POP modelling: evaluation of model performance

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POP modelling evaluation of model performance
Model review, Moscow, October 2005
Victor Shatalov, MSC-East
EMEP/MSC-E
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Model review
Model review, Moscow, October 2005
EMEP/MSC-E
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Model review
Model review, Moscow, October 2005
Model description
Sensitivity study
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List of chemicals
Model review, Moscow, October 2005

• PAHs (BaP, BbF, BkF, I(1,2,3-cd)P)
• PCBs (PCB-28, 52, 101, 118 138, 153, 180)
• PCDD/Fs (17 toxic congeners)
• Lindane (? -HCH)
• HCB
• New substances (BDE 47, 99, dicofol, )

EMEP/MSC-E
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Background information for model review (2005)
Model review, Moscow, October 2005

• EMEP/MSC-E Technical Report Regional
  Multicompartment Model MSCE-POP
• EMEP/MSC-E Technical Report Modelling of POP
  Contamination in European Region Evaluation of
  the Model Performance
• EMEP/MSC-E Technical Report POP Model
  Intercomparison Study. Stage II. Comparison of
  mass balance estimates and sensitivity studies

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Model structure
Model review, Moscow, October 2005
Model description
Atmosphere Gas/particle partitioning, advective
transport, diffusion, degradation
regional 5050 km hemispheric 2.5º 2.5º
Atmospheric buffer
Exchange between media wet deposition (gas
particles), dry particulate deposition, gaseous
depositions to the underlying surface (soil,
seawater, vegetation), re-emission from the
underlying surface
Soil buffer
Sea buffer
Vegetation buffer
Soil Partitioning, transport with convective
water fluxes, diffusion, bioturbation,
degradation.
Seawater Partitioning, advective transport,
diffusion, sedimentation, degradation.
Vegetation Defoliation, transport to soil,
degradation.
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Atmosphere
Model review, Moscow, October 2005
Model description

• advective transport and turbulent diffusion
• gas/particle partitioning
• degradation

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Process description
Model review, Moscow, October 2005
Model description
Gas/aerosol partitioning (Junge-Pankow model)
f c ? / (pOL c ?),
f fraction of aerosol phase c constant
0.17 Pa m ? specific surface of aerosol
particles, m2/m3 pOL subcooled liquid vapor
pressure, Pa
Degradation in the atmosphere (reaction with OH)
dCa/dt kd2 OH Ca,
Ca air concentration in gaseous phase,
ng/m3 OH concentration of OH-radical,
molec/m3 kd2 degradation rate constant,
m3/molec/s.
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Temperature dependence
Model review, Moscow, October 2005
Model description
Fraction of particulate phase
Degradation half-life in air
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Photodegradation of BaP
Model review, Moscow, October 2005
Model description
Experimental runs
dCapart/dt kdphoto TSR Capart
Capart air concentration in particulate
phase, ng/m3 TSR total solar radiation,
calories/cm2/s kdphoto photodegradation
rate constant, cm2/calories.
Rough assumption TSR OH
Numerical values
kd1,gas 4.410 5 s 1 (reaction with
OH-radical) kd1,part 9.710 6 s 1
(photodegradation) (calculated on the
basis of Chen et al., 2001).
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Soil
Model review, Moscow, October 2005
Model description

• partitioning between gaseous, solid and
  dissolved phases
• vertical transport due to convective water
  fluxes, diffusion and bioturbation
• degradation

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Partitioning in soil
Model review, Moscow, October 2005
Model description
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Vertical profile of soil concentrations
Model review, Moscow, October 2005
Model description
Calculated PCB-153 vertical soil concentration
profiles in comparison with measurements at three
locations in the UK
Measurements taken from Cousins I.T., B.Gevao
and K.C.Jones, Chemosphere, v.39, No.14, 1999
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Seawater
Model review, Moscow, October 2005
Model description

• advective transport with sea currents and
  turbulent diffusion
• partitioning between dissolved and particulate
  phases
• sedimentation
• degradation

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Redistribution between phases
Model review, Moscow, October 2005
Model description
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Sedimentation
Model review, Moscow, October 2005
Model description
Relative sedimentation fluxes of PCB-153 after 10
years of uniform flow to the ocean
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Exchange processes
Model review, Moscow, October 2005
Model description

• wet deposition (particles) similar to HM
  model
• wet deposition (gas) instantaneous equilibrium
  with rain water
• dry deposition (particles)
• direct gaseous flux to underlying
  surface (soil, seawater, vegetation)
• re-emission from environmental media

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Example air/soil exchange
Model review, Moscow, October 2005
Model description
Resistant analogy
Net gaseous exchange flux
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Program flow
Model review, Moscow, October 2005
Model description
Start
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Pollutant-specific parameters
Model review, Moscow, October 2005
Sensitivity study
Exemplified by PCB-153
Range is chosen to be an order of magnitude
(e.g. 1.2 12.0 for KH)
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Environmental parameters
Model review, Moscow, October 2005
Sensitivity study
Base values are characteristic of European
region Range is chosen in accordance with model
input data
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Sensitivity of model output
Model review, Moscow, October 2005
Sensitivity study
Sa DCa/DA (CaHigh CaLow)/CaBase/(AHigh
ALow)/ABase
Sensitivities of air concentrations averaged over
1000 km from the source
Dependence of sensitivity on the distance from
the source
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Sensitivity of air concentrations w.r.t. Henrys
law coefficient
Model review, Moscow, October 2005
Sensitivity study
Air concentrations of PCB-153, pg/m3
Low value of Henrys law coefficient
High value of Henrys law coefficient
Point source
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Sensitivity of air concentrations and depositions
w.r.t. Henrys law coefficient
Model review, Moscow, October 2005
Sensitivity study
Sensitivity of air concentrations Sa DCa/DKH
Sensitivity of depositions Sd DD/DKH
Point source
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Influence of re-emission from soil
Model review, Moscow, October 2005
Sensitivity study
DCa (Cam Ca0)/Cam 100, where Cam
concentration calculated taking re-emission into
account Ca0 concentration calculated without
re-emission
Contribution DCa of re-emission to air
concentrations
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Further discussion
Model review, Moscow, October 2005

• Comparison with monitoring data
• POP model intercomparison

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