Human activities such as burning coal, medical waste, and other materials containing mercury are major contributors to mercury pollution. Mercury enters the environment through air pollution and can harm human health, especially for fetuses and children. The largest source of mercury air pollution is coal-fired power plants, which emit around 70% of the mercury in the US. Capturing mercury from coal plant emissions is challenging given mercury's various chemical forms.

1. MERCURY POLLUTION
I. D. MALL
Professor, Dept. of Chemical Engineering, Indian Institute of Technology, Roorkee
Like all elements, the mercury has also existed on the planet since the Earth was
formed. Mercury moves through the environment as a result of both natural and human
activities. The human activities that are most responsible for causing mercury to enter
the environment are
burning materials (such as batteries), fuels (such as coal) that contain mercury,
171
and
certain industrial processes. These activities produce air pollution containing
mercury.
HOW MERCURY ENTERS THE ENVIRONMENT
Standard Information
Atomic number : 80
Atomic symbol : Hg
Atomic weight : 200.59
Group number : 12
Period number : 6
Standard state : liquid at 298 K
Color : silvery white
Highest specific gravity (among liquids)
Temperature : Specific gravity
0oC : 13.595
20oC : 13.595
100oC : 13.352

2. Freezing point : -38.89oC
Boiling point : 357.25oC
Vapour pressure : 0oC : 0.00019 mm Hg
20oC : 0.0012 mm Hg
Mercury
Inorganic Mercury
Compounds
• Mercuric sulfide,
• Mercuric chloride
• Mercury oxide
etc.
172
Heat of Vapourization: 16.46 KJ/mol
Mercury has high ionization potential
Ist 10.39 eV
IInd 18.65 eV
IIIrd 34.3 eV
Due to this mercury forms various compounds with active reagents, such as,
oxygen, acids etc.
Mercury is a good conductor of heat.
Mercury is a fair conductor of electricity.
Mercury works well with other metals, especially the amalgams.
High Electro – and heat conductivity, significant chemical stability
Catalytic Properties: Production of acetaldehyde from acetylene, analysis of organic
substances for the determination of nitrogen
Mercury vapour density is around 7 times heavier than air.
Vapourization: Colourless vapour in air, no odour, so illusion that it is not present
in the air. Mercury vapour: Dermal rate penetration.
As temperature rise from 20 to 30oC, vapour pressure increases and consequently
increase in concentration of mercury in air by 2.32 times.
30 – 40oC – at its own surface, concentration of mercury exceeds the maximum
permissible quantity for industrial sites 3000 – 6000 times.
TYPES OF MERCURY COMPOUNDS
Mercury is a naturally occurring element that is found in air, water and soil. It exists in
several forms:
Elemental/ or
Metallic Mercury
INORGANIC MERCURIC COMPOUNDS
Organic Mercury
Compounds
•Methyl mercury
•Ethyl mercury
•Dimethyl mercury
•Phenyl mercury
These include mercuric sulfide (HgS), mercuric oxide (HgO) and mercuric
chloride (HgCl2).
Also called mercury salts.
Most inorganic mercury compounds are white powders or crystals, except for
mercuric sulphide, which is red and turns black after exposure to light.

3. Some mercury salts (such as HgCl2) are sufficiently volatile to exist as an
173
atmospheric gas.
Water solubility and chemical reactivity of these inorganic (ionic) mercury
gases lead to much more rapid deposition from the atmosphere than for
elemental mercury. This results in significantly shorter atmospheric lifetimes for
these ionic (e.g. divalent) mercury gases than for the elemental mercury gas.
ORGANOMERCURIALS
When mercury combines with carbon, the compounds formed are called
organic mercury compounds or organomercurials.
e.g. dimethyl mercury, phenyl mercury, ethyl mercury and methyl mercury).
The most common organic mercury compound in the environment is methyl
mercury.
Like the inorganic mercury compounds, both methyl mercury and phenyl
mercury exist as salts (for example, methyl mercuric chloride or phenyl
mercuric acetate).
When pure, most forms of methyl mercury and phenyl mercury are white
crystalline solids. Dimethyl mercury, however, is a colourless liquid.
HEALTH EFFECTS
An exposure to the various forms of mercury will harm a person's health depends on a
number of factors. The factors that determine how severe the health effects are from
mercury exposure include these:
the chemical form of mercury (methylmercury is more toxic than elemental
mercury);
the dose; the amount of chemical entering the body
the age of the person exposed (the fetus is the most susceptible);
the duration of exposure;
the route of exposure -- inhalation, ingestion, dermal contact, etc.; and
the health of the person exposed.
MERCURY POISONING CAUSES
impaired neurological development in fetuses, infants, and children
impairment of the peripheral vision;
disturbances in sensations (pins and needles feelings, usually in the hands,
feet, and around the mouth);
lack of coordination of movements; impairment of speech, hearing, walking;
and muscle weakness
Elemental mercury poisoning causes motional changes (e.g., mood swings,
irritability, nervousness, excessive shyness);
insomnia;
neuromuscular changes (such as weakness, muscle atrophy, twitching);
headaches;
disturbances in sensations; changes in nerve responses; performance
deficits on tests of cognitive function.
At higher exposures there may be kidney effects,
respiratory failure and death.

4. Symptoms of high exposures to inorganic mercury include: skin rashes
and dermatitis; mood swings; memory loss; mental disturbances; and
muscle weakness
HLL closed the factory in May 2001 after the
local people, led by environmental groups,
brought to the notice of the Tamil Nadu
Pollution Control Board (TNPCB) the fact that
the company had dumped 7.4 tonnes of
mercury-contaminated glass waste at its
scrapyard, in the slopes in Munjikal, below the
rear wall of the factory. One gram of mercury
let into a 10-hectare lake for a few years can
poison it completely.) The scrap yard is located
in a crowded area of the town. Subsequently, the
TNPCB issued notice to the company to refrain
from carrying out any activity at the plant site. It
also cut water and power supply to the factory
The Factories Act, 1948 : The second schedule
Permissible Levels of certain Chemical substances in work Environment
Permissible limits of exposure
(mg/m3)
Short term exposure
limit (15 min)
Time weighted avg.
concentration (8h)
Substance
Mercury (as Hg) – skin
(i) Alkyl compounds 0.01 0.03
174
Mercury-contaminated glass
waste being packed at HLL's
scrapyard for shipment to
the United States, on the
orders of the Tamil Nadu
Pollution Control Board in
March.
The glass waste in the
scrapyard at HLL
(ii) All forms except 0.05 -
alkyl vapour

5. EPA daily exposure limit of Methyl Mercury
microgram (μg) /per kilogram (2.2 lbs)/ per day.
Assumes inhalation or ingestion, and not INJECTION.
Also assumes low background exposures not large bolus doses.
Different Emission Sources Causes Mercury Pollution
Combustion Manufacturing Miscellaneous
Utility Boilers Chlor-alkali production
Paints use Commercial/industrial boilers Lime manufacturing Mercury catalysts
175
Electric lamp
breakage
Carbon Hazardous waste black production
combustors
Landfills
Electrical apparatus Turf products
manufacturing
Sewage sludge
incinerators
Agricultural
burning
Geothermal power
plants
Mobile sources Medical waste incinerators Battery production
Explosives
manufacturing
Mercury compounds
production
Dental Municipal waste combustors
preparations
Primary mercury Pigment production
production
Laboratory use Residential boilers
Oil shale retorting
Area Point

6. Area Point
Combustion Manufacturing
Sludge application Byproduct coke production
Total
amount of
mercury
Number
of units
produced
450,000 70 tonnes
Some leading mercury users in India (1998-2001)
Sector Mercury (Hg) content per unit
About 200 gm mercury used per tonne of caustic tonnes/year soda produced.
All this mercury is passed on to the environment through emissions and
products.
Varies between 0.6 to 1 gm. 8957,0002 7.2 tonnes
Chlor-alkali
Thermo
meters
Batteries • Alkaline Not more than 25 mg NA
Total 33 to 50 per cent by weight of the battery 1,650 million3 25 tonnes5 Mercury
Zinc
Total 1per cent Hg by (LeClanche) weight of the battery NA
Zinc
Carbon
Fluorescent lamps 0.0252 to 0.080 gm / lamp6 150 million3 7.89 tonnes
Between 3 gm to 6gm6 4051,0004 18.23 tonnes Thermostat
switches
Average 0.6 or 0.7 gm per unit 1481,0002 0.96 tonnes
Alarm
clocks
0.4 gm per unit6 95,5003 0.04 tonnes Hearing
aids
Average annual mercury emissions
between 1991-92 and 2000-2001
176
Primary copper smelting
Cement manufacturing
Petroleum refininga
Instrument manufacturing
Secondary mercury
production
Zinc mininga
Fluorescent lamp recycling
Pulp and paper mills
Wood-fired boilers
Residential woodstoves
Crematories
Source: 1. Environmental Rating of Indian Caustic-Chlorine Sector, Green Rating Project ,(2002),Centre for Science and Environment.
2. Industrial Handbook, Centre for Industrial Economic Research (Delhi), 1998
3. Industrial Handbook, Centre for Industrial Economic Research (Delhi), 2000-01
4. http://www.indiainfoline.com/auto/db01.html
5. Telephonic conversation with Battery Industry official
6. Draft Wisconsin Mercury Sourcebook, Wisconsin Department of Natural Resources (USEPA grant), May 1997

7. Point Source Estimate of Mercury Discharge in the U.S.
Source: U.S. EPA, Office of Air Quality Planning and Standards. 1999 National
EmissionsInventory for Hazardous Air Pollutants.
http://www.epa.gov/ttn/chief/net/1999inventory.html#final3haps
MERCURY EMISSIONS FROM COAL -FIRED POWER PLANTS
Interesting facts about Coal-fired Power Plants and Mercury Pollution
Coal-fired power plants are the single largest source of mercury pollution
According to the US National Wildlife Federation (NWF), a single 100
megawatt (MW) coal-fired power plant emits approximately 25 pounds of
mercury a year.
According to the US Center for Clean Air Policy, 50% of the mercury emitted
from coal-fired power plants can travel up to 600 miles from the power plant.
According to NWF, as little as 0.002 pounds of mercury a year can contaminate
a 25-acre lake to the point where fish are unsafe to eat.
Coal Plants are Largest Mercury Source
Methylmercury contamination in food sources as low as one part per million has
been shown to cause death in some some animals.
The majority of the mercury entering lakes, streams, rivers, and oceans comes
from the atmosphere (i.e. air deposition)
85% of mercury emissions come from smokestacks, primarily power plants and
municipal and medical waste incinerators
177

8. 33% of all mercury emissions comes from utility boilers (coal- and oil-fired),
Source Tons/yr Percent(%)
Asia 860 58
Africa 197 13
Europe 186 13
N. America 105 7
Australia 100 7
S. America 27 2
178
the largest unregulated source.
Mercury Pollution Per Year
70% from Coal-fired Power Plants
ENVIRONMENTAL ISSUES WITH COAL AS FUEL
Burning coal without increasing global carbon dioxide levels is a major
technological challenge
Coal when burnt gives rise to a variety of wastes which must be accounted and
controlled
Mercury, NOx, SOx and Solid Particulate Matters in the form of ash are the
main pollutants
Solid and fly ash quantify as high as 50% of Indian Coal
Global warming associated with emission of CO2, NOx is a major issue with
world community
Burning coal without increasing global carbon dioxide levels is a major
technological challenge

9. Coal when burnt gives rise to a variety of wastes which must be accounted and
Year 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005
Consumption 332.2 358.5 362.9 375.4 406.1 413.6 430.6 430.6 N/A N/A
179
controlled
Worldwide Distribution of Mercury Emissions
Source: United Nations Environment Programme Global Mercury Assessment, 2002,
Mercury in Coal
Coal Production and Consumption in India, 1996-2005 (in millions of short tons)
n/a - not applicable
N/A – not available
412.95
n/a
382.61
24.34
389.20
n/a
361.24
27.96
367.29
n/a
341.27
26.02
352.60
n/a
327.79
24.81
337.94
n/a
313.69
24.25
326.58
n/a
304.10
22.48
319.93
n/a
296.51
23.42
323.63
n/a
300.40
22.23
311.96
n/a
289.32
22.64
295.56
n/a
273.41
22.15
Production
Anthracite
Bituminous
Lignite

10. note: components may not add to total due to rounding
Source: Government of India
Behavior of Mercury in Coal-fired Boilers
APCD
Entrained PM Inlet
140 °C
HCl N2 Hg
Mercury Partitioning
Mass Fraction
Hgo, Hg2+ compounds, particulate mercury Hg(p)
180
1500 °C
Hg°
Coal
MERCURY CAPTURE
CO2
H2O
SO2
NOx
Thermochemical Equilibrium
Calculations
HgCl Hg° 2
HgO
0 300 600 900 1200
Temperature, °C
Factors Affecting Speciation
Type and properties of coal
Time/temperature profile
Composition of flue gas
Fly ash and sorbent properties
Flue gas cleaning conditions
Hg(p) easily captured by electrostatic precipitators (ESPs) and fabric filters
(FFs)
Hg 2+ compounds are relatively soluble and can generally be captured in
scrubbers
Hg° is insoluble and must be adsorbed onto solids or converted to Hg 2+ for
capture by scrubbing
Typical Hg2+ to Hg° ratio in flue gas: bituminous coal subbituminous coal
lignite
SOURCE OF MERCURY IN COAL-FIRED THERMAL POWER PLANT
Mercury exists in trace amounts in fossil fuels (e.g., natural gas, oil, and coal),
vegetation, crustal material, and waste products. Through combustion, mercury vapor
can be released to the atmosphere, where it can drift for a year or more, spreading with
air currents over vast regions of the globe. In 1995, an estimated 5,500 tons of mercury
was emitted globally from both natural and anthropogenic sources.

11. ENVIRONMENTAL IMPACT OF CEMENT MANUFACTURE
181
INTRODUCTION
Major environmental issues are dust pollution of the atmosphere and
emission of Green House Gases (GHG), ecological concern arising from
the degradation of mined-out areas, noise transport pollution and
emission of mercury.
GHG emission from cement industries is about 1.4 x 103 million tonne of
CO2 equivalent against the total world greenhouse gas emissions of 44 x
103 million tonne of CO2 equivalent.
Cement related GHG emissions originate from
fossil fuel combustion at cement manufacturing operation (40%)
transport activities (5%)
combustion of fossil fuel that is required to make the electricity
(5%).
manufacturing process (about 50%)
Cement consumption 1985-2020E (million t)
Continent 1985 2003 2020 % pa growth 03 -20
Developed countries 323 410.5 475 0.80 %
Developing countries 363.7 1202.5 2586.5 4.30 %
Total 686.7 1612.9 3061.5 3.60 %

12. PRODUCT LIFE CYCLE OF CEMENT
Environmental Impact of Cement Manufacture
Energy Energy
EIA/LCA
MERCURY EMISSION FROM POWER PLANTS
Case study: Mercury Emissions from Thermal Power Plants, Singhrauli, M.P.
The Singhrauli area is a major site of thermal power generation in the country at
Present. Govind Ballabh Paant Sagar lake is surrounded by the super thermal
powerPlants(STPP) namely Singhrauli STPP, Vindhayachal SSTP, Rihand STPP,
Anpara A B STPP, Renusagar STPP. Besides Hindalco, High Tech Carbon and
Kanoria Chemical Industrial Units, which contribute towards thermal, chemical and
industrial effluents alongwith airborne pollutants.
The Power Plant Combustion Waste Stream (CW)
182
RAW MATERIAL
MINING
CLINKER
PRODUCTION
CLINKER
PRODUCTION
TRANSPORATION
CONCRETE
STRUCTURE
ITS USE
DEMOLITION
RECYCLE
Energy Energy Energy
Waste Waste
Waste Waste Waste
AIR POLLUTION: Particulate and Fugitive
emission,SOx, NOx.
PLANT PROCESS
Raw Material Preparation, Crushing and
Grinding, Pyroprocessing, Clinker Cooling,
Clinker and Gypsum grinding.
RAW MATERIAL MINING
Lime Stone, Laterite, Bauxite, Gypsum, Coal.
STORAGE AND TRANSPORTATION OF
FINISHED PRODUCT
AIR POLLUTION: Particulates, Fugitive
emission,SOx, NOx.
SOLID WASTE: Fly Ash, ETP Sludge, rejects.
ACIDIFICATION
CO2 EMMISSION
WATER POLLUTION: BOD, COD, TSS.
AIR POLLUTION: Particulate and Fugitive
emission.

13. This waste stream already contains about 40% of the mercury in coal mined for
20 g Elemental Hg (v)
60 g HgCl2 (v)
20 g HgCl2 (particle-bound)
183
power production.
Considerable evidence suggest that federal and state regulation of how these
wastes are managed does not adequately protect the environment.
Small amounts of mercury are contained in several waste types:
Flyash
Scrubber sludge
Active mercury control sorbents
Bottom ash
How Far does Mercury Travel in the Atmosphere emitted by coal-fired thermal
power plant?
EPA estimates 7 to 45% of mercury released from power plants is deposited
within a 30-mile radius.
The stack height at each plant, the chemical species of the mercury, and the
amount of rainfall at a given site all affect how much mercury is deposited
around the plant.
As shown in the table (next slide), power plants with shorter stacks will have
more local deposition than those with taller stacks, and more mercury is
deposited locally in a humid site compared to an arid site.
EPA’s Mercury Emissions Partitioning
Assume
100 g Total Hg
Global Cycle
64% Loss
Global Cycle
99% Loss
40.8 g HgCl2 (v)
Deposited
Only 48.2 g Total Hg Deposited
7.2 g HgCl2 (p-b)
Deposited
Global Cycle
32% Loss
1%
0.2 g Elemental Hg (v)
Deposited
Hazardous Waste
Combustion
Facility
36%
68%
Emission Rates
Hg0 = 0.2% of Total Hg
HgCl2 = 48% of Total Hg
Vapor Phase Fractions, Fv
Fv for Hg0 (0.2/0.2) = 1.0
Fv for HgCl2 (40.8/48.0) = 0.85

14. Elemental Mercury Phase, Upon Deposition
Hg0 (v) = 0.2% of Total Hg Emitted
Negligible Contribution to Soils, Water Bodies, and Plants Assumed
Only Direct Inhalation of Vapor is Evaluated for Elemental Mercury
Mercuric Chloride Phases, Upon Deposition
HgCl2 (v, particle-bound) = 48% of Total Hg emitted
Significant Contribution to Soils and Water
Direct Inhalation and Indirect Pathways are Evaluated for Mercuric Chloride
MERCURY TRANSPORT FATE: AFTER DEPOSITION
Deposition to Soils Water Body
= (7.2g HgCl2)pb + (40.8g HgCl2 + 0.2 g Hg0)v
Runoff
Ksr
Points in controlling Mercury pollution in coal-fired thermal power plant
The capture of mercury across existing air pollution control devices
(APCD) can vary significantly based on coal properties, fly ash
properties including unburned carbon, specific APCD configurations,
and other factors. ICR data indicates that for
For pulverized coal (PC) units (the predominant technology currently
used for electricity generation) the greatest co-benefit mercury control is
realized for bituminous-fired units equipped with a fabric-filter
baghouse (FF) for PM control and either wet flue gas desulfurization
(FGD) or spray dryer absorber (SDA) for SO2 control.
184
Volatilization
Ksv
Leaching
Ksl
Soil Losses
Ks = Ksg + Kse + Ksr + Ksl + Ksv
Runoff Load
Lri + Lr
Erosion Load
Le
Cs 98% HgCl2
2% MeHg
Cw 85% HgCl2
15% MeHg
Erosion
Kse
Total Load to Water Body
Ltotal = Ldep + Ldiff + Lri + Lr + Le
Prior to Soil Losses
47g HgCl2; 0.96g MeHg
Prior to Loads from Soils
40.8g HgCl2; 7.2g MeHg

15. The worst performing bituminous-fired PC units were equipped only
with a hot-side electrostatic precipitator (ESP).
Units burning subbituminous and lignite coals frequently demonstrated
significantly worse mercury capture than a similarly equipped
bituminous-fired unit.
For example, Figure 3 on previous slide presents the percent mercury
removal for bituminous, lignite, and subbituminous coal-fired plants
with cold-side ESPs.
Plants that burn bituminous coal typically have higher levels of oxidized
mercury than plants that burn lignite or subbituminous coal, possibly
due to the higher chlorine and/or sulfur content of bituminous coal.
185
Control technologies in use today
On average across U.S. coal-fired power plants, current technologies being used
to reduce particulate, NOx and SO2 emissions capture about 40% of the
mercury that enters the boilers with the coal.
However, the removal rate of mercury for any particular plant can vary from
10% to over 90%, depending on the type of coal and the air pollution control
device used.
In addition, a significant fraction of the eastern bituminous coal burned in
power plants is cleaned before it is shipped to the plant, and this process
removes, on average, 25-35% of the mercury in the coal.
Effectiveness of these technologies in reducing mercury emissions
The primary factors that affect the capture of mercury by existing air pollution
controls are the coal burned and the type of air pollution (NOx, SO2, particulate)
controls used at the plant.
Mercury in the flue gas appears as a mix of elemental (or metallic, non-water
soluble) and oxidized (water soluble) mercury, depending primarily on the coal
and to a lesser extent on the design of the boiler.
Some controls, such as scrubbers for SO2 reduction, capture only oxidized
mercury.
In some cases, selective catalytic reduction (SCR) for NOx control may increase
the percent of the mercury that is in the oxidized form, enabling a downstream
scrubber (if present at the power plant) to capture more of the mercury.
Coals and boilers that result in increased levels of carbon leaving the boiler
unburned tend to produce a fly ash that may adsorb some of the mercury.
The amount that would be adsorbed and subsequently captured by the
particulate control depends on the technology used – electrostatic precipitators
or bag houses – due to the difference in how the fly ash and flue gases contact
each other in these devices.
All these interactions depend on complex chemical reactions between various
species in the flue gas, especially chlorine, but we do not yet totally understand
this chemistry.

16. 186
Key findings of ITRC, Lucknow
Out of total 100 vegetable samples. 23% samples had mercury levels higher
than permissible limit
Mean mercury level; were significantly higher (p 001) food crops obtained
from Singhrauli region than mean levels of the samples collected from the
control areas.
Out of forty samples of drinking water collected from Singhrauli region, Six
samples showed higher values than the permissible level of 1 μg/l.
The mean mercury values of (30 samples) of mercury in fish collected from
Singrauli region were significantly higher (p 001) than the mean values of fish
collected from control areas.
19 milk samples out of 22 samples collected from the Singhrauli region had
mercury levels higher than the permissible levels of 3 μg/l.
http://www.cseindia.org/dte-supplement/70-71SPR.PDF

17. Summary of Pollution Sources Control : Techniques for Mercury
187
Restriction
without
pretreatment
like
recycling/sanitar
y-land fill, etc.
Solid waste
dumping
Process
change/restrictio
n in use of Hg
Process Pulp paper
change/use of
ventury
scrubber
Chlor-alkali
industries
Air pollution
control
Air borned Hg
particulate
deposition
Ion
exchange/neutra
lization
sedimentation
Mining
smelting
battery
Mercury E/P bughouse
Battery cell
Restriction in
use in
agriculture
Use as herbicide
Insecticide
Process
change/properly
designed tailings
disposal sys.
Chlor-alkali
industries
Conditioning of
Hg in
refrigeration
unit followed by
EP
Hg Mining
smelting
Control
measures
Control Soil pollution
measures
Water pollution
source
Control
measures
Air pollution
source