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ENVS 2203 > Final Exam > Flashcards

Final Exam Flashcards

1
Q

Brunisols

A

Less developed forest soils
Related to luvisols and podzols
Dependent on soil texture

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2
Q

Brunisol Great Groups

A

Melanic
Eutric
Sombric
Dystric

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3
Q

Basic Great Groups

A

Melanic

Eutric

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4
Q

Great Groups with Ah

A

Sombric

Melanic

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5
Q

Acidic Great Groups

A

Sombric

Dystric

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6
Q

Great Groups without Ah

A

Dystric

Eutric

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7
Q

Podzols

A

High precipitation
Highly acidic soils, enhanced weathering of primary minerals
Strong leaching = sandy

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8
Q

Podzolic Diagnostic Horizon

A 
Illuvial Ae above B
B >10cm thick
7.5 YR or redder
Coarse texture
Coastal forests and areas
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9
Q

Podzol Great Groups

A

Humic
Ferro-Humic
Humo-Ferric

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10
Q

Humic

A

Organic Matter forms Bh

A lot of organic matter production

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11
Q

Ferro-Humic

A

Bhf

Not as wet, not as dry, some organic matter, some Fe, not as dark, more red

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12
Q

Humo-Ferric

A

Bf
Dry
Less intense weathering

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13
Q

What soils do Eutric soils become?

A

Gray Luvisols

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14
Q

What soils do Melanic soils become?

A

Gray-Brown Luvisols

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15
Q

What soils do Dystric soils become?

A

Podozols

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16
Q

Types of space in soil

A

Pore Space

Solid Space

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17
Q

Pore Space

A

Gas or Liquid Void

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18
Q

Solid Space

A 
Mineral particles
Organic matter (disregard
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19
Q

Interactions of Solid Space and Pore Space

A

Open spaces called pores, pores fill with water (soil water), soil porosity influences soil water movement

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20
Q

Macropores

A

> 0.08mm
Water drainage
Habitat for arthropods
Gas exchange

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21
Q

Micropores

A 
<0.1mm
Water storage (where bacteria are)
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22
Q

Porosity

A

Doesn’t change
Volume of the pores divided by the bulk soil volume
Total percentage, doesn’t tell if micro or macro pores

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23
Q

Bulk Density

A 
Soil Mass/Soil Volume
Measured oven dry
Changes as pore space changes - compaction increases bulk density
Surface Soils = 1.1 - 1.4
Subsoils = 1.3 - 1.7
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24
Q

Factors on Bulk Density

A

Texture
Aggregation
Surface

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25
Q

Texture and Bulk Density

A

Finer textures = lower BD

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26
Q

Aggregation and Bulk Density

A

More Aggregates = lower BD

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27
Q

Particle Density

A 
Mass of particles divided by the volume of particles
Typically 2.65 g/cm3
Used with BD to caluculate porosity
Porosity = 1-BD/2.65 x 100
Influenced by structure and texture
BD increases, Porosity decreases
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28
Q

Adhesion Water

A 
Water attracted to solid surfaces
Held by strong electrical forces (low energy)
Little movement - held tight by soil
Exists as film, unavailable to plants
Removed by drying in oven
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29
Q

Cohesion water

A

Water attracted to other water molecules
Held by H bonding
Major source of water for plants
Greater energy than adhesion water

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30
Q

Gravitational Water

A

Water under the influence of gravity
Moves freely due to gravitational forces
Greatest energy
Exists in macropores

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31
Q

Potential Energy

A

Systems tend to change from a state of high energy to states of low energy
Behaviour of an object within a system is dictated by potential energy

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32
Q

Water Potential

A

Way to measure current energy state of unit of water

Water Behaviour

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33
Q

How does water flow in soils?

A

Upward and downward
Drier to wetter
Low concentration to high concentration

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34
Q

Soil Water Potential Types

A 
Matric Potential
Gravitational Potential (usually 0)
Osmotic Potential (usually 0)
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35
Q

Matric Potential

A

Major force
Adhesive forces
Cohesive forces
As soil dries, decreases (negative number)

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36
Q

Soil Water Classification

A

Unavailable to Plants

Plant Available

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37
Q

Unavailable to Plants

A

0 to -10 kPa

-1.5Mpa to -100Mpa

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38
Q

Available to Plants

A

-10 kPa (field capacity) to -1500 kPa (Wilting point)

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39
Q

Sandy Textured Soil and Water

A

Low available water

Large pores that cannot hold cohesive water, mostly gravitational

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40
Q

Clay Textured Soil and Water

A

Low available water

Small pores mostly under wilting point

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41
Q

Loam Textured Soils and Water

A

High available water
Even pore distribution
Lots of capillary water

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42
Q

Volumetric Water Content

A

Volume of water in a given water of soil

Amount of water

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43
Q

Gravimetric Water Content

A

Easiest, most used way
Mass of water in a given mass of soil
[wet soil (g) - drysoil (g)]/drysoil (g)

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44
Q

Infiltration

A

Water entering the soil from precipitation

45
Q

Infiltration is affected by:

A

Structure
Texture
Existing Water Conditions

46
Q

Infiltration Rate Behaviour

A

Highest when soil is very dry

Decreases as soil becomes wetter

47
Q

Effects of Soil Structure on Infiltration

A

Well aggregated granular and single grain have rapid flow
Subsurface structure has moderate
Massive structure and Platy have slower infiltration

48
Q

Preferential Flow

A

Deposits surface chemicals to deeper soil layer

49
Q

What affects saturated flow?

A

Soil texture, structure, existence of preferential flow channels
Moisture status of the soil

50
Q

Calculated Hydraulic Conductivity

A

Rate at which water moves through a material
Saturated flow
Pore size decreases, Kstat decreases

51
Q

Unsaturated Flow

A

Matric forces at play

Moves from wet to dry

52
Q

Aerobic Soil Respiration

A

Plant roots, soil bacteria and fungi

Conversion of O.M. create gradients of oxygen and carbon dioxide

53
Q

Anaerobic Soil Respiration

A

Bacteria can use compounds other than oxygen for respiration

Preferable compounds are nitrate and ferric iron

54
Q

Carbon Cycle

A

Conversion of soil carbon to carbon dioxide and methane

Loss of carbon from the soil

55
Q

Nitrogen Cycle

A

Conversion of soil nitrate to nitrous oxide and nitrogen gas (anaerobic)
Loss of nitrogen from soil

56
Q

Colloids

A

Particles less than 1 or 2 micrometers
Very large surface area
Very reactive chemically (cation exchange, ionic double layer)

57
Q

Components of Colloidal Fraction

A

Crystalline silicate clays
Non-crystalline silicate clays
Iron and Aluminium oxides
Humus

58
Q

Building Blocks for Crystalline Silicate Clay minerals

A

Silicon Tetrahedron

Aluminium octahedron

59
Q

Crystalline Silicate Clay Minerals

A

Pure form have no charge, changes at sheet edges and has negative charge

60
Q

Isomorphic Substitution

A

Tetrahedron - Al for Si

Octohedron - Mg for Al or Zn for Al

61
Q

Kaolinite

A

Bonding between layers are hydrogen bonds
No interlayer swelling
Little isomorphous substitution => lower negative charge
Lower surace area
1:1 sheet
Bonding between layers is hydrogen bonds (Strong)

62
Q

Montmorillonite

A 
2:1 clay
Extensive isomorphous substitution
Cations and water exist between unit layers
Swelling
Bonding between layers in cations (weak)
63
Q

Illite

A 
Isomorphic substitution (Si replaced by Al in tetrahedral sheet, Al substituted by Mg or Fe in octahedral sheet)
Charge deficiency is balanced by the potassium ion between layers
64
Q

Cation Exchange Capacity

A

Colloids have large amount of negative charge, attract positive charge (cations)

65
Q

Importance of CEC

A 
Fertility issues
Acidity &amp; liming rates
Pesticides
Contaminants
Base saturation
Chemical behaviour in soils
66
Q

Common Soil Cations

A

Ca, K, H, Na, Mg, Al

67
Q

Origin of Cations

A

Parent Geological Material

Additions

68
Q

Parent Geological Materal

A

Soil minerals

Released through weathering

69
Q

Additions

A 
Atmospheric deposition (wind erosion, ash particles, cosmic dust)
Fertilization
70
Q

Fate of cations

A

Added/released to the soil
Switches between soil solution and plant biomass before being leached out of the soil (only leached out of soil from soil solution)

71
Q

Rules of Cation Exchange

A

Cation Selectivity
Cation Equivalence
Ratio Law
Complementary Cations

72
Q

Cation Selectivity

A

Large cations are held more tightly than small cations

73
Q

Cation Equivalence

A

High charge cations are held more tightly than low charge cations
Al>Ca>Mg>K>Na

74
Q

Ratio Law

A

Any one cation can replace any other if its concentration is high enough (all are reversible)

75
Q

Mass Action Rule (part of ratio law)

A

Al will always win when 1 to 1

H will win when up agains 1000

76
Q

Complementary Cations

A

The combined influence of charge equivalencies ion selectivity and complementary ions drive the exchange at cations
Lower charge gets knocked off easier
Generally cation with largest ionic radius and lowest hydration energies that absorb more strongly on the permanent charge sites

77
Q

Quantifying CEC

A

Measuring positive charges of cation, quantifying amount of positive charges supplied by soils

78
Q

Measuring CEC

A
  1. Known volume/concentration of NH4
  2. Replace all cations in soil with NH4
  3. lush with K
  4. Measure NH4 in leachate, NH4 concentration = TCEC
79
Q

CEC and Fertility

A

CEC measures the total ability of a soil to retain cations

Does not provide information about what types of cations are retained

80
Q

Calculations using CEC

A

Base Saturation

Percentage affects uptake by plants

81
Q

Base Saturation

A

Measure of base cations located on exchange sites

82
Q

Sources of Acidity in Soils

A 
Carbonic and other organic acids
Accumulation of OM
Oxidation Reactions
Plant uptake of Cations
Free Al
Human Activities
83
Q

Carbonic and Other organic Acides

A

Dessolved CO2 in rainwater

84
Q

Accumulation of OM

A

Carboxyl group (COOH)

85
Q

Oxidation Reactions

A

Microbial usage produces H

86
Q

Plant Uptake of Cations

A

Removal of base cations

87
Q

Free Al

A

Weathering

88
Q

Human Activities

A

Acid rain is important one

89
Q

Mineral Weathering and Aluminum

A
  1. Weathering of Aluminum releases it into soil

2. Reaction of Al with H2O creates excess H in soil

90
Q

Acid Rain

A

Fossil Fuel combustion creates NOx and SOx

Dissolve in rainwater to produce nitric and sulfuric acids

91
Q

Fertilization

A

Intentional

Unintentional

92
Q

Intentional Fertilization

A

Adding acidifying agents to alkaline soils

93
Q

Unintentional Fertilization

A

Oxidation of Ammonium to Nitrate

Removal of base cations by harvesting plants that took cations out of soil

94
Q

Pools of Acidity in Soils

A

Active (Small/Reactive)
Exchangeable (Large/Reactive)
Residual (Largest/Unreactive)

95
Q

Active Acidity

A

H in the soil solution

Determines solubility of many substances in soil

96
Q

Exchangeable Acidity

A

H &Al associated with colloidal cation exchangesites

97
Q

Residual Acidity

A

Associated with structural H and Al in physillicate structures
Slowly released by weathering

98
Q

Base Cations

A

Ca, Mg, K, Na

99
Q

How do base cations act as bases?

A

Exchange places with H in solution

100
Q

Leaching Losses of Base Cations

A

Acidifying processes continually add H with cations lost to leachingB
Gradual increase in soil pH as H dominates

101
Q

Buffering Actions

A

Carbonate Buffering

Aluminium Buffering

102
Q

Carbonate Buffering

A

pH>8
Ca exchanges with H and Al
CO3 reacts with free H and Al

103
Q

Aluminium Buffereing

A

pH<5
Al absorbs OH
Resists rise in pH

104
Q

Soil Nutrients

A

Macronutrients

Micronutrients

105
Q

Macronutrients

A

Inhibited by low pH

106
Q

Micronutrients

A

Inhibited by high pH

107
Q

pH effects on Plants and Soils

A

Excess H = leaching loss of soil nutrients
Direct tissue damage
Change in soil bacteria

108
Q

ALuminium Toxicity

A

Blocks Ca from entering into plants
Binds with Phosphorus in ATP
Restricts cell wall expansion

ENVS 2203 (1 decks)

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