Mercury hemispheric modelling: EMEP experience

Transkript

1 Mercury hemispheric modelling: EMEP experience Oleg Travnikov EMEP/

2 Outline Processes affecting the intercontinental transport and deposition of Hg Long-term monitoring of Hg Hemispheric Hg modelling within EMEP Evaluation of model uncertainty

3 What are the pathways of Hg intercontinental transport? GEM vertical profiles in the Arctic (Banic et al., 23) Hg 8 Hg HgII Oxidation Hg HgII HgII HgII Hg Hg HgII Altitude (km) 4 3 Continent A Continent B 2 1

4 Major atmospheric processes Anthropogenic and natural emissions

5 Anthropogenic emissions of Hg (199, 1995, 2) CGEIC website AMAP website amap.no/resources/hgemissions Natural emissions of Hg E estimates EMEP/ E Report 6/22 Re-emission emission of Hg Assimilation of observations Multi-compartment modelling Hg emissions

6 Major atmospheric processes Anthropogenic and natural emissions Gas-phase and aqueousphase chemistry

7 Major uncertainties: Atmospheric chemistry Uncertainty of the reaction constants Chemical transformations of Hg (Lin et al., 26) Reaction Rate Gas-phase reactions cm 3 molec -1 s -1 Hg + O HgO + O2 Hg products Hg ( 3( ( s, ( g + ( ) OH( + + H O ( 2 2( + products + Cl2( + Br2( + Cl( + Br( (3 49) 1-2 (8.7 9) < (7.6 1) BrO( (1 1) 1-15 Aqueous-phase reactions aq ) + O3 ( Hg aq + OH aq Hg ( ) ( ) ( + HOCl( + Cl + OH + OCl( + Cl + OH + HOBr( + Br + OH M -1 s OBr( + Br + OH + Br2( + 2Br HgSO ( aq ) Hg 3 ( + S( VI) 2 SO3) 2( aq ) + S( VI) Texp(31.971T-12595)/T s -1 << 1-4 s -1 OH) 2 ( aq ) + UV s -1 II + HO Hg products s -1 ) ( aq ) 2 ( aq ) + ) ( aq

8 Major uncertainties: Atmospheric chemistry Uncertainty of the reaction constants Unknown products of the reactions. What is RGM? Chemical transformations of Hg (Lin et al., 26) Reaction Rate Gas-phase reactions cm 3 molec -1 s -1 Hg + O HgO + O2 Hg products Hg ( 3( ( s, ( g + ( ) OH( + + H O ( 2 2( + products + Cl2( + Br2( + Cl( + Br( (3 49) 1-2 (8.7 9) < (7.6 1) BrO( (1 1) 1-15 Aqueous-phase reactions aq ) + O3 ( Hg aq + OH aq Hg ( ) ( ) ( + HOCl( + Cl + OH + OCl( + Cl + OH + HOBr( + Br + OH M -1 s OBr( + Br + OH + Br2( + 2Br HgSO ( aq ) Hg 3 ( + S( VI) 2 SO3) 2( aq ) + S( VI) Texp(31.971T-12595)/T s -1 << 1-4 s -1 OH) 2 ( aq ) + UV s -1 II + HO Hg products s -1 ) ( aq ) 2 ( aq ) + ) ( aq

9 Major uncertainties: Atmospheric chemistry Uncertainty of the reaction constants Unknown products of the reactions. What is RGM? Unknown role of aqueous sorption by insoluble particles Chemical transformations of Hg (Lin et al., 26) Reaction Rate Gas-phase reactions cm 3 molec -1 s -1 Hg + O HgO + O2 Hg products Hg ( 3( ( s, ( g + ( ) OH( + + H O ( 2 2( + products + Cl2( + Br2( + Cl( + Br( (3 49) 1-2 (8.7 9) < (7.6 1) BrO( (1 1) 1-15 Aqueous-phase reactions aq ) + O3 ( Hg aq + OH aq Hg ( ) ( ) ( + HOCl( + Cl + OH + OCl( + Cl + OH + HOBr( + Br + OH M -1 s OBr( + Br + OH + Br2( + 2Br HgSO ( aq ) Hg 3 ( + S( VI) 2 SO3) 2( aq ) + S( VI) Texp(31.971T-12595)/T s -1 << 1-4 s -1 OH) 2 ( aq ) + UV s -1 II + HO Hg products s -1 ) ( aq ) 2 ( aq ) + ) ( aq

10 Major atmospheric processes Anthropogenic and natural emissions Gas-phase and aqueousphase chemistry Wet and dry depositions

11 Deposition processes Hg emissions GEM RGM+TPM Peculiarities of Hg removal: Close connection with emissions speciation and atmospheric chemistry Dry deposition of Hg Hg depositions to forest (accumulation in foliage) from GEM emissions Hg depositions from RGM and TPM emissions

12 Deposition processes Peculiarities of Hg removal: Close connection with emissions speciation and atmospheric chemistry Dry deposition of Hg Hg depositions to forest (accumulation in foliage) Hg deposition, μg/m 2 /y Modelled vs. measured Hg deposition to forest (Munthe et al., 25) Steinkreuz, Steinkreuz, DE DE Lehstenbach, Lehstenbach, DE DE Urani, Urani, FI FI Svartberget, Svartberget, FI FI Throughfall Litterfall Throughfall Model

13 Major atmospheric processes Anthropogenic and natural emissions Gas-phase and aqueousphase chemistry Wet and dry depositions Air-surface exchange

14 Long-term monitoring of Hg Hg monitoring sites in the Northern Hemisphere Lista, Norway (199-23) 4 Hg concentration in precipitation, ng/l ` air concentration - wet deposition - air conc. & wet deposition Measuring Hg parameters Air conc. Wet Dry EMEP GEM, HgP + NADP/MDN + CAMNet GEM +

15 EMEP mercury transport models Hemispheric model (MSCE-HM-Hem) Coverage Northern Hemisphere Resolution One-way nesting EMEP region Regional model (MSCE-HM) Coverage EMEP region Resolution 5 5 km 2

16 Hg intercontinental transport Contribution of non-european sources to Hg depositions in the NH Hg deposition to Germany Global sources 24% Germany 49% Natural (Europe) 1% Others 8% Belgium 3% Netherlands 7% France 8% EMEP region Hg deposition to the UK Global sources 6% Natural (Europe) 1% Others 3% Netherlands 1% France 2% 25-6% of Hg depositions in Europe comes from global sources Germany 4% UK 29%

17 Hg intercontinental transport Hg deposition in Europe Total annual Hg deposition in the Northern Hemisphere Total Hg deposition, t/y % 15% 5% Natural Anthropogenic 3% 12% 4% Europe Asia North America Africa Oceans South. Hem.

18 Hg intercontinental transport Hg deposition in North America Total annual Hg deposition in the Northern Hemisphere Total Hg deposition, t/y % 24% 33% 3% Natural Anthropogenic 18% 8% Europe Asia North America Africa Oceans South. Hem.

19 Pollution of remote regions Hg deposition in the Arctic Total annual Hg deposition in the Northern Hemisphere Total Hg deposition, t/y % 33% 1% 4% Natural Anthropogenic 24% 7% Europe Asia North America Africa Oceans South. Hem.

20 Model evaluation Sensitivity analysis Evaluation vs. measurements Models-to-model intercomparison

21 Sensitivity analysis (regional) GEM concentration Boundary (GEM) Anthrop. emission Emission speciation Natural and re-emission Cloud water ph Oxidation by O3 (gas) Wet deposition Dry deposition Cloud LWC Henry's constant Hg Oxidation by O3 ( Upper boundary Oxidation by OH (gas) Dry deposition (fo Dry deposition (GEM) Aerosol solubility Sensitivity coefficient Hg total deposition Boundary (GEM) Anthrop. emission Emission speciation Natural and re-emission Cloud water ph Oxidation by O3 (gas) Wet deposition Dry deposition Cloud LWC Henry's constant Hg Oxidation by O3 ( Boundary (TPM) Oxidation by OH (gas) Dry deposition (fo Dry deposition (GEM) Aerosol solubility Sensitivity coefficient

22 Sensitivity analysis (regional) Uncertainty of input parameters Input parameters ε x Anthropogenic emissions 5% Speciation of anthropogenic emission 4% Natural emission and re-emission 9% Wet deposition coefficient Dry deposition velocity Boundary concentration GEM 75% 75% 2% Eddy diffusion coefficient 5% Liquid water content Oxidation rate by O 3 5% 5% Oxidation rate by OH 75% Oxidation rate by Cl 2 9% Reduction rate in aqueous phase 5% Hg ion-chloride equilibrium constant 5% Solution-adsorption equilibrium constant 5% ph of cloud water 2% Chloride ion concentration 9% Aerosol solubility 5% Uncertainty, % Estimated model uncertainty Conc in air Conc in prec Total depos

23 Evaluation vs. measurements Spatial variation (annual mean values) TGM concentration 2 Hg wet deposition 3. - air concentrations -wet deposition flux Model, ng/m % -3% C mod =.88 C obs R corr = Model, g/km 2 /y % -5% F mod = 1.13 F obs R corr = Observed, ng/m 3 Observed, g/km 2 /y Measurement data on Hg part and RGM concentrations and Hg dry deposition is required

24 Evaluation vs. measurements Long-term trends (199-23) Lista Lista (NO99) Hg concentration in precipitation, ng/l Model Observed 1 ` De Zilk De Zilk (NL91) Hg concentration in precipitation, ng/l Model Observed Monthly statistics NO99 NL91 Correlation Bias -9% -1% `

25 Hg models intercomparison EMEP intercomparison study for Hg models Stage I. Stage II. Stage III. Comparison of chemical modules Comparison with short-term field measurements Comparison of long-term results and atmospheric budgets Model Institution Country EMAP Institute of Meteorology and Hydrology Bulgaria GRAHM Environment Canada Canada ADOM GKSS-Forschungszentrum Germany CMAQ US EPA USA DEHM Environmental Research Institute Denmark HYSPLIT NOAA USA CAM Swedish Environmental Research Institute Sweden MCM Atmospheric and Environmental Research, Inc. USA MSCE-HM EMEP MSCE-HM-Hem EMEP

26 Hg models intercomparison Stage III. Comparison of long-term modelling results Location of monitoring sites Intercomparison of Hg dry deposition Dry deposition, g/km 2 /mn August, DE1 DE9 NL91 NO99 SE2 SE11 SE12 SE5 FI96 ADOM CMAQ DEHM EMAP GRAHM HYSPLIT MSCE-HM MSCE-HM-Hem

27 Hg models intercomparison Stage III. Comparison of long-term modelling results Atmospheric budget of Hg deposition to Poland Total deposition, kg/mn August 1999 ADOM EMAP MSCE- HM MSCE- HM-Hem HYSPLIT DEHM National Global European European+global

28 Conclusions Current understanding of Hg atmospheric processes is incomplete and requires further research In spite of significant uncertainties, available Hg models reflect general Hg atmospheric cycle and can be used for evaluation of the intercontinental transport Model predictions show that the intercontinental transport significantly contribute to Hg depositions (4% in Europe and 7% in North America) Evaluation of the model uncertainty can include sensitivity analysis, comparison with long-term measurements and model intercomparisons

29 Further research Development of global Hg emission inventories from anthropogenic (speciation) and natural sources Refinement of Hg atmospheric chemistry (reaction constants, products etc.) Monitoring of Hg species (Hg part, RGM) and dry deposition fluxes Extension of the Hg models intercomparison activities to the hemispheric scale Application of multi-compartment modelling for evaluation of Hg cycling on hemispheric/global scale