TFMM Zagreb April 2005 Multicompartment modelling of POPs

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

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

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, …) 3 EMEP/MSC-E

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 Soil: Seawater: Vegetation: Partitioning, transport with convective water fluxes, diffusion, bioturbation, degradation. EMEP/MSC-E Partitioning, advective transport, diffusion, sedimentation, degradation. Defoliation, transport to soil, degradation. 4

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

Model description TFMM, Zagreb, April 2005 Description of processes Gas/aerosol partitioning (Junge-Pankow model) φ = c · θ / (p. OL + c · θ), φ – fraction of aerosol phase c – constant = 0. 17 Pa · m θ – specific surface of aerosol particles, m 2/m 3 p. OL – subcooled liquid vapor pressure, Pa Degradation in the atmosphere (reaction with OH) d. Ca/dt = – kd 2 · [OH] · Ca, Ca – air concentration in gaseous phase, ng/m 3 [OH] – concentration of OH-radical, molec/m 3 EMEP/MSC-E kd 2 – degradation rate constant, m 3/molec/s. 6

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

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

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 0 0. 2 0. 4 0. 6 0. 8 1 0 depth, cm 2 Measurements taken from: Cousins I. T. , B. Gevao and K. C. Jones, Chemosphere, v. 39, No. 14, 1999 4 6 8 10 calculated park grass moorland woodland 9 EMEP/MSC-E

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

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

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

Model description TFMM, Zagreb, April 2005 Program flow Start 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 EMEP/MSC-E End 13

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. 14 EMEP/MSC-E

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) ALow Range of A AHigh A DA = (AHigh – ALow)/ABase – relative deviation of A Sensitivities of model output with respect to A: Air concentrations Sa = DCa/DA; DCa = (Ca. High – Ca. Low)/Ca. Base Depositions Sd = DD/DA; DD = (DHigh – DLow)/DBase 15 EMEP/MSC-E

Sensitivity study TFMM, Zagreb, April 2005 Pollutant-specific parameters Exemplified by PCB-153 Notation Base value Range Henry’s law constant at 10 ºC, Pa·m 3/mol KH 3. 8 1. 2 – 12. 0 Subcooled liquid vapor pressure at 10 ºC, Pa p. OL 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 Kd 1. 2 · 10 -7 3. 7 · 10 -8 – 3. 7 · 10 -7 Parameter Degradation coefficient, 1/s Order of magnitude (e. g. 1. 2 – 12. 0 for KH) EMEP/MSC-E 16

Sensitivity study TFMM, Zagreb, April 2005 Environmental parameters Notation Base value Range Atmospheric aerosol specific surface, m 2/m 3 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/cm 3 COH 1. 0· 106 1. 0· 105 – 5. 0· 106 Precipitation amount, mm/hour Prec 0. 1 0. 01 – 0. 5 foc 0. 05 0. 01 – 0. 1 Parameter Organic carbon fraction in soil Range is chosen in accordance with model input data 17 EMEP/MSC-E

Sensitivity study TFMM, Zagreb, April 2005 Sensitivity of model output Air concentrations of PCB-153, pg/m 3 “Low” value of Henry’s law coefficient EMEP/MSC-E “High” value of Henry’s law coefficient Point source 18

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

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 20 EMEP/MSC-E

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

Sensitivity study TFMM, Zagreb, April 2005 Gaseous deposition to soil: temperature dependence 0. 5 1. 0 0. 4 0. 8 0. 3 0. 6 0. 2 0. 4 0. 1 0. 2 0. 0 0 5 10 15 20 25 Gas fraction Deposition velocity, cm/s Deposition velocity of direct gas flux Vdgsoil = fgsoil / (Cagas + Capart) 30 Temperature, 0 C Deposition velocity 1 / Resist Gas fraction The temperature dependence is investigated EMEP/MSC-E 22

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 p. OL • Atmospheric aerosol specific surface q • Organic carbon fraction in soil foc 23 EMEP/MSC-E

Sensitivity study TFMM, Zagreb, April 2005 Base Low KH High KH 0. 8 0. 4 Sensitivity, Sgsoil Deposition velosity, Vdgsoil , cm/s Sensitivity to Henry’s law constant KH 0. 3 0. 2 0. 1 0. 6 0. 4 0. 2 0 0 0 5 10 15 20 25 30 T , o. C Variations of deposition velocity 0 5 10 15 20 25 T , o. C Sensitivity: Sgsoil = D Vdgsoil / DKH, D – relative deviation 24 EMEP/MSC-E 30

Sensitivity study TFMM, Zagreb, April 2005 Gaseous deposition to soil: sensitivity 0. 6 Pollutant-related parameters Environmental parameters Specific aerosol surf. Vapor pressure Octanol/water part. coeff Henry's law coeff 0 Fraction of OC 0. 2 Temperature Sensitivity 0. 4 Sensitivities Sgsoil of Vdgsoil with respect to selected parameters: Sgsoil = D Vdgsoil / DA EMEP/MSC-E 25

Sensitivity study TFMM, Zagreb, April 2005 Wet deposition Result (sensitivity of Vd) • Washout ratio for particulate phase 0. 6 0. 4 26 EMEP/MSC-E Specific aerosol surf. 0. 0 Precipitation rate 0. 2 Temperature • Atmospheric aerosol specific surface Environmental parameters 0. 8 Henry's law coeff • Precipitation rate Pollutant-related parameters Vapor pressure • Henry’s law coefficient 1. 0 Sensitivity • Subcooled liquid vapor pressure 1. 2 Washout ratio Parameters

Sensitivity study TFMM, Zagreb, April 2005 Re-emission flux from soil Parameters Result (sensitivity of flux) 0. 14 0. 08 0. 06 0. 04 0. 02 Vapor pressure 0. 00 Henry's law coeff • Subcooled liquid vapor pressure 0. 10 Octanol/water part. coeff • Henry’s law coefficient 0. 12 Sensitivity • Octanol/water partitioning coefficient 27 EMEP/MSC-E

Sensitivity study TFMM, Zagreb, April 2005 Sensitivity of model output 0. 16 0. 1 Pollutant-related parameters 0. 08 Environmental parameters 0. 06 0. 04 0. 02 Theta OH conc foc Precip Temperature Degr 0 Kavconif KOW p. OL 0 KOA 0 KH Wash. P Kavdec 0 Sensitivities of air concentrations averaged over 1000 km from the source EMEP/MSC-E Dependence of sensitivity on the distance from the source 28

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 29 EMEP/MSC-E

Sensitivity study TFMM, Zagreb, April 2005 Influence of re-emission from soil DCa = (Cam – Ca 0)/Cam · 100%, where Cam – concentration calculated taking re-emission into account Ca 0 – concentration calculated without re-emission Contribution DCa of re-emission to air concentrations 30 EMEP/MSC-E

TFMM, Zagreb, April 2005 Conclusions q 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. q High spatial variability is characteristic of sensitivity of model output with respect to all considered parameters. q The influence of re-emission process is significant after long-term period of POP application especially in the remote regions. 31 EMEP/MSC-E

Thank you for your attention! 32

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 33 EMEP/MSC-E

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 34

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