Chemical Transport of Atmospheric Mercury over the Pacific

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1 Chemical Transport of Atmospheric Mercury over the Pacific C. Jerry Lin 1, Li Pan 1, David G. Streets 2, Carey Jang 3, and Terry Keating 4 1 College of Engineering, Lamar University, Beaumont, TX 2 ANL Decision & Information Sciences Division, Argonne, IL 3 USEPA OAQPS, Research Triangle Park, NC 4 Office of Air & Radiation (OAR/OPAR), USEPA, Washington, DC TF HTAP Workshop St. Petersburg, Russia April 3, 2009

2 Trans-Pacific Transport of Hg Mercury is a global pollutant with yrs atmospheric lifetime (Hg o ) Recent concerns of mercury export from Asian countries (Jaffe et al., 2005, 2007; Kim et al., 2008) Trans-Pacific transport of air pollutants has been identified (Jaffe et al., 2002; HTAP 2007; Fiore et al., 2008; Wang et al., 2009)

3 Key Questions What is the mercury transport budget in the source region (East Asia)? What is the transport pathway? What is the impact of Asian plume on the concentration and deposition in North America? What is the relative importance of foreign vs. local mercury emission?

Multiple Model Assessments Box model: evaluating the regional emission contribution to the global Hg background Full chemistry simulation in East Asia: quantifying regional mercury transport budget

4 Multiple Model Assessments Box model: evaluating the regional emission contribution to the global Hg background Full chemistry simulation in East Asia: quantifying regional mercury transport budget from East Asia Reactive tracer simulation over the Pacific: HTAP TP1x experiment for Hg tracers Full chemistry simulation over the Pacific: HTAP SR7 experiments (20% anthropogenic mercury emission reduction in EA and NA) & emission zeroout scenarios NA EU SA EA

5 Model and Data Model: CMAQ V4.6 (released Oct. 2006), chemistry codes modified for reactive tracer simulations Modeling period: Year 2001 (SR), Years 2 & 3 (TP1x) Domain: ICAP trans-pacific domain in Lambert Conformal projection covering EA and NA, 108-km spatial resolution Emission Inventory: NOx, VOCs & PM based on NEI99 and modified Trace-P (SRs); Hg inventory by Pacyna (2006), Streets et al. (2005), and HTAP TP1x inventory. Meteorology: ICAP 2001 MM5, model-ready Chemistry: CB-IV/AERO4(SR), 1 st order decay (TP1x) Initial and boundary conditions: re-gridded from GEOS- Chem (SRs) and Mozart (TP1x)

6 Mercury budget in East Asia Domain Boundary In Atmospheric Processes Processes (GEM, RGM, PHg) Out Emission Deposition Acc. = F.C. I.C. = In Out + Emission Deposition Mass Flow (Transport Budget) = In Out = F.C. I.C. Emission + Deposition

CMAQ-Hg July Simulation Species GEM RGM PHg Initial Condition 389.3 3.6 1.6 Final Condition 423.2 4.0 1.6 Emission 181.2 22.8 7.5 Wet Deposition 0.015 7.7 7.3 Dry Deposition 16.9 13.2 0.

7 CMAQ-Hg July Simulation Species GEM RGM PHg Initial Condition Final Condition Emission Wet Deposition Dry Deposition Mass Flow (outflow) (outflow) (removed) Net Mass Budget Outflow Outflow mainly in the form of GEM, RGM & PHg readily removed in domain Seasonal variation in the outflow, largest outflow in July due to natural emission

8 Emission Scenarios (Mg/yr) Adjusted (2)

9 What is the net transport budget of mercury from East Asia? Adjusted = 1521 Mg/yr

10 CMAQ_Hg (µg m -2 yr -1 ) Annual Mean Hg Conc. & Deposition SR1: TGM Conc. SR1 Dry Deposition ng/m 3 ng/m 2 /day 24 R=0.82 R 2 = ng/m 2 /day SR1 Wet Deposition MDN(µg m -2 yr -1 ) Comparison with MDN wet deposition

11 Hg Tracers - Effect of Lifetime TP1X: = 180 days TP1X: = 360 days ng/m 3 2 ng/m 3 2 ng/m 3 TP1X: = 540 days 2 SR1: TGM Conc. ng/m 3 4

Hg Tracer - Effect of Elevation 0-3 Km: Hg360EA/Hg360 0.

12 Hg Tracer - Effect of Elevation 0-3 Km: Hg360EA/Hg Km: Hg360EA/Hg360 Stronger transport at higher elevation 0.6

13 Transport Pathways - East ng/m 3 SR1: TGM Conc.

14 Transport Pathways - West ng/m 3 SR1: TGM Conc.

15 Sensitivity cases #1: Base-case EI including anthropogenic & natural/re- emission of mercury #2: Zero out all natural/re- emission #3: Zero out anthropogenic emission in EA #4: Zero out both anthropogenic, and natural/reemission in EA #5: Zero out anthropogenic emission in NA #6: Zero out ALL emissions to study the chemistry forcing on mercury deposition from initial and boundary conditions SR7: 20% emission cut in EA & NA individually*

16 Contribution from direct plume transport

Source Contribution in the Domain Hg(T) Concentration, ng/m 3 Hg(T) Dry Deposition Flux, µg m -2 yr -1 1.23, 86.4% 0.19, 13.6% 0.01, 0.5% 0.07, 4.8% 0.07, 4.8% 0.05, 3.5% 9.75, 87.1% 1.44, 12.9% 0.

17 Source Contribution in the Domain Hg(T) Concentration, ng/m 3 Hg(T) Dry Deposition Flux, µg m -2 yr , 86.4% 0.19, 13.6% 0.01, 0.5% 0.07, 4.8% 0.07, 4.8% 0.05, 3.5% 9.75, 87.1% 1.44, 12.9% 0.15, 1.3% 0.08, 0.7% 1.16, 10.3% 0.06, 0.5% Hg(T) Wet Deposition Flux, µg m -2 yr -1 Oth. Nat. Hg(T) Total Deposition Flux, µg m -2 yr , 0.2% 0.19, 0.7% 0.15, 0.9% 0.23, 0.8% 15.49, 95.6% 0.71, 4.4% 0.43, 2.7% 25.24, 92.1% 2.15, 7.9% 1.59, 5.8% 0.09, 0.6% 0.15, 0.5%

18 Contribution to global Hg pool Without counting re-emission Counting re-emission from the source region

19 Import Sensitivity on Wet Deposition Import Sensitivity Import Sensitivity on Dry Deposition 14 Import Sensitivity ( Hg EA / Hg NA ) in NA by 20% emission reduction TGM Conc Dry Dep J F M A M J J A S O N D Month in J F M A M J J A S O N D Month in 2001 Foreign impact is important because: (1) the greater Hg emission in EA compared to that of NA (2) Hg deposition driven by oxidation of background GEM except near the emission sources Wet Dep J F M A M J J A S O N D Month in 2001

20 Conclusions Trans-Pacific transport events of Hg identified in 2001 (Mar.-Apr. & Oct.-Nov.), contributing ng/m 3 GEM in NA west coast. The direct impact of EA Hg emissions on deposition in NA is small. However, their contribution to global background can be significant. Local emission can contribute significantly to both dry and wet depositions. Chemistry forcing of out-of-boundary transport (IC/BCs) dominate Hg deposition in NA. The concentration and deposition of mercury in NA is more sensitive to EA anthropogenic emission than NA emission, although the forcing magnitude is small.

21 Acknowledgements Task Force of Hemispheric Transport of Air Pollutants (TF HTAP) United States Environmental Protection Agency (USEPA) Texas Commission on Environmental Quality (TCEQ)

Global Mercury Modeling at Environment Canada. Ashu Dastoor &Didier Davignon. Air Quality Research Division Environment Canada

Global Mercury Modeling at Environment Canada Ashu Dastoor &Didier Davignon Air Quality Research Division Environment Canada Atmospheric Mercury Cycling in Environment Canada s Mercury Model - GRAHM Transport