Atmospheric Pollution

    Cards (65)

    • Proportion of pollution
      • Pollutants in the atmosphere often behave very differently from those in water, or on the ground
    • Smoke and smoke smogs
      1. Smoke is made up of the atmospheric particulates produced by the incomplete combustion of carbon-based materials
      2. Smoke is often categorised by the size range of the particles: PM10, PM5, PM1
      3. Particle size is important because smaller particles remain in the atmosphere for longer so they are more likely to be inhaled
      4. Toxic chemicals found in smoke can include fluorides, aluminium, lead, acids and organic compounds such as phenol
      5. Smoke can act synergistically with other atmospheric pollutants such as sulfur dioxide
    • Sources of smoke
      • Combustion of coal, diesel, general combustible wastes especially in urban areas
      • Combustion of crop waste, wood fuel, grasslands, forests in rural areas
    • Effects of smoke pollution
      • On humans: respiratory disease, more difficult to clear inhaled particles and bacteria from the lungs
      • On other living organisms: reduced photosynthesis, increased risk of infections, some chemicals may be carcinogenic
      • On non-living objects: damage buildings due to the acids and organic solvents, cleaning dirty buildings is expensive
      • On the climate: large releases of smoke can reduce temperatures because the high albedo of the smoke reflects light so it does not reach the ground where it may have been absorbed and converted to heat
    • Smoke particles are small and can remain suspended in the atmosphere for long periods, especially in the stratosphere where there is no rain to wash it out
    • Smoke in the stratosphere can also deplete the ozone layer
    • Smoke smogs

      1. Smoke + Fog = Smog
      2. Fog tends to form when moist air is cooled until it reaches its dew point
      3. Temperature inversions make the formation of fog more likely
      4. Smoke that is part of a smog is more easily inhaled
      5. Smog has a very high albedo so the temperature inversion can last for long periods of time allowing pollutant levels to rise to a high level
    • The London smog of 1952 caused about 12,000 deaths, mainly people who were old, very young or had existing respiratory health problems
    • Smoke pollution control measures
      1. Legislation: Clean Air Act (1956) restricted the use of fuels that produce smoke in large urban areas
      2. Domestic sources: increased use of fuels that do not produce smoke, for example, natural gas, electricity
      3. Transport sources: Diesel Particulate Filters (DPF) fitted in the exhaust pipes of diesel engines trap up to 80% of smoke particles
      4. Industrial sources: Electrostatic precipitators, Cyclone separators, Scrubbers, Coal treatment, Bag filters
    • More efficient combustion technology can reduce smoke particles, for example, turbo chargers in diesel engines enable more air and oxygen to be delivered to the combustion chamber
    • Photochemical smogs
      1. Involve a wide variety of reactions between primary and secondary pollutants, in the presence of sunlight including UV light
      2. Sources of primary pollutants: oxides of nitrogen (NOx) released in exhaust gases, unburnt hydrocarbons from fuel, solvents, propellants
      3. Pollutants involved: NOx, unburnt hydrocarbons, PANS (Peroxyacetyl nitrates)
      4. Effects: NOx increase respiratory infections, PANS are toxic at low concentrations, tropospheric ozone is also toxic
    • Control of photochemical smogs
      1. NOx and hydrocarbons can both be controlled using catalytic converters in vehicle exhaust systems
      2. Catalytic converters chemically reduce NOx to nitrogen and oxygen, and oxidise hydrocarbons to carbon dioxide and water
      3. Hydrocarbon vapours can also be collected and adsorbed onto activated carbon filters
    • If the primary pollutants are controlled, the secondary pollutants will not be formed because the reactants will not be present
    • Acid rain is the combination of the pollution problems caused by a range of acidic gases and other pollutants that contribute to the problem
    • Acid rain
      Rain that is more acidic than pH 5.6 due to dissolved pollutants
    • Pollutants involved in acid rain
      • Sulfur dioxide
      • Sulfur trioxide
      • Oxides of nitrogen
      • Hydrogen chloride
      • Ozone
    • Sulfur dioxide
      Dissolves in water to produce sulfurous acid
    • Sulfur trioxide
      Produced by the oxidation of sulfur dioxide, dissolves to produce sulfuric acid which is a much more powerful acid than sulfurous acid
    • Oxides of nitrogen
      Dissolve to produce nitrous and nitric acids
    • Sources of the gases involved in acid rain
      • Combustion or oxidation of materials containing sulfur, especially burning coal and smelting sulfide ores
      • High temperature combustion, especially in power stations and petrol and diesel internal combustion engines
      • A secondary pollutant produced by photochemical reactions involving oxides of nitrogen
      • The combustion of coal and the incineration of waste
    • Acid rain can damage buildings and other structures
    • Sulfur dioxide dissolves in water to produce sulfurous acid
    • Sulfur dioxide oxidation
      1. Sulfur dioxide may be oxidised in the atmosphere by gases such as ozone to produce sulfur trioxide
      2. Sulfur trioxide is dissolved to produce sulfuric acid which is a much more powerful acid than sulfurous acid
    • Oxides of nitrogen dissolving
      Oxides of nitrogen dissolve to produce nitrous and nitric acids
    • Hydrogen chloride dissolving
      Hydrogen chloride dissolves to form hydrochloric acids
    • Ozone is involved in the oxidations of sulfur dioxide to sulfur trioxide
    • Ozone also harms plants directly
    • Sources of the gases involved in acid rain
      • Sulfur dioxide
      • Oxides of nitrogen
      • Ozone
      • Hydrogen chloride
      • Sulfur trioxide
    • Sulfur dioxide
      Main sources are combustion or oxidation of materials containing sulfur, especially burning coal and smelting sulfide ores
    • Oxides of nitrogen
      Main sources are high temperature combustion, especially in power stations and pet and diesel internal combustion engines
    • Ozone
      A secondary pollutant produced by photochemical reactions involving oxides of nitrogen
    • Hydrogen chloride
      Main sources are the combustion of coal and the incineration of wastes containing chlorine, for example, PVC plastic waste
    • Sulfur trioxide

      Main source is the oxidation of sulfur dioxide by ozone
    • Acid deposition corrodes metals, causing damage to railway lines, metal railings, water pipes, pylons, and overhead powerlines
    • Limestone structures such as buildings and statues are damaged as the acids dissolve the surface layers and weaken the stone structure of porous limestone
    • Acids are harmful to all living organisms although the range of tolerance differs between species
    • Low pHs denature proteins in cell membranes and can inhibit enzyme action
    • Tissues which have living cells exposed to the environment are most likely to be damaged, such as eggs, and fish gills
    • Invertebrates with exoskeletons may die as the acids dissolve the calcium compounds that form the skeleton
    • Lichens are very sensitive to acidic conditions and their size, state of health, abundance and diversity may be used in a biotic index to monitor acid rain pollution
    See similar decks