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Sequential Extractions:

Sequential Extractions: Wet chemical procedures utilizing progressively stronger reagents/“solvents” to preferentially remove mineral species, or compounds, to separate them from a complex matrix. Individual procedures are dictated by sample chemistries.

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Sequential Extractions:

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  1. Sequential Extractions: • Wet chemical procedures utilizing progressively stronger reagents/“solvents” to preferentially remove mineral species, or compounds, to separate them from a complex matrix. • Individual procedures are dictated by sample chemistries.

  2. Weathering crusts forming on the Henryville bed (HEN-2). (photo: Nelson Shafer, IGS) Example 1: Copiapites: a hydrated iron sulfate mineral with a formula: Fe2+Fe3+4(SO4)6(OH)2·20(H2O) X-ray Diffraction (XRD) 10 cm Zc Ac Zc Ac G Zc G Ac A A G G A Q

  3. in 250 ml glass beaker 1-9 g, dry sulfate crust, homogenized stirred for 24 hours, at 70oC, filtered with 0.8µm cellulose nitrate filter, supernatant reserved, residue subtracted from initial mass 100 ml 1.0N HCl supernatant transferred to a 100 ml volumetric flask and filled to volume de-ionized H2O 10 ml supernatant transferred back to 250 ml beaker and NaOH pellets added to remove Fe-hydroxides. Sample filtered, Fe-hydroxides discarded. BaCl2added to supernatant to precipitate BaSO4 90 ml supernatant reserved for AAS metals analysis 10 ml 0.5M BaCl2 0.02% HNO3

  4. Example 2: Bloomington Soil Pb 34000 32000 house paint road

  5. in 50 ml centrifuge tube 2 g, dry soil, homogenized 25 ml 0.5M KNO3 stirred for 16 hours, centrifuged, filtered with Whatman#42 filter, supernatant reserved for analysis Exchangeable Fraction stirred for 2 hours, centrifuged, filtered, supernatant reserved for analysis 25 ml distilled H2O Absorbed Fraction Organically-Bound Fraction 25 ml 0.5M NaOH stirred for 16-21 hours, centrifuged, filtered, supernatant reserved for analysis stirred for 6 hours, centrifuged, filtered, supernatant reserved for analysis Carbonate-Bound Fraction 25 ml 0.05M Na-EDTA heated (70-80oC) for 16-21 hours in an oven, centrifuged, filtered, supernatant reserved for analysis 25 ml 4.0M HNO3 Residual Fraction Sposito, G., Lund, L.J., and Chang, A.C., 1982, Trace Metal chemistry in arid-zone field soils amended with sewage sludge: I. Fractionation of Ni, Cu, Zn, Cd, and Pb in solid phases: SSSA Journal, 46:260-264.

  6. Alva, A.K., Huang, B., Paramasivam, S., 2000, Soil pH affects copper fractionation and Phytotoxicity: Soil Science Society of America Proceedings, 29:955-962.

  7. Bruchert, V., 1998, Early diagenesis of sulfur in estuarine sediments: the role of sedimentary humic and fulvic acids: Geochimica et CosmochemicaActa, 62:1567-1586.

  8. Chao, T.T., and Theobald, Jr., P.K., 1976, The significance of Secondary Iron and Manganese Oxides in Geochemical Exploration: Economic Geology, 71:1560-1569.

  9. Li, X., Coles, B.J., Ramsey, M.H., Thornton, I., 1995, Sequential extraction of soils for multielement analysis by ICP-AES: Chemical Geology, 124:109-123. (N. Atlantic seafloor manganese nodules )

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