1 / 39

Soil Mineralogy and Chemistry

Lecture 4. Soil Mineralogy and Chemistry. Phyllosilicate Minerals. tet. tet. tet. tet. tet. tet. oct. oct. oct. Phyllosilicates, NO layer charge. trioctahedral. dioctahedral. T:O (class). oct. octahedra. gibbsite. brucite. 1:1. oct. kaolinite. serpentine. oct. 2:1.

alijah
Télécharger la présentation

Soil Mineralogy and Chemistry

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Lecture 4 Soil Mineralogy and Chemistry

  2. Phyllosilicate Minerals

  3. tet tet tet tet tet tet oct oct oct Phyllosilicates, NO layer charge trioctahedral dioctahedral T:O (class) oct octahedra gibbsite brucite 1:1 oct kaolinite serpentine oct 2:1 talc pyrophyllite

  4. Building of Tetrahedral Sheets * Linked SiO4 tetrahedra

  5. SiO4 Tetrahedron

  6. z y x

  7. Si6O18

  8. Linking Rings to FormTetrahedral Sheets

  9. Tetrahedral Sheet Si:O 2:5

  10. Building of Octahedral Sheets

  11. Al(OH)6 or Mg (OH)6 Octahedra OH

  12. Octahedral Sheet OH

  13. A Georgian Ultisol

  14. Octahedral-Tetrahedral Linkage

  15. Sharing of Apical Oxygens in Tetrahdral Sheet with Hydroxyls of Octahedral Sheet Serpentine (1:1 trioctahedral mineral) tet oct

  16. Sharing of Apical Oxygens in Tetrahdral Sheet with Hydroxyls of Two Octahedral Sheets Talc (2:1 trioctahedral mineral) tet oct tet

  17. Short-hand Symbols tet oct Short hand, Block notation

  18. tet tet tet tet tet tet oct oct oct Phyllosilicates, NO layer charge trioctahedral dioctahedral T:O (class) oct octahedra gibbsite brucite 1:1 oct kaolinite serpentine oct 2:1 talc pyrophyllite

  19. Charge Development Isomorphic Substitution  permanent (layer) charge

  20. Isomorphic Substitution tet Al3+ Si4+ oct Al3+, Fe3+ Mg2+

  21. NET Charge - - - - - - - 0 ++ ++ ++ ++ ++ ++ ++ - - - - - - - Isomorphic substitution - - - - - - - -2 ++ + ++ ++ ++ + ++ - - - - - - -

  22. Charge Development Terminal Bonds • pH-dependent charge (ionizable functional groups)

  23. Terminal Bonds terminal bonds

  24. Terminal Bonds: Ionizable Functional Groups O Al Al-OH2+ Al-OHo + H+  Al-O- + H+ Low pH High pH • pH-dependent charge • edges of phyllosilicates; all surface on Fe- and Al-oxides

  25. tet tet tet tet tet tet tet tet oct oct oct oct Phyllosilicates: 2:1 with layer charge micas 2:1 clay minerals K+ K+ K+ Ca2+ H2O K+ H2O H2O 1 unit of (-) layer charge per formula unit < 1 unit of (-) layer charge per formula unit

  26. Swelling Potential?

  27. Interlayer Status: d-spacing d-spacing Structure K+ (and mica)

  28. CEC cmol/Kg Properties of Clay Minerals

  29. Accessory Minerals Kaolin and Oxide Rich Soil Western GA Ultisol

  30. Smectite Soil Iron and Al-oxide Rich ? NE Montana Vertisol Hawaiian Oxisol

  31. Clay mineralogy reflects weathering processes Micas  Vermiculite  Smectite  Kaolinite  Al,Fe-Oxides • Young, weakly weathered soils • = fine-grained mica, chlorite, vermiculite • (Entisol, Inceptisol) • Intermediate weathering • = vermiculite, smectite, kaolinite • (Mollisol, Alfisol, Ultisol) • Strong weathering • = kaolinite, hydrous oxides • (Ultisol--> Oxisol)

  32. Mol E/I E/I Alf Ult

  33. Organic Matter - reactive functional groups: carboxyl, hydroxyl, phenolic * Humus, Humic Acid, Fulvic Acid

  34. + Flocculation (chemical) Aggregation Flocculation and Aggregation (organic gluing)

  35. Organic Matter Promoted Aggregation

More Related