Environmental Engineering Reference
In-Depth Information
still used in a number of developing countries. Lead used in ammunition,
which is the largest non-battery end-use, has remained fairly constant in
recent years. However, even the use of lead in bullets and shot as well as in
i shing sinkers is being reduced because of its harm to the environment.
Most lead used by industry comes from mined ores or from recycled scrap
metal or batteries. However, most of the high levels found throughout the
environment come from human activities. Environmental levels of lead
have increased more than 1,000 fold over the past three centuries as a result
of human activity. Lead can enter the environment through releases from
mining lead and other metals, and from factories that make or use lead,
lead alloys, or lead compounds.
Zinc is one of the most common elements in the Earth's crust. Zinc is
found in the air, soil, and water and is present in all foods. Metallic zinc
has many uses in industry. A common use for zinc is to coat steel and
iron as well as other metals to prevent rust and corrosion. Metallic zinc
is also used to make dry cell batteries. Zinc can also combine with other
elements, such as chlorine, oxygen, and sulfur, to form zinc compounds.
Zinc compounds that may be found at hazardous waste sites are zinc chlo-
ride, zinc oxide, zinc sulfate, and zinc suli de. Most zinc ore found natu-
rally in the environment is in the form of zinc suli de. Zinc compounds
are widely used in industry. Zinc suli de and zinc oxide are used to make
white paints, ceramics, and other products. Zinc enters the air, water, and
soil as a result of both natural processes and human activities. Most zinc
enters the environment as the result of mining, purifying of zinc, lead,
and cadmium ores, steel production, coal burning, and burning of wastes.
h ese activities can increase zinc levels in the atmosphere. Waste streams
from zinc and other metal manufacturing and zinc chemical industries,
domestic wastewater, and run-of from soil containing zinc can discharge
zinc into waterways [31].
Cobalt is a naturally-occurring element that has properties similar to
those of iron and nickel. It has an atomic number of 27. Small amounts of
cobalt are naturally found in most rocks, soil, water, plants, and animals,
typically in small amounts. Cobalt is also found in meteorites. Soils near
ore deposits, phosphate rocks, or ore smelting facilities, and soils contami-
nated by airport trai c, highway trai c, or other industrial pollution may
contain high concentrations of cobalt [29]. Small amounts of cobalt may
be released into the atmosphere from coal-i red power plants and incinera-
tors, vehicular exhaust, industrial activities relating to mining and process-
ing of cobalt-containing ores, and the production and use of cobalt alloys
and chemicals. Cobalt is even found in water in dissolved or ionic form,
typically in small amounts. A biochemically important cobalt compound
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