140
THE ESSEX NATURALIST
Figure 1. See page 154 for legend.
winter levels of sulphur dioxide (μg/m3) obtained from standard smoke and
sulphur dioxide gauges are published by Warren Spring Laboratory,
Stevenage. Selected sites from and near the area under study are tabulated
below.
From these data a general picture of the region can be obtained. It is
obvious that the densely populated urban areas to the west and south still
have high levels of sulphur dioxide (despite smoke control) and that this
has begun to 'level off' in recent years, after falling dramatically during the
early sixties. What is of particular significance is the similarity between the
high levels in these long-established residential and industrialised areas
and the comparatively new town of Basildon. The high levels at Basildon,
which have been consistent since 1968, help to substantiate the view of
Warren Spring Laboratory (1972) that it is domestic heating and the small
industrial plant which are responsible for the main sulphur dioxide
emissions into the air near ground level. Laundon (1973) showed that
residential infilling between Bookham Commons, to the south-west of
London, and London itself, was the source of the sulphur dioxide pollution