View report page

116
during a period of calm weather the sulphur dioxide concentrations
may be ten times the readings taken in windy conditions.
This makes it difficult to determine over short periods what
improvements are being achieved. By taking annual averages the
effect of calm or turbulent air conditions may be expected in
most years to balance themselves out, but the figures so produced
tend to rise or fall according to the severity or mildness of the
winters. This effect is what one would expect, considering the
greater amount of fuel burned during cold weather, and it is confirmed
by comparing graphs of pollution averages for the Guildhall
site and "degree days" (Figure l) "Degree days"are an estimate
of the number of degrees below 60 P. maintained for 24 hours
aggregated over a period (in this case annually). It will be
seen that rises and falls in "degree days" are nearly always
accompanied by similar movements in pollution but there is also a
strong overall tendency for the pollution figures to fall so that
although the "degree day" graph shows that the winter of 1966-67
was of about the same severity as 1953-59, the sulphur dioxide
concentrations were over 30% lower and smoke concentrations about
66% lower. The graph (Figure l) shows that the very cold
weather experienced in the winter of 1962-63 caused a marked rise
in pollution, but from the graph for domestic coal consumption it
is seen that there was no increase in the amount of coal used in
that year although the prevailing tendency for this figure to
fall was temporarily arrested. Since coal burnt in domestic
grates is the main source of smoke pollution, the rise in 1962-63
wa3 probably due to the prevalence of calm and often foggy conditions
associated with very cold weather such as was experienced
in that winter, allowing pollution to accumulate near ground
level.
Figure 2 shows the monthly variations in smoke and sulphur
dioxide concentrations at Alpha Road, Surbiton and Figure 3 compares
the annual averages of smoke and sulphur dioxide concentrations
at all four sites.
Deposit Gauges.
Two deposit gauges for the monthly measurement of grit and
dust fall are located at Canbury Gardens and Tiffin Girls' School,
Kingston upon Thames. Figure 4 shows the average annual deposit
at the two sites for the years 1952 to 1967.
12. COMPLAINTS.
The following is a brief list of causes for complaints
received during 1967 which resulted in investigation by the
Department and in all cases where necessary, appropriate action
was taken.