Liquids and Gases

Question 1

Soil air compared to atmospheric…

Answer 1

Similar composition however organism influences with increased CO2 relative to O2

Question 2

Importance of air/water independently?

Answer 2

Air allows aerobic organisms to thrive whilst rain causes saturation

Question 3

Contamination in soils…

Answer 3

Volatile Organic Compounds, contaimination varying with organism presence, so anaerobic organisms produce CH4, N2O, H2S when low in O2

Question 4

Relative Humidity

Answer 4

Measure of how much water vapor in a water air mixture compared to the maximum amount possible

Question 5

What is the average relative humidity in soils?

Answer 5

99-100%

Question 6

What does RH depend on?

Answer 6

Increased temperature holds more water vapour

Question 7

What does diffusion depend on?

Answer 7

Conc Grad, water content, size/number of pores, temperature and molecule type

Question 8

Diffusion and pores?

Answer 8

Total porosity more important than pore size, and pore continuity with increasing speed with higher connectivity

Question 9

When does mass flow of gases happen in soil?

Answer 9

Soil temp changes, gas velocity, atmosphere pressure changes, plant water extraction, wind blowing over surface increasing evaporation, flooding

Question 10

Tortuosity

Answer 10

Ratio of actual flow path relative to straight distance from end to end

Question 11

Bulk Density

Answer 11

This is the weight of material including the air space in unit volume

Question 12

What does bulk density indicate?

Answer 12

Compaction and porosity, being soill mass/V

Question 13

Specific Gravity

Answer 13

This is mass to volume ratio of a mineral relative to water at 4C

Question 14

Unique proeprties of water?

Answer 14

Polarity, hydrogen bonding, surface tension, cationic hydration with binding

Question 15

Common H2O binding cations…

Answer 15

Na, Ca, Mg, K attracted to O

Question 16

What are the most common solutes?

Answer 16

Ca, Mg, K, Cl, NO3, SO42, H2PO4, HPO42, HCO3

Question 17

When does leaching occur?

Answer 17

Water enters soil, dissolving soluble compounds, redistributing nutrients

Question 18

How may climate influence soil?

Answer 18

Tropics high temp and precip means high biological activity, whilst humid climates with cold temp not

Question 19

Field Capacity

Answer 19

This is the amount of water within a soil after excess water has drained away

Question 20

Permanent Wilting Point

Answer 20

The point at which no water is avaiable to the plant

Question 21

What two states represent moisture of soils?

Answer 21

Field Capacity
Permanent Wilting Point

Question 22

Ion Exchange

Answer 22

Electrostatic interactions between ions, or solute/surface binding, solid phase dissolution in solution, solid precipitation, organic molecule weak soprtion pore retention and phase partinioning

Question 23

Charge of clays and OM?

Answer 23

Anionic: clays due to isomorphic substituion and H+ loss in humus

Question 24

Why does ionic exchange occur?

Answer 24

Coulombic forces being weaker than the covalent ones

Question 25

What determines equilibrium of cationic exchange?

Answer 25

Small hydrated radius held tighter and exchange less easily than larger cations due to closeness to exchange complex and larger size meaning tighter hold

Question 26

What element has highest electrostatic adsorption?

Answer 26

Al

Question 27

How may elements with lower electrostatic adosrption displace higher?

Answer 27

High concentrations

Question 28

Why is H+ low competitive?

Answer 28

Larger hydrated radius, singular charge and low concentrations, however acidificfaction for pH-dependent surface charge readily adsorb it

Question 29

Importance of Anionic Exchange Capacity...

Answer 29

Lower influence but affects anionic pesticides like 2, 4-D and retention of Cl-, NO3- and SO42-

Question 30

Cation Exchange Capacity

Answer 30

This measures total amount of cations that can be held by a given mass of soils

Question 31

How is ions equivalent weight measured?

Answer 31

Atomic Weight divided by charge

Question 32

How many CEC be determined by Clay/OM?

Answer 32

Isomorphic Substitution, pH, Humus greatly increases CEC

Question 33

London Forces

Answer 33

Resonances between transient dipoles of adjacent atoms

Question 34

Hydrogen Bonding

Answer 34

Electron sharing between two permanent dipoles

Question 35

Impotance of Van der Waals forces...

Answer 35

Ionicaly bind organic ions to clays or humus allows pesticide retention and proteins acting as external enzymes

Question 36

Soils anti-pollutant affects?

Answer 36

Sorption of nonpolar, hydrophobic organic compounds, assimilate alkenes, aromatics, petroelum, pesticides