largely differed between soil materials (13-4861 µmol g -1 ) and was directly related with the soil vermiculite content (r ) 0.70). Our results, validated in a wide variety of soils, show that both vermiculitic minerals and plant roots act as competitive sinks for 137 Cs + in the rhizosphere. They further support that many 137 Cs-polluted soils in semi-natural environments can act as a potential source for long-term contamination of the above standing vegetation because they have low K availability.

Inventories and concentration profiles of 137Cs in undisturbed soils in the northeast of Buenos Aires Province, Argentina

“…The principal factors affecting 137 Cs migration in the soil are, among others, pH, organic matter content, textural class, mineralogy, competitive ions and concentration of radionuclides in the soileliquid phase (Sawhney, 1964;Cornell, 1993;Staunton et al, 2002;Giannakopoulou et al, 2007;Singh et al, 2009). Cesium migration in soils is a very slow process and its retention is generally admitted to be controlled by weathered mica (Delvaux et al, 2000). Some micaceous minerals, such as illite and vermiculite, tend to catch Cs in their interlayers.…”

Radiocesium interception potential (RIP) of smectite and kaolin reference minerals containing illite (micaceous mineral) as impurity

“…In particular, Cs + has the lowest hydration energy of these cations so that strong adsorption occurs in the FES. Radiocesium may also be strongly adsorbed in the hydrated interlayer spaces in vermiculite, as indicated by Delvaux et al (2000) for European soils.…”

Understanding Root Uptake of Nutrients, Toxic and Polluting Elements in Hydroponic Culture

“…In this respect, the culture devices with substrate (device 3) allow to study the impact of the chemical environment of rhizosphere on the mobilization of elements from the solid phases in soil (Hinsinger et al, 1992;Delvaux et al, 2000;Rufyikiri et al, 2004). In the study of Rufyikiri (2004) (Fig.…”