Assessing the fate of radioactive nickel in cultivated soil cores.
Parameters regarding fate of (63)Ni in the soil-plant system (soil: solution distribution coefficient, K(d) and soil plant concentration ratio, CR) are mostly determined in controlled pot experiments or from simple models involving a limited set of soil parameters. However, as migration of pollutants in soil is strongly linked to the water migration, variation of soil structure in the field and seasonal variation of evapotranspiration will affect these two parameters. The aim of this work was to explore to what extent the downward transfer of (63)Ni and its uptake by plants from surface-contaminated undisturbed soil cores under cultivation can be explained by isotopic dilution of this radionuclide in the pool of stable Ni of soils. Undisturbed soil cores (50 cm x 50 cm) were sampled from a brown rendzina (Rendzic Leptosol), a colluvial brown soil (Fluvic Cambisol) and an acidic brown soil (Dystric Cambisol) using PVC lysimeter tubes (three lysimeters sampled per soil type). Each core was equipped with a leachate collector. Cores were placed in a greenhouse and maize (DEA, Pioneer) was sown. After 44 days, an irrigation was simulated at the core surfaces to supply 10 000 Bq (63)NiCl(2). Maize was harvested 135 days after (63)Ni input and radioactivity determined in both vegetal and water samples. Effective uptake of (63)Ni by maize was calculated for leaves and kernels. Water drainage and leaching of (63)Ni were monitored over the course of the experiment. Values of K(d) in surface soil samples were calculated from measured parameters of isotopic exchange kinetics. Results confirmed that (63)Ni was strongly retained at the soil surface. Prediction of the (63)Ni downward transfer could not be reliably assessed using the K(d) values, since the soil structure, which controls local water fluxes, also affected both water and Ni transport. In terms of (63)Ni plant uptake, the effective uptake in undisturbed soil cores is controlled by isotope dilution as previously shown at the pot experiment scale.
Denys
Sébastien
S
Laboratoire Sols et Environnement, UMR 1120 ENSAIA-INPL/INRA, 2 avenue de la Forêt de Haye, Vandoeuvre-lès-Nancy, France. Sebastien.Denys@ineris.fr
Echevarria
Guillaume
G
Florentin
Louis
L
Leclerc
Elisabeth
E
Morel
Jean-Louis
JL
D007700:Kinetics; D009532:Nickel / Q000032:analysis* / Q000378:metabolism; D011834:Radiation Monitoring; D011868:Radioisotopes / Q000032:analysis* / Q000378:metabolism; D012987:Soil / Q000032:analysis*; D012990:Soil Pollutants, Radioactive / Q000032:analysis* / Q000378:metabolism; D003313:Zea mays / Q000378:metabolism
D011868:Radioisotopes; D012987:Soil; D012990:Soil Pollutants, Radioactive; D009532:Nickel