Chapter 2 Inorganic Solids in Soil continued - PowerPoint PPT Presentation

View by Category
About This Presentation
Title:

Chapter 2 Inorganic Solids in Soil continued

Description:

Nuclei repel, but are attracted by the pair of negative electrons. ... Inherited from sedimentary rocks. Predominant in clay fraction ( 2 m) ... – PowerPoint PPT presentation

Number of Views:44
Avg rating:3.0/5.0
Slides: 21
Provided by: April58
Learn more at: http://aces.nmsu.edu
Category:

less

Write a Comment
User Comments (0)
Transcript and Presenter's Notes

Title: Chapter 2 Inorganic Solids in Soil continued


1
Chapter 2 Inorganic Solids in Soil continued
2
http//www.uwgb.edu/dutchs/graphic0/rockmin/ion-co
v.gif
3
What holds a covalent bond together?
Nuclei repel, but are attracted by the pair of
negative electrons.
http//www.webchem.net/images/bonds/covale2.gif
4
Paulings Rules predict configuration of atoms
into a crystal structure
http//www.gly.fsu.edu/salters/GLY1000/6_Minerals
/6_Minerals_index.html
5
Soil clay minerals Silica Tetrahedrons one
building block of soil minerals
Crystal pictures are from Bob Harter at Univ. of
New Hampshire http//pubpages.unh.edu/harter/cry
stal.htm2120MINERALS
6
Various linkages of the tetrahedra create
classes of silicates
www.indiana.edu/geol116/ week2/sillmin.jpg
www.winona.edu/geology/MRW/minrx.htm
7
socrates.berkeley.edu/eps2/wisc/Lect4.html
8
Figure 1 Single silica tetrahedron (shaded) and
the sheet structure of silica tetrahedrons
arranged in a hexagonal network.
http//www.britannica.com/ebc/article-80127
9
clay mineral hexagonal tetrahedral sheets
                                   
http//www.britannica.com/ebc/article-80127
10
Aluminum Octahedrons another building block or
layer in minerals
11
Single octahedron (shaded) and the sheet
structure of octahedral units.
http//www.britannica.com/ebc/article-80127
12
Primary Soil Minerals
  • Not chemically altered or significantly weathered
  • Inherited from original crystallization or
    deposition
  • Found mostly in the sand and silt fractions
  • Ex Quartz, Feldspars/Plagioclases, Amphiboles,
    Pyroxenes, etc. (Sparks, Table 2.2 p. 46)
  • Source of Na, Mg, K, Ca, Mn, and Fe ions as they
    weather/decompose.
  • Also source of trace elements and heavy metals in
    soils.

13
http//www.mineralogie.uni-wuerzburg.de/gallery/Se
iten/quartz2.htm
Photograph taken by Klaus-Peter Kelber
14
Secondary Soil Minerals
  • Low-temperature weathering product of primary
    minerals
  • Structural alteration of primary minerals
  • Precipitation out of solution
  • Inherited from sedimentary rocks
  • Predominant in clay fraction (lt2µm)
  • Very reactive chemically and physically
  • Source of readily available nutrient ions (Ca,
    Mg, K, NH4, S, Fe)
  • Ex Phyllosilicates (kaolins, smectites,
    illites) oxides and hydroxides, carbonates,
    sulfates, etc.

15
Phyllosilicates or layer silicates
  • Most abundant in the clay-sized fraction (hence
    referred to as clay minerals
  • Very high surface area unsatisfied charges
    very reactive
  • (both physically and chemically)
  • Composed of sheets of SiO4 tetrahedra Al or Mg
    octahedra
  • Strong ionic/covalent internal bonding and weaker
    H or van der Waals bonding between the layers

16
Ionic radius (size) determines the coordination
with ligands (O or OH)
-face-
-edge-
17
http//intro.chem.okstate.edu/1314F97/Chapter8/Ion
ic20Radii3.Gif
18
Isomorphous Substitution
  • Substitution, during formation, of one ion for
    another of similar SIZE (but not necessarily the
    same charge) in an ionic solid without changing
    the structure (shape, morphology) of the crystal.
  • Isomorphic same shape

19
Schematic representation of 21 clay mineral such
as montmorillonite, indicating locations of
substitution sites on tetrahedral and octahedral
layers and the hydrated interlayer cations.
www.sandia.gov/geobio/randy.html
20
Layer charge
  • Results from isomorphic substitution with ions of
    different charge
  • Al3 for Si4 in tetrahedra -1
  • Mg2 for Al3 in octahedra -1
  • Fe2 for Al3 -1
  • Li for Mg2 or Al3 -1 or -2

Negative charge must be neutralized by cations
adsorbed on the mineral surface or in the
interlayer (between the sheets) region
About PowerShow.com