Environmental Engineering Reference
In-Depth Information
atmosphere system, to such an extent that normal
environmental processes are adversely affected.
Contamination is not always serious, however.
The environment has a considerable capacity for
ridding itself of pollutants, and problems only
begin to arise when the input of contaminants
exceeds the ability of the environment to deal
with them. In modern times, this situation has
become common as a result of the tremendous
amount of waste generated by human activities
and deposited in the environment. In the 1960s
and 1970s, the most pressing popular concerns
were often local in origin, dealing with such
problems as urban air pollution or reduced water
quality in rivers and lakes, although consideration
was given to the environment as a whole in the
academic and scientific community (e.g. Detwyler
1971). Along with increased concern there was
also increased understanding of the environment,
brought about by the development of educational
programmes at all levels, from elementary school
to university, and by judicious use of the media
by environmental groups such as the Sierra Club,
Friends of the Earth, Pollution Probe and
Greenpeace. The high level at which public
interest in environmental affairs was sustained
during the years when improvement was
marginal is in no small measure attributable to
these groups.
Public pressure forced the political and
industrial establishment to reassess its position
on environmental quality. Oil companies, the
forest products industry and even automobile
manufacturers began to express concern for
pollution abatement and the conservation of
resources. Similar topics began to appear on
political platforms, particularly in North
America, and although this increased interest was
regarded with suspicion, and viewed as a public
relations exercise in some quarters, legislation
was gradually introduced to alleviate some of the
problems. By the early 1970s some degree of
control seemed to be emerging. While this may
have helped to reduce anxiety over environmental
concerns, progress was slow, and some observers
attribute the decline in interest in all things
environmental at about this time to
disenchantment rather than recognition that the
problems were being solved (Bach 1972).
Whatever the reason, the level of concern had
peaked by then, and when the oil crisis struck in
1973, energy quickly replaced environmental
issues in the minds of the politicians, academics
and the public at large. In the first half of the
1990s, the energy situation is perceived as less
critical, the dire predictions of the economists
and energy futurists have not come to pass, and
the waning of interest in energy topics has been
matched by a resurgence of environmental
concern, particularly for problems involving the
atmosphere. The new issues are global in scale
and, at first sight, may appear different from
those of earlier years; in fact, they share the same
roots. Current topics such as acid rain and global
warming are linked to the sulphurous urban
smogs of two or three decades ago by society's
continuing dependence on fossil fuels to meet its
seemingly insatiable demand for more energy.
Population pressures on land of limited carrying
capacity contribute to famine and desertification
much as they did in the past. The depletion of
the ozone layer, associated with modern chemical
and industrial technology, might be considered
as only the most recent result of mankind's
continual, and seemingly inherent, desire to
improve its lot—all the while acting in ignorance
of the environmental consequences.
Many of the problems currently of concern
have causes which can be traced to ignorance of
the workings of the atmosphere. This is
particularly true when the impact of air pollution
on climate is considered. Almost all human
activities produce waste products, and some of
these are introduced into the atmosphere. This
presented no great problem when populations
were small, and technological levels were low,
for the atmosphere includes mechanisms designed
to keep such emissions in check. For every process
adding material to the atmosphere, there is
another which works to remove or reduce the
excess, either by neutralizing it or by returning it
to the earth's surface. Gases, for example, may
be absorbed by vegetation, neutralized by
oxidation or dissolved in water and precipitated.
