10. Pollution

• State of matter: whether a pollutant is a solid, liquid, or gas affects its ability to be dispersed by moving water or air. solids are deposited close to the source
• Density: the density of a material will affect its disposal
• persistence: a measure of the length of time that a pollutant remains in the environment before it degrades
• toxicity: a measure of how poisonous a substance is to living organisms. the harm is usually caused by damage to proteins, inhibiting the enzyme action
• specificity: the number of different organisms that the pollutant affects
• reactivity: can affect the severity of the pollution caused by increasing or reducing the problems caused
• Primary pollutants: released by human activities
• secondary pollutant: produced by chemical reactions between one or more primary pollutants
• Solubility in water: high solubility in water means that pollutants are easily dispersed in water bodies
• solubility in lipids: substances that dissolve in lipids may be able to pass through cell membranes and are stored within cells
• bioaccumulation: the amount of substance within an organism increases. involves the long term digestion of small doses of protein
• biomagnification: substances will become more concentrated as they pass along a food chain
• synergism: involves two or more pollutants where the effects interact to create a different effect, usually more serious
• mutagenic action: mutagens are agents which cause changes in the chemical structure of DNA by damaging chromosomes and rearranging the DNA structure
• carcinogenic action: mutagens that cause cancer
• teratogenic action: cause birth abnormalities by preventing normal gene expression
• mobility: the ability of a pollutant to move in the environment depends upon other properties
• temperature effecting degradation: most chemical reactions will speed up when temp increases. degradable pollutants like sewage will breakdown faster
• light levels affecting degradation: light can provide the activation energy that drives chemical reactions e.g. photodegradation
• oxygen: used in aerobic decomposition of pollutants and oxidation of pollutants
• pH: can affect the solubility of substances
• Pollutant interactions: the behaviour of a pollutant may be affected by the presence of other pollutants
• wind and water affecting dispersal: velocity and direction of air and water currents will affect how far a pollutant is dispersed, but also how it is diluted
• temperature inversions affecting dispersal: temp of warm pollutant gases, released at ground level, makes them less dense and more buoyant than the cooler surrounding air. this allows them to rise, disperse and become diluted. they cool down as they rise but they remain buoyant and continue to rise
• factors that allow temperature inversions to form:

  • valleys: where colder denser air can collect
  • low wind velocity: air layers with different temperatures do not mix
  • cloudless skies: infrared energy can be radiated from the ground, allowing the ground to cool down
  • mist or fog during the day: water vapour that condenses in the cooler ground layer has a high albedo and will reflect sunlight and slow the heating of the ground that would cause the temperature inversion to be broken down
• Presence of absorbent materials: pollutants may absorb onto materials such as clay particles or organic materials in aquatic sediments
• critical pathway analysis: used to predict the movement of pollutants in the environment to assess the severity and location of the pollution that may occur
• critical group monitoring: assesses the risk to members of the public who are most likely to be at risk
• Control of emission location: severity of pollution is affected by the location where the waste is released
• acute: events that occur instantly or quickly
• Chronic: events occur more slowly
• controlling pollution:

  • pollution prevention
  • prevention of release
  • post-release remediation
  • alternative processes
• Smog:

  1. Suspended particle matter smog (SPM)
  2. Photochemical smog
• smoke: made from atmospheric particulates produced by the incomplete combustion of carbon-based materials
• categories of smoke:

  • PM10 - particulate matter less than 10 microns in diameter
  • PM5 - particulate matter less than 5 microns in diameter
  • PM1 - particulate matter less than 1 micron in diameter
• main sources of smoke:

  • combustion of fossil fuels (urban areas)
  • combustion of crop waste, wood fuel, grasslands and forests (rural areas)
• SPM smog: made up of small solid particles suspended in the air
• impacts of SPM smog:

  • corrosion of buildings
  • respiratory diseases
  • reduction in photosynthetic efficiency
• control measures of smog:

  • legislation (clean air act)
  • domestic energy use (increased use of gas or oil-fired boilers)
  • transport energy use (diesel particulate filters)
• Photochemical smog: exhaust emissions from vehicles are converted into toxic chemicals by UV radiation forming a photochemical smog