AIR POLLUTION SOURCES 95
Part 1. Pollutant Emissions (continued)Pollutant types Sources and abundance Abatement and controlMajor sources:
1) Oil-fired boilers—0.9% phosphorus in
fly ash.
2) Iron and steel industry—phosphorus
pentoxide accounts for an average of 0.2% of
the total weight of fume from furnances.
3) Transportation sources: Organophosphorus
compounds used as fuel additives.
Natural abundance: Natural phosphates are
divided into three classes on the basis of the
metal or metals to which it is bound. The
three major classes are aluminium (iron)
phosphates, calcium-aluminum (iron)
phosphates, and calcium phosphates.
c. SELENIUM: This is a non-metallic element
chemically resembling sulfur and tellurium,
occurring in several allotropic forms. The soils of the
midwestern U.S. are particularly high in selenium
content. Selenium has also been found to be an
essential nutrient for animals and may be necessary
for humans.Major sources: The sources of atmospheric
selenium are believed to be terrestrial, such
as fuels and ores used by industry (copper
refinery), or possibly the burning of trash,
particularly paper.
Natural abundance: In nature, selenium is
widely distributed in the earth’s crust at a
concentration of about 0.09 ppm. Selenium
can also be found in coal and igneous rock.
Approximately 0.001 mg/m^3 of selenium has
been found in samples of rain, snow, and air.No study has been made of the
methods for control of selenium and
its compounds. However, based on
the properties and on the methods of
recovery and purification of
selenium wet scrubbers and high-
voltage electrostatic precipitators
should be effective.- Heavy metals. These are the chemically inert
electronegative metals with densities of 5 gm/cm^3
and greater. They are chemically inert because their
electrons are tightly bound to the metal’s nuclei and
are unable to readily combine with other elements.
However, heavy metals are toxic to the human
physiology in that the heavy metals try to bond with
enzymatic sulfur atoms in the body. They also attack
free amino (–NH 2 ) and organic acid (–COOH)
groups found in proteins. A few heavy metals
combine with and precipitate some of the body’s
vital phosphate compounds; other heavy metals
catalyze the decomposition of phosphates. Mercury,
lead, cadmium, copper combine with all membranes
and interfere with the transport of chemicals in and
out of the cell. As a result of this heavy metal
combination with the tissue, a variety of diseases
ranging from cancer to heart disease occurs. The
following is a list of metals that are considered to be
most detrimental to human health.
a. MERCURY: A high density, silver-white metal, is
liquid at normal ambient temperatures. Although it is
contained in at least 25 minerals, the chief source is
cinnabar (HgS).
Major sources: The combustion of coal was the
largest source of mercury emissions in the
United States in 1968.
The paint industry was the source of more than
25% of lead emissions in the U.S. in 1968.
Marine anti-fouling paints contain mercurial
compounds as a toxicant; latex paints use
mercurial compounds as a preservative.
The third largest source of mercury emissions is
the combustion of wastes which accounted
for almost 17% of all mercury emissions in
1968.
Other sources of mercury include mining and
processing of ore. In industrial applications
mercury is used in rectifiers, mercury
precision lighting, batteries (mercury cell and
alkaline energy cell). Laboratory equipment
and instruments—such as barometers,
thermometers, flow meters, pressure-sensing
devices, switches and relays all contain
mercury (spillage creates droplets which
vaporize). Electrolytic preparation of
chlorine. Agricultural use of mercury
compounds as pesticides (now declining).For applications which use mercury at
normal temperatures:
1) Proper ventilation in work areas.
2) Cleaning up spilled mercury
(sweeping with special vacuum
cleaners or chemical treatment).
3) Use of non-porous material for
floors, working surfaces and
protective clothing.
4) Conventional control of pesticides.
For applications which use mercury at
high temperatures:
Condensing mercury vapors by:
Cold-water jacketed condensers,
impregnated charcoal.
Water scrubbers.b. LEAD: Lead is a heavy, soft malleable, bluish-gray
metallic element. It is the sulfide ore, galena, soil,
water, vegetation and animal. It is introduced into the
body with the intake of water and in air. Most lead
air pollution is in the form of aerosols, fume, and
sprays. The largest use of lead 39% of the total in
1968 is in the construction of storage batteries. The
second largest use is in the manufacture of gasoline
and tetramethyl lead. Approximately 1.30 million
tons of lead were consumed in the United States in
1968.Major sources: The major source of airborne
lead in urban areas is the exhaust from
gasoline powered vehicles.
Other man-made sources are manufacturing of
lead additives for gasoline, processing and
manufacture of lead products, the combustion
of coal.1) From vehicle sources: Reduction or
elimination of lead in fuel; use of
particulate traps on vehicle exhausts.
2) From lead processing and the
manufacture of lead products:
Control of operating conditions
(temperature and timing): Use of
oconventional air cleaning techniques
(bag house filters, scrubbers,
electrostatic precipitators).(continued)C001_006_r03.indd 95C001_006_r03.indd 95 11/23/2005 9:42:40 AM11/23/2005 9: