type of soil, condition, physical and chemical properties

1. Migration Of Ions And
Molecules In Soil
Department of Chemistry
Submitted by:
Marwa AL-A’qarbeh (9130134)

2. PART (I): Soil Definitions, Formation, and
properties (physical & Chemistry)
PART (II): Mechanism of Ions and molecules
Migration
PART (III): Research Examples of Ion and
molecules Migration
Topics:

3. PART (I): Soil Definitions, Formation,
And Properties
(Physical & Chemistry)

4. Soil Definition
Soil: is complex mixtures of minerals, organic
matter, gases, liquids and a myriad of micro- and
macro- organisms that can support plant life.
Soil is considered as the "skin of the earth" which
interfaces between the lithosphere, hydrosphere,
atmosphere, and biosphere “ecosystem”.
soil consists of a solid phase (minerals & organic
matter) and porous phase that holds gases and
water.

5. 50%
pore
space
50%
solid
material
25% air
25% water
45 to 48%
mineral
matter
2 to 5% organic matter
Soil componant

6. Soil Formation “Pedogenesis”

7. Rock type
Igneous
sedimentary
Metamorphic
Typical soil mineral materials are
Quartz: SiO2
Gypsum: CaSO4·2H2O
Calcite: CaCO3
Feldspar: KAlSi3O8
Mica (biotite): K(Mg,Fe)3AlSi3O10(OH)2

9. Chemical decomposition “chemical weathering”
Hydrolysis is the transformation of minerals into polar molecules , This results in
soluble acid-base pairs.
carbonation, the reaction of carbon dioxide in solution with water forms carbonic
acid. Carbonic acid will transform calcite into more soluble calcium bicarbonate
Hydration is the inclusion of water in a mineral structure, causing it to swell and
leaving it more stressed and easily decomposed.
Oxidation of a mineral compound causes it to swell and increase its oxidation
number, leaving it more easily attacked by water or carbonic acid.
Redox rxn change of oxidation state of minerals leaves them electrically unstable,
more soluble and internally stressed and easily decomposed.

10. Physical disintegration “Physical weathering”
Temperature fluctuations
Humidity
Wind
Water
Ice
gravity

11. Soil definitionSoil Formation Factors

12. Soil horizons
Principal (master) soil horizons found in
managed agricultural fields are:
A horizon or mineral surface soil (if
the soil has been plowed, this is called
the Ap horizon).
B horizon or subsoil.
C horizon or partially weathered
parent material.
rock (R) or parent materials similar to
that from which the soil developed.
Unmanaged forest soils also commonly
contain:
O (organic) horizon on the surface
E horizon: a light-colored leached
zone just below the A horizon.
.

13. Surface soil horizons: Ap or A + E
Ap or A+ E horizons:
Contains more organic matter than
the other soil layers.
Often coarser than the subsoil
layer (B horizo).
 Ap horizon tends to be more
fertile and have a greater
concentration of plant roots than
any other soil horizon.
Ap

14. I. Soil texture
II. Soil structure
III. Bulk density
IV. Porosity
V. Soil water-holding capacity Soil water-holding
capacity
VI. Conductivity
VII. Soil color
Physical Properties of Soil:

15. Soil physical properties: Soil texture

16. Soil physical properties: Soil texture
 Sand:
Particles range in size
from very fine (0.05 mm)
to very coarse (2.0 mm) in
average diameter.
Most particles can be
seen without a
magnifying glass.
Feel coarse and gritty
when rubbed between the
thumb and fingers, except
for mica flakes.
Sand texture

17. Soil physical properties: Soil texture
Silt:
Particles range in size
from 0.05 mm to 0.002
mm.
Cannot usually be seen
by the unaided eye
When moistened, silt
feels smooth but is not
slick or sticky. When dry,
it is smooth and floury Silt loam texture

18. Soil particles
 Clay:
Particles are finer than
0.002 mm.
Can be seen only with the
aid of an electron
microscope.
Feels extremely smooth
or powdery when dry, and
becomes plastic and
sticky when wet.
Clay texture

19. The USDA textural triangle

20. The USDA textural triangle

21. Soil structure
Granular
Platy
Blocky
(Angular)(Subangular)
Wedge
ColumnarPrismatic

22. Soil structure
 Soil particles are grouped together during the aggregation
process to form structural units (or peds).
 These units vary in size, shape, and distinctness (also known
as strength or grade).
The structure of the soil affects on pore space size and its
distribution and therefore, rates of air and water movement. “Well
developed structure allows favorable movement of air and water,
and root development”

23. Types of structure: Granular
Granular:
Soil particles are arranged in small, rounded units.
Common in surface soils (A horizons).
Most distinct in soils with relatively high organic matter
content.
Prismatic
Structureless:
Granular
Blocky
Prismatic
Structureless:
Granular
Blocky
Prismatic
Structureless:
Granular
Blocky

24. Types of structure: Blocky
Blocky:
Soil particles are arranged to form block-like units, which are
about as wide as they are high or long.
Some blocky peds are rounded on the edges and corners;
others are angular.
Blocky structure is commonly found in the subsoil, although
some eroded fine-textured soils have blocky structure in the
surface horizons.
Blocky

25. Types of structure: Platy
Platy:
Soil particles are arranged in plate-like sheets, which are
approximately horizontal in the soil and may occur in either
the surface or subsoil, although they are most common in the
subsoil.
Platy structure strongly limits downward movement of water,
air, roots and may result from compaction.
Prismatic
Structureless:
massive
Structureless:
single grain
Granular
Blocky
Platy
Prismatic
Structureless:
massive
Structureless:
single grain
Granular
Blocky
Platy
Prismatic
Structureless:
massive
Structureless:
single grain
Granular
Blocky
Platy

26. Types of structure: Prismatic
Prismatic:
Soil particles are arranged into large
peds with a long vertical axis.
Well developed subsoil prisms are
associated with fragipans (dense
subsoil layers), or soils that swell
when wet and shrink when dry,
reducing air and water movement.
Most clayey subsoils exhibit
prismatic macro-structures to some
extent.
PrismaticGranular PrismaticGranular PrismaticGranular

27. Structureless:
Two types:
•Massive: no definite
structure or shape, as in
some C horizons or
compacted material.
•Single grain: typically
individual sand grains in
A or C horizons not held
together by organic
matter or clay.
Types of structure: Structureless
Prismatic
Structureless:
massive
Structureless:
single grain
Granular
Blocky
Platy
Prismatic
Structureless:
massive
Structureless:
single grain
Granular
Blocky
Platy
Prismatic
Structureless:
massive
Structureless:
single grain
Granular
Blocky
Platy

28. Bulk density is the dry mass of soil solids per unit volume of soils.
Bulk densities of mineral soils are usually in the range of 1.1 to 1.7
g/cm3
. A soil with a bulk density of about 1.32 g/cm3
will generally
possess the ideal soil condition of 50% solids and 50% pore space.
bulk density

29. Soil porosity: Macropores and micropores
The size of the individual
pore spaces, rather than
their combined volume,
will have the most effect
on air and water movement
in soil.
Pores smaller than about
0.05 mm (or finer than
sand) in diameter are
typically called micropores.
Pores larger than 0.05
mm are called macropores.
micro-
pores
macro-
pores

30. Soil porosity: Macropores and micropores
Macropores allow the ready movement
of air, roots, and percolating water.
Movement of air and water through a
coarse-textured sandy soil is often
rapid despite its low total porosity
because of the dominance of
macropores.
Micropores in moist soils are typically
filled with water, and this does not permit
much air movement into or out of the soil.
Movement of air and water through a
fine textured clay soil may be slow
(see picture at right) despite high
total porosity because of the
dominance of micropores.

31. Soil water-holding capacity
Soil water-holding capacity is determined largely by the
interaction of soil texture, bulk density/pore space, and
aggregation:
Sands hold little water because their large pore spaces allow
water to drain freely from the soils.
Clays adsorb a relatively large amount of water, and their
small pore spaces retain it against gravitational forces.
Clayey soils hold water much more tightly than sandy soils,
so that not all the moisture retained in clayey soils is available
to growing plants.

32. Soil water-holding capacity

33. Soil chemistry

34. Element Ion or molecule
Carbon CO2 (mostly through leaves)
Hydrogen H+
, HOH (water)
Oxygen O2-
, OH -
, CO3
2-
, SO4
2-
, CO2
Phosphorus H2PO4 -
, HPO4
2-
(phosphates)
Potassium K+
Nitrogen NH4
+
, NO3 -
(ammonium, nitrate)
Sulfur SO4
2-
Calcium Ca2+
Iron Fe2+
, Fe3+
(ferrous, ferric)
Magnesium Mg2+
Boron H3BO3, H2BO3 -
, B(OH)4 -
Manganese Mn2+
Copper Cu2+
Zinc Zn2+
Molybdenum MoO4
2-
(molybdate)
Chlorine Cl -
(chloride)

35. Soil organic matter
Soil organic matter:
Plant and animal residues in various
stages of decay.
Sources: dead roots, root exudates, litter
and leaf drop, and the bodies of soil
animals such as insects and worms.
Primary energy and nutrient source for
insects, bacteria, fungi, and other soil
organisms.
After decomposition, nutrients released
from the residues available for use by
growing plants.
Soil humus:
Fully decomposed and stable organic matter.
Most reactive and important component of soil organic matter.
Form of soil organic material that is typically reported as “organic
matter” on soil testing reports.

37. Soil pH
Soil pH is a measurement of hydrogen ion (H+
) activity, or
effective concentration, in a soil and water solution.
Soil pH is expressed in logarithmic terms, which means that
each unit change in soil pH amounts to a tenfold change in acidity
or alkalinity.
Soil pHSoil pH

38. • one of its most important properties
• it affects so many other soil properties, (e.g. ion exchange
and nutrient availability)
• soil pH comes about from a balance between acidic and
alkaline species
• reflects mainly the levels of dissolved H+
and OH-
, but also
the adsorbed H+
on cation exchange sites
• normally ranges from 4-9
Soil pH

39. Sources of soil acidity
rain - polluted or fresh will be slightly acidic due to
dissolved gases
microbial and root respiration – this produces CO2,
which is slightly acidic in solution
oxidation of organic matter – this produces organic acids
known as humic acids, together with nitric and sulfuric
acids
Soils become acidic when basic cations (such as
calcium, or Ca2+
) held by soil colloids are leached from the
soil, and are replaced by aluminum ions (Al3+
), which then
hydrolyze to form aluminum hydroxide (Al(OH)3) solids
and H+
ions in solution.
Soil pHSoil pH

40. Sources of soil alkalinity
carbonate minerals – calcium and magnesium carbonate are
common materials
Na & K are known as bases because of their association with
alkaline soils
mineral weathering – many primary minerals as they weather
release hydroxide salts of the basic cations, in minerals they are
slightly soluble in water, and produce OH-
as they dissolve
Soil pHSoil pH

41. Trends in soil pH
Soil pHSoil pH
as soils age by weathering and leaching,
they tend to become more acidic
primary minerals that release alkaline
materials are replaced by neutral or slightly
acidic secondary minerals
leaching removes the carbonate minerals
weathering occurs from the surface
downwards so that the A and B horizons will
tend to be more acidic than the C horizon

42. Significance of soil pH
effect on soil organisms – soil organisms prefer different pH
levels
acid-sulfate soils - soils that are rich in inorganic sulfide
minerals, such as pyrites:
can lead to the formation of excessive levels of sulfuric acid
through oxidation
soil pH dives to very low levels
Effect on toxicty levels of aluminium, manganese and iron
from soil minerals
plant preferences – most alkaline soils; a few which need acidic
soils
nutrient availability – the ability of plants to take up nutrients is
very much dependent on the soil pH

43. Buffering capacity
The resistance of soils to changes in pH of the soil solution is
termed buffering capacity.
Buffering capacity increases with the amount of clay and
organic matter:
Soils with high clay and organic matter content (high buffer
capacity) require more lime (CaCO3) to increase pH than sandy
soils with low amounts of organic matter (low, or weak, buffer
capacity).
BufferinBufferin
gg
CapacityCapacity

44. Application on migration of ions and molecule process
oPlant nutrition
oFertilizer & pesticide
oSoil heavy metal toxicity