New combination of EXAFS spectroscopy and density fractionation for the speciation of chromium within an andosol.

Studying speciation of heavy metals instead of their total concentration in a complex matrix such as soil is a scientific challenge that requires a combination of different analytical techniques. We compared the speciation of Cr within an andosol (island of Réunion) by using X-ray absorption spectroscopy (XAS) and sequential extraction. Contradictory results were obtained since the fraction of Cr bound to organic matter was detected only with the latter method. As bulk soil is rather complex, its fractionation by a densimetric method decreased its heterogeneity. We found that 60% Cr was within chromite-type primary minerals. Weathering of these phases led to Fe and Cr release, eventually resulting in either coprecipitation as mixed FeCr oxyhydroxide (16% total Cr) or precipitation of a Cr oxyhydroxide (5% total Cr). Our results also revealed that 13% Cr was bound to organic matter. The organic matter was complexed with mineral phases to form organomineral complexes with a density ranging from 1.9 to 2.6. The use of an original density fractionation-based sample preparation allowed identification of the role of organic matter in chromium speciation within an andosol and to overcome the difficulties of EXAFS to detect light elements in the vicinity of heavy elements.

[1]  Ruben Kretzschmar,et al.  Combining selective sequential extractions, X-ray absorption spectroscopy, and principal component analysis for quantitative zinc speciation in soil. , 2002, Environmental science & technology.

[2]  S. Rose-Pehrsson,et al.  Speciation of chromium in simulated soil samples using X-ray absorption spectroscopy and multivariate calibration , 2001 .

[3]  S. Fendorf.  Surface reactions of chromium in soils and waters , 1995 .

[4]  M Newville,et al.  ATHENA, ARTEMIS, HEPHAESTUS: data analysis for X-ray absorption spectroscopy using IFEFFIT. , 2005, Journal of synchrotron radiation.

[5]  J. Hazemann,et al.  XAS evidence of As(V) association with iron oxyhydroxides in a contaminated soil at a former arsenical pesticide processing plant. , 2005, Environmental science & technology.

[6]  G. Brown,et al.  Mineralogy of lead in a soil developed on a Pb-mineralized sandstone (Largentière, France) , 2001 .

[7]  J. Wong,et al.  Quantitative speciation of Mn-bearing particulates emitted from Autos burning (methylcyclopentadienyl)manganese tricarbonyl-added gasolines using XANES spectroscopy , 2000 .

[8]  H. S. Macary,et al.  Heavy metal content in soils of Réunion (Indian Ocean) , 2006 .

[9]  G. Franchini,et al.  Interaction between aqueous chromium solutions and layer silicates , 2000 .

[10]  Rainer Horn,et al.  Handbook of soil science. , 1996 .

[11]  Shunitz Tanaka,et al.  CHROMIUM (III) BINDING ABILITIES OF HUMIC ACIDS , 1995 .

[12]  Carlos Cervantes,et al.  Chromium toxicity in plants. , 2005, Environment international.

[13]  R. Parfitt.  Allophane in New Zealand - a review , 1990 .

[14]  T. Becquer,et al.  Chromium availability in ultramafic soils from New Caledonia. , 2003, The Science of the total environment.

[15]  L. Charlet,et al.  X-ray absorption spectroscopic study of the sorption of Cr(III) at the oxide-water interface: II. Adsorption, coprecipitation, and surface precipitation on hydrous ferric oxide , 1992 .

[16]  Z. Stasicka,et al.  Chromium occurrence in the environment and methods of its speciation. , 2000, Environmental pollution.

[17]  R. Coleman,et al.  Chromium geochemistry in serpentinized ultramafic rocks and serpentine soils from the Franciscan complex of California , 2004 .

[18]  Yu-Ling wei,et al.  XANES study of Cr sorbed by a kitchen waste compost from water. , 2005, Chemosphere.

[19]  J. M. Martín,et al.  Sequential extraction techniques: Promises and problems , 1987 .

[20]  R. Amundson,et al.  Mineral control of carbon pools in a volcanic soil horizon , 2007 .

[21]  Matthew A. Marcus,et al.  Quantitative Speciation of Heavy Metals in Soils and Sediments by Synchrotron X-ray Techniques , 2002 .

[22]  J. Bottero,et al.  Structure and affinity towards Cd2+, Cu2+, Pb2+ of synthetic colloidal amorphous aluminosilicates and their precursors , 1999 .

[23]  U. Schwertmann,et al.  Chromium-for-iron substitution in synthetic goethites , 1989 .

[24]  N. Köleli,et al.  Speciation of chromium in 12 agricultural soils from Turkey. , 2004, Chemosphere.

[25]  Emmanuel Doelsch,et al.  Impact of sewage sludge spreading on heavy metal speciation in tropical soils (Réunion, Indian Ocean). , 2006, Chemosphere.

[26]  The fate of chromium and nickel in subalpine soils derived from serpentinite , 1995 .