Soil Pollution:

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Soil Pollution

• The introduction of substances, biological
  organisms, or energy into the soil, resulting in
  a change of the soil quality, which is likely to
  affect the normal use of the soil or endangering
  public health and the living environment.

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• Soil contaminants are spilled onto the surface
  through many different activities.
• Most of these are the result of accidents
  involving the vehicles that are transporting
  waste material from the site at which it
  originated to the site at which it is to be
  disposed.

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• Others involve accidents involving vehicles
  (automobiles, trucks and airplanes) not
  transporting wastes, but carrying materials,
  including fuel, that when spilled contaminate the
  soil.

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• Still other spills are the direct action of
  humans pouring potentially toxic materials
  (solvents, paints, household cleaning agents,
  etc.) onto the ground surface rather than
  disposing these materials by more appropriate
  means.

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Pollutant on surface of soil

• When any liquid pollutant is on or just below the
  ground surface for any period of time, one of
  three things could happen to it, if it is not
  cleaned up first.
• 1- pollutant might be washed away by
  precipitation, causing little or no harm to the
  ground on which it was found ( however,
  pollutants will simply accumulate somewhere else)

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• 2- the pollutant, if volatile, could evaporate,
  again causing little harm to the soil ( however,
  not a solution to the bigger pollution problem,
  as it might become a source of air pollution).
• 3- pollutant could infiltrate through the
  unsaturated soil, in much the same way as ground
  water.

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• Agricultural practices, including the use of
  agricultural chemicals, are another primary
  source of pollution on or near the ground
  surface.
• Most agricultural chemicals are water-soluble
  nitrates and phosphates that are applied to
  fields, lawns and gardens to stimulate the growth
  of crops, grass and flowers.

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Ag Chemicals

• When not used by the plants the nutrients can
  enter streams and lakes during the run-off or
  leaching events.
• Once in a body of water, these chemicals continue
  to promote the growth of plants, the resulting
  plant detritus is food for micro-organisms, and
  as the population of such organisms grows, the
  supply of oxygen in the water is depleted.

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• "Biochemical Oxygen Demand", or "BOD". This means
  that the water is capable of supporting a large
  population of bacteria that will have a high
  demand for oxygen.

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Biocontrol- avoiding use of chemicals

• Choose a cover crop as a bio-control for a
  specific pest
• Time tillage to give crops the best advantage
  from the resulting biological activity
• Manage habitats at the edge of fields to support
  predators of pests

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Biocontrol

• Choose pesticides partially based on the
  non-target organisms they affect
• Choose a source of compost and manure based on
  how it impacts disease or crop-enhancing organisms

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Soil Pollution

• Information needed to clean up materials added to
  soil include
• 1) Kind of material - organic or inorganic - is
  the material biodegradable, is the material
  dangerous to animals and humans,
• 2) how much material was added to the soil, will
  it overload the organisms in the soil
• 3) CN ratio of the material, are additional
  nutrients needed ( N P)

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Soil Pollution

• 4) Kind of Soil - will the soil be able to
  handle the material before groundwater is
  contaminated,
• 5) Growing conditions for the soil organisms - is
  it too cold, too wet etc.
• 6) How long has the material been on the site -
  is there evidence of environmental problems, is
  it undergoing decomposition.
• 7) Immediate danger to people and the
  environment - Urgency of the situation.

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Bioremediation

• A treatment process that uses microorganisms
  (yeast, fungi, or bacteria) to break down, or
  degrade, hazardous substances into less toxic or
  nontoxic substances (carbon dioxide and water)

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Conditions that favor Bioremediation

• Temperature favorable for organisms
• Water available (near field capacity)
• Nutrients (N, P, K) in adequate supply
• CN ratio of material lt 301
• Material added is similar to naturally occurring
  organic material
• Oxygen in sufficient quantity

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In-situ-Bioremediation

• Biostimulation (stimulates biological activity)
• Bioventing (Inject air/nutrients into unsaturated
  zone good for midweight petroleum, jet fuel)
• Biosparging (Inject air/nutrients into
  unsaturated and saturated zones)
• Bioaugmentation (inoculates soil with microbes)

• Less expensive
• Creates less dust
• Less possibility of contaminant release into
  environment
• Good for large volumes
• Slower
• Doesnt work well in clays or highly layered
  subsurfaces

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Biostimulation
Biosparging
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Ex-situ -Bioremediation

• Slurry-phase
• Soil combined with water/additives in tank,
  microorganisms, nutrients, oxygen added
• Solid-phase
• Land-farming soil put on pad, leachate collected
• Soil biopiles soil heaped, air added
• Composting biodegradable waste mixed with
  bulking agent

• Easier to control
• Used to treat wider range of contaminants and
  soil types
• Costly
• Faster

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Slurry/Solid Phase
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Processes affecting the dissipation of organic
chemicals
detoxication
crop removal
photo-dec.
Runoff
volatilization
absorption exudation
chemical decomposition
Biological degradation
may be transformed into - harmful or harmless
leaching
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Affect of soil pH on adsorption of 4 heavy metals
Pb
Adsorption
Cu
Zn
Cd
3 3.5 4 4.5 5 5.5 6
6.5 7.0
Soil pH
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Forms of heavy metals found in soils that had
received sewage sludge (45mg/ha) for 5 years
of Elements in each form
Forms Cd Cr Cu
Ni Pb Zn
Exchangeable/adsorbed 1 1
2 5 1 2 Organically bound
20 5 34 24
3 28 Carbonate/iron oxides 64
19 36 33 85 39 residual
16 77
29 40 12 31
sulfides and other very insoulble forms
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Dyad on Pollution

• 1) Describe a situation that would cause the soil
  to become polluted with an organic waste.
• 2) Describe what you would do to clean up this
  pollution.

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The End