title: Distribution and speciation of ambient selenium in contrasted soils, from mineral to organic rich.
abstract: Selenium adsorption onto oxy-hydroxides mainly controls its mobility in volcanic soils, red earths and soils poor in organic matter (OM) while the influence of OM was emphasized in podzol and peat soils. This work aims at deciphering how those solid phases influence ambient Se mobility and speciation under less contrasted conditions in 26 soils spanning extensive ranges of OM (1-32%), Fe/Al oxy-hydroxides (0.3-6.1%) contents and pH (4.0-8.3). The soil collection included agriculture, meadow and forest soils to assess the influence of OM quality as well. Trace concentrations of six ambient Se species (Se(IV), Se(VI) and 4 organo-Se compounds) were analyzed by HPLC-ICP-MS in three extractants (ultrapure water, phosphate and sodium hydroxide) targeting Se associated to different soil phases. The Kd values determined from ultrapure water extraction were higher than those reported in commonly used short-term experiments after Se-spiking. Correlations of ambient Se content and distribution with soil parameters explained this difference by an involvement of slow processes in Se retention in soils. The 26 Kd values determined here for a wide variety of soils thus represent a relevant database for long-term prediction of Se mobility. For soils containing less than 20% OM, ambient Se solubility is primarily controlled by its adsorption onto crystalline oxy-hydroxides. However, OM plays an important role in Se mobility by forming organo-mineral associations that may protect adsorbed Se from leaching and/or create anoxic zones (aggregates) where Se is immobilized after its reduction. Although for the first time, inorganic Se(IV), Se(VI) and organo-Se compounds were simultaneously investigated in a large soil collection, high Se proportions remain unidentified in each soil extract, most probably due to Se incorporation and/or binding to colloidal-sized OM. Variations of environmental factors regulating the extent of OM-mineral associations/aggregation may thus lead to changes in Se mobility and bio-availability.
authors.affiliation: Laboratoire de Chimie Analytique Bio-Inorganique et Environnement (LCABIE), IPREM, Université de Pau et des Pays de l'Adour/CNRS UMR 5254, Hélioparc, 2 Avenue du Président Angot, 64053 Pau Cedex 9, France; Andra, Research and Development Division, Parc de la Croix Blanche, 1/7 rue Jean Monnet, 92298 Châtenay-Malabry Cedex, France. Electronic address: julietolu@hotmail.com.
authors.forename: Julie
authors.initials: J
authors.lastname: Tolu
authors.affiliation: Andra, Research and Development Division, Parc de la Croix Blanche, 1/7 rue Jean Monnet, 92298 Châtenay-Malabry Cedex, France.
authors.forename: Yves
authors.initials: Y
authors.lastname: Thiry
authors.affiliation: Laboratoire de Chimie Analytique Bio-Inorganique et Environnement (LCABIE), IPREM, Université de Pau et des Pays de l'Adour/CNRS UMR 5254, Hélioparc, 2 Avenue du Président Angot, 64053 Pau Cedex 9, France.
authors.forename: Maïté
authors.initials: M
authors.lastname: Bueno
authors.affiliation: Institut National de La Recherche Agronomique (INRA), US 1106 INFOSOL, 2163 avenue de la Pomme de Pin, CS 40001 Ardon, 45075 Orléans Cedex 2, France.
authors.forename: Claudy
authors.initials: C
authors.lastname: Jolivet
authors.affiliation: Laboratoire de Chimie Analytique Bio-Inorganique et Environnement (LCABIE), IPREM, Université de Pau et des Pays de l'Adour/CNRS UMR 5254, Hélioparc, 2 Avenue du Président Angot, 64053 Pau Cedex 9, France.
authors.forename: Martine
authors.initials: M
authors.lastname: Potin-Gautier
authors.affiliation: Laboratoire de Chimie Analytique Bio-Inorganique et Environnement (LCABIE), IPREM, Université de Pau et des Pays de l'Adour/CNRS UMR 5254, Hélioparc, 2 Avenue du Président Angot, 64053 Pau Cedex 9, France.
authors.forename: Isabelle
authors.initials: I
authors.lastname: Le Hécho
mesh_terms: D000383:Agriculture; D004784:Environmental Monitoring; D012643:Selenium / Q000032:analysis*; D012987:Soil / Q000737:chemistry*; D012989:Soil Pollutants / Q000032:analysis*
chemical_list: D012987:Soil; D012989:Soil Pollutants; D012643:Selenium
keywords: Ambient selenium; Distribution; Organic matter; Oxides; Soils; Speciation