Chemical Pollution

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Chemical Pollution and Soils

• Introduction
• Types of Contaminants in Soils
• Behavior of Organic Contaminants in Soils
• Remediation of Organic Contaminated Soils
• Inorganic Contaminants in Soils
• Behavior of Inorganic Contaminants in Soils
• Remediation of Inorganic Contaminated Soils

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Introduction

• We throw away stuff that we do not need.
• Some strong chemicals are needed at home for
  cleaning of all types.
• There is need to use chemicals to increase food
  production to feed the growing population.
• Industries excavate, smelt, manufacture and in
  those processes manage a lot of chemicals.
• All these activities generate wastes chemicals.

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Introduction

• By design or accident, the soil is sole recipient
  of wastes and chemicals
• Once wastes and chemicals enter the soil, they
  become part of biological cycles.
• The main objective of studying soils and
  pollution is to understand how these materials
  affect biological cycles and, in turn, plant and
  animal life.

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Introduction

• Once we can understand their reactions in soils,
  we can devise alternative ways of managing them,
  destroying them or inactivating them.

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What types of Chemicals?

• Toxic Organic Chemicals
• Toxic Inorganic Chemicals

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Toxic Organic Chemicals

• Plastics, Lubricants, Fuels, Solvents,
  Pesticides, Preservatives
• These compounds are called xenobiotics
• Toxic to living organisms
• Resistant to biological decay
• Difference between these compounds and naturally
  occurring compounds
• Insertion of halogen atoms (Cl, F, Br) into the
  structure
• Insertion of multivalent nonmetal ions (S, N)
  into the structure

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Kinds of Organic Contaminants

• Industrial organics
• Petroleum products used for fuel gasoline,
  benzene
• Polycyclic aromatic hydrocarbons (PAH)
• Trinitro-toluene (TNT)
• Trichloroethylene (TCE)
• Polychlorinated biphenyls (PCB)
• These compounds have been found to cause birth
  defects, hormonal problems and cancer in humans

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Kinds of Organic Contaminants

• Pesticides
• Classified according to group of pests organisms
  targeted
• Insecticides
• Fungicides
• Herbicides
• Rodenticides
• Nematocides

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The Pesticide Problem

• Pesticides are simply chemicals designed to kill
  pests over 600 chemicals today.
• Advantages
• Help to control vectors of human diseases
• Protect crops and livestock against insects and
  diseases
• Controls weed without damaging the environment

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• Problems with Pesticides
• Contamination of both surface and groundwater
• Detrimental to microbial communities
• Nontarget damages
• Biological magnification
• Alternatives
• Organic farming
• Use with a lot of caution last resort

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Fate (Behavior) of Organic Chemicals

1. Volatility
2. Adsorption by soil
3. Leaching to groundwater
4. Chemical reactions
5. Microbial metabolism
6. Surface runoff to streams and rivers
7. Plant absorption or animal uptake

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Behavior of Organic Chemicals
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Remediation of Organic Chemical Contaminated Soils

• Natural attenuation
• Physical and chemical methods
• Bioremediation
• Phytoremediation

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Contamination with Toxic Inorganic Substances

• Inorganic substances
• Arsenic
• Cadmium
• Mecury
• Lead
• Nickel
• Copper

• Boron
• Manganese
• Zinc
• Chromium
• Molybdenum
• Selenium
• Fluoride

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Sources and Accumulation

• Burning of fossil fuels
• Lead. Nickel, Boron, are gasoline additives
• Smelting
• Copper, Lead, Zinc, are mined and smelted
• Soil amendments
• Cadmium, Copper, Manganese, Nickel, Zinc, B
  fertilizers
• Arsenic, Mercury, used for pesticides

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• Heavy metals in Sewage Sludge
• Most heavy metals are found in sludges
• The elements have been found to be associated
  with
• Soil organic matter
• Carbonates
• Oxides
• OR in soluble, and exchangeable forms.
• If moderately applied at not very acid pH, the
  elements are bound to soil constituents.
• Bio-concentration
• Contaminants of all sources reach the soil
• Become part of the food chain
• They can accumulate in animal and human body
  tissues to toxic levels

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Remediation of Inorganic Chemical Contaminated
Soils

1. Eliminate or drastically reduce soil application
   of toxins
2. Immobilize toxins by good soil management
3. Remove toxin by physical, chemical or biological
   remediation