Unit 3: Properties of Pollutants

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  • Properties of Pollutants
    • Toxicity
      • Poisonous and harms biological processes - damaging proteins
      • Carbon monoxide, lead, DDT
      • Not all pollutants are toxic (some change environmental factors)
    • Specificity
      • Different organisms have different sensitivities to substances
      • Effective for pesticides - kills target species but not others
    • Persistence
      • The longer the pollutant remains in environment, more harm it can do
      • Not used for substances that never break down (non-biodegradable)
      • CFCs, DDT, Heavy metals
    • Biodegradability
      • Rate is affected by environmental factors e.g. temp, oxygen
      • Biodegradable - sewage, paper
    • Mobility
      • More mobile pollutants travel longer distances - affect further places
      • More likely to become diluted and less locally harmful
      • CFCs, sulphur dioxide (acid rain), smoke, suspended solids
    • Solubility
      • Water-soluble - can be mobile in hydrosphere e.g. sulphur dioxide, nitrates
      • Lipo-soluble - dissolves in lipids so can be stored in body for long periods e.g. dioxins
    • Bioaccumulation
      • Chronic exposure to small doses over long periods of time
      • Liposoluble pollutants more likely to bioaccumulate
      • DDT, heavy metals
    • Biomagnification
      • Stored pollutants in animals may be eaten by animals in next tropic level
      • Predators eat lots so more concentrated in them
    • Synergism
      • Oxides of nitrogen and sulphur dioxide, zinc and cadmium
      • Two pollutants produce greater effect
      • Difficult to predict - not possible to test all combinations
    • Mutagenicity
      • DNA changes in gametes may cause birth abnormalities
      • DNA changes in body cells may cause cancer
      • Ionising radiation, asbestos
    • Carcinogenicity
      • Cells produced unable to carry out normal functions = cancerous tumors
      • Asbestos, DDT
    • Teratogenicity
      • Birth abnormalities are non-inherited and cannot be passed on as DNA is unaltered
      • Inhibit enzyme/protein function in embryo
      • Herbicides, mercury


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