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Multicompartment modelling of POPs

TFMM, Zagreb, April 2005. Multicompartment modelling of POPs. Victor Shatalov, MSC-East. EMEP/MSC-E. TFMM, Zagreb, April 2005. Outline. Model description. Sensitivity analysis with respect to pollutant-specific and environmental parameters. www.msceast.org. EMEP/MSC-E. Model description.

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Multicompartment modelling of POPs

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  1. TFMM, Zagreb, April 2005 Multicompartment modelling of POPs Victor Shatalov, MSC-East EMEP/MSC-E

  2. TFMM, Zagreb, April 2005 Outline Model description. Sensitivity analysis with respect to pollutant-specific and environmental parameters. www.msceast.org EMEP/MSC-E

  3. Model description TFMM, Zagreb, April 2005 List of chemicals • PAHs (B[a]P, B[b]F, B[k]F) • PCBs (PCB-28, 52, 101, 138, 153, 180) • PCDD/Fs (17 toxic congeners) • Lindane (-HCH) • HCB • New substances (BDE 47, 99, dicofol, …) EMEP/MSC-E

  4. Model description TFMM, Zagreb, April 2005 Model structure Atmosphere:Gas/particles partitioning, advective transport, diffusion, degradation regional: 50×50 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 Seawater:Partitioning, advective transport, diffusion, sedimentation, degradation. Soil:Partitioning, transport with convective water fluxes, diffusion, bioturbation, degradation. Vegetation:Defoliation, transport to soil, degradation. EMEP/MSC-E

  5. Model description TFMM, Zagreb, April 2005 Atmosphere • advective transport and turbulent diffusion (presentation on HMs) • gas/particle partitioning • degradation EMEP/MSC-E

  6. Model description TFMM, Zagreb, April 2005 Description of processes Gas/aerosol partitioning (Junge-Pankow model) φ = c · θ / (pOL + c · θ), φ – fraction of aerosol phase c – constant = 0.17 Pa · m θ – 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. EMEP/MSC-E

  7. Model description TFMM, Zagreb, April 2005 Soil • partitioning between gaseous, solid and dissolved phases • vertical transport due to convective water fluxes, diffusion and bioturbation • degradation EMEP/MSC-E

  8. Model description TFMM, Zagreb, April 2005 dCa/dt = k(Cd – Ca) dCd/dt = k(Ca – Cd) k – exchange rate coefficient Ca – concentration of accessible form Cd – concentration in deeply sorbed form Instantaneous equilibrium Partitioning in soil and gaseous exchange Partitioning in soil EMEP/MSC-E

  9. Model description TFMM, Zagreb, April 2005 0 0.2 0.4 0.6 0.8 1 0 2 4 depth, cm 6 8 10 calculated park grass moorland woodland Vertical profile of soil concentrations Calculated PCB-153 vertical soil concentration profiles in comparison with measurements at three locations in the UK; relative units Measurements taken from: Cousins I.T., B.Gevao and K.C.Jones, Chemosphere, v.39, No.14,1999 EMEP/MSC-E

  10. Model description TFMM, Zagreb, April 2005 Velocities of sea currents (cm/s), upper sea layer, January 1 Isolines of mixed layer depth (m), January Seawater • advective transport with sea currents and turbulent diffusion • partitioning between dissolved and particulate phases • sedimentation • degradation EMEP/MSC-E

  11. Model description TFMM, Zagreb, April 2005 Vegetation • defoliation and transfer to the upper soil layer • degradation Three types of vegetation: deciduous forest coniferous forest grass Information on Leaf Area Index (LAI) with monthly resolution EMEP/MSC-E

  12. Model description TFMM, Zagreb, April 2005 Ecosystem-dependent scheme Resistant analogy Exchange processes • wet deposition (gas + particles) – similar to HM model • dry particulate deposition – similar to HM model • gaseous depositions to underlying surface (soil, seawater, vegetation) • re-emission from environmental media EMEP/MSC-E

  13. Model description TFMM, Zagreb, April 2005 Calculating fluxes between media Determination of time steps Filling in flux buffers Assimilating atm. fluxes Assimilating soil fluxes Assimilating sea fluxes Assimilating veg. fluxes Atmospheric module Soil module Sea module Vegetation module End Program flow Start EMEP/MSC-E

  14. Model description TFMM, Zagreb, April 2005 Sensitivity analysis Model input and output Emphasis:atmospheric concentrations and depositions. Media are used to take into account re-emission process. EMEP/MSC-E

  15. Sensitivity study TFMM, Zagreb, April 2005 Sensitivities of model output with respect to A: Air concentrations Sa = DCa/DA; DCa = (CaHigh – CaLow)/CaBase Depositions Sd = DD/DA; DD = (DHigh – DLow)/DBase Sensitivity: definitions List of input parameters used in the model is determined For each input parameter A: ABase (model value) A Range of A AHigh ALow DA = (AHigh – ALow)/ABase – relative deviation of A EMEP/MSC-E

  16. Sensitivity study TFMM, Zagreb, April 2005 Pollutant-specific parameters Exemplified by PCB-153 Order of magnitude (e.g. 1.2 – 12.0 for KH) EMEP/MSC-E

  17. Sensitivity study TFMM, Zagreb, April 2005 Environmental parameters Range is chosen in accordance with model input data EMEP/MSC-E

  18. Sensitivity study TFMM, Zagreb, April 2005 Sensitivity of model output Air concentrations of PCB-153, pg/m3 “Low” value of Henry’s law coefficient “High” value of Henry’s law coefficient Point source EMEP/MSC-E

  19. Sensitivity study TFMM, Zagreb, April 2005 Sensitivity of model output Sensitivity of air concentrations with respect to Henry’s law coefficient: Sa = DCa/DKH Sensitivity of depositions with respect to Henry’s law coefficient: Sd = DD/DKH Point source EMEP/MSC-E

  20. Sensitivity study TFMM, Zagreb, April 2005 Sensitivity of model output: deposition processes Input parameters (pollutant-specific and environmenal) Vd = Vdwet + Vdpart + Vdsoil· φsoil + Vdsea· φsea + Vdveg· φveg Output parameters (air concentrations and depositions) φsoil, φsea, φveg – fractions of soil, sea and vegetation surfaces in a cell Underlying surface: average for Europe EMEP/MSC-E

  21. Sensitivity study TFMM, Zagreb, April 2005 Sensitivity of processes • Gaseous deposition to soil • Gaseous deposition to vegetation • Gaseous deposition to seawater • Wet deposition (gas + particles) • Re-emission EMEP/MSC-E

  22. Sensitivity study TFMM, Zagreb, April 2005 0.5 1.0 0.4 0.8 0.3 0.6 Deposition velocity, cm/s Gas fraction 0.2 0.4 0.1 0.2 0.0 0.0 0 5 10 15 20 25 30 0 Temperature, C Deposition velocity 1 / Resist Gas fraction Gaseous deposition to soil: temperature dependence Deposition velocity of direct gas flux Vdgsoil = fgsoil / (Cagas + Capart) The temperature dependence is investigated EMEP/MSC-E

  23. Sensitivity study TFMM, Zagreb, April 2005 Gaseous deposition to soil Parameters used for model description: • Henry’s law constant KH • Octanol/water partitioning coefficient KOW • Vapor pressure over subcooled liquid pOL • Atmospheric aerosol specific surface q • Organic carbon fraction in soil foc EMEP/MSC-E

  24. Sensitivity study TFMM, Zagreb, April 2005 Base Low KH High KH 0.8 0.4 , cm/s 0.6 gsoil gsoil 0.3 d V S 0.4 0.2 Sensitivity, Deposition velosity, 0.2 0.1 0 0 0 5 10 15 20 25 30 0 5 10 15 20 25 30 o o T , C T , C Sensitivity to Henry’s law constant KH Variations of deposition velocity Sensitivity: Sgsoil = DVdgsoil / DKH, D – relative deviation EMEP/MSC-E

  25. Sensitivity study TFMM, Zagreb, April 2005 0.6 Pollutant-related Environmental parameters parameters 0.4 Sensitivity 0.2 0 Vapor pressure OC Fraction of Temperature Henry's law coeff Specific aerosol surf. Octanol/water part. coeff Gaseous deposition to soil: sensitivity Sensitivities Sgsoil of Vdgsoil with respect to selected parameters: Sgsoil = D Vdgsoil / DA EMEP/MSC-E

  26. Sensitivity study TFMM, Zagreb, April 2005 Parameters Result (sensitivity of Vd) • Washout ratio for particulate phase • Subcooled liquid vapor pressure • Henry’s law coefficient • Precipitation rate • Atmospheric aerosol specific surface 1.2 Pollutant-related Environmental 1.0 parameters parameters 0.8 Sensitivity 0.6 0.4 0.2 0.0 aerosol Specific surf. Washout ratio Vapor pressure Precipitation rate Henry's law Temperature coeff Wet deposition EMEP/MSC-E

  27. Sensitivity study TFMM, Zagreb, April 2005 Result (sensitivity of flux) 0.14 0.12 0.10 0.08 Sensitivity 0.06 0.04 0.02 0.00 Vapor pressure Henry's law coeff Octanol/water part. coeff Re-emission flux from soil Parameters • Octanol/water partitioning coefficient • Henry’s law coefficient • Subcooled liquid vapor pressure EMEP/MSC-E

  28. Sensitivity study TFMM, Zagreb, April 2005 0.16 0.1 Pollutant-related Environmental 0.08 parameters parameters 0.06 0.04 0.02 0 KH foc KOW KOA0 pOL0 Degr0 Theta Precip Kavdec WashP Kavconif OH conc Temperature Dependence of sensitivity on the distance from the source Sensitivity of model output Sensitivities of air concentrations averaged over 1000 km from the source EMEP/MSC-E

  29. Sensitivity study TFMM, Zagreb, April 2005 Uncertainty of model output Under above assumptions on uncertainties of input parameters: In reality uncertainties could be less EMEP/MSC-E

  30. Sensitivity study TFMM, Zagreb, April 2005 Influence of re-emission from soil 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 EMEP/MSC-E

  31. TFMM, Zagreb, April 2005 Conclusions • Model output (air concentrations and depositions) is mostly sensitive to to washout ratio for particulate vvphase and Henry’s law constant Among environmental vvparameters the ambient temperature plays essential vvrole. • High spatial variability is characteristic of sensitivity of model output with respect to all considered parameters. • The influence of re-emission process is significant after long-term period of POP application especially in the remote regions. EMEP/MSC-E

  32. Thank you for your attention!

  33. Model description TFMM, Zagreb, April 2005 Distribution of pollutants between media PCB-153: is mainly accumulated in soil has essential fractions of both particulate and gaseous phases Emphasis to: the atmosphere soil EMEP/MSC-E

  34. Model description TFMM, Zagreb, April 2005 Model structure Atmosphere Underlying surface Model versions: regional (EMEP), 50 × 50 km hemispheric, 2.5° × 2.5° EMEP/MSC-E

  35. Model description TFMM, Zagreb, April 2005 PCB-28 PCB-153 PCB-180 PCB-28 PCB-153 PCB-180 100% 300 250 80% 200 60% , days 150 Fraction of particulate phase 1/2 T 40% 100 50 20% 0 0% -20 -15 -10 -5 0 5 10 15 20 25 30 1 6 11 16 21 26 31 36 41 46 51 o T, C o T, C Temperature dependence Fraction of particulate phase Degradation half-life in air EMEP/MSC-E

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