Modeling the Atmospheric Transport and Deposition of Mercury

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Modeling the Atmospheric Transport and
Deposition of Mercury
Dr. Mark Cohen NOAA Air Resources Laboratory 1315
East West Highway, R/ARL, Room 3316 Silver
Spring, Maryland, 20910 301-713-0295
x122 mark.cohen_at_noaa.gov http//www.arl.noaa.gov/
ss/transport/cohen.html
Materials assembled for Mercury in Maryland
Meeting, Appalachian Lab, Univ. of Maryland
Center for Environmental Science 301 Braddock
Road, Frostburg MD, Nov 2-3, 2005
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• What do atmospheric mercury models need?

• Atmospheric mercury modeling

• Why do we need atmospheric mercury models?

• Some preliminary results
• Model evaluation
• Source Receptor Information

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• What do atmospheric mercury models need?

• Atmospheric mercury modeling

• Why do we need atmospheric mercury models?

• Some preliminary results
• Model evaluation
• Source Receptor Information

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Atmospheric Mercury Fate Processes
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NOAA HYSPLIT MODEL
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• What do atmospheric mercury models need?

• Atmospheric mercury modeling

• Why do we need atmospheric mercury models?

• Some preliminary results
• Model evaluation
• Source Receptor Information

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Why do we need atmospheric mercury models?

• to get comprehensive source attribution
  information ---
• we dont just want to know how much is
  depositing at any given location, we also want to
  know where it came from
• to estimate deposition over large regions,
• because deposition fields are highly spatially
  variable,
• and one cant measure everywhere all the time
• to estimate dry deposition
• to evaluate potential consequences of alternative
  future emissions scenarios

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But modelsmust have measurements
Modeling needed to help interpret measurements
and estimate source-receptor relationships
Monitoring required to develop models and to
evaluate their accuracy
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• What do atmospheric mercury models need?

• Atmospheric mercury modeling

• Why do we need atmospheric mercury models?

• Some preliminary results
• Model evaluation
• Source Receptor Information

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What do atmospheric mercury models need?
Emissions Inventories
Meteorological Data
Scientific understanding of phase partitioning,
atmospheric chemistry, and deposition processes
Ambient data for comprehensive model evaluation
and improvement
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Why is emissions speciation information critical?
Logarithmic
Hypothesized rapid reduction of Hg(II) in plumes?
If true, then dramatic impact on modeling
results
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Atmospheric Chemical Reaction Scheme for Mercury
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Some Additional Measurement Issues (from a
modelers perspective)

• Data availability
• Simple vs. Complex Measurements

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Some Additional Measurement Issues (from a
modelers perspective)

• Data availability
• Simple vs. Complex Measurements

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Data availability
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Some Additional Measurement Issues (from a
modelers perspective)

• Data availability
• Simple vs. Complex Measurements

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Simple vs. Complex Measurements 1. Wet
deposition is a very complicated phenomena...
?

• many ways to get the wrong answer incorrect
  emissions, incorrect transport, incorrect
  chemistry, incorrect 3-D precipitation, incorrect
  wet-deposition algorithms, etc..

?
?
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Simple vs. Complex Measurements 2. Potential
complication with ground-level monitors...
(fumigation, filtration, etc.)...
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• Simple vs. Complex measurements - 3. Urban areas
• Emissions inventory poorly known
• Meteorology very complex (flow around buildings)
• So, measurements in urban areas not particularly
  useful for current large-scale model evaluations

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Simple vs. Complex Measurements 4 extreme
near-field measurements
Sampling site?
Ok, if one wants to develop hypotheses regarding
whether or not this is actually a source of the
pollutant (and you cant do a stack test for some
reason!).

• Sampling near intense sources?
• Must get the fine-scale met perfect

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Complex vs. Simple Measurements 5 Need some
source impacted measurements

• Major questions regarding plume chemistry and
  near-field impacts (are there hot spots?)
• Most monitoring sites are designed to be
  regional background sites (e.g., most Mercury
  Deposition Network sites).
• We need some source-impacted sites as well to
  help resolve near-field questions
• But not too close maybe 20-30 km is ideal (?)

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• What do atmospheric mercury models need?

• Atmospheric mercury modeling

• Why do we need atmospheric mercury models?

• Some preliminary results
• Model evaluation
• Source Receptor Information

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Participants
D. Syrakov .. Bulgaria. NIMH A.
Dastoor, D. Davignon Canada...... MSC-Can J
. Christensen . DenmarkNERI G.
Petersen, R. Ebinghaus ...... GermanyGKSS J.
Pacyna . Norway.. NILU J. Munthe,
I. Wängberg .. Sweden.. IVL R. Bullock
USAEPA M. Cohen, R. Artz, R.
Draxler USANOAA C. Seigneur, K. Lohman
.. USA... AER/EPRI A. Ryaboshapko, I.
Ilyin, O.Travnikov EMEP MSC-E
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Intercomparison Conducted in 3 Stages

• Comparison of chemical schemes for a cloud
  environment
• Air Concentrations in Short Term Episodes
• Long-Term Deposition and Source-Receptor Budgets

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Participating Models
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Anthropogenic Mercury Emissions Inventoryand
Monitoring Sites for Phase II(note only showing
largest emitting grid cells)
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Total Gaseous Mercury (ng/m3) at Neuglobsow June
26 July 6, 1995
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Total Particulate Mercury (pg/m3) at Neuglobsow,
Nov 1-14, 1999
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Reactive Gaseous Mercury at Neuglobsow, Nov 1-14,
1999
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• What do atmospheric mercury models need?

• Atmospheric mercury modeling

• Why do we need atmospheric mercury models?

• Some preliminary results
• Model evaluation
• Source Receptor Information

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Example of Detailed Results 1999 Results
for Chesapeake Bay
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Geographical Distributionof 1999 Direct
Deposition Contributions to the Chesapeake Bay
(entire domain)
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Geographical Distribution of 1999 Direct
Deposition Contributions to the Chesapeake Bay
(regional close-up)
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Geographical Distribution of 1999 Direct
Deposition Contributions to the Chesapeake Bay
(local close-up)
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Largest Regional Individual Sources Contributing
to1999 Mercury Deposition Directly to the
Chesapeake Bay
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Largest Local Individual Sources Contributing
to1999 Mercury Deposition Directly to the
Chesapeake Bay
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Emissions and Direct Deposition Contributions
from Different Distance Ranges Away From the
Chesapeake Bay
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Top 25 Contributors to 1999 Hg Deposition
Directly to the Chesapeake Bay
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Preliminary Results for other Maryland Receptors
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Maryland Receptors Included in Recent Preliminary
HYSPLIT-Hg modeling (but modeling was not
optimized for these receptors!)
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Largest Modeled Atmospheric Deposition
Contributors Directly to Deep Creek Lake based
on 1999 USEPA Emissions Inventory (national view)
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Largest Modeled Atmospheric Deposition
Contributors Directly to Deep Creek Lake based
on 1999 USEPA Emissions Inventory (regional view)
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Largest Modeled Atmospheric Deposition
Contributors Directly to Deep Creek Lake based
on 1999 USEPA Emissions Inventory (close-up view)
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Some Next Steps
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Conclusions
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Thanks
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EXTRA SLIDES
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Why might the atmospheric fate of mercury
emissions be essentially linearly independent?

• Hg is present at extremely trace levels in the
  atmosphere

• Hg wont affect meteorology (can simulate
  meteorology independently, and provide results
  to drive model)

• Most species that complex or react with Hg are
  generally present at much higher concentrations
  than Hg

• Other species (e.g. OH) generally react with many
  other compounds than Hg, so while present in
  trace quantities, their concentrations cannot be
  strongly influenced by Hg

• Wet and dry deposition processes are generally
  1st order with respect to Hg

• The current consensus chemical mechanism
  (equilibrium reactions) does not contain any
  equations that are not 1st order in Hg

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Spatial interpolation
Impacts from Sources 1-3 are Explicitly Modeled
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RECEPTOR
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• Perform separate simulations at each location for
  emissions of pure Hg(0), Hg(II) and Hg(p)
• after emission, simulate transformations
  between Hg forms
• Impact of emissions mixture taken as a linear
  combination of impacts of pure component runs on
  any given receptor

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Chemical Interpolation
Impact of Source Emitting Pure Hg(0)
0.3 x
Impact of Source Emitting 30 Hg(0) 50
Hg(II) 20 Hg(p)


Impact of Source Emitting Pure Hg(II)
0.5 x

Impact of Source Emitting Pure Hg(p)
0.2 x
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Standard Source Locations in Maryland region
during recent simulation
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Eulerian grid models givegrid-averaged estimates
difficult to compare against measurement at
a single location
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Geographic Distribution of Largest Anthropogenic
Mercury Emissions Sources in the U.S. (1999) and
Canada (2000)
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• In principle, we need do this for each source in
  the inventory
• But, since there are more than 100,000 sources in
  the U.S. and Canadian inventory, we need
  shortcuts
• Shortcuts described in Cohen et al Environmental
  Research 95(3), 247-265, 2004

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Cohen, M., Artz, R., Draxler, R., Miller, P.,
Poissant, L., Niemi, D., Ratte, D., Deslauriers,
M., Duval, R., Laurin, R., Slotnick, J.,
Nettesheim, T., McDonald, J. Modeling the
Atmospheric Transport and Deposition of Mercury
to the Great Lakes. Environmental Research
95(3), 247-265, 2004. Note Volume 95(3) is a
Special Issue "An Ecosystem Approach to Health
Effects of Mercury in the St. Lawrence Great
Lakes", edited by David O. Carpenter.
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• For each run, simulate fate and transport
  everywhere,
• but only keep track of impacts on each selected
  receptor
• (e.g., Great Lakes, Chesapeake Bay, etc.)
• Only run model for a limited number (100) of
  hypothetical, individual unit-emissions sources
  throughout the domain
• Use spatial interpolation to estimate impacts
  from sources at locations not explicitly modeled

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0.1o x 0.1o subgrid for near-field analysis
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0.1o x 0.1o subgrid for near-field analysis
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Hypothesized rapid reduction of Hg(II) in plumes?
If true, then dramatic impact on modeling
results
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Why is emissions speciation information critical?
Linear
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Why is emissions speciation information critical?
Logarithmic
Linear
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Emissions and Chemistry

• The form of mercury emissions (elemental, ionic,
  particulate) is often very poorly known,
• but is a dominant factor in estimating
  deposition (and associated source-receptor
  relationships)
• Questions regarding atmospheric chemistry of
  mercury may also be very significant
• The above may contribute more to the overall
  uncertainties in atmospheric mercury models than
  uncertainties in dry and wet deposition
  algorithms

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Total Gaseous Mercury at Neuglobsow June 26
July 6, 1995
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Total Gaseous Mercury (ng/m3) at Neuglobsow June
26 July 6, 1995
The emissions inventory is a critical input to
the models
Using default emissions inventory
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Some Additional Measurement Issues (from a
modelers perspective)

• Data availability
• Simple vs. Complex Measurements
• Process Information

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Process Information 1. Dry Deposition -
Resistance Formulation

• 1
• Vd --------------------------------- Vg
• Ra Rb Rc RaRbVg
• in which
• Ra aerodynamic resistance to mass transfer
• Rb resistance of the quasi-laminar sublayer
• Rc overall resistance of the canopy/surface
  (zero for particles)
• Vg the gravitational settling velocity (zero
  for gases).

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Dry Deposition

• depends intimately on vapor/particle partitioning
  and particle size distribution information
• resistance formulation Ra, Rb, Rc...
• for gases, key uncertainty often Rc (e.g.,
  reactivity factor f0)
• for particles, key uncertainty often Rb
• How to evaluate algorithms when phenomena hard to
  measure?

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Particle dry deposition phenomena
Atmosphere above the quasi-laminar sublayer
Ra
Very small particles can diffuse through the
layer like a gas
Very large particles can just fall through the
layer
Quasi-laminar Sublayer ( 1 mm thick)
In-between particles cant diffuse or fall easily
so they have a harder time getting across the
layer
Rb
Wind speed 0 (?)
Rc
Surface
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Vd settling velocity
Diffusion low Settling velocity low Vd
governed by Rb
Diffusion high Vd governed by Ra
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Process information needed1. For particle dry
deposition, must have particle size distributions!
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ATMOSPHERE
Particle-Phase Pollutant
Gas-Phase Pollutant
PROCESS INFORMATION 2. The gas-exchange flux at
a water surface depends on the concentration of
pollutant in the gas-phase and the
truly-dissolved phase (but these are rarely
measured)
Pollutant Truly Dissolved in Water
Pollutant on Suspended Sediment
LAKE