Soil pollution occurs when soil quality degrades due to contamination from natural or human sources. Common causes of soil pollution include industrial waste, urban waste, agricultural practices, and chemical/metallic pollutants. Pollutants such as heavy metals, pesticides, radioactive materials, and biological agents can enter the soil. Pollution transport processes that spread contaminants through soil include convection, diffusion, and dispersion. Mathematical models can simulate how different pollutants move through soil over time.

1. Soil
Pollution
By
1305053 Tahmid Imran Imon
Land
Reclamation
Engineering

2. What is Soil?
Soil is unconsolidated natural
bodies or materials
Forming by natural action
By weathering process
Composed of mineral matter,
organic matter, air and water
Differentiated by different
horizons.
2
Fig 1: Soil

3. What is Soil Pollution?
 The change in physical ,
chemical and biological
conditions of the soil
 Through man’s or natural
intervention
 Resulting in degradation in
quality.
3
Fig 2: Soil Pollution

4. Causes
4
MANMADE CAUSESNATURAL CAUSES
Fig 3: Natural Pollution Fig 4: Manmade Pollution

5. 5
Fig 5: Chart of pollution caused by humans and nature

6. Soil Pollution Around The World
6Fig 6 : Soil Pollution Around The World

7. Sources of Soil Pollution
Industrial Wastes-
 fly ash,
 organic compound, inorganic complexes, non-biodegradable material
Urban Waste-
 Domestic waste
 Solid waste- garbage and rubbish material-plastic, glasses, metallic cans,
fibers, paper, rubbles, fuel residues, leaves, containers.
Radioactive Pollutants-
 Nuclear dust and radioactive waste
 Thorium, Uranium, Carbon (C-14) substance in soil, rock, water and air
 Nuclear fission, heavy water (Sr-90, Cs-137) cause gamma radiation.
7

8. Sources of Soil Pollution
Agricultural Practices-
 Pesticides, insecticides, weedicides and herbicides
 Toxic metal-lead, arsenic, mercury, cobalt, cadmium, cyanide etc.
Chemical and Metallic Pollutants-
 Different type chemical, metallic and fertilizer industries.
 Organic and Inorganic pollutants (Fe, Cu, Co, Zn, Hg, As, Ni, Cd, Pb, alkalis and
acid etc.) Affect soil texture, fertility and stabilization of soil.
Biological Agents-
 Large quantity of animal, birds and human etc. cause land pollution
 Leached in soil and cause chronic salts hazardous to plants and animal.
 Pathogenic organism by naturally, Pathogenic organism by human , Pathogenic
organism by animal . 8

9. Sources of Soil Pollution
 Soil Erosion-
 Natural process of detachment and removal of soil material (water, wind, ice or gravity).
 Due to running of water, wind, ice or geological agent.
 Agriculture development, construction and mining activities.
 Acid Rain-
 Air pollution- motor vehicle, factory emission etc. cause acid rain (HNO3, H2SO4)
 Other Sources-
 Absorption of toxic metal
 Soluble salts, Mining
 Wastewater applied soils
 Solid waste applied soils,
 Food processing waste,
 Sugarcane trash in field,
 Municipal garbage & composed etc. 9

10. Types of Soil Pollution
Agricultural Soil Pollution
i) pollution of surface soil
ii) pollution of underground soil
Soil pollution by industrial effluents and solid wastes
i) pollution of surface soil
ii) disturbances in soil profile
Pollution due to urban activities
i) pollution of surface soil
ii) pollution of underground soil
10

11. Fig 8: Excess application of pesticides
Fig 9: Excess use & disposal of
Plastics and Polyethene wastes
Fig 7: Drought
Fig 10: Disposal of oil
11

12. Fig 12: Industrial wasteFig 11: Solid waste
Fig 14: Volcanic eruptionFig 13: Mining 12

13. Pollutants in Soil
 Chemical and metallic pollutants
o Different type industries
o Metallic industries
o Inorganic pollutants (Fe, Cu, Co, Zn, Hg, As, Ni, Cd, Pb, alkalis and acid
etc.
 Agro-chemicals
o Pesticides, insecticides, weedicides and herbicides
o lead, arsenic, mercury, cobalt, cadmium, cyanide.
13

14. Pollutants in Soil
 Radioactive material
o Thorium, Uranium, Carbon (C-14) etc.
 Biological agents
o Algae, fungi, bacteria, protozoa, viruses, nematodes, worm etc.
o Industries waste,
o Enter in air, water and food chain.
14

15. Common chemicals causing soil pollution
 Petroleum
hydrocarbons
 gasoline,
 jet fuels,
 mineral oils etc.
 Heavy metals
 arsenic,
 cadmium,
 led etc. 15
Fig 15: Gasoline
Fig 16: Cadmium

16. Common chemicals causing soil pollution
 Pesticides
 bifenthrin,
 captan,
 carbaryl etc.
 Solvent
 toluene,
 turpentine,
 acetone,
 methyl-
acetate etc. 16
Fig 17: Turpentine
Fig 18: Carbaryl

17. Pollution Transport Process
There are many processes that contributes the movement of soil pollution.
Among these 3 main physical process are:
1) Convection
2) Diffusion and
3) Dispersion.
17

18. Convection
The process by which heat is transferred by the movement of heated fluid.
 In pollution transport system we focus on the convection
as vertical movement of air.
 In environmental studies, mainly in meteorological studies
convection also includes horizontal movement of fluid.
18Fig 19: Convection

19. Pollution by Convection
Pollutants mixes with air
Air gets warm and light
It rises up
Becomes cold
Condenses
Forms convictive cloud
Falls in the earth and waterbodies
with pollutants 19Fig 20: Pollution by convection

20. Diffusion
 Diffusion means mixing and spreading out.
 The diffusion of gases and liquids refers to their mixing
without external force.
 Diffusion is the process through which pollutant
molecules move through air or water.
 As the molecules move, they eventually strike other
Molecules which sends them in opposite ways.
 Diffusion moves pollutants from high concentration to
low concentration, spreading them out
20Fig 21: Diffusion

21. Pollution by Diffusion
 Consider the dye in this picture as pollutant.
 Which is dropped in the jar of fresh water.
 The dye will dissolved in the water uniformly.
 After sometimes the dye will mix in such
manner
 That the mixture can not be traced back to
single source.
 In this process the pollutants moves through
the soil in fluid form, causing soil pollution.
21Fig 22: Pollution by diffusion

22. Dispersion
Dispersion is a mixture
In which fine particles of one
substance are scattered throughout
another substance.
A dispersion is classed as a
suspension, colloid, or solution.
22Fig 23: Dispersion

23. Pollution by Dispersion
 Dispersion is caused by different flow paths
that a fluid takes in a geological medium.
 Some paths are fast as the fluid may pass
through the big pore spaces.
 Some paths are slow as the fluid may
encounter friction while passing through the
narrow paths.
 During the flow different pollutant may come
in contact with the fluid hence cause soil
pollution.
23Fig 24: Pollution by dispersion

24. Mathematics
 The bulk motion of the fluid, and controls contaminant transport through
the soil column by molecular diffusion and mechanical dispersion.
 In this study selenium, nitrogen and pesticide were modeled.
 Steady–state water flow condition the transport terms for selenium are:
………. (1)
Where,
Js = total selenium flux,
JDL = the diffusion flux in the liquid phase and
JCL = the convection flux in the liquid phase.
24

25. Mathematics
 In the case of diffusion in a porous media, the equation represented by,
………….(2)
Where,
CL = concentration in the liquid phase and
DM(θ) = the molecular diffusion coefficient
 The value of DM(θ) can be estimated as:
………….(3)
Where,
DOL = the diffusion coefficient in a pure liquid phase and
a, b = empirical constants 25

26. Mathematics
 The convective flux of selenium can be represented as:
………….(4)
Where,
q = the water flux, and
Dh (q) = hydrodynamic dispersion coefficient
 Combining the diffusion coefficient and dispersion coefficient as:
………….(5)
Where,
D (θ, q) = the apparent diffusion coefficient
26

27. Mathematics
 Substituting equations (2), (4)and (5) into equation (1) the overall selenium
flux is given as:
………….(6)
 Partitioning selenium between absorbed and solution phases, adsorption of
selenium are assumed taken to be nonlinear equilibrium process described by:
………….(7)
Where,
Cs = the concentration of selenium absorbed on the soil
Ks = the adsorption coefficient for selenium,
C = the concentration of selenium in the soil solution
n = exponent for selenium.
27

28. Mathematics
 The total amount of selenium (CT) contained in the solution and adsorbed
phases in a soil volume of one liter are:
………….(8)
Where,
ρ = the soil bulk density
 Substituting equation (7) for Cs in equation (8) one can get the convection-
dispersion equation:
………….(9)
 Selenium transports in soil system occur under unsteady water flow condition.
The water content (θ ) and water flux (q) both vary with depth and time. 28

29. Mathematics
 Using continuity relationships of mass over space and time gives:
………….(10)
Where,
CT = total selenium concentration in sorbed and
Φ = solution phases and represents all sources of selenium.
 Substituting equation (4) and (9) into (10) gives general one-dimensional
transport equations for selenium transport:
………….(11)
Where,
C = concentration of all selenium species in soil solution,
Φ = solution phases and represents all sources of selenium. 29

30. Mathematics
 The above equation is in general form, similar equation can be written
for different nitrogen and pesticides species in soil column.
 One dimentional water Flow and contaminant transport model was
applied to simulate Selenium in soil column.
 The equation predicts the concentration of different contaminant.
30

31. Breakthrough Curve
 When you infiltrate a solution of some substance
in to packed bed column
 The solution travels through the pore spaces from
inlet to outlet.
 Some of the solution will travel faster than average
 Some slower than average, because some routes
are faster than others.
 The breakthrough curve is a plot of the
concentration measured at a fixed point in the
column
 Usually at or near to the outlet, versus time.
 It is a “S” shaped curve. Fig 25: Breakthrough Curve

32. Breakthrough Curve Analysis
Breakthrough happens when an adsorption column is saturated. So,
 First pass a solution through a column of substance with a constant flow
rate.
 The solution will travel through the pore spaces of the substance.
 Some solution will travel faster and some will be slow due to the friction
and size of the pore spaces.
 As the column gets saturated, the solvent starts appearing.
 The concentration is usually measured near or at the outlet 32

33. Breakthrough Curve Analysis
33Fig 26: Breakthrough Curve Analysis

34. Breakthrough Curve Analysis
 Find how much volume can pass per minute or second (mL/min).
 Then begin to pass your solution and collect each 10 mL.
 Then draw the results of your analyzed target with the time using your flow rate.
 It is usually a S shape curve
 When this curve no longer changes, the column is saturated.
 Specifically you can look at the slope of the central part of the S curve.
 When the slope stays constant, you've achieved column saturation. 34

35. References
₪ International Journal of Environmental Science & Technology
₪ Soil contamination – Wikipedia
₪ Google image – soil pollution
₪ Slideshare.net – soil pollution
₪ Soil-Net.com - Soil pollution
₪ List of Pollutants • Environmental Pollution - Tropical Rainforest Animals
₪ Powershow.com
₪ Giphy.com
₪ www.journals.elsevier.com/environmental-pollution
₪ www.en.wikipedia.org/wiki/Total_petroleum_hydrocarbon
₪ www.conserve-energy-future.com/causes-and-effects-of-soil-pollution.php
₪ Researchgate.net
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