Jacobson M.Z. Atmospheric Pollution

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August 27, 1987. All four modes (one nucleation, two subaccumulation,

and one

coarse particle mode) are most noticeable in the number concentration distribution.

The nucleation mode is marginally noticeable in the area concentration distribution

and invisible in the volume concentration distribution.

5.2. SOURCES AND COMPOSITIONS OF NEW PARTICLES

New aerosol particles originate from two sources: emissions and homogeneous nucle-

ation. Emitted particles are called primary particles. Particles produced by

homogenous nucleation, a gas-to-particle conversion process, are called secondary

particles. Primary particles may originate from point, mobile, or area sources.

5.2.1. Emissions

Aerosol particle emission sources may be natural or anthropogenic. Natural emission

processes include volcanic eruptions, soil-dust uplift, sea-spray uplift, natural biomass

burning ﬁres, and biological material release. Major anthropogenic sources include

fugitive dust emissions (dust from road paving, passenger and agricultural vehicles,

and building construction/demolition), fossil-fuel combustion,

anthropogenic biomass

burning, and industrial emissions.

In the United States in 1997, about 37 million short tons of particulates smaller

than 10 m were emitted (Table 3.9). Of these emissions, about 67 to 71 percent were

anthropogenic in origin. On a global scale, more than half of all particle emissions are

anthropogenic in origin.

Table 5.2 summarizes the natural and anthropogenic sources of the major compo-

nents present in aerosol particles. These sources are discussed in more detail shortly.

5.2.1.1. Sea-Spray Emissions

The most abundant natural aerosol particles in the atmosphere in terms of mass

are sea-spray drops. Sea spray forms when winds and waves force air bubbles to

burst at the sea surface (Woodcock, 1953). Sea spray is emitted primarily in the

118 ATMOSPHERIC POLLUTION: HISTORY, SCIENCE, AND REGULATION

-1

100

150

200

250

300

0.01 0.1 1 10

Particle diameter (D, μm)

x = a(μm

-3

)

x = v(μm

-3

)

dn (particles cm

-3

)/d log

D (μm)

dx/d log

D (μm)

Figure 5.2. Number (n, particles cm

3

), area (a, m

3

), and volume (v, m

3

) con-

centration size distribution of par

ticles at Clar

emont, California, on the mor

ning of August

27, 1987. Sixteen model size bins and four lognormal modes were used to simulate the dis-

tribution (Jacobson 1997a).

coarse mode of the particle size distribution. Winds also tear off wave crests to form

larger drops, called spume drops, but these drops fall back to the ocean quickly. Sea

spray initially contains all the components of sea water. About 96.8 percent of sea-

spray weight is water and 3.2 percent is sea salt, most of which is sodium chloride.

Table 5.3 shows the relative composition of the major constituents in sea water. The

chlorine-to-sodium mass ratio in sea water, which can be obtained from the table, is

about 1.8:1.

When sea water is emitted as sea-spray or spume drops, the chlorine-to-sodium

mass ratio, originally 1.8:1, sometimes decreases because the chlorine is removed by

sea-spray acidiﬁcation (e.g., Ericksson, 1960; Duce, 1969; Hitchcock et al., 1980).

Sea-spray acidiﬁcation occurs when sulfuric or nitric acid enters a sea-spray drop and

forces chloride to evaporate as hydrochloric acid [HCl(g)]. Some sea-spray drops lose

all of their chloride in the presence of nitric or sulfuric acid.

The size of a sea-spray drop is also affected by dehydration. Dehydration (loss of

water) occurs when water from a drop evaporates due to a decrease in the relative

humidity between the air just above the ocean surface and that a few meters higher.

Dehydration increases the concentration of solute in a drop.

AEROSOL PARTICLES IN SMOG AND THE GLOBAL ENVIRONMENT 119

Table 5.2. Nontrivial Sources of Major Components of Aerosol-P

articles

Black carbon (C) X X X X

Organic matter (C,H,O,N) X X X X X X

Ammonium (NH



)XXX

Sodium (Na



) XXXX X

Calcium (Ca

2

) XXXX X

Magnesium (Mg

2

) XXXX X

Potassium (K



) XXXX X

Sulfate (SO

2

) XXXX X X

Nitrate (NO



)XX

Chloride (Cl



) XXXX X

Silicon (Si) X X X X

Aluminum (Al) X X X X

Iron (Fe) X X X X X

Fossil-Fuel

Fossil-Fuel and Metal

Combustion Combustion

Sea-Spray Soil-Dust Volcanic Biomass for Transportation for Industrial

Emissions Emissions Emissions Burning and Energy Processes

Table 5.3. Mass Percentage of Major Constituents in Sea Water

Water 96.78 Sulfur 0.0876

Sodium 1.05 Calcium 0.0398

Chlorine 1.88 Potassium 0.0386

Magnesium 0.125 Carbon 0.0027

Mass Percentage in Mass Percentage in

Constituent Sea Water Constituent Sea Water

The concentration of these constituents, including water, in sea water is 1,033,234 mg/L.

Source: Lide (1998).

5.2.1.2. Soil-Dust and Fugitive-Dust Emissions

Soil is the natural, unconsolidated mineral and organic matter lying above bedrock

on the surface of the Earth. A mineral is a natural, homogeneous, inorganic, solid sub-

stance with a characteristic chemical composition, crystalline structure, color, and

hardness. Minerals in soil originate from the breakdown of rocks. Organic matter orig-

inates from the decay of dead plants and animals. Rocks are consolidated or

unconsolidated aggregates of minerals or biological debris.

Three generic rock families exist: sedimentary, igneous, and metamorphic.

Sedimentary rocks cover about 75 percent of the Earth’s surface and form primarily

on land and the ﬂoors of lakes and seas by the slow, layer by layer deposition and

cementation of carbonates, sulfates, chlorides, shell fragments, and fragments of exist-

ing rocks. An example of a sedimentary rock is chalk, made of skeletons of

microorganisms. Igneous rocks (“rocks from ﬁre” in Greek) form by the cooling of

magma, which is a molten, silica-rich mixture of liquid and crystals. Igneous rocks can

form either on the Earth’s surface following a volcanic eruption or beneath the surf

ace

when magma is present. Granite is an igneous rock. Metamorphic rocks (rocks that

“change in form”) result from the structural transformation of existing rocks due to

high temperatures and pressures in the Earth’s interior. During metamorphosis, no rock

melting or change in chemical composition occurs; elements merely rearrange them-

selves to form new mineral structures that are stable in the new environment. Marble

is a metamorphic rock.

Breakdown of Rocks to Soil Material

Breakdown of rocks to soil material occurs primarily by physical weathering.

Physical weathering is the disintegration of rocks and minerals by processes that do

not involve chemical reactions. Disintegration may occur when a stress is applied to a

rock, causing it to break into blocks or sheets of different sizes and ultimately into ﬁne

soil minerals. Stresses arise when rocks are subjected to high pressure by soil or other

rocks lying above. Stresses also arise when rocks freeze then thaw or when saline

solutions enter cracks and cause rocks to disintegrate or fracture. Salts have higher

thermal expansion coefﬁcients than do rocks, so when temperatures increase, salts

within rock fractures expand, forcing the rock to open and break apart. One source of

salt for rock disintegration is sea spray transported from the oceans. Another source is

desert salt (from deposits) transported by winds. Physical weathering of rocks on the

Earth’s surface can occur by their constant exposure to winds or running water.

Another process that causes some rocks to break down and others to reform is

chemical weathering. Equation 3.20, which showed calcium carbonate breaking

down on reaction with dissolved carbonic acid, was a chemical-weathering reaction.

Another chemical weathering reaction is

CaSO

2H

O(s)

2

 SO

2

 2H

O(aq)

Calcium sulfate Calcium Sulfate Liquid (5.1)

dihydrate (gypsum) ion ion water

which occurs when gypsum dissolves in water. Alternatively

, when high sulfate and

calcium ion concentrations are present in surface or groundwater, Reaction 5.1 can

proceed to the left, producing gypsum. Gypsum can form when sulfate-containing par-

ticles from the air dissolve in stream water containing calcium ions. Crystalline

gypsum can also form when sea-spray drops, which contain calcium, collide with vol-

canic aerosol particles, which contain sulfate.

120 ATMOSPHERIC POLLUTION: HISTORY, SCIENCE, AND REGULATION

Types of Minerals in Soil Dust

Table 2.2 showed the most abundant elements in the Earth’s continental crust. Soil-

dust particles, emitted from the top layer of the crust, contain minerals made of these

elements and organic matter. Minerals in soil include quartz, feldspars, hematite, cal-

cite, dolomite, gypsum, epsomite, kaolinite, illite, smectite, vermiculite, and chlorite.

Pure quartz [SiO

(s)] is a clear, colorless mineral that is resistant to chemical

weathering. The Greeks thought it was a frozen water, and its name originates from the

Saxon word querkluftertz, which means “cross-veined ore.”

Feldspars, which make up at least 50 percent of the rocks on the Earth’s surface,

are by far the most abundant minerals on Earth. The name feldspar originates from the

Swedish words feld (“ﬁeld”) and spar (the name of a mineral commonly found overly-

ing granite). Two common types of feldspars are potassium feldspar [KAlSi

(s)]

and plagioclase feldspar [NaAlSi

-CaAl

(s)].

Hematite [Fe

(s)] (Greek for “bloodlike stone”) is an oxide mineral because it

includes a metallic element bonded with oxygen. The iron within it causes it to appear

reddish-brown.

Calcite [CaCO

(s)] and dolomite [CaMg(CO

)

(s)] are carbonate minerals. The

name calcite is derived from the word calcspar, which was derived from the Greek

word for limestone, khálix. Dolomite is similar in form to calcite. It was named after

French geologist and mineralogist Silvain de Dolomieu (1750–1801).

Gypsum [CaSO

-2H

O(s)] and epsomite [MgSO

-7H

O(s)] are two of only a

handful of sulfate-containing minerals. Gypsum, which is colorless to white, was

named after the Greek word gypsos (“plaster”). Epsomite was named after the location

it was ﬁrst found, Epsom, England. As seen in Table 2.2, sulfur is not an abundant

component of the Earth’s crust.

Kaolinite, illite, smectite, vermiculite, and chlorite are all clays, which are odorous

minerals resulting from the weathering of rocks. Clays are usually soft, compact, and

composed of aggregates of small crystals. The major components of clays are oxygen,

silicon, aluminum, iron, and magnesium. Kaolinite [Al

(OH)

(s) in pure form]

was named after the Chinese word kauling (“high ridge”), which is the name of a hill

near Jauchu Fa, where clay for the manufacture of porcelain was dug. Early porcelain

clay was called kaolinite. Illite is a mineral group name, originating from the state

name for Illinois, where many illite minerals were ﬁrst studied. Smectite is a mineral

group name, originating from smectis, a Greek name for “fuller’s earth.” Vermiculite

is a mineral group name that originates from the Latin word vermiculari (“to breed

worms”), which refers to the mineral’s ability to exude wormlike structures when

rapidly heated. Chlorite is a mineral group name, originating from the Greek word for

green, which is the common color of this group of clays.

In addition to containing minerals, soils contain organic matter, such as plant litter

or animal tissue broken down by bacteria.

Soil dust, which consists of the minerals and organic material making up soil, is

lifted into the air by winds. The extent of lifting depends on the wind speed and

particle mass. Most mass of soil dust lifted into the air is in particles larger than 1 m

in diameter; thus, soil-dust particles are predominantly coarse-mode particles. Those

larger than 10 m fall out quite rapidly, but those between 1 and 10 m can stay in

the air for days to weeks or longer, depending on the height to which they are

originally lifted. Table 5.4 shows the time required for particles of different diameters

to fall 1 km in the air by sedimentation. The table indicates that particles 1 m in

diameter fall 1 km in 328 days, whereas those 10 m in diameter fall 1 km in

AEROSOL PARTICLES IN SMOG AND THE GLOBAL ENVIRONMENT 121

Figure 5.3. Dust storms originating from northwest Africa and Portugal/Spain, captured by

SeaWiFS satellite, February 28, 2000. Courtesy of SeaWiFS Project, NASA/Goddard Space

Flight Center and ORBIMAGE.

3.6 days. Although most soil-dust particles are not initially lofted more than 1 km in

the air, many are, and these particles can travel long distances before falling to the

ground.

Source regions of soil dust on a global scale

include deserts (e.g., the Sahara in North Africa, Gobi

in Mongolia, Mojave in southeastern California) and

regions where foliage has been cleared by biomass

burning and plowing. Figure 5.3 shows a satellite

image of soil-dust plumes originating from the

Sahara Desert. Soil dust also enters the air when off-

road and agricultural vehicles drive over loose soil or

when on-road vehicles resuspend soil dust. Dust is

also resuspended during construction or demolition.

Fifty percent of all soil dust emitted may be due to

anthropogenic activities (Tegen et al., 1996).

122 ATMOSPHERIC POLLUTION: HISTORY, SCIENCE, AND REGULATION

Table 5.4. Time for Particles to Fall 1

km in the Atmosphere by

Sedimentation Under Near-Surface

Conditions

0.02 228 years

0.1 36 years

1.0 328 days

10.0 3.6 days

100.0 1.1 hours

1,000.0 4 minutes

5,000.0 1.8 minutes

Particle Diameter (m) Time to Fall 1 km

AEROSOL PARTICLES IN SMOG AND THE GLOBAL ENVIRONMENT 123

5.2.1.3. Volcanic Eruptions

The word volcano originates from the ancient Roman god of ﬁre Vulcan, after

whom the Romans named an active volcano, Vulcano. Today, more than 500 volcanos

are active on the Earth’s surface. Figure 5.4 shows emissions from the Mount

St. Helens eruption in 1982. Volcanos result from

the sudden release of gases dissolved in magma,

which contains 1 to 4 percent gas by mass. Water

vapor is the most abundant gas in magma, making

up 50 to 80 percent of its mass. Volcanic magma

also contains carbon dioxide [CO

(g)], sulfur dioxide

[SO

(g)], carbonyl sulﬁde [OCS(g)], and molecular

nitrogen [N

(g)]. Lesser gases include carbon

monoxide [CO(g)], molecular hydrogen [H

(g)],

molecular sulfur [S

(g)], hydrochloric acid [HCl(g)],

molecular chlorine [Cl

(g)], and molecular ﬂuorine

(g)].

Volcanos emit particles that contain the elements

of the Earth’s mantle (e.g., Table 2.2). The most

abundant particle components in volcanic eruptions

are silicate minerals (minerals containing Si).

Emitted volcanic particles range in diameter from

smaller than 0.1 to larger than 100 m. As seen in

Table 5.4, particles 100 m in diameter take 1.1

hour to fall 1 km by sedimentation. The only vol-

canic particles that survive more than a few months

before falling to the ground are those smaller than 4

m. Such particles require no less than 23 days to

fall 1 km. Larger volcanic particles fall to the ground

quickly. Volcanic particles of all sizes are also

removed by rain. Volcanic particles contain the com-

ponents listed in Table 5.2.

Volcanic gases, such as carbonyl sulﬁde [OCS(g)] and sulfur dioxide [SO

(g)], are

sources of new particles. When OCS(g) is injected volcanically into the stratosphere,

some of it photolyzes, and its products react to form SO

(g), which oxidizes to gas-

phase sulfuric acid [H

(g)], which nucleates to form new sulfuric acid–water

aerosol particles. A layer of such particles, called the Junge layer, has formed in the

stratosphere by this mechanism (Junge, 1961). The average diameter of these particles

is 0.14 m. Sulfuric acid is the dominant particle constituent, aside from liquid water,

in the stratosphere and upper troposphere. More than 97 percent of particles in the

lower stratosphere and 91 to 94 percent of particles in the upper troposphere contain

oxygen and sulfur in detectable quantities (Sheridan et al., 1994).

5.2.1.4. Biomass Burning

Biomass burning is the burning of evergreen forests, deciduous forests, woodlands,

grasslands, and agricultural lands, either to clear land for other use, stimulate grass

growth, manage forest growth, or satisfy a ritual. Biomass ﬁres are responsible for a

large portion of particle emissions. Such ﬁres may be natural or anthropogenic in ori-

gin. Figure 5.5 shows smoke from a ﬁre set intentionally to burn dry vegetation in

South Africa.

Figure 5.4. Dome-shattering eruption from

Mount St. Helens in the fall of 1982. Photo by

Peter Frenzen, available from Mount St. Helens

National Monument photo gallery.

Figure 5.5. Aircraft photograph of smoldering ﬁre set to burn dry vegetation near Kruger National

Park, South Africa, September 7, 2000. Photo by NASA/GSFC/JPL, MISR, and Air MISR teams.

Biomass burning produces gases, such as CO

(g), CO(g), CH

(g), NO

(g), and

ROGs, and particles, such as ash, plant ﬁbers, and soil dust (Fig. 5.6) as well as organic

matter and soot. Ash is the primarily inorganic solid or liquid residue left after bio-

mass burning, but may also contain organic compounds oxidized to different degrees.

Organic matter (OM) consists of carbon- and hydrogen-based compounds and often

contains oxygen (O), nitrogen (N), etc., as well. It is usually grey (e.g., Fig. 5.5), yel-

low, or brown. Soot contains black carbon (BC) (carbon atoms bonded together)

coated by OM in the form of aliphatic hydrocarbons, polycyclic aromatic hydrocar-

bons (PAHs), and small amounts of O and N (Chang et al., 1982; Reid and Hobbs,

1998; Fang et al., 1999). The ratio of BC to OM produced in smoke depends on tem-

perature. High-temperature ﬂames produce more BC than OM; low-temperature

ﬂames (such as in smoldering biomass) produce less. Because BC is black, the more

BC produced, the blacker the smoke (Fig. 5.7).

Vegetation contains low concentrations of metals, including titanium (Ti), man-

ganese (Mn), zinc (Zn), lead (Pb), cadmium (Cd), copper (Cu), cobalt (Co),

124 ATMOSPHERIC POLLUTION: HISTORY, SCIENCE, AND REGULATION

AEROSOL PARTICLES IN SMOG AND THE GLOBAL ENVIRONMENT 125

(a) (b)

Figure 5.6. Scanning electron microscopy (SEM) images of (a) an ash aggregate, (b) a com-

busted plant ﬁber, (c) an elongated ash particle, and (d) soil-dust particles collected from

forest-ﬁre emissions in Brazil by Reid and Hobbs (1998).

antimony (Sb), arsenic (As), nickel (Ni), and chromium (Cr). These substances

vaporize during burning, then quickly recondense onto soot or ash particles. Young

smoke also contains K



,Ca

2

,Mg

2

,Na



,NH



,Cl



,NO



, and SO

2

(Reid

et al., 1998; Ferek et al., 1998; Andreae et al., 1998). Young smoke particles are

found in the upper-nucleation mode and lower-accumulation mode.

5.2.1.5. Fossil-Fuel Combustion

Fossil-fuel combustion is an anthropogenic emission source. Fossil fuels that pro-

duce aerosol particles include coal, oil, natural gas, gasoline, kerosene, and diesel.

Coal is a combustible brown-to-black carbonaceous sedimentary rock formed by

compaction of partially decomposed plant material. Metamorphisis of plant material to

black coal goes through several stages, from unconsolidated brown-black peat to con-

solidated, brown-black peat coal, to brown-black lignite coal, to dark-brown-to-black

bituminous (soft) coal, to black anthracite (hard) coal. Countries with the largest

bituminous and anthracite coal reserves are the United States (29.8 percent of world-

wide reserves in 2000), Russia (20.5 percent), China (13.4 percent), India (10.2

percent), South Africa (7.7 percent), and Australia (6.9 percent). The United States

doubled coal production between 1923 and 1998. Even at the present rate of recovery,

U.S. reserves will last at least 250 years. Today, more than 25 percent of the world’s

electricity is generated from coal (NMA, 2000).

Oil (or petroleum) is a natural greasy, viscous, combustible liquid (at room tem-

perature) that is insoluble in water. It forms from the geological-scale decomposition

of plants and animals and is made of hydrocarbon complexes. Oil is found in the

Earth’s continental and ocean crusts. Natural gas is a colorless, ﬂammable gas, made

primarily of methane but also of other hydrocarbon gases, that is often found near

petroleum deposits. As such, natural gas is often mined along with petroleum.

Gasoline is a volatile mixture of liquid hydrocarbons derived by reﬁning petroleum.

Kerosene is a combustible, oily, water-white liquid with a strong odor that is distilled

from petroleum and used as a fuel and solvent. Diesel fuel is a combustible liquid

distilled from petroleum after kerosene. Diesel fuel is named after Rudolf Diesel

(1858–1913), the German automotive engineer who designed and built the ﬁrst engine

to run on diesel fuel.

Particulate components emitted during the combustion of fossil fuels include soot

(BC and OM), OM alone, sulfate (SO

2

), metals, and ﬂy ash. Coal combustion

results in the emission of submicron soot, OM, and sulfate and sub/supermicron ﬂy

ash. The ﬂy ash consists of oxygen, silicon, aluminum, iron, calcium, and magnesium

in the form of quartz, hematite, gypsum, and clays. Combustion in gasoline engines

usually results in the emission of submicron OM, sulfate, and elemental silicon, iron,

zinc, and sulfur. Combustion in diesel engines usually results in the emission of these

components plus soot and ammonium. Diesel-powered vehicles emit 10 to 100 times

more particulate mass than do gasoline-powered vehicles; thus, it is harder for diesel-

powered vehicles than for gasoline-powered vehicles to meet particulate emission

standards. In the United States, 99 percent of heavy-duty trucks and buses but only 0.1

percent of light-duty vehicles run on diesel. In Europe, 99 percent of heavy-duty

trucks and buses and 25 percent of light-duty vehicles run on diesel (Cohen and

Nikula, 1999). In the United Kingdom, 80–95 percent of soot originates from diesel

engines (Pooley and Mille, 1999).

126 ATMOSPHERIC POLLUTION: HISTORY, SCIENCE, AND REGULATION

Figure 5.7. Soot emissions from a prescribed burn at Horse Creek Mesa, Big Horn National

Forest, Wyoming, October 9, 1981. Photo by U.S. Forest Service staff, available from the

National Renewable Energy Laboratory.

Most soot from fossil-fuels originates from coal, diesel-fuel, and jet-fuel combus-

tion. Soot emitted during fossil-fuel combustion contains BC covered with a layer of

polycyclic aromatic hydrocarbons (PAHs) and coated by a shell of organic and inor-

ganic compounds (Steiner et al., 1992). In the case of diesel exhaust, the PAHs include

nitro-PAHs (PAHs with nitrogen-containing functional groups), which may be harm-

ful. Most fossil-fuel soot from vehicles is emitted in particles less than 0.2 m in

diameter (Venkataraman et al., 1994; Maricq et al., 1999; ACEA, 1999). Thus, fossil-

fuel combustion usually results in the emission of upper nucleation mode and lower

accumulation mode particles.

5.2.1.6. Industrial Sources

Many industrial processes involve burning of fossil fuels together with metals. As

such, industrial processes emit soot, sulfate, ﬂy ash, and metals. Fly ash from industrial

processes usually contains Fe

(s), Fe

(s), Al

(s), SiO

(s), and various carbona-

ceous compounds that have been oxidized to different de

grees (Greenberg et al.,

1978). Fly ash is emitted primarily in the coarse mode (2.0 m diameter). Metals are

emitted during high-temperature industrial processes, such as waste incineration,

smelting, cement kilning, and power-plant combustion. In such cases, heavy metals

vaporize at high temperatures, then recondense onto soot and ﬂy-ash particles that are

emitted simultaneously. Table 5.5 lists some metals present in ﬂy ash of different

industrial origin.

Of all the metals emitted into the air industrially, iron is by far the most abundant.

Lead, a criteria air pollutant, is emitted industrially from lead-ore smelting, lead-acid

battery manufacturing, lead-ore crushing, and solid waste disposal. Because lead is no

longer used as an additive in gasoline in the United States, its ambient concentrations

have declined since the early 1980s. Lead is still used in gasoline in several countries.

5.2.1.7. Miscellaneous Sources

Additonal particle types in the air include tire-rubber particles, pollens, spores,

plant debris, viruses, and meteoric debris. Tire-rubber particles are emitted due to

the constant erosion of a tire at the tire-road interface. Such particles are generally

larger than 2 m in diameter. Pollens, spores, plant debris, and viruses are biological

particles lifted by the wind. They often serve as sites on which cloud drops and ice

crystals form. A stratosphere source of new particles is meteoric debris. Most

meteorites disintegrate before they drop to an altitude of 80 km. Those that reach the

stratosphere contain iron (Fe), titanium (Ti), and aluminum (Al), among other ele-

ments. The net contribution of meteorites to particles in the stratosphere is small

(Sheridan et al., 1994).

AEROSOL PARTICLES IN SMOG AND THE GLOBAL ENVIRONMENT 127

Smelters Fe, Cd, Zn

Oil-ﬁred power plants V, Ni, Fe

Coal-ﬁred power plants Fe, Zn, Pb, V, Mn, Cr, Cu, Ni, As, Co, Cd, Sb, Hg

Municipal waste incineration Zn, Fe, Hg, Pb, Sn, As, Cd, Co, Cu, Mn, Ni, Sb

Open-hearth furnaces at steel mills Fe, Zn, Cr, Cu, Mn, Ni, Pb

Source Metals Present in Fly Ash

Table 5.5. Metals Present in Fly Ash of Different Industrial Origin

Sources: Pooley and Mille, 1999; Henry and Knapp, 1980; Schroeder et al., 1987; Ghio and

Samet, 1999.