"Soil Contamination: Risk Assessment and Remediation""

1. WELCOME
TO
CREDIT SEMINAR

2. Sher-e-Kashmir University of Agriculture Science and Technology
Faculty of Agriculture, Wadura, Sopore - 193201.

Name : Mir Shareen Mehraj
Reg. No. : 44/Ag(SS)/19-M
Degree Programme : M.Sc. (Soil Science and Agri-Chemistry)
Seminar In-charge : Dr. M.H. Chisti
Major Advisor : Dr. Inayat M. Khan

4. OVERVIEW
 What is soil contamination?
 Sources of soil contamination.
 Causes of soil contamination.
 Risk assessment
 Remediation.
 Case studies.
 Conclusion.

5. What is soil contamination
 The build-up of persistent
toxic compounds, chemicals,
salts, radioactive materials, or
disease causing agents in soil
which have adverse effects on
plant growth and animal
health.

6. Different ways due to which
soil Contamination occurs are:
 Seepage from a landfill
 Discharge of industrial waste into the
soil
 Percolation of contaminated water
into the soil
 Rupture of underground storage tanks
 Unabated use of Agrochemicals
 Solid waste seepage
The most common agents of soil
contamination are:
 Petroleum hydrocarbons
Heavy metals
 Pesticides

7. Inorganic toxic compounds
and organic wastes
 Inorganic residues from industrial
wastes cause serious problems
owing to their disposal because of
the presence of several toxic metals.
 Copper, Mercury, Cadmium, Lead,
Nickel, Arsenic are the elements
which can accumulate in the soil if
they get entry either through
sewage, industrial waste or mine
washings.

8.  Organic wastes of various types like
domestic garbage, municipal sewage
and industrial wastes when left in
heaps or improperly disposed seriously
affect health of human beings, plants
and animals.
 The main organic contaminants are
phenols and coal.
 Asbestos, combustible materials, gases
like methane, carbon dioxide,
hydrogen sulphide, carbon monoxide,
sulphur dioxide, petrol are also
contaminants.

9. Sewage and sewage sludge
 Soil contamination is often caused by the uncontrolled
disposal of sewage and other liquid wastes resulting from
domestic uses of water, industrial wastes containing a variety
of pollutants, agricultural effluents from animal husbandry
and drainage of irrigation water and urban runoff.
 Sewage sludges pollute the soil by accumulating the metals
like lead, nickel, zinc, cadmium, etc. This may lead to the
phytoxicity of plants.

10. Heavy metal pollutants
 Heavy metals are elements having a density greater than five
in their elemental form.
 Mainly urban and industrial aerosols, combustion of fuels,
mining wastes, industrial and agricultural chemicals etc. are
contributing heavy metal pollution.
 Heavy metals are present in all uncontaminated soils as the
result of weathering from their parent materials.

12.  In agricultural soils, the
concentration of these
elements may be significantly
increased in several ways, like
through applications of
chemicals, sewage sludge,
farm slurries, etc.
 Likewise, some fertilizers
when applied to soils, they
add certain heavy metals
which are given in Table 02 :

13. Table 2. Heavy metal content of fertilizers (ug/gm)

14. Table 3. Heavy metal contents in sludges (ppm)

15. Sources of heavy metals

16. Organic pesticides
 Accumulation of residues of
pesticides in higher concentrations
are toxic.
 Pesticides persistence in soil and
movement into water streams may
also lead to their entry into foods and
create health hazards.
Pesticides particularly aromatic
organic compounds are not degraded
rapidly and therefore, have a long
persistence time which can be seen
in table 04:

17.  Table 4. Persistence time for some selected pesticides.

18.  Mercury, Cadmium and Arsenic are common constituents of
pesticides and all these heavy metals are toxic.
 At present DDT and a number of organochlorine compounds
used as insecticides have been declared harmful and banned
in U.S.A. and England.
 The rodenticides too add to soil contamination .

19. Types of soil contamination
 Agricultural Soil contamination:
a) Contamination of surface soil.
b) Contamination of underground soil.
 Soil contamination by industrial effluents and solid wastes:
a) Contamination of surface soil.
b) disturbances in soil profile.
 contamination due to urban activities:
a) contamination of surface soil .
b) contamination of underground soil.

20. Sources of soil contamination
 The sources which contaminate the soil
are: Agricultural sources and non-
agricultural sources.
a. Agricultural sources :Soil contamination
comes from different sources including
agriculture and animal husbandry. Some
of the agricultural practices lead to soil
pollution.
b. Non-agricultural sources: Soil pollution
by non-agricultural sources is usually
the direct result of urban sprawl caused
by rapidly increasing population and
huge quantity of waste related to our
modern way of life.

21.  contamination in soil is
associated with:
 Indiscriminate use of fertilizers.
 Indiscriminate use of pesticides,
insecticides and herbicides.
 Dumping of large quantities of
solid wastess.

22.  Indiscriminate use of
fertilizers :
 Fertilizers contaminate the soil
with impurities, which come from
the raw materials used for their
manufacture.
 Excess Potassium content in soil
decreases vitamin C and carotene
content in vegetable and fruits.

23. Indiscriminate use of pesticides, insecticides
and herbicides

24. Dumping of solid wastes:
 The portion of solid waste that is
hazardous such as oils, battery metals,
heavy metals from smelting industries
and organic solvents are the ones we
have to pay particular attention to.
These can in the long run, get
deposited on the soils of the
surrounding area and contaminate
them by altering their chemical and
biological properties.

25.  Soil contamination due to
urbanization:
Pollution of surface soils occurs
due to many materials (like
vegetables, animal wastes,
papers, wooden pieces, carcasses,
plant twigs, leaves, cloth wastes
as well as sweepings) and many
non-biodegradable materials
(such as plastic bags, plastic
bottles, plastic wastes, glass
bottles, glass pieces, stone /
cement pieces).

27.  Contamination of underground soils.
Underground soil in cities is likely to be contaminated by:
 Industrial wastes.
 sanitary wastes.
• Many dangerous chemicals like cadmium, chromium, lead,
arsenic, selenium products are likely to be deposited in
underground soil.

28. Risk Assessment
 An assessment of contaminated soil is typically performed to
determine the need for remediation, the efficacy of past
remediation efforts, or to determine if compensation is
required for injuries to natural resources.
 One of the most important federal laws governing assessment
of soil contamination is the Comprehensive Environmental
Response, Compensation and Liability Act, or “Superfund”.

29.  The U.S. Environmental
Protection Agency (US EPA)
has developed both human
health risk assessment
(HHRA) and ecological risk
assessment (ERA) guidance
to help meet the
“environmental response”
part of Superfund.

30.  The US EPA advocates performing HHRA and ERA through
three stages.
 Ecological risk assessment proceeds through:

31.  Human health risk assessment has following stages:

32. Factors influencing risk
assessment
Toxicity
Reactivity
corrosivity
Ignitability

33. Remediation of Contaminated Soils.
 Metals do not degrade like carbon-based (organic) molecules.
The only exceptions are Mercury and Selenium which can be
transformed and volatilized by microorganisms. However, in
general, it is very difficult to eliminate metals from the
environment.
 Traditional treatments for metal contamination in soils are
expensive and cost prohibitive when large areas of soil are
contaminated. Treatments can be done in situ (on-site), or ex
situ (removed and treated off-site). Both are extremely
expensive.

34.  Some treatments that are available include:
1. High temperature treatments (produce a vitrified,
granular, non-leachable material).
2. Solidifying agents (produce cement-like material).
3. Washing process (leaches out contaminants).

35. Remediation of soil contaminated with heavy
metals.
 There are different methods to remove the contaminants
which include physical, chemical, biological methods.
1. Physical method: soil replacement and thermal desorption
are the physical remediation methods.
There are three types of soil replacement:
• Soil replacement.
• New soil importing.
• Soil spading.

36. 2. Chemical Fixation: In this method
chemicals are used which may
degrade or inhibit the soil
contamination.

37. 3. Biological remediation: The biological remediation includes
Phytoremediation, bioremediation and the combining
remediation.

38. A. Phytoremediation: use of green plants to fix, inhibit and
adsorb contaminants and clean the contaminants from soil
is known as Phytoremediation. It is a cost effective
procedure.

39.  Phyto-remediation techniques have been
categorized into:
I. Phyto-degradation.
II. Phyto-stimulation/Rhizo-degradation.
III. Phyto-volatilization.
IV. Phyto-extraction.
V. Phyto-stabilization.
VI. Rhizo-filteration.

40. I. Phytodegradation: It is the process in which we use plants to
store, uptake and degrade the contaminants within its
tissues.It is also known as phytotransformation.
II. Phyto-stimulation/rhizo-degradation: In this method
rhizosphere is associated between the symbiotic soil
microbes and plants to degrade the contaminants.
III. Phyto-volatilization: In this process contaminants are
released in the atmosphere in volatile form through the
process of transpiration. This process occurs when plants
absorb water and organic contaminants. This method is
primarily used to remove toxic element mercury (Hg).
IV. Phyto-extraction: Phyto-extraction is a process in which
plants are used to degrade contaminants, mostly heavy
metals from soil and water which may be harmful for other
organisms.

41. V. Phyto-stabilization : It basically reduces the mobility and
flexibility of heavy metals in soil.
VI. Rhizo-filteration: It is a form of phyto-remediation that
involves filtering contaminated groundwater, surface water
and wastewater through a mass of roots to remove toxic
substances or excess nutrients.

42. CASE STUDIES

43. CASE STUDY-01
Soil Pollution along Kalwa Bridge at Thane
Creek of Maharashtra, India.
(Pravin U. Singare, Ram S. Lokhande, Pragati P. Pathak,
2010)

50. CONCLUSION
• The experimental data on the soil contamination
status along the Kalwa bridge of Thane creek suggest
a need to implement common objectives,
compatitable policies and programmes for
improvement in the industrial waste water treatment
methods.
• If the present conditions continue for a long period,
the Thane creek area may soon become ecologically
inactive.

51. CASE STUDY- 02
Surface Soil Pollution By Heavy Metals: A Case
Study Of Two Refuse Dumpsites In Akure
Metropolis.
(Anietie Olayemi Victoria, Labunmi Lajide, 2015)

54. CONCLUSION
• Cadmium and Arsenic concentrations in the analyzed
dumpsite soils are at a critical levels, that is, they are above
the DPR target and intervention values, while other metals
concentrations were below the DPR target value except
Copper and Chromium concentrations which were above the
DPR target values at site B only.
• It can be concluded that Site B is more polluted than site A
and that the indiscriminate disposal of wastes on these land
had contributed to the increment in concentrations of these
metals in the land.

55. CONCLUSION

56. • Soil pollution is a result of many activities and experiments
done by mankind which end up contaminating the soil.
Industrial wastes such as harmful gases and chemicals,
agricultural pesticides, fertilizers and insecticides are the most
common causes of soil pollution. The others are ignorance
towards soil management and related systems, unfavourable
and harmful irrigation practices, improper septic system and
management and maintenance of the same, leakages from
sanitary sewage.
• There is urgency in controlling the soil pollution in order to
preserve the soil fertility and increase the productivity.