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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
Q

thermal conductivity

A

how much heat is moved or transferred from one point to another

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26
Q

Aspect

A

in northern hemisphere, south aspect gets more sunlight

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27
Q

compact/loose soil thermal coductivity

A

loose dry soil = low K
compact dry = medium K
compact wet = high K

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28
Q

mineral colloids

A

clay

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29
Q

organic colloids

A

humus

30
Q

three types of mineral clays

A

crystalline silicate clays, non-crystalline silicate clays, iron and aluminum oxides

31
Q

crystalline silicate clays

A

dominant type of colloid (except Andisols, Oxisols, Histosols)
layers of 2-4 sheets of closely packed and tightly bonded O-Si-Al atoms

32
Q

noncrystalline silicate clays

A

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
Q

Iron and Aluminum Oxides

A

Ultisols and Oxisols
Fe or Al atoms coordinated with O atoms
crystalline or noncrystalline

34
Q

Organic (Humus)

A

comes from decomposition of organic materials
charged functional groups

35
Q

Isomorphic substitution

A

one atom substitutes for another and the change in charge can give the whole structure a net negative charge

36
Q

Tetrahedron

A

silicon in the middle and oxygen on the sides

37
Q

Octahedron

A

aluminum or magnesium in the middle and hydroxide on the sides

38
Q

1:1 silicate clay

A

kaolinite
octahedron on a tetrahedron and they share an oxygen
don’t expand, no swelling

39
Q

2:1 silicate clay

A

two tetrahedral sheets with an octahedral sheet in the middle
non expanding mica group, expanding smectite group, expanding vermiculite group, non expanding chlorites

40
Q

Mica group (illite)

A

2:1 mineral clays
non expanding, minimum swelling
highly negative holes accommodate and hold K+ ions

41
Q

Smectite group

A

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
Q

Vermiculite group

A

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
Q

Chlorites

A

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
Q

Allophane

A

clay from volcanic ash
amorphous, chemically reaction, physically stable
fluffy, low density soils

45
Q

Hydrous oxides (sesquioxides) of Fe and Al

A

octahedral sheet
OH-OH
hydrogen bonding, non expanding, nonstick, stable
low CEC

46
Q

Hematite

A

iron oxide mineral
stacked sheets of Fe3+ ions in octahedral coordination

47
Q

pH dependent charges

A

H+ ion dissociation

48
Q

permanent charges

A

isomorphous substitution

49
Q

cation exchange capacity

A

negative particles attract positive nutrients, then to get them back cations have to be exchanges
electronegativity + surface area

50
Q

charge equivalency

A

charge for a charge
plant needs to release 2 hydrogen for 2 Ca2+ ion

51
Q

cation selectivity

A

some ions are held more tightly than others
the more charge, the more tightly its held by the colloid

52
Q

complementary cations

A

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
Q

water

A

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
Q

Cohesion

A

water attraction to itself

55
Q

adhesion

A

water attraction to solids

56
Q

capillarity

A

movement of water through tubes
the narrower the tube, the higher up water moves
smaller pore spaces will let water travel higher up

57
Q

soil water potential

A

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
Q

wet soils (soil moisture)

A

water molecules are loosely held, their energy status being relatively high compared to that of pure water

59
Q

dry soil (soil moisture)

A

water is held tightly by the soils’ solids and its energy status is much lower than that of pure water

60
Q

saturation

A

when all pore space is filled with water
water movement is result of gravimetric potential
total water potential = 0

61
Q

unsaturated

A

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
Q

wilting point

A

water no available for growth
-1500 kPa

63
Q

field capacity

A

water is available for plant growth
-10 kPa

64
Q

available soil water

A

held between the field capacity and the wilting coefficient

65
Q

least limiting water range

A

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
Q

liquid water losses

A

percolation or drainage that carriers plant nutrients, pesticides, etc
runoff water that carriers plant nutrients, finer fractions of soil, through erosion

67
Q

micro-irrigation

A

trickle or drip irrigation
very small quantities of water directed to or near the plant are most efficient since they minimize evaporation

68
Q

septic tank drain fields

A

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
Q

how to determine soil suitability for septic drain field

A

perc test
tests percolation to review water drainage

70
Q

control of soil temperature

A

mulch (plastic, organic, etc)
snow can be an insulator
conservation tillage..crop residues
poorly drained soils are cooler

71
Q

CEC is important in

A

soil fertility
groundwater protection
pesticide-soil interactions
toxic waste disposal (binds toxic metals)

ENST200 (5 decks)

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