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84
ATMOSPHERIC POLLUTION
There are seven combined smoke and sulphur dioxide atmospheric
pollution stations in the Borough and details of the measurements
of pollution are given in the following tables.
Two types of pollution are measured, namely smoke and sulphur
dioxide. Smoke pollution of the atmosphere includes all types of
suspended matter collected on the filter paper (these filter
papers are changed daily) but consists largely of smoke from the
burning of coal.
Smoke concentration is assessed by means of a Reflectometer
and the results are expressed as milligrammes of smoke per 100
cubic metres.
Sulphur dioxide which is given off in the burning of coal.
coke and oil in varying amounts according to the amount of sulphur
in the original fuel is measured by a chemical process. The
amount of sulphur dioxide is determined by combining the sulphur
dioxide in a known quantity of air with hydrogen peroxide to give
a dilute solution of sul phuric acid. The concentration of sulphuric
acid is determined by chemical titration and from this figure the
amount of sulphur dioxide can be calculated, the results being
expressed as parts of sulphur dioxide per hundred million parts
of air.
Atmospheric pollution in any given place depends on a number
of important factors, e.g. rainfall, direction and speed of
prevailing wind, turbulence, and seasonal and daily variations.,
(daily variations may be considerable, but sometimes variation
between night and day is even greater).
There is one distinct advantage in the measurement of these
types of pollution in that over a period of years changes in the
general trend of pollution can be observed.