Formation of Zn-rich phyllosilicate, Zn-layered double hydroxide and hydrozincite in contaminated calcareous soils

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Recent studies demonstrated that Zn-phyllosilicate- and Zn-layered double hydroxide-type (Zn-LDH) precipitates may form in contaminated soils. However, the influence of soil properties and Zn content on the quantity and type of precipitate forming has not been studied in detail so far. In this work, we determined the speciation of Zn in six carbonate-rich surface soils (pH 6.2 to 7.5) contaminated by aqueous Zn in the runoff from galvanized power line towers (1322 to 30090 mg/kg Zn). Based on 12 bulk and 23 microfocused extended X-ray absorption fine structure (EXAFS) spectra, the number, type and proportion of Zn species were derived ... continued below

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Jacquat, Olivier; Voegelin, Andreas; Villard, Andre; Marcus, Matthew A. & Kretzschmar, Ruben October 15, 2007.

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Recent studies demonstrated that Zn-phyllosilicate- and Zn-layered double hydroxide-type (Zn-LDH) precipitates may form in contaminated soils. However, the influence of soil properties and Zn content on the quantity and type of precipitate forming has not been studied in detail so far. In this work, we determined the speciation of Zn in six carbonate-rich surface soils (pH 6.2 to 7.5) contaminated by aqueous Zn in the runoff from galvanized power line towers (1322 to 30090 mg/kg Zn). Based on 12 bulk and 23 microfocused extended X-ray absorption fine structure (EXAFS) spectra, the number, type and proportion of Zn species were derived using principal component analysis, target testing, and linear combination fitting. Nearly pure Zn-rich phyllosilicate and Zn-LDH were identified at different locations within a single soil horizon, suggesting that the local availabilities of Al and Si controlled the type of precipitate forming. Hydrozincite was identified on the surfaces of limestone particles that were not in direct contact with the soil clay matrix. With increasing Zn loading of the soils, the percentage of precipitated Zn increased from {approx}20% to {approx}80%, while the precipitate type shifted from Zn-phyllosilicate and/or Zn-LDH at the lowest studied soil Zn contents over predominantly Zn-LDH at intermediate loadings to hydrozincite in extremely contaminated soils. These trends were in agreement with the solubility of Zn in equilibrium with these phases. Sequential extractions showed that large fractions of soil Zn ({approx}30% to {approx}80%) as well as of synthetic Zn-kerolite, Zn-LDH, and hydrozincite spiked into uncontaminated soil were readily extracted by 1 M NH{sub 4}NO{sub 3} followed by 1 M NH{sub 4}-acetate at pH 6.0. Even though the formation of Zn precipitates allows for the retention of Zn in excess to the adsorption capacity of calcareous soils, the long-term immobilization potential of these precipitates is limited.

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  • Journal Name: Geochimica et Cosmochimica Acta

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  • Report No.: LBNL-2117E
  • Grant Number: DE-AC02-05CH11231
  • Office of Scientific & Technical Information Report Number: 963326
  • Archival Resource Key: ark:/67531/metadc930231

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Reports, articles and other documents harvested from the Office of Scientific and Technical Information.

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  • October 15, 2007

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  • Nov. 13, 2016, 7:26 p.m.

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  • Jan. 4, 2017, 3:33 p.m.

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Jacquat, Olivier; Voegelin, Andreas; Villard, Andre; Marcus, Matthew A. & Kretzschmar, Ruben. Formation of Zn-rich phyllosilicate, Zn-layered double hydroxide and hydrozincite in contaminated calcareous soils, article, October 15, 2007; Berkeley, California. (digital.library.unt.edu/ark:/67531/metadc930231/: accessed April 26, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.