Soil Chemistry

Soil Chemistry - 1 Soil Chemical Properties Chapters 8 and...

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1 1 Soil Chemical Properties Chapters 8 and 9 Mineral Photos from Roth, 2000, Images from Minerals in Soil Environments, published by Soil Science Society of America 2 Colloids • < 0.002 mm in diameter • Minerals and organic particles • Very high surface area • Many are charged, permanent and variable – Usually negative charge – Sometimes positive charge • Adsorb water (adhesion) 3 Types of soil colloids • Crystalline silicate clays = layer silicates • Oxides • Poorly crystalline minerals •Humu s 4 Kaolinite 5 Smectite 6 Oxides • Contain O and/or OH • Fe, Al types most common (also Mn) • Variable charge • Nonexpanding • Very common in highly weathered soils • Fe oxides – yellow, red • Al oxides – white, gray • Mn oxides – black 7 Iron Oxides - Goethite FeOOH 8 Iron Oxides - Hematite Fe 2 O 3 9 Aluminum Oxides - Gibbsite Al(OH)
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2 10 Poorly crystalline minerals • Aluminosilicates – allophane and imogolite • Hydrated iron oxide – ferrihydrite (orange) • Very high surface area, very high microporosity • Variable charge • Common in volcanic ash soils • Ferrihydrite common in wetlands 11 Poorly crystalline minerals - Allophane and Imogolite Scale bar is 50 nm 12 Poorly crystalline minerals - Ferrihydrite
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This note was uploaded on 04/03/2008 for the course SS 121 taught by Professor Staff during the Winter '07 term at Cal Poly.

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Soil Chemistry - 1 Soil Chemical Properties Chapters 8 and...

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