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Sumber : classes.uleth.ca/200801/geog3080a/ SOILS %20PART%20V%202008. ppt ‎

KOLOID TANAH dan KTK. Sumber : classes.uleth.ca/200801/geog3080a/ SOILS %20PART%20V%202008. ppt ‎. Sumber : classes.uleth.ca/200801/geog3080a/ SOILS %20PART%20V%202008. ppt ‎. Koloid Tanah Partikel yng ukurannya kurang 1 -2 m bersifat sebagai koloid tanah

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Sumber : classes.uleth.ca/200801/geog3080a/ SOILS %20PART%20V%202008. ppt ‎

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  1. KOLOID TANAH dan KTK Sumber: classes.uleth.ca/200801/geog3080a/SOILS%20PART%20V%202008.ppt‎

  2. Sumber: classes.uleth.ca/200801/geog3080a/SOILS%20PART%20V%202008.ppt‎

  3. Koloid Tanah Partikelyngukurannyakurang 1 -2 m bersifatsebagaikoloidtanah Total luaspermukaannya 10-800 m2·g-1 Internal and external surfaces have electronegative or electropositive charges (electronegative charge dominant) Each micelle adsorbs thousands of hydrated Al3+, Ca2+, H+, K+, Mg2+ and Na+ ions (enclosed within several H2O molecules) Cation exchange occurs when ions break away into the soil solution and are replaced by other ions Ionic double layer: negatively charged micelle surrounded by a swarm of cations. Sumber: classes.uleth.ca/200801/geog3080a/SOILS%20PART%20V%202008.ppt‎

  4. Sumber: classes.uleth.ca/200801/geog3080a/SOILS%20PART%20V%202008.ppt‎

  5. LiatSilikatKristalin (Berbentuk Kristal) • Dominant colloid in most soils (not andisols, oxisolsor organic soils) • Crystals layered as in a book • 2-4 sheets of tightly-bonded O, Si and Al atoms • in each layer • Misalnya: Kaolinit, Montmorillonit. Sumber: classes.uleth.ca/200801/geog3080a/SOILS%20PART%20V%202008.ppt‎

  6. Sumber: classes.uleth.ca/200801/geog3080a/SOILS%20PART%20V%202008.ppt‎

  7. Sumber: classes.uleth.ca/200801/geog3080a/SOILS%20PART%20V%202008.ppt‎

  8. LiatSilikat Non-kristalin • Tidakterorganisirsebagailembarankristalin • Both + and – charges; can adsorb anions such as phosphate • Kapasitasmenyimpan (menahan) air sangatbesar • Malleable when wet, but not sticky • Often form in volcanic soils (especially in Andisols) • Mis. AllophanedanImogolite. Sumber: classes.uleth.ca/200801/geog3080a/SOILS%20PART%20V%202008.ppt‎

  9. Oksida-oksida Iron danAluminium • Ditemukandalamtanah-tanah yang sangatlapukdidaerahiklimhujiddanhangat (mis.. Oxisols) • Terdiriatas atom-atom Fe danAl yang dihubungkandnegan atom-atom oksigenataugugusanhidroksil • Some form crystalline sheets (eg. gibbsite and geothite), but often amorphous • Low plasticity and stickiness Sumber: classes.uleth.ca/200801/geog3080a/SOILS%20PART%20V%202008.ppt‎

  10. Humus • Adadalamkebanyakantanah, terutamaHorison A • Bukan mineral atauBukanKristalin • Consist of chains of C atoms, bonded to H, O & N • Very high water adsorption capacity • Not plastic or sticky • Bermuatanlistriknegatif. Sumber: classes.uleth.ca/200801/geog3080a/SOILS%20PART%20V%202008.ppt‎

  11. Sumber: classes.uleth.ca/200801/geog3080a/SOILS%20PART%20V%202008.ppt‎

  12. (Singer and Munns, 2002) Sumber: classes.uleth.ca/200801/geog3080a/SOILS%20PART%20V%202008.ppt‎

  13. Phyllosilicates • Tetrahedra: • Two planes of O, • with Si in between • Basic building block • is silicon atom, • connected to 4 O • atoms • Oktahedra: • Two planes of O, • with Al or Mg in • between • Basic building block • is Al (or Mg), • connected to six • hydroxyl groups or • O atoms. • There are many • layers in each micelle Sumber: classes.uleth.ca/200801/geog3080a/SOILS%20PART%20V%202008.ppt‎

  14. Dioctahedral Sheet Isomorphous substitution Trioctahedral Sheet 1 Al3+ atom, 1 Mg2+ atom Charge = -1 3 Mg2+ atoms Charge = 0 2 Al3+ atoms Charge = 0 Sumber: classes.uleth.ca/200801/geog3080a/SOILS%20PART%20V%202008.ppt‎

  15. SubstitusiIsomorfik • Each Mg2+ ion that substitutes for Al3+ causes a negative charge in a dioctahedral sheet • Each Al3+ ion that substitutes for Si4+ causes a negative charge in a tetrahedral sheet Sumber: classes.uleth.ca/200801/geog3080a/SOILS%20PART%20V%202008.ppt‎

  16. Sumber: classes.uleth.ca/200801/geog3080a/SOILS%20PART%20V%202008.ppt‎

  17. 1:1 Silicate Clay • Each layer contains one tetrahedral and one • octahedral sheet • Eg. Kaolinite, halloysite, nacrite and dickite • Sheets are held together because the apical oxygen • in each tetrahedron also forms the bottom corner of • one or more octahedra in the adjoining sheet Sumber: classes.uleth.ca/200801/geog3080a/SOILS%20PART%20V%202008.ppt‎

  18. Hydroxyl plane is exposed: removal or addition of • hydrogen ions can produce positive or negative • charges (hydroxylated surface also binds with anions) • Hydroxyls of octahedral sheet are alongside • Oxygens of the tetrahedral sheet: hydrogen bonding • results, with no swelling in kaolinites! • Kaolinite useful for roadbeds, building foundations • and ceramics (hardens irreversibly) Sumber: classes.uleth.ca/200801/geog3080a/SOILS%20PART%20V%202008.ppt‎

  19. 2:1 Silicate Clay Each layer contains one octahedral sheet sandwiched between two tetrahedral sheets. O on both ends No attraction without cations Sumber: classes.uleth.ca/200801/geog3080a/SOILS%20PART%20V%202008.ppt‎

  20. LiatSilikatTipe 2:1 Mengembang KelompokSmectite :Ekspansi (sifatmengembang) antarlapisandapatterjadikalau H2O mengisironggadiantaralapisandalamliat yang kering Montmorillonit : Liatsmectite yang sangatbanyakditemukan Smectitesmempunyaibanyakmuatannegatifkarenasubstitusiisomorfik Mg2+ often replaces Al3+ in the octahedral sheet Al3+ sometimes replaces Si4+ in the tetrahedral sheet 5. Weak O:cation linkages between layers leads to plasticity, stickiness, swelling and a very high specific surface area Sumber: classes.uleth.ca/200801/geog3080a/SOILS%20PART%20V%202008.ppt‎

  21. (Singer and Munns, 2002) Sumber: classes.uleth.ca/200801/geog3080a/SOILS%20PART%20V%202008.ppt‎

  22. KelompokVermikulit (LiatSilikatTipe 2:1 mengembang) Very high negative charge, due to frequent substitution of of Si4+ ions with Al3+ in the tetrahedral Sheets Cation exchange capacity is higher in vermiculites than in any other clay Swelling occurs, but less than in smectites due to strongly adsorbed H2O molecules, Al-hydroxy ions and cations, which act more as bridges than wedges. Sumber: classes.uleth.ca/200801/geog3080a/SOILS%20PART%20V%202008.ppt‎

  23. Mineral SilikatTipe 2:1 Tidak-mengembang Kelompok Mica (IllitdanGlauconit): Al3+substituded for 20% of Si4+ in tetrahedral sheets K+ fits tightly into hexagonal holes between tetrahedral oxygen groups: virtually eliminates swelling Sumber: classes.uleth.ca/200801/geog3080a/SOILS%20PART%20V%202008.ppt‎

  24. Khloritebersifat Non-expansive (Tidakmengembang): Mg-dominated trioctahedral hydroxide sheet fits between 2:1 layers (2:1:1). H-bonded to O atoms between sheets Fe or Mg occupy most octahedral sites Sumber: classes.uleth.ca/200801/geog3080a/SOILS%20PART%20V%202008.ppt‎

  25. Sumber: classes.uleth.ca/200801/geog3080a/SOILS%20PART%20V%202008.ppt‎

  26. OksidaBesidanOksidaAluminium Modified octahedral sheets with either Fe2+ or Al3+ in the cationpositions No tetrahedral sheets and no silicon Lack of isomorphous substitution (little negative charge) Small charge (+ or -) due to removal or addition of hydrogen ions from surface hydroxyl groups Non-expansive and relatively little stickiness, plasticity and cationabsorption Sumber: classes.uleth.ca/200801/geog3080a/SOILS%20PART%20V%202008.ppt‎

  27. Sumber: classes.uleth.ca/200801/geog3080a/SOILS%20PART%20V%202008.ppt‎

  28. Muatan yang Variable (pH-dependent) • Hydrous oxides whether crystalline or amorphous get their charge from surface protonation and deprotonation • >AlO- + H+ >AlOH + H+  AlOH2+ Negative Neutral Positive pH decreasing  • Layer aluminosilicates have a small amount of variable charge because of OH at the edges • Semuamuatannegatifpada humus bersifat variable • Oksida-oksida Hydrous bermuatan positive padatanah-tanah yang sangatmasamdanmembantumengikatanion. Sumber: classes.uleth.ca/200801/geog3080a/SOILS%20PART%20V%202008.ppt‎

  29. Muatan Negative menjadiMuatan Positive : As pH increases, more H+ ions bond to O atoms at the clay surface Protonation at very low pH (H+ ions attach to surface OH groups) MuatanNegatif: Dissociation of H+ ions, lack of Al & Si at edge to associate with O atom Sumber: classes.uleth.ca/200801/geog3080a/SOILS%20PART%20V%202008.ppt‎

  30. Sumber: classes.uleth.ca/200801/geog3080a/SOILS%20PART%20V%202008.ppt‎

  31. Pertukarankationkurangefektif Pertukarankationlebihefektif Sumber: classes.uleth.ca/200801/geog3080a/SOILS%20PART%20V%202008.ppt‎

  32. KapasitasTukarKation Nilainyasangattinggidalamtanah-tanah yang : Kaya humus Kapasitasmengembangsnagattinggi pH nyatinggi Sumber: classes.uleth.ca/200801/geog3080a/SOILS%20PART%20V%202008.ppt‎

  33. Humus Senyawaorganik, Non-crystalline Molekulorganik, ukurannyabesar 50% C, 40% O, 5% H, 3% N and sometimes S Strukturnyasangatvariabel. Very large negative charge due to three types of -OH groups (H+ ions gained or lost) (i) carboxyl group COOH (ii) phenolic hydroxyl group(due to partial decomposition of lignin by microorganisms) (iii) alcoholic hydroxyl group Sumber: classes.uleth.ca/200801/geog3080a/SOILS%20PART%20V%202008.ppt‎

  34. KeadaanBahanorganiksetelahsatutahundibenamkankedalamtanah Sumber: classes.uleth.ca/200801/geog3080a/SOILS%20PART%20V%202008.ppt‎

  35. SubstansiHumik • Mikroba mer9ombak komponen yang kompleks • Senyawa yang lebihsederhanadihasilkan; CO2dilepaskan • Sintesisbiomoleculesbaru, denganmenggunakan C, N, S dan O. • Lignin not completely broken down: complex residual molecules often retain lignin characteristics • Microbes polymerize new, simpler molecules with one another and with residual molecules • This creates long, complex chains, resistant to further decomposition • Chains interact with amino compounds • Polymerization process is stimulated by colloidal clays. Sumber: classes.uleth.ca/200801/geog3080a/SOILS%20PART%20V%202008.ppt‎

  36. Sumber: classes.uleth.ca/200801/geog3080a/SOILS%20PART%20V%202008.ppt‎

  37. Sumber: classes.uleth.ca/200801/geog3080a/SOILS%20PART%20V%202008.ppt‎

  38. Setelahsatutahun: • 1/5 hingga 1/3 jumlahKarbontetapdalamtanah • (i) live biomass (5%) • (ii) humic fraction (20%) • (iii) nonhumic fraction (5%) • SubstansiHumikmeliputi: • (i) Fulvic acids: lowest molecular weight and • lightest colour (most susceptible to microbes) • (ii) Humic acid (intermediate) • (iii) Humin: highest molecular weight, darkest, • least soluble and most resistant to microbes Sumber: classes.uleth.ca/200801/geog3080a/SOILS%20PART%20V%202008.ppt‎

  39. Humus: Amorphous and colloidal mixture of complex organic substances no longer identifiable as tissues Note: non-humic substances are biomolecules produced by microbes Sumber: classes.uleth.ca/200801/geog3080a/SOILS%20PART%20V%202008.ppt‎

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