Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

RENR 210 > MIDTERM 2 > Flashcards

MIDTERM 2 Flashcards

1
Q

What is a thin section analysis?

A

Historical technique
Soil cast in resin then cut into thin sections (<0.01mm width)
Allows light to penetrate and see details through it
See rocks/ceramics

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
1
Q

What is a scanning electron micrograph?

A

Modern technique
Soil encrusted in thin layer of gold
Bombarded with electrons, the reflection of which produces the image
<0.01mm - 1um
for the examination and analysis of micro- and nanoparticle imaging characterization of solid objects

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is the importance of porosity>

A

Water movement (infiltration)
Water availability (amount stored for plant use)
Root growth (easiest growth through pore space – decreased resistance)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is porosity/VS/VP?

A

Porosity(%) = pore space: the relative proportion of a volume of soil that is filled by air and water
VP: volume of pores (air and water)
VS: volume of solids (mineral and organic)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is soil bulk density?

A

Density = mass per unit volume
Bulk density = mass of soil per unit of volume

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What are 3 factors affecting bulk density?

A

Porosity: increased porosity = decreased bulk density
Texture: increased clay = decreased bulk density
Organic matter content = increased ogm = decreased bulk density

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is field capacity?

A

-33kpa

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is wilting point?

A

-1500kpa

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is the hygroscopic coefficient?

A

-3100kpa

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What are the water potentials?

A

Superfluous (gravitational) water = 0 to -33
Available water = -33 to -1500
Unavailable water = -1500 to -3100
Hygroscopic water = -3100 to solid

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

How do sandy soils affect FC, WP and AW?

A

Sandy soils: low porosity and large pores
FC = low WC
WP = very low WC
AW = low

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

How do clay soils affect FC, WP and AW?

A

Clay soils: high porosity and fine pores
FC = high WC
WP = high WC
AW = low to medium

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

How do loam soils affect FC, WP and AW?

A

Loam soils: range of pore size
FC and WP = low to medium WC
AW = high

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

How does Ogm affect WC and storage?

A

increases both

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is infiltration rate?

A

= rate of movement of water into soil pore space

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

How do soil structures affect infiltration rate?

A

Coarse soil increases it, fine soil decreases
Granular: rapid flow, small round peds
Blocky: moderate flow, angular peds
Prism: moderate flow, salt crust, osmotic potential is high
Platy: slow flow, horizontal peds

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Macro vs meso vs micro water capacity

A

Macro/transmission pores = 50um, drained at FC
Meso/storage = 0.5-50um, available water holding capacity
Micro/residual pores = <0.5um, mostly unavailable water

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is hydraulic conductivity?

A

measure of how easily water can pass through soil or rock: high values indicate permeable material through which water can pass easily; low values indicate that the material is less permeable
Darcy’s law
High K to low: coarse sand > organic matter > Bt (blocky) > Ae (has plates, slows water movement)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Ground water vs water table vs vadose zone vs capillary zone

A

Ground water: saturated zone

Water table: upper limit of the groundwater

Vadose zone: zone of unsaturated material above the water table (surface to groundwater)

Capillary fringe: zone of capillary rise (ground water seeps up from a water table by capillary action to fill pores)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What are the 3 types of weathering?

A

Physical: disintegration, freeze/thaw cycles
Chemical: decomposition, molecular changes (water is universal solvent)
Biological: decomposition mediated by organisms, done by enzymes and organic acids

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What are the 5 primary minerals?

A

Quartz: SiO2 – silicate framework (sand)
Muscovite (white mica)
Biotite (black mica)
Feldspar: Na, K, Ca, Mg are the base cations, bonded to a silicate framework
Albite (Na feldspar)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What soil texture is a primary mineral?

A

sand and silt

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What primary minerals are most to least hard?

A

Quartz>feldspar>micas

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What soil texture is a secondary mineral?

A

clay
Soil separate
Particle size is <2mm
Textural class
Secondary mineral
Component of the colloidal fraction of soils (soil colloid)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What are colloids?

A

a homogeneous mixture consisting of ultramicroscopic particles of one substance dispersed through a second substance. Colloids include gels, soils and emulsions: the particles don’t settle and cannot be separated out by ordinary filtering or centrifuging like those in a suspension
Particles <1-2um behave as colloids
Total SA ranges from 10-1000m2g-1

25
Q

What is the structure and function of colloids?

A

Internal and external surfaces have electronegative or electropositive charges (negative charge is dominant)
Each micelle adsorbs (passes through membrane of cells) 1000s of hydrated Al, Ca, H, K, Mg, Na ions (enclosed within several water molecules)

26
Q

What is the cation exchange?

A

occurs when ions break away into the soil solution and are replaced by other ions

27
Q

What is the ionic double layer?

A

negative charged micelle surrounded by a swarm of cations

28
Q

What are minerals?

A

composed of different elements, impart properties to soil

29
Q

What rock types are there?

A

igneous, metamorphic and sedimentary (different types have different types of minerals in them

30
Q

What is mineral soil?

A

decomposed rocks

31
Q

What are the 4 components of the colloidal fractions?

A
  1. Crystalline silicate clays: phyllosilicates = aluminosilicates (dominant colloid in AB soils)
  2. Non crystalline silicate clays (amorphous) – for instance, allophane and imogolite that are both present in volcanic soils
  3. Fe and Al oxides: fe adna Al atoms connected to O2 atoms and hydroxyl (OH) groups: may be either amorphous or organized in crystalline sheets – mostly present in more weathered soils (ex. podzols)
  4. Humus: OgM – functional groups R-OH
32
Q

What are the building blocks of silicate clay minerals?

A

Silicon tetrahedron – silicon and oxygen with silicon being the central cation
Aluminum octahedron – hydroxyl and aluminum (central cation)
Clay = 2 tetrahedral sheets outside a octahedral sheet (2:1 or 1:1 = 1 of each)

33
Q

What is kaolinite?

A

Secondary clay mineral (phyllosilicate)
Non expanding clay (no shrink swell)
1:1
Common in old soils (AUS)
Silicate framework (hydrophilic)
Hydrogen bonding between layers and no interlayer swelling
Little (low) isomorphous substitution – poor fertility
D spacing = 0.72nm
Good for construction (bricks), ceramics and magazines glossy coating
2-4 CEC

34
Q

What is d spacing?

A

the distance from the top of one platelet to the top of the next platelet

35
Q

What is montmorillonite?

A

Silicate framework (theoretical unsubstituted)
Extensive (high) isomorphous substitution
Water and cations exist between unit layers – interlayer bonding by cations (weak to no bonding)
High level of shrink swell with wetting
2:1 secondary clay mineral (phyllosilicate)
Common in young soils (AB)
1-2 nm d spacing
No attraction between the platelets – water can get into the interlayer and cause swelling (interlayer expands and contracts)
Good for nutrient retention, increases CEC, can be used in construction for sealing pipes, irrigation and wells
80-160 CEC

36
Q

What is illite/chlorite?

A

2:1
Some (medium) isomorphic substitution but charge satisfied by potassium
Fine grained mica
Low shrink swell
Illite: forms in potassium rich environments (calcareous soils)
Chlorite: lots in AB cause of magnesium rich PM (calcareous soils)
Lots in AB because of potassium rich PM and calcareous soils
Cation bridging
20-40 CEC

37
Q

What are the 2 sources of charges?

A

Isomorphous substitution (permanent charge)
2:1 and 1:1 clays
Not pH dependent
Hydroxyls (OH-) or other functional groups (non permanent charge)
releasing/accepting H+ ions
pH dependent
Common source of charge on: organic matter, iron and aluminum oxides and non-crystalline silicates

38
Q

What has more CEC?

A

OgM and increased fine texture

39
Q

What is cation exchange capacity?

A

a measure of the total negative charges within the soil that adsorb plant nutrient cations such as Ca, Mg, K, etc. – it is a property of a soil that describes its capacity to supply nutrient cations to the soil solution for plant uptake
Modifies chemical behaviour in soils
Increased CEC = increased fertility
Decreases with increasing weathering

40
Q

What is base saturation?

A

degree to which exchange sites are occupied by Ca, Mg, Na, K (influences pH of soil and are plant nutrients) – increases with increasing sediment geology

41
Q

What does CEC do?

A

Diffuse ions in solution – free in solution
Outer Sphere complexes (exchanged with ions in solution)
Inner Sphere complexes represents atoms that are covalently bonded with mineral structure – only released through weathering

42
Q

The ease of cation replacement depends on what?

A

Valences (primarily): higher valence cations can replace cations of lower valence
Ion size: cations with smaller hydrated radius have greater replacement power
Relative amount: high concentration of Na can displace Al
Li<Na<K<Cs<Be<Mg<Ca<Ba<Al<Fe

43
Q

What is anion exchange caused by?

A

caused by protonation of hydroxyl groups – increases with decreasing acidity (excess H+) and increases with weathering

44
Q

What are the 4 principles of ionic exchange?

A

Reversible reactions
Charge balance
Ion selectivity
(3a) = concentration

45
Q

What is the optimal pH for ag soils?

A

Optimal pH = 6.5 for agricultural soils (increases nutrient availability and allows microbes to thrive better)
In ag soils, affected by microorganisms (fungi and bacteria) and available nutrients

46
Q

How do you adjust pH?

A

lime/limestone

47
Q

What is soil reactivity?

A
48
Q

What are the affects of aluminum on plants?

A

Very toxic to plants
Can acidify soils under certain conditions because it reacts with water to form aluminum hydroxide (releases hydrogen into the soil)
Releases 3 H

49
Q

Active vs exchange vs residual activity

A

Active activity: H in soil solution, measured with a pH meter
Exchange activity: Al and H on exchange sites, measured by extraction (with CaCl2)
Residual activity: Al and H bound (trapped - might be released with some weathering) in non-exchangeable forms on clay surfaces, non-measurable

50
Q

Increased CEC affects what?

A

Increased CEC = increased pH = increased retention = more deprotonation (loose H = increase space to hold nutrients) = more negative charges on soil particle

51
Q

Leaching leads to what?

A

Leaching = eutrophication – doesn’t go to crops and therefore they can’t retain nutrients

52
Q

What is soil reactivity?

A

the ability of certain elements or ions in the soil to be replaced or exchanged with other ions in the soil solution (most common: Ca, Mg, K, Na)

53
Q

What is the soil buffering capacity?

A

the soils resistance to changes in pH when an acid (such as hydrogen ions, H) or a base (Hydroxide ions, OH) is added to the soil – measures the soils ability to maintain a relatively stable pH level even when external acids or bases are introduced
Higher with higher base saturation and CEC
High in chernozem, medium in luvisol, low in brunisol

54
Q

What are some consequences of soil acidity on plant growth and soil health?

A

Nutrient availability
Microbial processes
Restricted plant diversity
Soil erosion

55
Q

What are some soil acid forming processes?

A

carbonic acid, acids from biological metabolisms (decomposition), oxidation of N, oxidation of S, plant uptake, acid rain

56
Q

What is acid rain caused by?

A

sulfur dioxide and nitric oxide combine with water and oxygen in the air to for sulfuric acid and nitric acid (increase of H) – due to high population, industry and vehicle traffic
Not too much of a worry in AB as we have calcareous soils (alkaline)
Slightly more in edmonton, calgary and fort mac

57
Q

Salinity and sodicity promote what?

A

**salinity promotes soil flocculation
**sodicity promotes soil dispersion (deflocculation)

58
Q

What is electrical conductivity?

A

concentration and composition of all dissolved salts (over 4dS/m = plants suffer osmotic stress)

59
Q

Where are salt affected soils in Canada, what are the most common and how do salts move?

A

30% of canadian prairie region considered saline (salty – solonetzic soils)
Due to natural or anthropogenic activities
Most common salts in AB are NaCl and MgSO4
Salts move by leaching or capillary action

60
Q

Why is a salt crest bad?

A

makes hard for water infiltration and seed germination to occur

61
Q

What are some ways of fixing salt affected soils?

A

leaching, improved drainage, gypsum application and amending with organic matter

RENR 210 (3 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions