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18
There are other kinds of pollution which may result from
the combustion of coal, but the above three are the most
important. It will be appreciated that the amount each of
smoke, ash and sulphur dioxide recorded in any one particular
spot, would not necessarily correspond exactly to the constitution
of the products of combustion as emitted from the
chimney or group of chimneys in the neighbourhood. Ash, for
instances, being a mineral body, falls more rapidly to earth
than do the lighter particles in the form of smoke. The very
small particles which form visible smoke, being dependent on
their own weight for depositions, are carried over a mucn
larger area than the heavier particles of ash and grit. Gases,
such as sulphur dioxide, etc. are spread over an even larger
area than the smoke and ash. Some of the sulphur deposit is
removed from the air by the process of being dissolved in the
rain and water droplets of cloudS. The height at which the
pollution is discharged into the atmosphere is a very
important factor.
On June 1st, 1948 a standard deposit gauge was installed
on a site which was decided upon after consultation with the
Department of Scientific & Industrial Research. The site is
at the Canbury Gardens near to the new Power Station.
At the time the deposit gauge was installed the construction
of the new Electricity Power Station Buildings was not
completed. It was hoped, by means of the gauge, to obtain
data which would show the effect, (if any) of the Power
Station on the amount of atmospheric pollution in the area.
After the gauge was installed, a new wing was built on to the
station at the North end, near to the gauge, and dust from
building operations had a distinct effect on the amount of
solids deposited.
Following the opening of the Power Station in October
1948, one chimney stack only was used, and this remained
the case throughout the remainder of 1948 and the whole of
1949.
The gauge is so situate as to be within the proximity
of other potential sources of atmospheric pollutions, namely,
the Gas WorkS, and the Railway Goods sidings. Wind blowing
from any point between South West and South East could carry
pollution from any one or more of these sources and in
order to assist in determining the comparative effect of
wind direction on atmospheric pollution, wind readings have
been taken three times daily throughout the year.
Table I overleaf sets out the monthly rainfalls, the
deposit in tons per square mile, and the number of times
the wind was observed in the quarters mentioned. The
table covers the period from the date that observations
were commenced, to the end of 1949.