Transcript ENVS4450 - Robert Morris University

Environmental Modeling
Chapter 12:
Case Studies of Selected Pollutants
Copyright © 2006 by DBS
Quote
“the metal that slipped away”
-from Wisconsin Natural Resources Magazine, Katherine Esposito
Connections
What is a Heavy Metal?
Concepts
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Sources of Mercury
Fate and Transport
Case Studies
History of Global Mercury Pollution
Introduction
Quicksilver!
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1 of only 5 elements that are liquid at room temperature
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Heavy metal?
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Trace metal?
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Pathfinder element?
End
• Review
Sources
Natural (1/3)
• Volcanic eruptions
• Sedimentary erosion
• Emissions from earth’s
crust and ocean
Anthropogenic (2/3)
• Fossil Fuel Burning
• Waste incinerationn
• Mining
• Smelters
• Chlor-alkali Plants
x10
Biosynthetic
• Biological methylation
Mineral: Cinnabar (HgS)
Anthropogenic
Sources
Coal: ~ 1 ppm
Source
Any other material with this
content = hazardous waste
Electrical utilities
52.7
Incinerators
32.2
Coal burning:
residential and
industrial
12.8
Mining
6.7
Chlor-alkali
6.75
Misc
64.1
Total
200.1
Hg from coal burning has
been found at both Poles
Mg/yr
(N. America)
Seigneur et al. 2004
Uses
1. industrial chemicals – e.g. drugs, fungicides, and as a cathode in
chlorine and sodium hydroxide production (chlor-alkali process)
Cl2 ←NaCl → Na
Hg
H2 + NaOH ← Amalgam
Na forms amalgam with Hg,
otherwise Na would explode on
contact with water
2. electronics – switches, batteries, electrodes, mercury vapor +
fluorescent lamps
3. scientific instruments – barometer, thermometer, blood-presure meter
4. pesticides
5. Dentistry – amalgams
6. gold and silver extraction
Pathways
End
• Review
Speciation
Organic
Inorganic
Volatile
Reactive
Elemental Mercury
Mercury Ion Hg2+
Methyl Mercury
Hg0
AKA ‘reactive gaseous’
mercury’ (RGM) e.g. HgCl2(g)
CH3Hg+
Particulate bound
Dimethyl Mercury
Hg-P
CH3HgCH3
Regional
Local
Global
Emisson and Deposition
Mercury deposition is enhanced
by:
Oxidizing species
Particulate matter
Forest cover
Hg0 → Hg2+
‘smog’
Cl.
OH.
Proximity to sources
‘Watershed
Sensitivity’ creates
localized ‘hot-spots’
of Hg accumulation
Fate
Watershed-Lake Cycling
Atmosphere
UV
[O]
1-20
μg m2 yr-1
Waterways
pH/DOC
Fish
USGS
Fate
Both bioaccumulate x106
High: Shark, swordfish, king mackeral,
albacore tuna
Low: shrimp, tilapia, salmon, pollock, catfish
Methylmercury
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Methylmercury is in reality
CH3HgCl and CH3HgOH
– Written:
CH3HgX, MeHg or CH3Hg+
(Misleading since it is covalent)
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Occurs in anaerobic portion of lakes
– degraded by sunlight, most
important sink
Winfrey and Rudd, 1990
Health Effects
Toxicity
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Toxicity: all forms
MeHg >> vapor >> Hg2+ >> liquid
– Liquid Hg is readily excreted
– Hg2+ not readily transported across bio membranes
– Vapor – diffuses from lungs to bloodstream to brain
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Methylmercury is lipophillic (soluble in fatty tissue)
– More mobile – bioconcentrates, bioaccumulates and biomagnifies
– Converted to Hg2+ in brain (neurotoxin)
Usual barrier to Hg2+
is circumvented by
vapor and MeHg
Health Effects
Toxicity
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Pathways: Inhalation, ingestion,
dermal
Most Hg in humans is MeHg from
fish
Target organ: Brain
Symptoms: all brain associated,
may be chronic or acute
- numbness of limbs, loss of
vision, hearing and muscle
coordination
Health Effects
Mode of Action
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Biochemical mode of action: inhibition of enzymes
Affinity for
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-SH (sulfhydryl groups)
Occur in enzymes which control metabolic pathways
M2+ + 2 R-S-H → R-S-M-S-R + 2H+
End
• Review
Case Study
Minamata, 1953
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One of the worst industrial disasters in history
Minamata Bay, Japan. The Chisso Corporation, a fertilizer and later
petrochemical company, was found responsible for polluting the bay
from 1932–1968
Main diet of locals was fish + shellfish – 5-20 ppm (106 water)
Over 3,000 people suffered: Minamata disease / Dancing Cat Disease
various deformities, damage to nervous system, or death
Developing embryos are especially vulnerable
WHO limit 0.5 mg kg-1
Minamata 50 mg kg-1
End
• Review
History of Mercury Pollution
Site: Almadén, Spain
World’s largest Hg mine
Martínez-Cortizas et al., 1999
End
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Pathways
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Acidification of lakes enhances
solubility and methylation rates
Double-whammy effect of burning
fossil-fuels
Conc. Hg in standardized fish in
84 Ontario lakes
Lean, 2003
Pathways
End
• Review
Solutions
• Stop burning coal…not going to happen
• Pollution control measures – oxidation, electrostatic ppt
• Vegetarian fishes!
End
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Further Reading
Journals and Reports
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Betts, K. (2003) Dramatically improved mercury removal. Environmental Science and Technology, pp. 283284A.
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Cleckner, L.B., Garrison, P.J., Hurley, J.P., Olson, M.L., and Krabbenhoft, D.P. (1998) Trophic transfer of
methyl mercury in the northern Florida Everglades. Biogeochemistry, Vol. 40, No. 2-3, pp. 347-361.
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Crenson, S.L. (2002) Study Records Elevated Mercury. Associated Press. Sunday Oct 20th.
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Fitzgerald, W.F., Engstrom, D.E., Mason, R.P., and Nater, E.A. (1998) The case for atmospheric mercury
contamination in remote areas. Environmental Science and Technology, Vol. 32, pp. 1-7.
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Lean, D. (2003) Mercury pollution a mind-numbing problem: high levels of mercury lurk in our water supply,
and it is time to sound a global alarm. Canadian Chemical News, January, p. 23.
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Martínez-Cortizas, A., Pontrevedra-Pombal, X., Garcia-Rodeja, E., Nóvoa-Muñoz, J.C., and Shotyk, W.
(1999) Mercury in a Spanish peat bog: Archive of climate change and atmospheric deposition. Science, Vol.
284, pp. 939-942.
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Pacya, E.G., and Pacya, J.M. (2002) Global emission of mercury from anthropogenic sources in 1995. Water,
Air and Soil Pollution, Vol. 137, pp. 149-165.
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Renner, R. (2004) Mercury woes appear to grow. Environmental Science and Technology, Vol. 38, No. 8, pp.
144A.
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Rouhi, A.M. (2002) Mercury Showers. Chemical and Engineering News. April 15, p. 40
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Sarr, R.A. (1999) New Efforts to Uncover the Dangers of Mercury. New York Times, Health and Fitness
Section, p. D7, Tuesday, November 2.
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Seigneur, C., Vijayaraghaven, K., Lohman, K., Karamchandanai, P., and Scott, C. (2004) Global source
attribution for mercury deposition in the United States. Environmental Science and Technology, Vol. 28, No. 2,
pp. 555-569.
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Winfrey, M.R., Rudd, J.W.M., 1990. Environmental factors affecting the formation of methylmercury in low pH
lakes. Environmental Toxicology and Chemistry, Vol. 9, pp. 853-859.
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Wright, K. (2005) Our Preferred Poison. Discover, March.
Books
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Berry, L.G. and Mason, B. (1959) Mineralogy: Concepts, Descriptions,
and Determinations. W.H. Freeman, San Francisco.
Gribble, C.D. (1978) Rutley’s Elements of mineralogy, 27th edition.
Unwin Hyman, London
HBRF (2007) Mercury Matters. Hubbard Brook Research Foundation.
Movies
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FHS: the Ocean Sink (1990) 29 mins
FHS: Chemicals from NaCl: 1 20 mins
FHS: Salt 1992
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Minamata movie:
http://science.education.nih.gov/supplements/nih2/Chemicals/videos/ac
t5/minamata.htm
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People's Century: Endangered Planet (1999)