Soil Pollution

By1305053 Tahmid Imran Imon

Land Reclamation Engineering

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

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

Causes

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MANMADE CAUSESNATURAL CAUSES

Fig 3: Natural Pollution Fig 4: Manmade Pollution

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

Soil Pollution Around The World

6 Fig 6 : Soil Pollution Around The World

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

Sources of Soil PollutionAgricultural 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

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.

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Types of Soil PollutionAgricultural 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

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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

Fig 12: Industrial wasteFig 11: Solid waste

Fig 14: Volcanic eruptionFig 13: Mining 12

Pollutants in Soil Chemical and metallic pollutantso 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.

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Pollutants in Soil  Radioactive materialo 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.

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Common chemicals causing soil pollution Petroleum

hydrocarbons gasoline, jet fuels, mineral oils etc.

Heavy metals arsenic, cadmium, led etc.

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Fig 15: Gasoline

Fig 16: Cadmium

Common chemicals causing soil pollution Pesticides bifenthrin, captan, carbaryl etc.

Solvent toluene, turpentine, acetone, methyl- acetate etc. 16

Fig 17: Turpentine

Fig 18: Carbaryl

Pollution Transport ProcessThere are many processes that contributes the movement of soil pollution.

Among these 3 main physical process are:

1) Convection 2) Diffusion and 3) Dispersion.

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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.

18 Fig 19: Convection

Pollution by ConvectionPollutants 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 19 Fig 20: Pollution by convection

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

20 Fig 21: Diffusion

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.

21 Fig 22: Pollution by diffusion

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.

22 Fig 23: Dispersion

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.

23 Fig 24: Pollution by dispersion

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.

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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

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

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.

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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.

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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

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.

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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

Breakthrough Curve AnalysisBreakthrough 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

Breakthrough Curve Analysis

33 Fig 26: Breakthrough Curve Analysis

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

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 35

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