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

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

List of chemicals PAHs (B[a]P, B[b]F, B[k]F) 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

Model structure 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 Dioxin only one 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. EMEP/MSC-E

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

Description of processes 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

Soil partitioning between gaseous, solid and dissolved phases 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

Partitioning in soil and gaseous exchange Model description TFMM, Zagreb, April 2005 Partitioning in soil and gaseous exchange Instantaneous equilibrium 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 Partitioning in soil EMEP/MSC-E

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

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

Vegetation 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

Exchange processes Model description TFMM, Zagreb, April 2005 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 Ecosystem-dependent scheme Resistant analogy EMEP/MSC-E

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

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

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

Pollutant-specific parameters Sensitivity study TFMM, Zagreb, April 2005 Pollutant-specific parameters Exemplified by PCB-153 Parameter Notation Base value Range Henry’s law constant at 10 ºC, Pa·m3/mol KH 3.8 1.2 – 12.0 Subcooled liquid vapor pressure at 10 ºC, Pa pOL 9.7·10-5 3.1·10-5 – 3.1·10-6 Octanol/air partitioning coefficient at 10 ºC KOA 3.6·1010 1.2·1010 – 1.2·1011 Octanol/water partitioning coefficient KOW 7.9·106 2.5·106 – 2.5·107 Washout ratio for particulate phase Wp 1.5 ·105 4.7·105 – 4.7·106 Mass transfer coefficient to vegetation (deciduous forest), 1/s KAVdec 30 9.5 – 95 Mass transfer coefficient to vegetation (coniferous forest), 1/s KAVcon 4.6 1.5 – 15 Degradation coefficient, 1/s Kd 1.2 ·10-7 3.7 ·10-8 – 3.7 ·10-7 Order of magnitude (e.g. 1.2 – 12.0 for KH) EMEP/MSC-E

Environmental parameters Sensitivity study TFMM, Zagreb, April 2005 Environmental parameters Parameter Notation Base value Range Atmospheric aerosol specific surface, m2/m3 θ 1.5·10-4 1.5·10-5 – 1.5·10-3 Ambient air temperature, °C T 10 0 – 20 Concentration of OH radicals in the atmosphere, molecules/cm3 COH 1.0·106 1.0·105 – 5.0·106 Precipitation amount, mm/hour Prec 0.1 0.01 – 0.5 Organic carbon fraction in soil foc 0.05 0.01 – 0.1 Range is chosen in accordance with model input data EMEP/MSC-E

Sensitivity of model output 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

Sensitivity of model output 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

Sensitivity of model output: deposition processes 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

Sensitivity of processes 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

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

Gaseous deposition to soil 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

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

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

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

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

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

Uncertainty of model output Sensitivity study TFMM, Zagreb, April 2005 Uncertainty of model output Under above assumptions on uncertainties of input parameters: Air concentrations Depositions Pollutant-specific parameters only 30% 40% With environmental parameters 50% 70% In reality uncertainties could be less EMEP/MSC-E

Influence of re-emission from soil 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

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

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

Model structure 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

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