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LAND2003 Module 1
| Question | Answer |
|---|---|
| Primary mineral? | Minerals that were present in the parent rock which are resistant to weathering and persist in the soil |
| Secondary mineral? | Minerals that have formed through alteration of primary minerals or synthesized from components of previous mineral forms |
| As soil particle decreases.. | Surface area increases. Clay fraction has the largest surface area |
| Silicate mineral organisation #1- 4 co-ord tetrahedral arrangement. Describe | 4 x O2 (or hydroxyls) forming a regular tetrahedron enclosing the cation (usually Si4+) |
| Silicate mineral organisation #2- 6 co-ord octahedral arrangement. Describe | 6 x O2 (or hydroxyls) forming a regular octahedron enclosing the cation (Al3+) |
| Isomorphous replacement? Example | Replacement of elements without changing the structure and results in the mineral possessing a charge. Al3+ can substitute for Si4+ in tetrahedral while Mg2+ or Fe2+ can substitute Al3+ in octahedra |
| Why aren't Na+, K+ and Ca2+ apart of the silicate structure? | They aren't able to form the correct number of coordination bonds |
| Silicate minerals - Island structure. Explain | Whole charge neutralised by cations eg olivine or zircon. Easily subjected to weathering |
| Silicate minerals - Ring, chain or ribbon structure. Explain | 2-3 oxygens per tetrahedra are shared with the excess charge neutralised by cations |
| Silicate minerals - 3D structure. Explain | all 4 oxygens are shared and the linked tetrahedral extend in all 3 dimensions. Resists weathering |
| Silicate minerals - Planar sheet structure. Explain | 3 oxygens per tetrahedral are shared giving a sheet structure extending in 2 dimensions. Unshared oxygens bond with other sheets. Consist of 1 or more tetra sheets combined with an octa sheet |
| Structure of 1:1 kaolinites? | Single tetra sheet combined with single octa sheet with extensions in 2 dimensions |
| Basal spacing? | Distance between repeating planes of ions |
| Basal spacing in kaolinites? | Spacing is fixed due to string H bonding between sheets therefore won't shrink and swell |
| What is the arrangement of kaolinites that lead to strong H bonding? | O atoms in one layer adjoin OH groups in the next layer |
| Structure of 2:1 smectites/montmorillites? | Combination of 2 tetra sheets (silicate) and 1 octa sheet (Al) |
| Basal spacing in 2:1 smectites/montmorillites? | Spacing is not fixed due to lack of strong bonding between Si tetra layers therefore will shrink and swell. No H bonding so layers don't stick together |
| Compare isomorphous sub in 1:1 soils and 2:1 soils | 1:1's have little isomorphous sub so the framework charge is close to neutral. 2:1's have lots of isomorph sub and develops a large and permanent net -ve charge |
| Compare the dependency of pH in 1:1 and 2:1 soils | 1:1's are pH dependent - -ve charge increases as soil pH increases. 2:1's are not pH dependent |
| Rhizosphere? | Zone immediately surrounding plant roots |
| How are earthworms beneficial? | Ingest organic matter and soil and the casts produced are higher in plant nutrients than surrounding soil. Burrowing increases water infiltration and conductivity |
| Mycorrhizae? | Symbiotic relationship between fungi and roots of vascular plants - fungi increases availability of essential elements in infertile soils while plants supply fungi with energy-rich C compounds |
| Non-humic humus? |
Created by:
cmw001001
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