Scheda di dettaglio – i prodotti della ricerca
| Dato | Valore |
|---|---|
| Title | Speciation of arsenic in Greek travertines: Co-precipitation of arsenate with calcite |
| Abstract | he western part of the Chalkidiki peninsula in Northern Greece is a geothermally active area that contains high levels of naturally derived arsenic in its alkaline groundwaters (up to 3760 ?g/L). Near wells, equilibration of these groundwaters with atmospheric carbon dioxide leads to the precipitation of travertines that contain very high levels of arsenic (up to 913 mg/kg). To determine the mechanism of arsenic uptake in these travertines, we analyzed two different types of travertine from this region using both bulk and micro-focused X-ray absorption spectroscopy (XAS and ?-XAS) and micro-focused X-ray fluorescence spectroscopy (?-XRF). Bulk XAS showed that in all of the studied samples arsenic is present in the pentavalent oxidation state (arsenate). ?-XRF analyses indicated that arsenic is closely associated with the calcite matrix and that it generally does not correlate well with iron. The arsenic K-edge XAS spectra of all samples closely matched each other and closely resembled a reference spectrum for arsenate coprecipitated with calcite (rather than adsorbed or pure calcium arsenate). Iron on the other hand was found to be mainly present as a constituent of clay minerals, of presumably detrital origin, suggesting that iron-(hydr)oxides were not sufficiently abundant to act as major scavengers for arsenic in the Chalkidiki travertines. We estimated that calcite in these travertines could sequester at least 25% of aqueous arsenic in the form of As(V) and thus immobilize a substantial part of arsenic present in the geothermal groundwaters. These results may also be relevant for other areas where geothermal groundwaters carry arsenic to the surface and possibly as well for arsenic geochemistry in other environments with CO2-enriched water. |
| Source | Geochimica et cosmochimica acta 106, pp. 99–110 |
| Keywords | arsenic speciationcalcitecoprecipitationtravertine |
| Journal | Geochimica et cosmochimica acta |
| Editor | Pergamon Press., New York [etc.], Stati Uniti d'America |
| Year | 2013 |
| Type | Articolo in rivista |
| DOI | 10.1016/j.gca.2012.11.049 |
| Authors | Winkel L.H.E.; Casentini B.; Bardelli F.; Voegelin A.; Nikolaidis N.P.; Charlet L. |
| Text | 297939 2013 10.1016/j.gca.2012.11.049 Scopus 2 s2.0 84873135970 arsenic speciation calcite coprecipitation travertine Speciation of arsenic in Greek travertines Co precipitation of arsenate with calcite Winkel L.H.E.; Casentini B.; Bardelli F.; Voegelin A.; Nikolaidis N.P.; Charlet L. Eawag Swiss Federal Institute of Aquatic Science and Technology, Ueberlandstrasse 133, P.O. Box 611, 8600 Duebendorf, Switzerland; Institute of Biogeochemistry and Pollutant Dynamics, Department of Environmental Sciences, Swiss Federal Institute of Technology ETH Zurich, 8092 Zurich, Switzerland; Water Research Institute National Research Council, Via Salaria km 29, 300, 00015 Monterotondo, RM, Italy; Department of Environmental Engineering, Technical University of Crete, Polytechnioupolis, 73100 Chania, Greece; Institut des Sciences de la Terre, Universite Joseph Fourier, Grenoble, Maison des Geosciences, 1381 rue de la Piscine, 38400 Saint Martin d Heres, France he western part of the Chalkidiki peninsula in Northern Greece is a geothermally active area that contains high levels of naturally derived arsenic in its alkaline groundwaters up to 3760 g/L . Near wells, equilibration of these groundwaters with atmospheric carbon dioxide leads to the precipitation of travertines that contain very high levels of arsenic up to 913 mg/kg . To determine the mechanism of arsenic uptake in these travertines, we analyzed two different types of travertine from this region using both bulk and micro focused X ray absorption spectroscopy XAS and XAS and micro focused X ray fluorescence spectroscopy XRF . Bulk XAS showed that in all of the studied samples arsenic is present in the pentavalent oxidation state arsenate . XRF analyses indicated that arsenic is closely associated with the calcite matrix and that it generally does not correlate well with iron. The arsenic K edge XAS spectra of all samples closely matched each other and closely resembled a reference spectrum for arsenate coprecipitated with calcite rather than adsorbed or pure calcium arsenate . Iron on the other hand was found to be mainly present as a constituent of clay minerals, of presumably detrital origin, suggesting that iron hydr oxides were not sufficiently abundant to act as major scavengers for arsenic in the Chalkidiki travertines. We estimated that calcite in these travertines could sequester at least 25% of aqueous arsenic in the form of As V and thus immobilize a substantial part of arsenic present in the geothermal groundwaters. These results may also be relevant for other areas where geothermal groundwaters carry arsenic to the surface and possibly as well for arsenic geochemistry in other environments with CO2 enriched water. 106 Published version http //www.scopus.com/inward/record.url eid=2 s2.0 84873135970 partnerID=q2rCbXpz Speciation of arsenic in Greek travertines Co precipitation of arsenate with calcite Winkel_GCA_2013.pdf Articolo in rivista Pergamon Press. 0016 7037 Geochimica et cosmochimica acta Geochimica et cosmochimica acta Geochim. cosmochim. acta Geochimica et cosmochimica acta. fabriziobardelli BARDELLI FABRIZIO barbara.casentini CASENTINI BARBARA |