Geoscience Reference
In-Depth Information
efficiency by vehicles and catalytic converter
installation in the 1970s.
100
Rural
80
Gases
As well as particulate pollution produced by urban
and industrial activities involving coal and coke
combustion, there is the associated generation of
pollutant gases. Before the Clean Air Act in the
UK, it was estimated that domestic fires produced
80-90 percent of London's smoke. However, these
were responsible for only 30 percent of the sulfur
dioxide released into the atmosphere - the
remainder being contributed by electricity power
stations (41 percent) and factories (29 percent).
After the early 1960s, improved technology, the
phasing out of coal fires and anti-pollution
regulations brought about a striking decline in
sulfur dioxide pollution in many European and
North American cities (
Figure 12.21
). Neverthe-
less, the effect of the regulations was not always
clear. The decrease in London's atmospheric
pollution was not apparent until eight years
after the introduction of the 1956 Clean Air Act,
Suburbs
60
City center
40
20
London sunshine
(1921-1950)
(A)
0
180
London sunshine
(1958-1967)
160
City center
140
Suburbs
120
700
Rural
100
600
(B)
80
500
J
A
SOND
J
Month
FM
A
M
JJ
400
Figure 12.20
Sunshine in and around London. A:
Mean monthly bright sunshine recorded in the city
and suburbs for the years 1921-1950, expressed as
a percentage of that in adjacent rural areas. This
shows clearly the effects of winter atmospheric
pollution in the city. B: Mean monthly bright sun-
shine recorded in the city, suburbs and surrounding
rural areas during the period 1958-1967, expressed
as a percentage of the averages for the period
1931-1960. This shows the effect of the 1956 Clean
Air Act in increasing the receipt of winter sunshine,
in particular in central London.
Sources: A: After Chandler (1965); B: after Jenkins (1969). By
permission of Hutchinson and of the Royal Meteorological
Society.
New York
300
London
200
100
0
1960
1970
1980
Figure 12.21
Annual mean concentration of
sulfur dioxide (mg m
-3
) measured in New York and
London during a 25-30-year period. These show
dramatic decreases of urban pollution by SO
2
.
Source: From Brimblecombe (1986). By permission of
Cambridge University.
