lecture Soil pollution.ppt for education

Soil pollution

2. Soil Pollution

3. Formation of soil
The parent material (bedrock) after mechanical weathering of rocks
by temperature changes, abrasion, wind, moving water, glaciers,
chemical weathering activities and lichens converts into soil.
•Under ideal climatic conditions, soft parent material may develop
into 1 cm of soil within 15 years.

4. •O-horizon: freshly-fallen & partially-
decomposed leaves, twigs, animal
waste, fungi & organic materials.
Colour: brown or black.
•A-horizon: humus/partially
decomposed organic matter & some
inorganic mineral particles. darker &
looser than the deeper layers.
O & A-horizon: contain a large amount of
bacteria, fungi, earthworms, small
insects, forms complex food web in
soil, recycles soil nutrients, &
contribute to soil fertility.
•B-horizon /(subsoil): less organic
material & fewer organisms than A-
horizon.
•C-horizon: consists of broken-up
bedrock, does not contain any organic
materials. Chemical composition helps
to determine pH of soil & also
influences soil’s rate of water
absorption & retention.
•R-horizon: The unweathered rock
(bedrock) layer that is beneath all the
other layers

5. Soil Pollution
Soil pollution is caused by the presence of chemicals or other
alteration in the natural soil environment.
Resulting in a change of the soil quality
likely to affect the normal use of the soil or endangering public
health and the living environment.

6. CAUSES OF SOIL DEGRADATION
•Soil erosion/degradation is the loss of top soil
erodes fertility of soil & reduces its water-holding
capacity.
•Excessive farming, construction, overgrazing,
burning of grass cover and deforestation
•Excess salts and water (Salinization)
•Excessive use of fertilizers & pesticides
•Solid waste
:

7. Causes of Soil Pollution
•Corrosion of underground storage tanks.
•Application of pesticides and fertilizers.
•Mining
•Oil and fuel dumping
•Disposal of coal ash
•Leaching from landfills
•Direct discharge of industrial wastes to the
soil
•Drainage of contaminated surface water into
the soil

8. First effect of pollutants
•Washed away: might accumulates somewhere
•Evaporate: can be a source of air pollution
•Infiltrate through the unsaturated soil to the groundwater
•DDT: fat soluble, stored in fatty tissues
–Interferes with calcium metabolism
–Results in thin egg shells in birds
•Agent orange: code name for one of the herbicides and
defoliants (results in leaf fall) used by the U.S. military as part
of its herbicidal warfare program, During the Vietnam War,
between 1962 and 1971, the United States military sprayed
20,000,000
 US gallons (80,000,000 L) of chemical herbicides
and defoliants in Vietnam
– anti fertility, skin problems, cancer

9. Control of soil pollution
•Use of pesticides and fertilizers should be minimized.
•Cropping techniques should be improved to prevent growth of
weeds.
•Special pits should be selected for dumping wastes.
•Controlled grazing and forest management.
•Wind breaks and wind shield in areas exposed to wind erosion
•Afforestation and reforestation.
•3 Rs: reduce, reuse, recycle
9

10. Information needed to clean up materials added to soil
Kind of material-organic or inorganic- is the material
biodegradable/ dangerous to animals & humans
 How much material was added to the soil, will it overload
the organisms in the soil
C:N ratio of the pollutant material
Nature of soil: will the soil be able to handle the material
before groundwater is contaminated
Growing conditions for the soil organisms: - is it too cold,
too wet etc.
How long the material has been on site: is there evidence
of environmental problems, is it undergoing decomposition.
Immediate danger to people & environment: Urgency of
the situation.

11. Bioremediation
•The use of naturally occuring microorganisms such as bacteria, fungi &
plants to break down or degrade toxic chemical compounds that have
accumulated in the environment
•It is a method that treats the soils and renders them non-hazardous, thus
eliminating any future liability that may result from landfill problems or
violations.

12. Factors affecting bioremediation
•Microbial factors
•Temperature favorable for organisms
•Availability of water (Moisture content)
•Availability of nutrients (N,P,K)
•C: N (carbon: nitrogen) ratio of the contaminant
material< 30:1
•pH
•Availability of Oxygen in sufficient quantity in soil.

13. •In situ Bioremediation : The treatment in
place without excavation of contaminated
soils or sediments.
•Ex situ bioremediation: excavation of
contaminated soil prior to remediation
treatments.

14. Advantages of Using Bioremediation Processes
Compared With Other Remediation Technologies
(1)biologically-based remediation detoxifies hazardous
substances instead of merely transferring contaminants from
on environmental medium to another;
(2) bioremediation is generally less disruptive to the environment
than excavation-based processes; and
(3) The cost of treating a hazardous waste site using
bioremediation technologies can be considerably lower than
that for conventional treatment methods: vacuuming,
absorbing, burning, dispersing, or moving the material .

15. Pesticides
•Goal: to stop or limit pest occurrence
•Types:
–Insecticides – kill insects
–Herbicides – kill weeds
–Fungicides – suppress or kill fungi

16. Benefits
•Allow agricultural producers to improve the
quality, quantity, and diversity of our food
supply.
•Used in timber, turf, horticulture, aquatic,
and structural pest control industries.
•Homeowners and home gardeners often
use pesticides in their homes, yards, and
on pets.

17. What Happens after Application?
•When pesticides are applied the goal is that they
will remain in the target area long enough to
control a specific pest and then degrade into
harmless compounds without contaminating the
environment.
•Once applied, many pesticides are mobile in the
environment (air, soil, water).
•This movement can be beneficial (moving
pesticide to target area, such as roots) but can
also reduce the effect on the target pest and
injure nontarget plants and animals.

18. Pathways of pesticide movement
•Runoff
•Chemical degradation
•Volatilize (gas vapor)
•Leaching and breakdown in soil
•Leaching and degradation by microbes
•Photo degradation (sun)

19. Factors influencing a pesticide’s fate
•Properties of the pesticide
•Conditions where & when applied
•Application method

20. Properties of the pesticide
•Vapor Pressure (volatility) – pesticides
with a high vp are more likely to change to
a gas and escape into the atmosphere.
•Sorption – attraction to soil surfaces,
pesticides with higher sorption values
have reduced leaching

21. Properties of the pesticide
•Water Solubility/dissolvability - more
soluble pesticides have lower sorption and
are more mobile in the environment as
they are leached or moved with runoff.
•Persistence – the amount of time a
pesticide remains in the environment,
measured by half-life. Pesticides with
longer half-lives pose a greater threat to
the environment.

22. Conditions where & when applied
To maximize pesticide effectiveness and
minimize negative environmental impacts,
the pesticide must be compatible with the
physical, chemical, and biological
conditions of the application site.
•For pesticides use in crop or plant pest
control consider the following conditions:
•Soil: physical and chemical properties
(texture, amount of organic matter, pH).

23. Conditions where & when applied
•Geology – depth to water table (larger distances
give more soil to act as filter)
•Surrounding water sources – nearby water is
more susceptible to contamination when
pesticides are applied to highly erodible soils,
over-irrigated, or rain-soaked soils. Managing
crop residues and maintaining grass waterways
and filter strips help to protect surface waters
from sediment and pesticide pollution.

24. Conditions where & when applied
•Environmental conditions – heavy or sustained
rainfall or irrigation shortly after pesticide
application can increase runoff, leaching, and
volatilization.
•Soil temperatures (extremely high or low) can
interfere with pesticide performance. Pesticides
generally become more volatile in high
temperatures and windy weather.
•Pesticides can be incorporated (disked in) or
applied directly into the soil to decrease the
potential for drift and volatilization.

25. Application method
The challenge for pesticide applicators is to
maximize the benefits of pesticides through
sound management while reducing
environmental risks. This includes:
•Keeping current of the latest information.
•Taking all necessary preventive measures,
including transportation, secure storage, proper
disposal of containers and rinsate, and spill
prevention. Furthermore, avoid sensitive areas
such as sinkholes, depressions, wells, surface
water, public institutions and private buildings.

26. Product labels
•The pesticide label is a binding, legal
document. Compliance is required by state
and federal regulations.
•Label directions must be carefully followed
– from purchase to container disposal.
•High risk pesticides may only be
purchased and applied by certified
persons.

27. Pesticide Use
•Careful selection for a specific pest –
understand the pest, site, product, and
risks.
•Careful and responsible use.
…shows a consideration for the
environment.
….responsible stewardship