Eric M. Prestbo Frontier Geosciences: Seattle, Washington USA EricP@Frontier.wa

1. Design and Performance of an Atmospheric Reference Standard of Hg0 and HgCl2 to Evaluate State-of-the-Art Hg Speciation Measurement Methods Eric M. Prestbo Frontier Geosciences: Seattle, Washington USA EricP@Frontier.wa.com Robert K. Stevens Florida DEP at USEPA: Triangle Park, North Carolina USA, Stevens.Robert-K@epamail.epa.gov Steve Lindberg Oak Ridge National Laboratory: Oak Ridge, Tennessee USA sll@ornl.gov F. A. Schaedlich and D. R. Schneeberger Tekran Inc.: Toronto, Ontario Canada fhs@tekran.com Gerald Keeler University of Michigan: Ann Arbor, Michigan USA, jkeeler@sph.umich.edu

2. Method Development ChallengePrestbo and Bloom, 1996 International Hg Conference, Hamburg • Typical RGM = 20 pg/m3 = 2.2 ppq (quadrillion) • Must minimize possibilities for contamination by using clean equipment and handling protocols • Rule out Hg0 Hg(II) transformations during sampling • Rule out Hg(II) loss during sampling, storage or analysis • Is relative humidity important?

3. RGM Instrument Design Requirements • Method must be 1-2 orders of magnitude more sensitive than total Hg method • Must reject much larger Hg0 component • Exclude particulate bound Hg, however particulate filters can adsorb RGM • Instrument must pass RGM to the collector quantitatively • Automated to exclude handling contamination and provide high time resolution.

4. Crux of the Problem • To rigorously evaluate any RGM method, we need to have a laboratory system capable of generating quantified, constant, low, pg/m3 concentrations of HgCl2 and Hg0 in various atmospheric matrices. • Critically important to prove that there is no conversion of Hg0 to RGM.

6. RGM Method Testing System

7. KCl Thermal Converter Denuder

8. Impactor Inlet for Denuder

17. Results Summary • Capillary diffusion of HgCl2 from dodecane not initially effective • Heated URG-Teflon coated manifold greatly minimizes HgCl2 sticking and memory effect. • Ice-bath HgCl2 permeation source - poor temperature control at interface with heated manifold • No Hg0 observed in HgCl2 permeation source

18. Results Summary • Addition of %RH to manifold helped to reduce sticking of HgCl2, but also converted HgCl2 to Hg0 in system • Zero Hg system blanks with both cylinder N2, ambient air with gold scrubber and addition of %RH from bubblers • Real-time calibration with thermal conversion KCl-coated annular denuder

19. Results Summary • Responds to HgCl2 quantitatively • Blanks <1 pg/m3, Two-system method precision <10%, Est. DL = 1 pg/m3 • No HgCl2 breakthrough at high levels • Rugged - Operated for 10 days unattended • High sample frequency will allow for observation of anthropogenic source plumes

20. Results Summary • Addition of 80 ppbv of O3 to ~10 ng/m3 Hg0 produced a conversion to RGM of 0.13% = only a 2.6 pg/m3 bias at the 2 ng/m3 level • Field spiking/calibration method works well in laboratory - yet needs refinement • Future work will focus on application of the calibration/spiking method in the field

21. STOP

22. Mercury Nomenclature • TGM - Total Gaseous Mercury -Hg0 + Hg(II)? • GEM - Total Gaseous Elemental Mercury- Hg0 • TPM - Total Particulate Mercury - Hgp • RGM - Reactive Gaseous Mercury - HgCl2?

23. Purpose of Research: Big Picture • To quantify how much of the Hg deposition to sensitive aquatic ecosystems is the result of local, regional and global emissions sources of Hg. • Current understanding of the problem requires that we quantify atmospheric Hg species, Hg0, particulate Hg (PHg) and gas-phase Hg(II) - RGM.

25. Why Measure RGM • RGM (likely HgCl2) is emitted from coal combustion and waste incineration sources • RGM formed in atmosphere via oxidation by O3, Cl2 and likely heterogeneous rxns. • Atmospheric models predict that RGM dominates wet and dry deposition: Models are highly sensitive to RGM emissions and atmospheric concentrations

26. Purpose of Research: Detailed Picture • Build a laboratory system capable of generating atmospheric test matrices to calibrate and challenge the Tekran RGM Method • Develop a means to evaluate and calibrate the Tekran RGM method in the field.

27. Technical Challenges for Building a Laboratory RGM Test System • HgCl2 has a high sticking coefficient • Inert surfaces must be everywhere • Elevated and constant temperature • System blanks at the sub-pg/m3 level with both cylinder air, ambient air and RH addition • Absolute purity of Hg0 and HgCl2 sources • Monitoring HgCl2 levels in real-time

28. RGM Method Testing System

30. From Mercury over Europe (MOE) Campaign Courtesy of GKSS and IVL

32. Field Calibration • 10 l of Hg(II)/hexane is injected into cup at heated denuder inlet • Hexane and Hg(II) evaporate into KCl annular denuder as a calibration with zero air OR matrix spike in ambient air

33. Teflon HgCl2Calibration Cup

34. Calibration Curve Using HgCl2-Hexane Inject

35. Calibration Time-Series with HgCl2-Hexane

36. GOM Calibration ResearchRevisited ~2004-2006Dynamic Injection&Denuder Spiking

37. Schematic of RGM Calibration Method alkane (l) > alkane (g) 9 lpm or 90% of alkane exhausted to air HgCl2 adsorbs to denuder Inject 10 ul of HgCl2 in alkane 1 lpm or 10% of alkane through detector

38. Phase II – Heated Calibration Cup Standard Inlet Standard Denuder

39. www.tekran.com lab-air-info@tekran.com Success: transfer efficiency, high wall temp

40. Phase II Summary Calibration Results

41. Single Field Trial – Dynamic Injection

42. Denuder SpikingHgCl2 Applied to Denuder Installed in 1130 and Desorbed

43. Spike Denuder Holding Time Study

44. Field Trials – Denuder Spiking

45. Denuder Spiking with HgCl2(Olson – USGS & Kilner – Tekran) • Tests: accuracy of the GOM thermal desorption, line transfer, and quantification • 48.4 pg HgCl2 was added to each denuder, then shipped overnight for analysis the following day. • Each experiment had one blank for each instrument. • Four instruments were used in the experiments. GOM Surrogate Spiked Denuder