title: XAS study of lead speciation in a central Italy calcareous soil.
abstract: OBJECTIVE
  The Pb absorption processes on a heavy textured calcareous soil, typical of central Italy, were studied using synchrotron X-ray absorption spectroscopy (XAS) in order to probe, at molecular scale, the structure and chemical nature of Pb in contaminated soils and achieve precise description of Pb ions localization into these contaminated soils.
  
  
  METHODS
  In order to distinguish the role of the different components of soils in Pb retention, samples were prepared from the original soils removing the carbonate fractions, the organic matter, the metal oxides, or selecting the clay fractions. Then these samples were fortified with Pb simulating the natural interactions processes of heavy metal solutions with soils. The quantitative analysis of near edge (XANES) as well extended (EXAFS) regions of Pb L(III) edge absorption spectra, in comparison with Pb XAS data of selected reference compounds, allowed the precise determination of local structure and chemical environment of Pb ions in these soil samples.
  
  
  RESULTS
  Four components were individuated as the major responsible of Pb retention in calcareous soils: the carbonates, the metal oxide surfaces, the organic matter, and the colloidal inorganic surfaces containing clay components. The structural analysis suggests that, within these experimental conditions, the Pb adsorbed on the soil is generally present as Pb hydroxide with poor crystallization degree. However, the presence of carbonates (CaCO3) induces the co-precipitation of PbCO3-like phases with some degree of crystallinity.
authors.affiliation: Dipartimento di Fisica, Universitá di Roma TRE, via della Vasca Navale 84, 00146, Rome, Italy.
authors.forename: Tatiana
authors.initials: T
authors.lastname: Comaschi
authors.forename: Carlo
authors.initials: C
authors.lastname: Meneghini
authors.forename: Daniela
authors.initials: D
authors.lastname: Businelli
authors.forename: Settimio
authors.initials: S
authors.lastname: Mobilio
authors.forename: Mario
authors.initials: M
authors.lastname: Businelli
mesh_terms: D000327:Adsorption; D002118:Calcium / Q000032:analysis / Q000737:chemistry; D007558:Italy; D007854:Lead / Q000032:analysis / Q000737:chemistry*; D012987:Soil / Q000737:chemistry*; D012989:Soil Pollutants / Q000032:analysis / Q000737:chemistry*; D056928:X-Ray Absorption Spectroscopy
chemical_list: D012987:Soil; D012989:Soil Pollutants; D007854:Lead; D002118:Calcium