The aim of the study presented here is to determine the impact of short- and medium-term transformations (0-3 years) of the soil organic matter (SOM) on the major processes and parameters that enable or inhibit selenite, Se(+IV), transfers between the soil components (solid, liquid or gaseous). Three types of soil of similar mineralogical origin but containing diverse quantities and qualities of SOM were first contaminated with Se(+IV) and incubated at 28°C. Soils were sampled throughout the incubation period to characterise the mobility of Se (batch and soil column experiments) and also its fractionation within the soil compartments (selective extractions and size-density fractionation). The following are the main results obtained within the first month of incubation. (a) Selenium was partly volatilized during soil incubation (<0.1%), (b) Se extracted with CaCl2 (5×10-4 M) was equally small for the three soil samples (∼1-5%), suggesting that Se was strongly sorbed on the solid phase and (c) at least 10% of Se was associated to the particulate organic matter (POM > 50μm), whereas 60% of Se was extracted with soil humic substances. These results suggested that both SOM quantity and quality played a significant role in selenium retention. Furthermore, comparison between experimental and predicted variations of CO 2 fluxes (due to C mineralisation) and soil biomasses are presented. By this way, we estimated the capacity of the RothC model as an experimental gauging tool in the prediction of C turnover on a laboratory scale.
a- Laboratory of Radioecology and Ecotoxicology (LRE), IRSN/DEI/SECRE, Bldg. 186, Cadarache, BP 3, 13115 Saint Paul lez Durance Cedex, France
b- Laboratoire d'Ecologie Microbienne de la Rhizosphere, UMR 6191 CNRS-CEA-Univ. de la Méditerranée, CEA DEVM, 13115 Saint-Paul lez Durance Cedex, France
c- Laboratoire d'Étude des Transferts en Hydrologie et Environnement (LTHE), CNRS/INPG/IRD/UJF, University of Grenoble I, BP 53, 38041 Grenoble Cedex 9, France