The Influence of Calcium Carbonate Grain Coatings on Contaminant Reactivity in Vadose Zone Sediments

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Calcium carbonate (CaCO3) is widely distributed through the Hanford vadose zone as a minor phase. As a result of current and past geochemical processes, CaCO3 exists as grain coatings, intergrain fill, and distinct caliche layers in select locations. Calcium carbonate may also precipitate when high-level wastes react with naturally Ca- and Mg-saturated Hanford sediments. Calcium carbonate is a very reactive mineral phase. Sorption reactions on its surface may slow the migration of certain contaminants (Co, Sr), but its surface coatings on other mineral phases may diminish contaminant retardation (for example, Cr) by blocking surface reaction sites of the substrate. This ... continued below

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Zachara, John M.; Chambers, Scott; Brown Jr., Gordon E. & Eggleston, Carrick M. June 1, 2001.

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Calcium carbonate (CaCO3) is widely distributed through the Hanford vadose zone as a minor phase. As a result of current and past geochemical processes, CaCO3 exists as grain coatings, intergrain fill, and distinct caliche layers in select locations. Calcium carbonate may also precipitate when high-level wastes react with naturally Ca- and Mg-saturated Hanford sediments. Calcium carbonate is a very reactive mineral phase. Sorption reactions on its surface may slow the migration of certain contaminants (Co, Sr), but its surface coatings on other mineral phases may diminish contaminant retardation (for example, Cr) by blocking surface reaction sites of the substrate. This project explores the behavior of calcium carbonate grain coatings, including how they form and dissolve, their reactivity toward key Hanford contaminants, their impact (as surface coatings) on the reactivity of other mineral substrates, and on their in-ground composition and minor element enrichment. The importance of CaCO3 as a contaminant sorbent will be defined in all of its different manifestations in Hanford sediments: dispersed minor lithic fragments, pedogenic carbonate coatings on gravel and stringers in silt, and nodules in clay and paleosols. Mass action models will be developed that allow understanding and prediction of the geochemical effects of CaCO3 on contaminant retardation in Hanford sediments.

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  • Other Information: PBD: 1 Jun 2001

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  • Report No.: EMSP-70121--2001
  • Grant Number: FG07-99ER15024
  • Grant Number: FG07-99ER15019
  • DOI: 10.2172/833529 | External Link
  • Office of Scientific & Technical Information Report Number: 833529
  • Archival Resource Key: ark:/67531/metadc780236

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  • June 1, 2001

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  • Dec. 3, 2015, 9:30 a.m.

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  • March 22, 2016, 1:29 p.m.

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Zachara, John M.; Chambers, Scott; Brown Jr., Gordon E. & Eggleston, Carrick M. The Influence of Calcium Carbonate Grain Coatings on Contaminant Reactivity in Vadose Zone Sediments, report, June 1, 2001; United States. (digital.library.unt.edu/ark:/67531/metadc780236/: accessed September 24, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.