Atmospheric Deposition of Mercury

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Atmospheric Deposition of Mercury

• U. Shankar, J. Hunn and B. LeBron
• Team Project Presentation - ENVR 468
• November 28, 2006

2
Outline

• Background
• Atmospheric Mercury Cycle
• Emission Source Uncertainties
• Bioaccumulation in Fish
• Environmental Regulations
• Data Sources
• Exploratory Data Analysis
• Conclusions

3
Atmospheric Mercury Cycle

• Natural - 20
• Volcanoes
• Degassing from the earths crust
• Release from ores on land and from surface waters
• Anthropogenic - 80
• Electric utilities
• Waste combustors
• Boilers
• Medical waste incinerators
• Total in U.S. 158 T/yr
• Dry and wet removal mainly responsible for Hg in
  water bodies (up to 83 of load in Great Lakes
  up to 50 of load in Chesapeake Bay)

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Forms of Mercury

• Elemental mercury (Hg(0) or Hg0)
• Atmospheric lifetime 1 year
• Globally distributed through large-scale
  atmospheric circulations
• Divalent mercury (Hg(II) and Hg(p))
• Hg(II) is the highly reactive oxidized form
• Hg(p) is the particulate-bound form
• Occur in dissolved state in cloud water
• Gaseous phase deposits out faster (in hours) than
  particle-bound (months)

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Uncertainties in Sources of Deposition

• Uncertainties exist in sources of deposition due
  to
• uncertainties in speciated emissions (Hg(0) vs.
  Hg(II) fractions)
• vastly different atmospheric lifetimes of species
• evasion (re-emission) from the ground and water
  bodies gt
• uncertainty in natural vs. anthropogenic source
  contributions
• Subsequent difficulty in establishing
  source-to-receptor relationships and control
  regulations
• Regional sources implicated as main contributor
  to depositions in modeling studies of long-range
  transport (Constantinou et al., 1995)
• Other models and monitoring studies also point to
  local source contributions to depositions
  (Galbreath and Zygarlicke, 1996 Lindberg and
  Stratton, 1998)

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Bioaccumulation in Fish

• Oxidized Hg(II) deposited to water bodies and
  then to sediment is chemically reduced
• Transformation is through both biotic (enzymatic
  catalysis) and abiotic processes
• End product is methyl mercury (CH3Hg) that
  bioaccumulates in fish (accounts for 100 of Hg
  in fish tissue)
• Hg levels in fish sensitive to various factors
• dissolved oxygen and sulfate in some waters
  (G.L.)
• dissolved organic carbon content in sediment
• exchange rate between sediment and water column

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Regulations Clean Mercury Rule

• No regulations as such, due to source-level
  uncertainties previously mentioned
• Two proposals under Clean Mercury Rule limit Hg
  emissions from power plants
• Controls implemented according to Maximum
  Achievable Control Technology guidelines under
  112 of the Clean Air Act
• If implemented U.S. Hg emissions ? 29 by 2007
• Two-phase reductions first phase is market-based
  cap-and-trade program, including co-benefit
  controls achieved as a result of NOx and SOx
  controls due by 2010 more aggressive reductions
  implemented through CAA 112
• U.S. Hg emissions ? 69 when fully implemented

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Regulations Clean Water Act

• Priority Pollutant Table provides recommendations
  for Hg and CH3Hg
• CH3Hg recommended 0.3 mg/kg in fish and shell
  fish
• Criteria Max Conc. (mg/L) for Hg in fresh water
  1.4 in salt water 1.8
• Criteria Continuous Conc. (mg/L) for Hg in fresh
  water 0.77 in salt water 0.94

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Data Source

• Mercury Deposition Network
• Part of the National Atmospheric Deposition
  Network
• Begun in 1995 with 13 sites
• Now has over 85 stations nationwide
• Independent agencies cover
• capital costs and perform
• sample collection duties

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Data Collection

• Aerochem Metrics model 301
• Collects weekly precipitation samples
• Processed by Frontier Geosciences
• Deposition calculated as
• the product of sample
• Hg concentration and
• total rainfall

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Site Locations
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Applicable Sites
National Atmospheric Deposition Program (NRSP-3).
2006. NADP Program Office, Illinois State Water
Survey, 2204 Griffith Dr., Champaign, IL 61820.
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Spatial Location
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Calculating Seasonal Trends
Fall 2001-2005
Aggregation 100 Days
Mean 4.69
St. Dev. 1.17
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Seasonal Trends
Winter 2004
Spring 2004
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Seasonal Trends
Summer 2004
Fall 2004
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Data Analysis
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Data Analysis, ctd.
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Data Analysis, ctd.
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Yearly Trends
Spring 2003
Spring 2004
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Yearly Trends
Fall 2004
Fall 2005
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Covariance and Error
300 Days
100 Days
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Covariance and Error
Fall
Aggregation 100 Days
C(x,r)0.29exp(-3r/1.3)exp(-3T/250)0.02exp((-3r2
)/(62))exp((-3T2)/(4002)
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Covariance and Error
Fall
Aggregation 300 Days
C(x,r)0.18exp(-3r/2.3)exp(-3T/200)0.02exp((-3r2
)/(52))exp((-3T2)/(4002)
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References
 
 

• Constantinou, E., M. Gerath, D. Mitchell, C.
  Seigneur, and L. Levin, 1994. Mercury from
  Power Plants Environmental Cycling and Health
  Effects. Water Air Soil Pollut. 80325-335.
• EPA, 1997 Chapter 2, Overview of Mercury Fate
  and Transport Mercury Study Report to Congress,
  Volume III, EPA Report No. EPA-452/R-97-005, U.
  S. Environmental Protection Agency,
  http//www.epa.gov/ttn/oarpg/t3/reports/volume3.pd
  f (and references therein)
• Galbreath, K. C., and C. J. Zygarlicke, 1996
  Mercury speciation in coal combustion and
  gasification flue gases, Environ. Sci. Technol.,
  30, 2421-2426.
• Lindberg, S. E., and W. J. Stratton, 1998
  Environ. Sci. Technol., 32, 49-57.
• Lindberg, S.E., O. R. Bullock, D. Ebinghaus, D.
  Engstrom, X. Feng, W. Fitzgerald, N. Pirrone, E.
  Pitsbo, and C. Seigneur, 2006 Ambio (in press).

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Questions?