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96
Table LXXV.—Atmospheric Pollution—Analyses of Deposited
Impurities.
1937.
Figures in English Tons per Square Mile.
Horseferry Road, S.W.I.
Farm Street, W.l.
Finsbury
Park.
Total
Solids.
Sulphur
SO3.
Daily
Average.
Total
Solids.
Sulphur.
so3.
Daily
Average.
Total
Solids.
January
45.61
5.15
1.47
30.70
4.43
0.99
19.75
February
51.89
5.16
1.86
27.14
3.24
0.97
17.38
March
135.93
7.29
4.39
30.80
3.92
0.99
14.43
April
62.63
5.70
2.09
32.55
3.58
1.08
15.02
May
48.16
3.97
1.55
29.40
3.29
0.95
20.84
June
31.35
1.95
1.05
31.29
4.49
1.04
15.93
July
26.94
1.28
0.87
24.02
2.15
0.77
12.37
August
30.41
2.4'i
0.98
29.46
4.27
0.95
19.34
September
28.37
4.26
0.94
21.14
4.70
0.70
12.16
October
37.96
4.57
1.22
38.57
5.46
1.24
14.30
November
41.02
4.73
1.36
37.98
4.38
1.26
26.60
December
44.16
5.74
1.42
40.18
5.69
1.29
17.39
It will be noted that high figures were returned for the gauge installed
at Horseferry Road, particularly during March, 1937. This was due to.
extensive building operations in the immediate locality.
(2) The quantitative estimation of suspended impurities in the air is
carried out by means of a colour standard. A measured volume of air
is drawn through a disc of filter paper, rotated at regular intervals during
every 24 hours and the colour of the resultant deposit is compared with
those on a chart of standard tints which represent the weight of dirt
per million cubic yards of air.
Chart "A" shows the amounts of suspended impurities for an average
day of 1937, together with a similar curve for the years 1931 to 1936. It
will be seen that there is a peak about 10 a.m. corresponding to the initial
lighting of fires and a secondary peak in the early evening, which
corresponds with the making up of fires in restaurants, hotels, etc.
(3) Estimation of sulphur gas (as sulphur dioxide). The method
employed is that of bubbling a measured volume of air through a solution
which has an affinity for sulphur. The sulphurous impurities retained
in the solution are measured by chemical analysis.
Chart "B" indicates graphically the amount of sulphur gas correlated
with visibility, wind direction and rainfall during 1937. The code used
for the "visibility" curve is that issued by the Meteorological Office and
is as follows:—