WATER POLLUTIONWater pollution
The quality of drinking water is very important to human welfare. The pollution of
water by sewage has been linked to the spread of diseases such as cholera and typhoid
fever. Elimination of these diseases in developed countries has been a direct result of
purification of such water, principally by disinfection using chlorine.
22.3
415nuclide from the radioactive decay of uranium in rocks. The gas passes through rocks
and enters buildings. Well insulated houses retain more radon gas than draughty
ones. The gas itself does not cause damage, but its radioactive disintegration products
cling to dust in the air; the contaminated dust can then stick to the lungs and damage
them. People living in Cornwall, Somerset, Northamptonshire and Derbyshire are
particularly affected because the local rocks contain more uranium.
Smog and soot from cars
The infamous ‘smog’ of Los Angeles and Tokyo (and of many large cities) is caused
mainly by the existence of a vast number of motor cars whose emissions are trapped
in a relatively small area. The cars emit NO 2 which (in the presence of sunlight and
unburned petrol) produces ozone and other chemical irritants. The NO 2 often gives
the air a ‘hazy brown’ coloration. Some cities give the predicted daily ozone levels
with the daily weather forecast! The ozone is purely destructive; it cannot reach the
ozone layer sufficiently fast to reduce ozone depletion.
Recent medical studies suggest that fine particles of soot emitted by vehicles (espe-
cially diesel-fuelled ones) may be the cause of many illnesses and premature deaths.
Infrared spectroscopy can be used to study the composition of exhaust gases. See
Figure 22.4.
Transmittance / %Wavenumber / cm–1Fig. 22.4An infrared spectrum of the exhaust gas from a petrol-powered car. Important peaks are labelled.