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Photochemical smog and its production is a reason that is causing wide concern.

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OXFORD CAMBRIDGE AND RSA EXAMINATIONS CHEMISTRY (SALTERS) Lawrence Johnson OPEN BOOK PAPER Photochemical smog and its production is a reason that is causing wide concern. It happens when primary pollutants, which are air pollutants that enter the atmosphere directly from things such as motor vehicles, power stations, industry and domestic sources, interact under the influence of sunlight to produce secondary pollutants. Secondary pollutants are therefore atmospheric pollutants that are created chemically when primary pollutants and other components of air react. The main primary pollutants emitted as a result of motor vehicles are Nitrogen oxides (NO?) hydrocarbons(C?H?), Carbon Monoxide (CO) and Sulphur oxides (SO?). The main secondary pollutants formed as a result of vehicle emissions are Ozone (O?) and peroxyacetyl nitrate) H O. (1) Coal fired power stations are another way in which primary pollutants are emitted into the air and thus contribute to the production of photochemical smog. This is because the outputs as a result of fuel combustion are things such as NO? gases. The emission of these nitrogen oxides occurs as flue gases from burning the coal contain oxides of nitrogen. ...read more.


A further condition is a strong inversion as it caps the atmosphere that will result in a very small mixing layer. Finally, valleys as they exaggerate the small mixing region. (2) These conditions are outlined in the diagram below. (3) Tropospheric ozone can act both as a direct greenhouse gas and as an indirect controller of greenhouse gas lifetimes. As a direct greenhouse gas, it is thought to have caused around one third of all the direct greenhouse gas induced warming seen since the industrial revolution. High concentrations of it is largely due to an influx from the stratosphere, however a large source is produced by the photochemical reactions, the amounts increasing with high levels of air pollution. This is shown in the reactions below: As we know a main source of primary pollutants are power stations however, one power station, Longannet has methods of taking 'the best environmental option' (BEPO) when it comes to pollutant emissions. To control its SO? emissions Longannet uses a process called 'seawater scrubbing'. ...read more.


Chemists play a huge part today's research on photochemical smog and have done for the past few years. Chemists have strong research programmes in atmospheric chemistry ranging from laboratory and field measurements to global numeric modelling. Chemists today now monitor troposheric pollutants to get an accurate idea of way the pollutants react and their concentrations in the troposphere. They also study individual reactions, which they simulate in the laboratory. This allows them to make a record of the types and times of reactions that take place. This means chemists can predict the rate at which a reaction will happen in given conditions. A major experiment done by chemists is the monitoring the behaviour of photochemical smog in a smog chamber. This is where "Primary pollutants are mixed in a huge plastic bag (smog chamber) and exposed to sunlight under carefully controlled conditions" (5) All these things are being done by chemists on a wide scale to increase our knowledge on photochemical smog and its behaviour. Source Index (1) Assisting source Storylines, DF5 pg 33-35 (2) Green House Gases article. Times (3) http://www.yorku.ca/hastie/pollution.PDF (4) Assisting source www.bbc.co.uk/searchlogannetinfo (5) Storylines, DF6 ...read more.

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