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ENST200 > Exam 2 > Flashcards

Exam 2 Flashcards

1
Q

Hydrologic Cycle

A

cycling of water from the earths surface to the atmosphere and back again

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2
Q

watershed

A

an are of land drained by a single system of streams and bound by ridges that separate it from adjacent watersheds

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3
Q

water balance equation

A

P = ET + SS + D
precipitation = evapotranspiration + soil storage + discharge

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4
Q

factors affecting infiltration

A

timing
vegetation
soil management
urban watersheds
soil properties

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5
Q

water losses from soil surface and transpiration are determined by

A

climatic conditions, plant cover in relation to soil surface, efficiency of water use, length and season of plant-growing period

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6
Q

runoff rate

A

= precipitation rate - infiltration rate - soil storage

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7
Q

benefits of artificial soil drainage

A

-increased bearing strength and soil workability
-reduced frost-heaving for construction
-enhanced rooting depth and plant productivity
-reduced levels of fungal disease infestation in seeds or young plants
-rapid warming in spring
-less production of methane and nitrogen gases
-removal of excess salts, prevention of salt accumulation

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8
Q

detrimental effects of artificial soil drainage

A

-loss of habitat
-reduced nutrient assimilation
-increased leaching
-accelerated loss of soil organic matter
-increased frequency of flooding due to loss of runoff water retention capacity
-greater cost of damages

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9
Q

Aerenchyma tissue

A

bigger openings where plants can get oxygen from the top of the plant and supply to the plants roots

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10
Q

Mass flow

A

air enhanced by fluctuations in soil moisture content that force air in or out of the soil and by wind and changes in barometric pressure

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11
Q

diffusion (air)

A

each case moves in a direction determined by its own partial pressure
net movement of CO2 going out into atmosphere and O2 going into the soil from the atmosphere

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12
Q

factors affecting soil aeration

A

-drainage of excess water
-rates respiration in the soil
-subsoil versus topsoil (subsoil less O2 and lower macro pore space)
-soil heterogeneity
-seasonal differences
-effects on tillage

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13
Q

Gaseous exchange impacted by season

A

spring = wet and lower gaseous exchange
summer = drier and increased gaseous exchange

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14
Q

Soil aeration status characterized by:

A

-O2 content of soil
-proportion of the pore space filled with air
-redox potential of soil

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15
Q

Redox Potential

A

potential of electrons to be transferred from one substance to another

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16
Q

hydrophytic plants

A

plants that can grow in water
rice, mangroves, fragmites, cattails

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17
Q

anaerobic conditions

A

in saturated soils, oxygen diffusion slows dramatically and all remaining O2 is used up as an electron acceptor

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18
Q

Order of chemicals/gases microbes use for redox

A

oxygen –> nitrogen –> manganese –> iron –> sulfur –> methano-genesis (carbon)
Only Northern Marshes Feel So Cold

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19
Q

factors leading to reduction in soil

A

-saturated or inundated to exclude atmosphere O2
-contain organic tissues that can be oxidized or decomposed
-microbial population must be respiring and oxidizing organic tissues
-water should be stagnant or moving slowly

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20
Q

wetlands

A

wetland hydrology…pattern of flooding or saturation
hydrophytic vegetation…plants that prefer wet soils
hydric soils…saturated for long enough during biological activity to result in anearobic conditions

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21
Q

hydric soil indicators

A

gray colors…gleying
black organic matter accumulation
red oxidized root zones of hydrophilic plants

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22
Q

benefits of wetlands

A

-water quality improvement (trap sediment, trap/remove nitrogen and phosphorus)
-shoreline erosion control
-natural products
-aesthetics and recreation
-habitat for fish and wildlife and hydrophytic plants

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23
Q

Temperature of soil is determined by

A

solar radiation
specific heat of soil
energy needed to evaporate soil

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24
Q

heat capacity

A

how much heat is needed to change the temperature of the soil itself

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25
thermal conductivity
how much heat is moved or transferred from one point to another
26
Aspect
in northern hemisphere, south aspect gets more sunlight
27
compact/loose soil thermal coductivity
loose dry soil = low K compact dry = medium K compact wet = high K
28
mineral colloids
clay
29
organic colloids
humus
30
three types of mineral clays
crystalline silicate clays, non-crystalline silicate clays, iron and aluminum oxides
31
crystalline silicate clays
dominant type of colloid (except Andisols, Oxisols, Histosols) layers of 2-4 sheets of closely packed and tightly bonded O-Si-Al atoms
32
noncrystalline silicate clays
tightly bonded Si-Al-O atoms allophane and imogolite usually from volcanic ash (Andisols) high water holding capacity high capacity to adsorb phosphate and other anions, especially under acid conditions
33
Iron and Aluminum Oxides
Ultisols and Oxisols Fe or Al atoms coordinated with O atoms crystalline or noncrystalline
34
Organic (Humus)
comes from decomposition of organic materials charged functional groups
35
Isomorphic substitution
one atom substitutes for another and the change in charge can give the whole structure a net negative charge
36
Tetrahedron
silicon in the middle and oxygen on the sides
37
Octahedron
aluminum or magnesium in the middle and hydroxide on the sides
38
1:1 silicate clay
kaolinite octahedron on a tetrahedron and they share an oxygen don't expand, no swelling
39
2:1 silicate clay
two tetrahedral sheets with an octahedral sheet in the middle non expanding mica group, expanding smectite group, expanding vermiculite group, non expanding chlorites
40
Mica group (illite)
2:1 mineral clays non expanding, minimum swelling highly negative holes accommodate and hold K+ ions
41
Smectite group
2:1 mineral clays expanding, max swelling tetrahedral oxygen ions face each other and repel clay swells as water molecules enter the interlayers, forcing layers apart
42
Vermiculite group
2:1 mineral clays expanding, some swelling significant Al3+ substitution for Si4+ water molecules, Mg2+, and other ions help keep the clays from being too expansive by providing some attraction
43
Chlorites
2:1 mineral clays non expanding, minimum swelling Al substitution = negative charged tetrahedral sheets highly negative holes hold hydroxy sheets mutual attraction holds layers together, preventing swelling
44
Allophane
clay from volcanic ash amorphous, chemically reaction, physically stable fluffy, low density soils
45
Hydrous oxides (sesquioxides) of Fe and Al
octahedral sheet OH-OH hydrogen bonding, non expanding, nonstick, stable low CEC
46
Hematite
iron oxide mineral stacked sheets of Fe3+ ions in octahedral coordination
47
pH dependent charges
H+ ion dissociation
48
permanent charges
isomorphous substitution
49
cation exchange capacity
negative particles attract positive nutrients, then to get them back cations have to be exchanges electronegativity + surface area
50
charge equivalency
charge for a charge plant needs to release 2 hydrogen for 2 Ca2+ ion
51
cation selectivity
some ions are held more tightly than others the more charge, the more tightly its held by the colloid
52
complementary cations
the likelihood that a given adsorbed cation will be displaced from a colloid is influenced by how strongly its neighboring cations are adsorbed to the colloidal surface loose --> large oscillation zones tight --> small oscillation zones
53
water
polar structure with its hydrogen (positive) end and hydroxyl (negative) end is responsible for the attraction of water molecules for each other (cohesion) and for solid surfaces (adhesion)
54
Cohesion
water attraction to itself
55
adhesion
water attraction to solids
56
capillarity
movement of water through tubes the narrower the tube, the higher up water moves smaller pore spaces will let water travel higher up
57
soil water potential
the difference in energy level of water determines the direction and rate of water movement in soils and plants gravitational potential + osmotic potential + matrix potential
58
wet soils (soil moisture)
water molecules are loosely held, their energy status being relatively high compared to that of pure water
59
dry soil (soil moisture)
water is held tightly by the soils' solids and its energy status is much lower than that of pure water
60
saturation
when all pore space is filled with water water movement is result of gravimetric potential total water potential = 0
61
unsaturated
some moisture, but not all pore space is filled with water water moves as a result of matric potential and osmotic potential water potential <0
62
wilting point
water no available for growth -1500 kPa
63
field capacity
water is available for plant growth -10 kPa
64
available soil water
held between the field capacity and the wilting coefficient
65
least limiting water range
water contents ranging between when the soil is so hard that roots cannot penetrate to when the soil is so wet that roots cannot get enough oxygen water content range that doesn't limit growth
66
liquid water losses
percolation or drainage that carriers plant nutrients, pesticides, etc runoff water that carriers plant nutrients, finer fractions of soil, through erosion
67
micro-irrigation
trickle or drip irrigation very small quantities of water directed to or near the plant are most efficient since they minimize evaporation
68
septic tank drain fields
wastewater is piped to a septic tank where solids settle out and decompose liquid effluent overflows into a series of perforated pipes buried in septic drain field
69
how to determine soil suitability for septic drain field
perc test tests percolation to review water drainage
70
control of soil temperature
mulch (plastic, organic, etc) snow can be an insulator conservation tillage..crop residues poorly drained soils are cooler
71
CEC is important in
soil fertility groundwater protection pesticide-soil interactions toxic waste disposal (binds toxic metals)

ENST200 (5 decks)

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