Tekran ® Automated Mercury Speciation

1. Tekran® Automated Mercury Speciation F.H. Schaedlich1 , Robert K. Stevens2, D.R. Schneeberger2 , Eric Prestbo3, Steve Lindberg4 , Gerald Keeler5 1 Tekran Inc., 1-132 Railside Rd. Toronto, Canada M3A 1A3, 2 Florida Dept. Environmental Protection at USEPA, Res Triangle Park, NC 27711, 3 Frontier Geosciences Inc., 414 Pontius Ave. N., Suite B, Seattle, WA 98109 4 Oak Ridge National Lab. PO Box 2008, Oak Ridge, TN 37831-6038 5 University of Michigan, School of Public Health, 109 Observatory Street, MI 48109.

2. Objectives • Development of automated methods to measure and differentiate between: • Reactive Gaseous Mercury (RGM) in ambient air • Total Particulate Mercury (TPM) in ambient air • Elemental mercury (Hg0) in ambient air

3. Ambient Air Mercury Speciation • Different forms of gaseous Hg have very different behaviors. • Forms can interconvert in the atmosphere and in various reservoirs. • Classes of mercury in ambient air: • Elemental mercury: Hg0. • Reactive mercury: HgII, RGM, Hg2+. • Particulate mercury: HgP, TPM.

4. Model 2537A Mercury Analyzer • Provides continuous total gaseous (TGM) readings with update rate as low as 2.5 minutes. • Detection limit < 0.1 ng/m3(5 min. samples). • Automatic recalibration with internal Hg0 permeation source. • Capable of unattended operation for extended periods.

5. Model 2537A Analyzer

6. Flow Diagram of Model 2537A Mercury Analyzer

7. Elemental Mercury: Hg0 • Typically 90+% of atmospheric Hg loadings. • Relatively inert. Long residence time. • Hg0 sources impact large areas. • Sources: chlor-alkali plants, gold and Hg mining, thermal power plants.

8. Part 1Reactive Gaseous Mercury Monitoring

9. Why Bother Measuring RGM ? • RGM (as HgCl2) is emitted from power plants and incinerators. • RGM is removed rapidly via wet and dry deposition. • Often responsible for contamination of sensitive nearby ecosystems. (Florida Everglades, Arctic).

10. Reactive Mercury: Hg(II) or RGM • Consists of reactive, water soluble forms, primarily HgCl2. • Usually only a few percent of total gaseous mercury present in the atmosphere. • Short range: deposits relatively close to the source of emission. • Primary sources: Coal burning power plants, waste incinerators. (Chlor-alkali plants?)

11. Difficulties Measuring RGM • Method must be 1-2 orders of magnitude more sensitive than total mercury methods. • Reject much larger elemental component. • Exclude particulatebound mercury, however, particulate filters have problems passing RGM. • Apparatus must pass RGM to the collector quantitatively.

12. Model 1130 - Principles of Operation • Quartz, specially coated annular denuder is thermally desorbed and regenerated. • Sampling Phase. • Absorbs RGM while passing all elemental Hg. • Model 2537A reads Hg0 during this phase. • Desorption/Analysis Phase. • Zero air used as carrier. • RGM released as elemental mercury.

13. RGM Sampling Phase • Denuder is slightly warm. • Inlet slightly warm. • Denuder captures all RGM while passing Hg0. • Total sample flow is 10 lpm. • Analyzer measures Hg0 during this time.

14. Analysis Phase • Denuder is heated to 500°C. • Inlet heated to clean upstream glassware. • Denuder releases captured RGM as Hg0. • Excess zero air flow cleans upstream components. • Instrument measures accumulated RGM as Hg0.

15. Lab RGM Apparatus

16. Quartz Denuder Assembly

17. Model 1130Denuder & Pump Module

18. Preliminary Results - Toronto

19. Preliminary Results - Toronto

20. Lab Testing: Frontier Geosciences

21. Seattle RGM Data Ambient Air - Downtown Seattle Courtesy: Frontier Geosciences

22. Mercury Levels - Rural Michigan Courtesy: UMAQL

23. Summary - RGM • A quartz annular denuder coated with KCl quantitatively collects HgCl2 but does not retain Hg0. • HgCl2 collected on a denuder is thermally desorbed as Hg0. • The automated instrument that uses this denuder technology measures RGM concentrations down to 1 pg/m3. • Denuder lasts 1 - 2 weeks between recoatings.

24. Part 2: Particulate Mercury Monitoring

25. Why Bother Measuring TPM ? • Particulate bound mercury (TPM / HgP) is created directly by some industrial processes and also formed downwind of sources by the combination of mercury with existing particulates. • TPM is removed rapidly via wet and dry deposition.

26. Particulate Mercury: TPM • Consists of various compounds of mercury bound onto particles. • Size range: Generally < 3 um. • Usually only a few percent of total mercury present in the atmosphere. • Short range: deposits relatively close to the source of emission.

27. Difficulties Measuring TPM • Method must be 1-2 orders of magnitude more sensitive than total mercury methods. • Must reject much larger elemental component. • Method must exclude reactive gaseous mercury, however, normal particulate filters have problems in that they retain RGM.

28. Model 1135 - Principles of Operation • Sampling Phase • Quartz, regenerable particulate filter (RPF) captures fine fraction (< 2.5 um) particulates after air has passed through impactor and denuder • Desorption/Analysis Phase • Zero air used as carrier • Downstream pyrolyser is activated first • RPF is heated to desorb captured particulates

29. Model 1135 – Particulate Mercury Monitor • Unit stacks on top of Model 1130 • Allows simultaneous deter-mination of Hg0, RGM and HgP • Detection limit ~ 1 pg/m3

30. Model 1130& Model 1135 Flow Path

31. Ambient Air Speciation

32. Conclusions - HgP • A quartz RPF quantitatively collects particulate mercury but does not retain Hg0 • HgP collected on a denuder is thermally desorbed and converted to Hg0 in the pyrolyzer • Carbon based particulate matter on the filter is oxidized to CO2 during desorption cycle • Filter is usable for 1 – 2 weeks before requiring restuffing