Environmental Engineering Reference
In-Depth Information
8
In a short period (about 150 years after the Industrial Revolution), the environment-
al impacts, in terms of magnitude, of human activities became comparable to the
ones caused by natural effects. Humans have become a force of geological propor-
tions. For example, natural forces (such as wind, erosion, rain, volcanic eruptions)
move about 50 million tons of material a year. The present population of the Earth
uses an average of 8 tons of mineral resources per capita per year, moving about 48
billion tons. A century ago, the world population was 1.5 billion and the amount
of resources used was smaller than 2 tons per capita: the total impact was 16 times
smaller. As a result of this increased impact, new problems or areas of interest in
the environmental field have turned into an object of study and concern.
The environmental problems are usually grouped into three categories:
- Local
- Regional, and
- Global.
Local pollution
deals with clean air, fresh supplies of clean water, the removal and
disposal of solid wastes and liquid effluents, street cleaning, and so on. Such activ-
ities have characterized “good” small and medium sized cities since Roman times.
Yet in many developing countries, a large fraction of the population lives among
the rubble and residues it produces, owing to the lack of resources to remove waste
and to build sewers and engineer works for the supply of water. This is quite evid-
ent in the slums of the big cities that, generally speaking, surround “islands of
prosperity,” where the well-to-do succeed in obtaining a quality of life that is com-
parable to that of Europe or the United States. Local pollution goes hand in hand
with poverty and is usually dealt with by local governments.
Regional pollution
is caused mainly by automobiles, energy production, and
heavy industry, which are inherent to more prosperous societies. Large cities and
adjoining areas, such as Los Angeles, Mexico City, and São Paulo, have long been
