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The instruments in use throughout 1955 were:
Seven deposit gauges for collection of matter settling from the atmosphere or washed down
by rain ; these deposits are analysed monthly.
Ten lead peroxide ' candles ' for the comparative measurement of the amount of sulphur dioxide
in the air ; the amount of peroxide converted to sulphate is found by analysis each month.
Three sets of volumetric apparatus for the dual measurement of smoke and sulphur dioxide ;
this equipment normally requires daily attention. *
Seven multiple-circuit sets of volumetric apparatus with which up to six consecutive samples
can be taken before the filters and solutions need to be examined and renewed. This automatic
sampler, recently devised in the laboratory, facilitates the study of peak concentrations of pollutants,
and enables detailed observations to be made without manual attention during night and
weekend periods. Air flow through the separate circuits is controlled by magnetic valves activated
in sequence by a time switch, the duration of each test being varied according to weather conditions.
The observations made during the year again showed a marked difference between
rural and urban conditions, as did those in different localities within the County
due to the varying amount of pollution from local sources. Seasonal fluctuations were
clearly marked at all sites, the generally higher level of pollution in winter being due
to the combined effect of increased coal consumption and the occurrence of meteorological
conditions unfavourable to the dispersion of chimney gases. When the results
are examined over a period of years the main change is a trend towards a slight reduction
in the amounts of tarry matter and smoke ; this can be accounted for by the replacement
of many domestic fires by the more efficient combustion units of blocks of flats.
In the central area of London where the fuel consumption in office blocks and other
centrally-heated buildings exceeds that of local fireplaces, the ratio of smoke (black
suspended matter) to sulphur dioxide is less than that found in more residential areas.
This is attributable to the better combustion conditions obtainable in large furnaces
as compared with small grates burning coal. Use of the new time-controlled sampler
enabled a more detailed analysis to be made of fluctuations of pollution during the daily
cycle. Again a distinction could be drawn between the effects of domestic and industrial
combustion. For example, on weekdays the smoke to sulphur ratio is at a minimum
during the night, when most domestic fires die down whilst some industry keeps
running. At weekends, when a greater proportion of industry is closed down, and
domestic fires are burning for longer periods, this ratio is found to be higher than for
comparable periods during the week.
The long-term investigation of the common major pollutants of the atmosphere
was supplemented by a special investigation directed towards the detection of various
minor pollutants. In addition dust separated from large volumes of air was examined
for radioactive constituents. The atmosphere has a small content of radioactive matter
arising from natural causes, and the amount of this varies from day-to-day with changing
meteorological conditions. There is also a very small proportion of such matter produced
by nuclear explosions. The order of magnitude of both of these sources of radioactivity
is being measured to provide a basis for future comparisons.
On three occasions during the year apparatus and specimens were provided for
public exhibitions.
By a standing agreement with the Ministries concerned, the Scientific Adviser or
his deputy accompanied the Chief Alkali Inspector of the Ministry of Housing and
Local Government on visits of inspection to test the efficiency of the flue gas working
plants at Battersea and Bankside Power Stations.
Public health
During the year, the water supplies to 24 establishments served by wells were regularly
examined and visits were made to other premises to check the suitability of water from
various sources and to give advice. The 571 bacteriological samples, 59 chemical and
516 free chlorine tests ensured that the water was efficiently chlorinated and at all times
in satisfactory condition.
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