Environmental Engineering Reference
In-Depth Information
FIGURE 7.2
General Wind and Pressure Belts over
the Earth
High Pressure
Descending Air
Moist, high
precipitation,
cool
90
N
Simplifi ed air circulation is in the form
of giant convection cells. Actual air
movement can fl uctuate widely at any
given time and place, making forecast-
ing wind and weather notoriously
diffi cult.
Source:
Steward 2005
Polar Easterlies
Low Pressure
Raising Air
60
N
Dry, high
evaporation,
warm
High Pressure
Descending Air
Horse
latitudes
30
N
Wet, high
precipitation,
hot
Low Pressure
Raising Air
Doldrums
0
High Pressure
Descending Air
Horse
latitudes
30
S
Dry, high
evaporation,
warm
Low Pressure
Raising Air
60
S
Polar Easterlies
Moist, high
precipitation,
cool
90
S
High Pressure
Descending Air
Nobel laureate Paul Crutzen estimates that at least 3 million people die each year from
diseases triggered by air pollution.
Most jurisdictions now recognize that people have a right to breathe air that is not harm-
ful to their health and that sustainable economic vitality is tied to proper air resource pro-
tection. Ambient air quality standards are designed to protect health, environment, and the
quality of life from the pervasive threat of air pollution. The six most common pollutants are
ozone, particulate matter (PM), carbon dioxide, nitrogen dioxide, sulphur dioxide, and lead.
Mining and mineral processing have the potential to contribute to air pollution in vari-
ous ways. Particulate matter (dust) is usually the most obvious air pollutant associated with
mining. Particulate matter (PM) may well be the air pollutant that most commonly affects
people's health.
Airborne particles come in different shapes or sizes, and may be solid particles or liquid
droplets. Larger particles (PM
10
) range between 2.5 and 10 micrometres (from about 25 to
100 times thinner than a human hair). These cause less severe health effects than smaller
particles. Small particles (PM
2.5
), less than 2.5 micrometres in size, travel over longer dis-
tances, and penetrate deeper in the respiratory system. But size is not the only difference;
particle composition also counts. Pyrometallurgical processes may emit small particles
Particulates matter (PM) may
well be the air pollutant that
most commonly affects people's
health.
Airborne particles come in
different shapes or sizes, and
may be solid particles or liquid
droplets.
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