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رابطه آب خاك و گیاه تكميلی حاج عباسی. Isfahan University of Technology. WATER-The Substance of Life. Limits Kinds and Amounts of Vegetation on Earth Limits Growth of Cities and Kinds of Industry. رابطه آب خاك و گیاه تكميلی حاج عباسی. Isfahan University of Technology. EARTH’S WATER SUPPLY.

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Water the substance of life

رابطه آب خاك و گیاه تكميلی

حاج عباسی

Isfahan University of Technology

WATER-The Substance of Life

  • Limits Kinds and Amounts of Vegetation on Earth

  • Limits Growth of Cities and Kinds of Industry


Water the substance of life

رابطه آب خاك و گیاه تكميلی

حاج عباسی

Isfahan University of Technology

EARTH’S WATER SUPPLY

  • 70% of Earth’s Surface

  • covered by water

  • 97% of Earth’s water supply

    in oceans

  • Ice at Polar Caps next most

    abundant supply (>2%)

  • Groundwater next most

    abundant supply (~0.5%);

    approximately 50% of ground

    water is > 0.5 miles deep

  • Fresh water in lakes, ponds

    and streams ~0.008%

  • Soil and atmospheric water

    ~ 0.001%

  • Biological water ~0.0001%

  • Average annual rainfall on land

    ~ 30 inches


Water the substance of life

رابطه آب خاك و گیاه تكميلی

حاج عباسی

Isfahan University of Technology

Precipitation

Soil-Air Interface

Vadose Zone

Evaporation

Portion of aquifer where pore spaces are occupied with water and air (unsaturated zone)

Applications of soil physics are crucial to sustainable use of natural resources for agricultural and other land uses

Soil-Water Interface

Capillary fringe zone

Ground water


Water the substance of life

رابطه آب خاك و گیاه تكميلی

حاج عباسی

Isfahan University of Technology

تبخیر و تعرق

نزولات جوی

آبیاری

نفوذ

روان آب

ذخیره در خاک

نفوذ عمقی

جریان داخلی

عمق خاک


Precipitation evaporation

رابطه آب خاك و گیاه تكميلی

حاج عباسی

Isfahan University of Technology

Precipitation/Evaporation

  • P/E>0.75= Humid (Forests)

  • P/E >0.5= Sub-Humid (Mixed Forest and Grasslands)

  • P/E >0.25= Semi-Arid (Mixed Grasslands and Semi-Deserts)

  • P/E <0.25= Arid (Deserts)


Soil water relationships

رابطه آب خاك و گیاه تكميلی

حاج عباسی

Isfahan University of Technology

Soil Water Relationships


Water the substance of life

رابطه آب خاك و گیاه تكميلی

حاج عباسی

Isfahan University of Technology

  • Bulk Density (b)

    • b = soil bulk density, g/cm3

    • Ms = mass of dry soil, g

    • Vb = volume of soil sample, cm3

  • Typical values: 1.1 - 1.6 g/cm3

  • Particle Density (p)

    • P = soil particle density, g/cm3

    • Ms = mass of dry soil, g

    • Vs = volume of solids, cm3

  • Typical values: 2.6 - 2.7 g/cm3


Water the substance of life

رابطه آب خاك و گیاه تكميلی

حاج عباسی

Isfahan University of Technology

  • Porosity ()

  • Typical values: 30 - 60%


Water in soils

رابطه آب خاك و گیاه تكميلی

حاج عباسی

Isfahan University of Technology

Water in Soils

  • Soil water content

    • Mass water content (m)

    • m = mass water content (fraction)

    • Mw = mass of water evaporated, g (24 hours @ 105oC)

    • Ms = mass of dry soil, g


Water the substance of life

رابطه آب خاك و گیاه تكميلی

حاج عباسی

Isfahan University of Technology

  • Volumetric water content (v)

    • V = volumetric water content (fraction)

    • Vw = volume of water

    • Vb = volume of soil sample

    • At saturation, V = 

    • V = As m

    • As = apparent soil specific gravity = b/w (w = density of water = 1 g/cm3)

    • As = b numerically when units of g/cm3 are used

  • Equivalent depth of water (d)

    • d = volume of water per unit land area = (v A L) / A = v L

    • d = equivalent depth of water in a soil layer

    • L = depth (thickness) of the soil layer


Volumetric water content equivalent depth

رابطه آب خاك و گیاه تكميلی

حاج عباسی

Isfahan University of Technology

Volumetric Water Content & Equivalent Depth

(cm3)

Equivalent Depth

(cm3)

(g)

(g)


Volumetric water content equivalent depth typical values for agricultural soils

رابطه آب خاك و گیاه تكميلی

حاج عباسی

Isfahan University of Technology

Volumetric Water Content & Equivalent DepthTypical Values for Agricultural Soils

Soil Solids (Particles): 50%

0.50 in.

1 in.

Very Large Pores: 15% (Gravitational Water)

0.15 in.

Total Pore Space: 50%

Medium-sized Pores: 20% (Plant Available Water)

0.20 in.

Very Small Pores: 15% (Unavailable Water)

0.15 in.


Water holding capacity of soil effect of soil texture

رابطه آب خاك و گیاه تكميلی

حاج عباسی

Isfahan University of Technology

Water-Holding Capacity of SoilEffect of Soil Texture

Coarse Sand Silty Clay Loam

Dry Soil

Gravitational Water

Water Holding Capacity

Available Water

Unavailable Water


Water the substance of life

رابطه آب خاك و گیاه تكميلی

حاج عباسی

Isfahan University of Technology

Soil Water Content

Soil Moisture Content

Water that may be evaporated from soil by heating at 1050C to a constant weight

mass of water evaporated (g)

Gravimetric moisture content (w) =

mass of dry soil (g)

volume of water evaporated (cm3)

Volumetric moisture content (q) =

volume of soil (cm3)

bulk density of soil

q = w *

density of water

mass of dry soil (g)

Bulk density of soil (r) =

volume of soil (cm3)


Water the substance of life

رابطه آب خاك و گیاه تكميلی

حاج عباسی

Isfahan University of Technology

Soil Moisture Content: Methods of Measurement

  • Difficulties encountered for accurate moisture measurement in the field:

  • Soils are highly variable

  • Soil moisture is highly dynamic (spatial temporal variability)

  • Plant water uptake is highly variable depending upon the stage of growth

  • State of growth is again dependent upon nutrient application, water availability, pests etc.

  • Chemicals present in the soil can make measurements unreliable

  • Costs involved


Water the substance of life

رابطه آب خاك و گیاه تكميلی

حاج عباسی

Isfahan University of Technology

Methods for soil water content

Direct method (Gravimetric; Thermogravimetric)

Indirect methods

Electrical properties

Acoustic method

Thermal properties

Chemical methods

Radiation technique

-Neutron scattering

-g- ray attenuation

Methods of soil water content determination

Electrical Conductance

Dielectric constant

TDR

- Gypsum blocks

- Nylon blocks

- Change in conductance

Principles underlying different methods of

assessment of soil water content


Water the substance of life

رابطه آب خاك و گیاه تكميلی

حاج عباسی

Isfahan University of Technology

DIRECT

Gravimetric: evaporating water at 1050C.

Thermogravimetric: Soil sample is weighted and saturated with alcohol and burned several times until a constant dry weight is obtained

INDIRECT

Electrical Conductance


Water the substance of life

رابطه آب خاك و گیاه تكميلی

حاج عباسی

Isfahan University of Technology

DIRECT

Gravimetric: evaporating water at 1050C.

Feel Method:

Thermogravimetric: Soil sample is weighted and saturated with alcohol and burned several times until a constant dry weight is obtained

Advantages: ensures accurate measurements, not dependent on salinity and soil type, easy to calculate

Disadvantage: destructive test, time consuming, inapplicable to automatic control, must know dry bulk density to transform data to volume moisture content, inaccurate because of soil variability

There are many classifications for soil types and major differences within each classification

Soil management can have a major impact upon these soil properties. Compaction is the major cause of error in bulk density.

http://edis.ifas.ufl.edu/


Water the substance of life

رابطه آب خاك و گیاه تكميلی

حاج عباسی

Frequency Domain Reflectometry: radio frequency (RF) capacitance techniques

Actually measures soil capacitance

A pair of electrodes is inserted into the soil

Soil acts as the dielectric completing a capacitance circuit, which is part of a feedback loop of a high frequency transistor oscillator

Isfahan University of Technology

As high frequency radio waves (about 150 MHz) are pulsed through the capacitance circuitry, a natural resonant frequency is established which is dependent on the soil capacitance, which is related to the dielectric constant by the geometry of the electric field established around the electrodes

Two commercially available instruments using this technique: the Troxler Sentry 200-AP probe and the Aquaterr probe


Water the substance of life

رابطه آب خاك و گیاه تكميلی

حاج عباسی

Isfahan University of Technology

Time Domain Reflectometry (TDR): q, 28 s

The soil bulk dielectric constant (K) is determined by measuring the time it takes for an electromagnetic pulse (wave) to propagate along a transmission line (L) that is surrounded by the soil

Since the propagation velocity (v) is a function of K, the latter is therefore proportional to the square of the transit time (t, in seconds) down and back along the L

K= (c/v)2 = ((c.t)/(2.L))2

where c is the velocity of electromagnetic waves in a vacuum (3•108 m/s or 186,282 mile/s) and L is the length embedded in the soil (in m or ft)


Water the substance of life

رابطه آب خاك و گیاه تكميلی

حاج عباسی

Isfahan University of Technology

  • TDR determinations involve measuring the propagation of electromagnetic (EM) waves or signals

  • Propagation constants for EM waves in soil, such as velocity and attenuation, depend on soil properties, especially q and EC

The propagation of electrical signals in soil is influenced by q and EC

The dielectric constant, measured by TDR, provides a good measurement of this soil water content

Disadvantage: Costly, not really independent of salt content


Water the substance of life

رابطه آب خاك و گیاه تكميلی

حاج عباسی

Isfahan University of Technology

Time Domain Transmission (TDT)

This method measures the one-way time for an electromagnetic pulse to propagate along a transmission line (L). Thus, it is similar to TDR, but requires an electrical connection at the beginning and ending of the length.

Notwithstanding, the circuit is simple compared with TDR instruments.

Disadvantages: Reduced precision, because the generated pulse is distorted during transmission; soil disturbance during installation; needs to be permanently installed in the field


Water the substance of life

رابطه آب خاك و گیاه تكميلی

حاج عباسی

Isfahan University of Technology

NUCLEAR TECHNIQUES: Neutron Scattering, q, 1 to 2 min

With this method, fast neutrons emitted from a radioactive source are thermalized or slowed down by hydrogen atoms in the soil

Since most hydrogen atoms in the soil are components of water molecules, the proportion of thermalized neutrons is related to q

Advantages: can measure a large soil volume, can scan at several depths to obtain a profile of moisture distribution, nondestructive, water can be measured in any phase

Disadvantages: high cost of the instrument, salinity, must calibrate for different types of soils, excess tube, radiation hazard, insensitivity near the soil surface, insensitivity to small variations in moisture content at different points within a 30 to 40 cm radius, and variation in readings due to soil density variations (error rate of up to 15 percent)


Water the substance of life

رابطه آب خاك و گیاه تكميلی

حاج عباسی

Isfahan University of Technology

Gamma Attenuation: volumetric water content, < 1 min

  • This method assumes that the scattering and absorption of gamma rays are related to the density of matter in their path

  • The specific gravity of a soil remains relatively constant as the wet density changes with increases or decreases in moisture

  • Changes in wet density are measured by the gamma transmission technique and the moisture content is determined from this density change

Advantages: can determine mean water content with depth, can be automated for automatic measurements and recording, can measure temporal changes in soil water, nondestructive measurement

Disadvantages: restricted to soil thickness of 1 inch or less, but with high resolution, affected by soil bulk density changes, costly and difficult to use, large errors possible when used in highly stratified soils


Water the substance of life

رابطه آب خاك و گیاه تكميلی

حاج عباسی

Isfahan University of Technology

Soil and Water

evaporation


Water content

LIQUID

Gravimetric (Mass/Mass)

Volumetric

(Volume/Volume)

Relative

VAPOR

Concentration

(Mass/ volume air)

Pressure

(KPa)

Relative Humidity

WATER CONTENT


Uses of water in plants

USES of WATER in PLANTS

  • 1. Constituent

  • 2. Solvent

  • 3. Reactant-product

  • 4. Turgidity

  • 5. Temperature Control


Constituent

CONSTITUENT

  • Water constitutes more than 70% of fresh weight of most plants (Seeds are exception)

  • Between 60-90% of the water is contained in the plant cell providing both biological and physical functions.

  • The remaining 10-40% is contained as liquid in cell walls providing a continuum between the soil supply and the living cell.


Solvent

SOLVENT

  • Dissolves both organic and inorganic constituents essential for life

  • Dissolves gases-CO2


Reactant product

REACTANT-PRODUCT

  • Photosynthesis

    CO2+ H2O = SUGAR

  • Respiration

    CH2O + O2 = CO2 + H2O


Energy balance

ENERGY BALANCE

  • Evaporation dissipates heat

  • Condensation-precipitation releases heat

  • Amount of water passing through plants as transpiration depends on environment and species

    Wheat 1000 kg H2O per kg dry matter

    Cotton 5000 kg H2O per kg lint


Water the substance of life

1 mole water ~ 18 cm3 contains 6.02 x 1023 molecules

1 cm3 ~ 3.3 x 1022 (33 thousand billion billion)

Consider a beach 1.6 x 106 m (1000 miles) long

200 m (656 feet) wide

100 m (328 feet) deep

Volume beach = 3.2 x 1010 m3 sand

Assume that each grain = a sphere 1 mm diameter

With loose packing 109 (one billion) grains in 1 m3

Entire beach 3.2 x 1019 sand grains, 1000 < number

of molecules in 1 cm3 water

رابطه آب خاك و گیاه تكميلی

حاج عباسی

It would take 1000 beaches to contain as many sand grains as molecules in 1 cm3 of water

Each water molecule is ~ 3 A (3 x 10-10 m)

It would take 33 x 106 layers to form a layer

of water 1 cm deep.


Unique properties of water

UNIQUE PROPERTIES of WATER

+

+

H

H

105O

O

-


Water the substance of life

رابطه آب خاك و گیاه تكميلی

حاج عباسی

Isfahan University of Technology

Hydrogen bond

H+

O--

-

H2O

= +

H+

Gives structural strength

Bond depends on temperature:

Higher is the temperature weaker is bond

Positive end attraction with -ve end of other water molecules


Water the substance of life

رابطه آب خاك و گیاه تكميلی

حاج عباسی


Water the substance of life

رابطه آب خاك و گیاه تكميلی

حاج عباسی

Isfahan University of Technology

Electro positive

Hydrogen

Hydrogen

H-O : 0.97 A

H-H : 1.54 A

1050

Oxygen

Polarity

angstroms

Negative

Symmetrical


Water the substance of life

رابطه آب خاك و گیاه تكميلی

حاج عباسی

Isfahan University of Technology

Polymer type of grouping

H+

H+

O-

Cations: Na+, K+, Ca2+ : become hydrated through their attraction to the Oxygen

Anions or negatively charged clay surfaces: attract water through hydrogen


Water the substance of life

رابطه آب خاك و گیاه تكميلی

حاج عباسی


Water the substance of life

رابطه آب خاك و گیاه تكميلی

حاج عباسی

Isfahan University of Technology

Some definitions

Adhesion - the attraction or clinging together of unlike substances

Cohesion - the attraction of a substance for itself; the mutual attraction among molecules or particles comprising a substance tat allows it to cling together as a continuous mass.

absorption - the process by which one substance is taken into and included within another substance, as the absorption of water by soil or nutrients by plants.

adsorption - the increased concentration of molecules or ions at a surface, including exchangeable cations and anions on soil particles.

flickering clusters refers to the quasicrystalline state of water molecules while in a liquid state. The molecules associate and dissociate repeatedly in transitory or flickering polymer groups. Water molecules are attracted to one another due to the hydrogen bonding that takes place between the negatively charged end of the oxygen atom in the molecule and the positively charged ends of hydrogen atoms in adjacent water molecules.


Water the substance of life

رابطه آب خاك و گیاه تكميلی

حاج عباسی

Isfahan University of Technology

heat of fusion (ice) The amount of energy required to turn a liquid into a solid.

heat of vaporization The amount of energy required to turn a liquid to a vapour (to overcome the attractive forces between adjacent molecules in a liquid).

dipole moment a measure of the tendency of a polar molecule to be affected by an electrical or magnetic field (i.e., NMR - Nuclear magnetic resonance)

Volumetric heat capacity is the change in the heat content of a unit volume per unit change in temperature.

Specific heat is the change in the heat content of a unit mass per unit change in temperature.

surface tension A molecule at the surface of a liquid is not completely surrounded by other molecules of the liquid. The forces acting upon it are unbalanced, with the result that it experiences a stronger attraction into the body of the liquid (cohesion) rather than into the less dense gaseous phase. This unbalanced force draws the surface molecules inward with and results in the tendency for the surface to contract and the molecules to be slightly denser at the surface.


Water the substance of life

رابطه آب خاك و گیاه تكميلی

حاج عباسی

Isfahan University of Technology

sublimation the direct transition from the solid state to the vapor state

hydrophobic water repellent

capillary attraction - a liquid's movement over or retention by a solid surface due to the interaction of adhesive and cohesive forces.

capillary fringe a zone just above the water table that is maintained in an essentially saturated state by capillary forces of lift.

viscosity (centipose, cP, N s m-2 x 10-3, kg m-1 s-1). When a fluid is moved in shear (that is to say, when adjacent layers are fluid are made to slide over each other), the force required is proportional to the velocity of shear. Viscosity is the proportionality factor. It is the property of the fluid to resist the rate of shearing and can be visualized as an internal friction. Fluids of lower viscosity flow more readily. Thus oil has a higher viscosity than water.

Fluidity is the reciprocal of viscosity. Viscosity is the preferred term.


Water the substance of life

رابطه آب خاك و گیاه تكميلی

حاج عباسی

Cohesive – forces of attraction between like

molecules.

At an air-water interface– surface tension.

Adhesion – attraction of one substance for a

substance of another kind.

Tensile strength – work that must be done to

create or extend a new or

larger surface.

Viscosity – resistance to flow.


Water the substance of life

رابطه آب خاك و گیاه تكميلی

حاج عباسی

Isfahan University of Technology

If water were an ordinary compound whose molecules are subject to weak forces, its boiling and freezing point would fall below hydrogen sulfide

Strong hydrogen bonding between water molecules prevents this

Water occurs in all three states (solid, liquid, and gaseous) at prevailing temperatures on the earth’s surface

Example: Ice cubes in a glass at room temperature


Water the substance of life

رابطه آب خاك و گیاه تكميلی

حاج عباسی

Isfahan University of Technology

Why water wets clean glass?

  • Surface of glass has O and unpaired electrons

  • Water molecules form hydrogen bond

  • Force stronger than gravity

Why water does not stick to glass surface coated with grease?

  • Surface of grease has no O and free electrons

  • Water molecules cannot form hydrogen bond

  • Therefore, water do not stick


Water the substance of life

رابطه آب خاك و گیاه تكميلی

حاج عباسی

Isfahan University of Technology

Forces acting on a water molecules

Air-water Interface

Air

At point A:

Attraction of air for water molecules is much less than that of water molecules for each other.

A

B

At point B:

Forces acting on water molecule are equal in all direction

Water

Consequently, there is a net downward force on the surface molecules, and result is something like a compressed film at the surface. This phenomenon is called surface tension


Water the substance of life

رابطه آب خاك و گیاه تكميلی

حاج عباسی

Isfahan University of Technology

Surface Tension

The cohesive forces between liquid molecules are responsible for the phenomenon known as surface tension

The molecules at the surface do not have other like molecules on all sides of them and consequently they cohere more strongly to those directly associated with them on the surface. This forms a surface "film" which makes it more difficult to move an object through the surface than to move it when it is completely submersed.

  • Surface tension is typically measured in dynes/cm. The force in dynes required to break a film of length 1 cm

  • Equivalently, it can be stated as surface energy in ergs/cm2

  • Water at 20°C has a surface tension of 72.8 dynes/cm compared to 22.3 for ethyl alcohol and 465 for mercury


Water the substance of life

رابطه آب خاك و گیاه تكميلی

حاج عباسی

Isfahan University of Technology

Contact Angle

  • Solid

  • Liquid

  • Gas

Liquid and gas (air) in contact with solid

Interface between air and water forms a definite angle “contact angle”

Young’s equation

L

Air

gsa > gsw; cos a = + or a < 900

Angle of contact is acute in a liquid that wets the solid

Solid

L

Air

Angle of contact is obtuse (between 90 and 180) in a liquid that does not wet the solid

Solid


Water the substance of life

رابطه آب خاك و گیاه تكميلی

حاج عباسی

Isfahan University of Technology

Hydrophilic Versus Hydrophobic Soils

When the adhesive forces between water molecules and an object are weaker than the cohesive forces between water molecules, the surface repels water and is said to be hydrophobic. Hydrophobic soils restrict the entry of water, which 'balls up' or sits on the soil in beads rather than infiltrating the soil.

Hydrophobic soils exhibit an obtuse (greater than or equal to 90o) wetting angle that causes capillary repulsion, so preventing water from entering soil pores

Hydrophilic or normally wettable soils display an acute (less than 90o) angle of contact with water, allowing infiltration. adhesive forces between water molecules and an object are stronger than the cohesive forces between water molecules


Water the substance of life

رابطه آب خاك و گیاه تكميلی

حاج عباسی

Isfahan University of Technology

Capillary Fundamentals and Soil Water

Cohesion: Attraction of molecules for each other

Adhesion: Attraction of water molecules for solid surfaces

By adhesion, solids hold water molecules rigidly at their soil-water surface

By cohesion water molecules hold each other away from solid surfaces

Gravity

Together it is possible for soil solids to retain water and control it’s movement

Capillary


Water the substance of life

رابطه آب خاك و گیاه تكميلی

حاج عباسی

Isfahan University of Technology

The dipolar interaction between water molecules represents a large amount of internal energy (the energy associated with the random, disordered motion of molecules) and is a factor in water's large specific heat (the amount of heat per unit mass required to raise the temperature by one degree Celsius).

The dipole moment of water provides a "handle" for interaction with microwave electric fields in a microwave oven.

Microwaves can add energy to the water molecules, whereas molecules with no dipole moment would be unaffected.

Dipolar Bonding in Water


Water the substance of life

رابطه آب خاك و گیاه تكميلی

حاج عباسی

Isfahan University of Technology

Water rises in the capillary against the force of gravity

!!!! What happens if there is no force of gravity !!!!!

Water

Water


Water the substance of life

رابطه آب خاك و گیاه تكميلی

حاج عباسی

Isfahan University of Technology

Capillary Mechanism

2 r1

2 r2

Rise continues till:

Weight of water in the tube (force of gravity) = Total cohesive and adhesive forces

h1

h2

Water


Water the substance of life

رابطه آب خاك و گیاه تكميلی

حاج عباسی

Isfahan University of Technology

2 r

Force of gravity = Mass of water column * Acceleration

= (volume of water * density) * g

= (p * r2* h) *dw * g …………(A)

Total cohesive and adhesive forces

= (perimeter) * surface tension

= 2 * p * r * g …………(B)

h

Water

At equilibrium: A = B

(p * r2* h) *dw * g = 2 * p * r * g

use

g = 72.75 dynes/cm

dw= 0.9982 g/cm3

g = 980 cm/s2

Show


Water the substance of life

رابطه آب خاك و گیاه تكميلی

حاج عباسی

Isfahan University of Technology

If two principle radii r1 and r2

r = 0.1 cm; h = 1.5 cm

r = 1.0 cm; h = 0.15 cm

r = 10 cm; h = 0.015 cm

  • This relationship tells us that:

  • Capillary rise is higher in small pores

Capillary Rise

Radius


Water the substance of life

رابطه آب خاك و گیاه تكميلی

حاج عباسی

Isfahan University of Technology

  • The inverse relationship between height of rise of water and radius of soil pores may not be always valid:

  • Soil pores are not straight uniform openings as a tube

  • Some soil pores may entrap air and slow down the capillary rise

Soil solids

Tortuous flow paths of water

Entrapped air

water


Water the substance of life

رابطه آب خاك و گیاه تكميلی

حاج عباسی

Isfahan University of Technology

Capillary water

Enlarged soil particles or aggregates

Adsorbed water

Two forms of water in soil

Soil solids tightly absorb water

Capillary forces hold water in capillary pores


Water the substance of life

رابطه آب خاك و گیاه تكميلی

حاج عباسی

Isfahan University of Technology

Loam

Sand

Clay compacted

Height (cm)

Time (days)

Brady,1984


Unique properties of water1

UNIQUE PROPERTIES of WATER

  • TEMPERATURE RELATIONS

    • Heat of Vaporization = 540 [email protected] 2.45 MJ/kg

    • Heat of Fusion = 80 [email protected]

    • Heat Capacity = 1.0 cal/g

    • Thermal Conductivity = High


Water the substance of life

رابطه آب خاك و گیاه تكميلی

حاج عباسی


Water the substance of life

رابطه آب خاك و گیاه تكميلی

حاج عباسی


Unique properties of water2

UNIQUE PROPERTIES of WATER

  • DENSITY

    • 0.9998 g/cm3 at 0 oC

    • 1.0 g/cm3 at 4 oC

    • 0.9956 g/cm3 at 30 oC


Water the substance of life

رابطه آب خاك و گیاه تكميلی

حاج عباسی

Isfahan University of Technology

Temperature range in liquid phase for H+ compounds

100

Boiling point

Freezing point

H2O

(2+16=18)

50

Hydrogen telluride

Temperature (0C)

0

H2Te

(130)

Hydrogen sulfide

H2Se

-50

(80)

H2S

Hydrogen selenide

(2+32=34)

-100

0

50

100

Molecular Weight


Water the substance of life

رابطه آب خاك و گیاه تكميلی

حاج عباسی

Isfahan University of Technology

Does water swell and shrink with Temperature?

1

0.998

40C

0.996

0.994

0.992

Density (g cm-3)

0.990

Temperature (0C)

-10

0

20

10

30

40

50


Water the substance of life

رابطه آب خاك و گیاه تكميلی

حاج عباسی


Water the substance of life

رابطه آب خاك و گیاه تكميلی

حاج عباسی


Unique properties of water3

UNIQUE PROPERTIES of WATER

  • SOLVENT

    • Small Size

    • Polar characteristics

    • High Dielectric Constant


Unique properties of water4

UNIQUE PROPERTIES of WATER

  • Transparent to Visible Radiation

    (400-700nm)

  • Highly Absorbent in Infra-Red

    (>1000 nm)


Unique properties of water5

UNIQUE PROPERTIES of WATER

  • HIGH SURFACE TENSION

    • Adhesion

    • Cohesion

    • Tensile Strength

      ( >30MPa ~4000#/in2)


Unique properties of water6

UNIQUE PROPERTIES of WATER

  • IONIZATION

    • Only 1 molecule out of 55 x 107 is ionized

      pH ~ - Log (H+)


Water the substance of life

رابطه آب خاك و گیاه تكميلی

حاج عباسی

Isfahan University of Technology

مقايسه‌ نقطه‌ ذوب‌ (MP) نقطه‌ جوش‌ (BP ) ووزن‌ ملكولي‌ (MW )

چندين‌ ماده‌باآب‌

CH4 NH3 H20 C2H6 C5H12 C6H16 C4H30

MP5.591- 130-172-078- 184-

BP2519836 36- 100 33-161-

MW 198100 72 30 1817 16


Water the substance of life

رابطه آب خاك و گیاه تكميلی

حاج عباسی

Isfahan University of Technology

Properties of Water

Fig. 1. Temperature range of various hydride groups.


Water the substance of life

رابطه آب خاك و گیاه تكميلی

حاج عباسی

Isfahan University of Technology

باوجوداينكه‌وزن‌ ملكولي‌ آب‌ نسبتاكم‌ است‌ ولي‌ مقاومت‌ پيوند هيدروژني‌ وساختمان‌ دروني‌ آن‌ باعث‌شده‌تادردرجه‌ حرارت‌ طبيعي‌ بصورت‌ مايع‌ باشدنه‌ بصورت‌ بخاربدين‌ معني‌ كه‌عناصري‌ باوزن‌ ملكولي‌ تقريباشبيه‌به‌ آب‌ در درجه‌ حرارتهاي‌ بسيارپايين‌ ذوب‌ مي‌ شوندويابجوش‌ مي‌ آيندازطرف‌ ديگر عناصرديگربايدوزن‌ ملكولي‌بسياربالايي‌ داشته‌باشندتابتواننددردرجه‌حرارتهاي‌ ذوب‌ ياجوش‌ آب‌ ذوب‌ يابحالت‌ جوش‌ درآينديعني‌ آب‌ درحالت‌مايع‌ مانند ملكولهاي‌ بسيارسنگين‌ عمل‌ مي‌ كند.


Colligative properties of aqueous solutions

COLLIGATIVE PROPERTIESofAQUEOUS SOLUTIONS

PROPERTYPURE WATER1.O M SOLUTION

1. Vapor Pressure 0.61 [email protected] Decreased according

101.3 [email protected] Raoult’s Law

2. Boiling Point 100oC 100.52oC

3. Freezing Point 0oC -1.86oC

4. Osmotic Potential 0 -2.27 MPa

5. Chemical Potential 0 Decreased


Water vapor

WATER VAPOR


Water the substance of life

DRY AIR = 1. 205 Kg m-3

SATURATED AIR= 1.194 Kg m-3

Vapor pressure=4.62 x10-4 vdT


Water the substance of life

Wet bulb

Dew Point


Rauolt s law

RAUOLT’S LAW

e = eo Nw

Nw+Ns

e= Vapor Pressure of solution

eo= Vapor Pressure of pure water

Nw= moles of solvent

Ns= moles of solute


Osmotic pressure van t hoff equation

OSMOTIC PRESSUREVan’t Hoff equation

 = NsRT

V

 = osmotic pressure in Mega Pascals

Ns= moles of solute

R= gas constant (0.0083 L MPa /mol @273o)

T= absolute temperature

V= volume of solvent in Liters

(RT= 2.272 @) 0oC &2.437 @ 20oC literMPamol-1)


Chemical potential of water in a solution

CHEMICAL POTENTIAL of WATER in a SOLUTION

A measure of the ability of WATER to do work

Go = partial molal Gibb’s free energy

DGo = -RTlnK (K = equilibrium constant)

A B DG Negative = Spontaneous

DG Positive = Additional Energy Required


Chemical potential of water

CHEMICAL POTENTIAL of WATER

µw-µwo = RT lnNw

µw= chemical potential of water in solution (Jmol-1)

µwo= chemical potential of pure water

R= Gas constant = 8.314 J mol-1 K-1

T= Absolute temperature

Nw= mole fraction of water in solution-can

be replaced by ln e/eo


Water potential pressure units

WATER POTENTIAL(PRESSURE UNITS)

w = RT ln e/eo

Vw

The water potential of a solution is decreased by those factors which reduce the vapor pressure

1. Addition of solutes (Osmotic)

2. Matric forces ( Interfacial Adhesive Forces)

3. Reduction in Temperature

4. Tension


Water the substance of life

LIQUID STATE

Potential Gradient

Hydraulic Conductivity

(Cells 7 x 10-13ms-1)

(Soil 10-2 – 10-10 m2 sec-1)

VAPOR STATE

Vapor Pressure Gradient

Diffusion Coefficient

(2.4 x 10-5 m-2s-1)

Resistance

WATER MOVEMENTFlux Jw (moles per meter2 per second) = Concentration Gradient ( - D mols/DDistance;DY)* Diffusion Coefficient (DW)


Water the substance of life

رابطه آب خاك و گیاه تكميلی

حاج عباسی

Isfahan University of Technology

Forces that affect movement of water into the soil

Gravity: a constant force that pulls the water downward

Cohesion: attraction of water molecules for each other. It is the force that holds a droplet of water together

Adhesion: attraction of water molecules to other substances. This force causes water molecules to adhere to other objects, such as soil particles

Placing a drop of water on a piece of newsprint paper

Force of adhesion between the water molecules and the paper molecules is greater than the force of cohesion that holds the water molecules together

The water droplet spreads out and soaks into the paper

Placing a drop of water on a piece of waxed paper

Force of adhesion between the water molecules and the paper molecules is lower than the force of cohesion that holds the water molecules together

The water droplet remains intact


Total water potential

TOTAL WATER POTENTIAL

W = p – (+ m+ g)

W = Total Water Potential

p =Pressure Potential

 = Osmotic Potential

m = Matric Potential

g =Gravitational Potential


Water potential

SOIL SYSTEM

Matric Forces

Surface Tension

Electrostatic Association

Osmotic

PLANT SYSTEM

Surface Tension

Cohesion

Osmotic

Pressure

WATER POTENTIAL


Diffusion coefficients 10 5 m 2 s 1

DIFFUSION COEFFICIENTS(10-5 M 2 S-1)


Water the substance of life

رابطه آب خاك و گیاه تكميلی

حاج عباسی

Physical Properties of Water

lLiquid phases in soil and plant are similar

l In both systems the liquid is a solution of

water and dissolved substances

l Physical properties of water


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