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Assessing GOM Capture Efficiency

Assessing GOM Capture Efficiency. Mark L Olson National Atmospheric Deposition Program Atmospheric Mercury Network Site Liaison. CEEPAMS. Chimney Experiment to Establish Precision and Accuracy for Mercury Species 3 instrument manifold experiment 2 Tekran speciation systems

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Assessing GOM Capture Efficiency

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  1. Assessing GOM Capture Efficiency Mark L Olson National Atmospheric Deposition Program Atmospheric Mercury Network Site Liaison

  2. CEEPAMS • Chimney Experiment to Establish Precision and Accuracy for Mercury Species • 3 instrument manifold experiment 2 Tekran speciation systems 1 modified DOHGS system for total Hg • Vertical Manifold with inlets are same location • HgCl2 and HgBr2 permeation tubes • Speciation systems set to AMNet protocols • Record temperature and relative humidity

  3. Temp and RH Inlet Total Hg Speciation 1 Speciation 2 Vertical manifold Inlets at 120o around manifold Inlets sealed and protrude into manifold Permeation tubes on inlet screen

  4. Tekran Systems • Speciation 1 (Sp1) and 2 (Sp2) are set to AMNet Protocols • 10 lpm, inlet 50oC, 2 hour sampling, zero air flush • Modified DOHGS (THg) system • 4 lpm, inlet at 50oC, 2 hour sampling, zero air flush • Uncoated Denuder held at 550oC • Add varying amounts of HgBr2 and/or HgCl2

  5. Limitations • Sources dependent on ambient conditions • Temperature influences emissions • PBM must remain low • Total Hg system not designed to convert PBM(?)

  6. GOM Comparison • GOM from two speciation systems, Sp1:Sp2 • May 29, - September 3, 2015 • 44 no addition periods (Bkgd), none were excluded • 23 GOM added, 4 lost to data capture Precision Estimates

  7. Denuder to Denuder Comparison GOM Added No GOM Added Sp2 Denuder Mass (pg) Sp2 Denuder Mass (pg) Sp1 Denuder Mass (pg) Sp1 Denuder Mass (pg)

  8. Denuder to Denuder by Species • Denuder mass (pg) to Denuder mass for HgCl2, HgBr2 and both combined HgCl2 HgBr2 Both Sp2 Denuder Mass (pg) Sp1 Denuder Mass (pg) Sp1 Denuder Mass (pg) Sp1 Denuder Mass (pg)

  9. Mass to Temperature by Species • Denuder mass to air temperature for HgCl2, HgBr2 and both combined • Not what I expected Both HgCl2 HgBr2 Denuder Mass (pg) Temperature (oC) Temperature (oC) Temperature (oC)

  10. GEM from GOM Sources • GEM increased with GOM addition • GOM added 1 hour into 2 hour sampling period • % GEM = (Σ SpX GEMPost – Σ SpX GEMPre)/(Σ THg GEMPost – Σ THg GEMPre) x100 Mass (pg) 5 minute GEM

  11. Percent GEM from GOM Sources Percentages from Calc GOM, not Denuder concentrations

  12. GOM Recoveries • GOM added 1 hour into 2 hour sampling period • Calculate GOM mass for each observation • Calc GOM = difference GOM = Σ THg(Mass) – Σ Sp1 (or Σ Sp2)(Mass) Percent Recovery = Denuder GOM/Calc GOM Mass (pg) 5 minute GEM

  13. Percent Recoveries

  14. Where is variability? y = 1.2595x - 214.01 R² = 0.8956 Tweaker Sp2 Calc GOM (pg) Sp2 Denuder GOM (pg) Sp1 Calc GOM (pg) Sp1 Denuder GOM (pg)

  15. Examples from 9/1/2015 (HgBr2)Addition at 1 hour into 2 hour sampling cycle Mass (pg) Mass (pg) 5 minute GEM Cycle 5 minute GEM Cycle Mass (pg) Mass (pg) 5 minute GEM Cycle 5 minute GEM Cycle Is that real? Bias high for Calc GOM and low for % Rec What % is on first 2 reading? #1 27.5% #2 20.7% #3 20.2%

  16. What if the initial GEM spike isn’t real? • Using Median vs. Average on 9/1/2015

  17. HgBr2 left in place, 9/5/2015 examples Mass (pg) Mass (pg) Round 2 5 minute GEM Cycle 5 minute GEM Cycle Mass (pg) Mass (pg) Round 4 Round 3 5 minute GEM Cycle 5 minute GEM Cycle

  18. What if the initial GEM spike isn’t real? • % Recovery 9/1 : 9/5/2015 using average masses

  19. Percent Recovery to Relative Humidity HgCl2 HgBr2 Percent Recovery Percent Recovery Relative Humidity (%) Relative Humidity (%) All Results HgCl2 + HgBr2 Percent Recovery Percent Recovery Relative Humidity (%) Relative Humidity (%) Note changing Y axis

  20. Recoveries to Absolute Humidity Percent Recovery Absolute Humidity

  21. GOM to Temperature Calc GOM Mass (pg) Temperature (oC)

  22. Inlet to 100oCHgCl2 and HgBr2 (from previous slide) Sp2 Inlet held at 100 for sampling and desorb Sp2 Inlet 50oC, Mass (pg) Sp1 Inlet 50oC, Mass (pg) Sp2 Inlet 100oC Note working range ~15% increase with inlet at 100oC Sp1 Inlet 50oC

  23. GEM data, constant source Sp2 inlet at 100oC Where’s the initial spike coming from? Mass (pg) Not zero 5 minute GEM THg and Sp2 inlets at 100oC Mass (pg) 5 minute GEM

  24. Initial GEM spike cause? • Dead space in the inlet? • From zero air inlet down is exhausted • Dead volume in elutriator? • GOM converting to GEM? • Difficult to quantify GOM loss • Other ideas??? 1 lpm 5 – 7 lpm ??

  25. Modified Inlet Heater

  26. Perm Source • First cut • 6 cm HgBr2 kept at 75oC @ 1.5 lpm • From zero air to Argon for source • Initial problems with mixing

  27. Zero Air Source for Manifold • Very large volumes of Zero air needed to overwhelm manifold • Ideas?

  28. Special Thanks • Equipment • New York State Department of Environmental Conservation • Florida Department of Environmental Protection, • National Oceanic and Atmospheric Administration, • Tekran • Advice and support • David, Bob and Mark from NADP, Vid, Dave, Eric, Mae, Sandy, Winston, XinRong, PK…

  29. What’s next? • Perm Source needed, getting colder • Perform experiments in zero air • Solve GEM pulse with inlet temp @ 100oC • Test different denuder coatings? • Incorporate PBM into study(?) • Work with others to improve data quality • Make changes to AMNet Std Operating Practices (Thursday)

  30. Questions?Comments?Guidance? Tukka, my lab assistant

  31. GEM Work

  32. WI07 Horicon, WI USA • 17 month Tekran collocation experiment • 12 months with 2 speciation systems (2537X:2537B) • GEM hourly average, 4% difference. T=3.43 P=<0.00 • 5 months with 3 speciation systems (2537X:B:B) • GEM 3.3% difference • 2.9% of time one was > 10% • > 90% data completeness • T-stat at 0.05 • 2 passed, 1 failed (t=0.23, p=0.41)

  33. Instrument Detection Limit • - Route cell vent into sample train • - Supplement sample volume with zero air • - Add 7 pg of Hg to injection port • - Goal: daisy chain all 3 together for • between instrument comparison, this did not work • IDL 2537X = 0.51 pg 2537X 2537B #396 2537B’s Positive Pressure Negative Pressure Replicate Mass (pg) 2537B #349 Replicate

  34. Method Detection Limit • Cell vent into ambient air sample stream • Two instruments evaluated, one left to monitor ambient air • Repeated 3 times, similar results • 2537X = 1.85 pg • 2537B = 2.16 pg GEM (ng/m3) Replicate

  35. Detection Limit Concentrations Instrument Detection Limit GEM Method Detection Limit

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