Ecosystem Mercury Modeling at Environment Canada

Transcription

1 Ecosystem Mercury Modeling at Environment Canada Ashu Dastoor Environment Canada Studies: HTAP, INCATPA-IPY, AMAP, Arctic-Net, CARA-Hg Team: Daniel Figueras, Dorothy Durnford, Andrei Ryjkov, Reed Harris, Peter Dillon Collaborators: Mercury Emissions, Measurements, Field Process Studies and Laboratory Chemical Kinetic studies are basis for model development.

2 Ecosystem Mercury Modeling Objectives 1. Define the baseline mercury budgets in the atmosphere, terrestrial and aquatic environments through modeling 2. Analyze air concentration and deposition source attribution 3. Assess benefits of reductions in mercury air emissions to fish mercury concentrations 3. Model mercury trends in air and at surface to evaluate model s predictive capability and explain measurements 4. Model future scenarios: changes in emissions, climate, acidification

3 Ecosystem Mercury Model Atmospheric Hg Model (GRAHM: Ashu Dastoor) Terrestrial Hg Model (INCA Hg: Peter Dillon) Aquatic Hg Models (D-MCM: Reed Harris) Emissions from terretrial and aquatic systems are significant and dynamic. Explicit coupling with dynamic surface mercury models is needed to model surface emissions.

4 Atmospheric Mercury Cycling in Environment Canada s Mercury Model - GRAHM Transport Met model Volcanic emissions Gas-phase chemistry GEM RGM TPM O 3, Halogens In boundary layer Polar Regions Evaporation Gas/liquid exchange GEM RGM TPM O 3, OH, (Cl), SO 3, aerosols Cloud properties Met models Evaporation Met model Transport Met model Anthropogenic emissions GEM, RGM, TPM Wet deposition Met model Planetary Boundary Layer Point sources Plume rise Bio-mass burning emissions Dry deposition Surface natural and re-emission: soils, vegetation, water bodies, snow, oceans Turbulent mixing met model Area emissions Snow/Ice dynamics Dry deposition

5 Terrestrial Model (INCA-Hg) Key Processes: 1) Wet and dry atmospheric Hg deposition 2) Surface emission of Hg 3) Litter fall and through fall 4) emission from soil to vegetation 5) Snow melt into soil 6) Snow melt contributing to runoff 7) Soil water contributing to runoff 8) Surface water entering lake 1 2 Vegetation 9 10 Atmosphere Litter & Soil Snow Surface Water 14

6 Terrestrial Sub-Model 1) Throughfall 2) Litterfall 3) Emission from litter layer 4) Dissociation of solid Hg in litter layer 5) Association of dissolved Hg in litter layer 6) Flux from litter layer to surface water 7) Percolation from litter layer to organic soil 8) Re-emission from organic soil to atmosphere 9) Dissociation of solid Hg from organic soil 10) Association of dissolved Hg to organic soil 11) Flux from organic soil to surface water 12) Percolation from organic soil to mineral soil 13) Dissociation of solid Hg from mineral soil 14) Association of dissolved Hg to mineral soil 15) Flux from mineral soil to surface water Litter Solid 4 5 Organic Soil Solid 9 10 Mineral Soil Solid Dissolved 7 8 Dissolved 12 Dissolved

7 D-MCM Aquatic Model

8 Lake 658: 2001 Deposition Estimates from GRAHM (Experimental Lake Area, Ontario, Canada) Month Wet deposition Monthly precipitation [THg] in wet deposition Dry deposition Wet & dry deposition ug/m2 metres ng/l ug/m2 ug/m2 January February March April May June July August September October November December Totals or Averages total total average total Total Observed (St. Louis) ~6.5

9 Simple watershed runoff model based on DOC: Modeled Hg in runoff depends on decades or centuries of deposition.

10 Preliminary Model calibration for 2001 Lake 658 observations Hintelmann Hintelmann Blanchfield

11 Model simulated annual mean concentration of gaseous elemental mercury (ng m -3 ), total deposition (μg m -2 yr -1 ), wet deposition and dry deposition from GRAHM for Circles present measured values from long-term observations from the AMAP, EMEP, CAMnet, MDN networks and at some other monitoring sites. Gaseous Elemental Mercury Total Deposition Wet Deposition Dry Deposition

12 Prediction of episodic outflow of Asian mercury on April 25, 2004 measured at Mt. Bachelor observatory, Oregon, USA Mercury deposition from Canadian Point Sources Mercury deposition attribution to selected Canadian lakes

13 Latitudinal trend of anthropogenic fluxes of mercury in 49 dated sediment cores compared with predictions for each lake location using GRAHM (Muir et al. 2008) flux ug m -2 y Observed Anthropogenic Flux Predicted using GRAHM Latitude * fluxes adjusted for sedimentation rates and particle focussing

14 Long Range Transport of Mercury to the Arctic: INCATPA IPY Study 7 Measurement sites Barrow sea level Reifel Island sea level Alert sea level Little Fox Lake 1.1 km Whistler 2.2 km Ny-Ålesund sea level Amderma

15 Observed and modeled gaseous mercury concentrations: Reifel Island Alert Barrow Ny-Alesund

16 Source attribution land/ocean masks Europe Russia North America Asia Total emissions from a source region and surrounding oceans are considered.

17 North America Europe Russia Asia Total mercury deposition from the four regions

18 Source attribution of Gaseous Elemental Mercury (GEM) and deposition Reifel Island Whistler GEM Deposition

19 Little Fox Lake Barrow GEM Deposition

20 Alert Ny-Alesund GEM Deposition

21 Conclusion: Little Fox lake is best suited for identifying hemispheric transport of mercury with no AMDEs and no local sources masking long range transport. Modeling trends and response to future emission scenarios and climate change requires dynamic representation of terrestrial and oceanic emissions in the models. Net atmospheric mercury accumulation should be simulated along with deposition.