Tekran

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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.
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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

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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.

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Model 2537A Mercury Analyzer

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

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Model 2537A Analyzer
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Flow Diagram of Model 2537A Mercury Analyzer
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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.

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Part 1Reactive Gaseous Mercury Monitoring
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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).

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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?)

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Difficulties Measuring RGM

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

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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.

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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.

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Analysis Phase

• Denuder is heated to 500C.
• 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.

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Lab RGM Apparatus
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Quartz Denuder Assembly
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Model 1130Denuder Pump Module
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Preliminary Results - Toronto
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Preliminary Results - Toronto
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Lab Testing Frontier Geosciences
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Seattle RGM Data
Ambient Air - Downtown Seattle
Courtesy Frontier Geosciences
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Mercury Levels - Rural Michigan
Courtesy UMAQL
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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.

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Part 2 Particulate Mercury Monitoring
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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.

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Particulate Mercury TPM

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

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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.

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Model 1135 - Principles of Operation

• Sampling Phase
• Quartz, regenerable particulate filter (RPF)
  captures fine fraction (lt 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

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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

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Model 1130 Model 1135 Flow Path
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Ambient Air Speciation
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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