CALFEDCalifornia BayDelta Authority Mercury Studies Quality Assurance Oversight Program Results from

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CALFED/California Bay-Delta AuthorityMercury
StudiesQuality Assurance Oversight
ProgramResults from Intercomparison Study
2November 2005

• Presented by Beverly H. van Buuren
• February 22, 2006
• San Francisco Estuary Institute
• Third Annual Mercury Coordination Meeting
• Regional Water Quality Board, Oakland, California

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QA Oversight Program Goals
Data that supports Decisions
Develop Comparability Between Hg Projects Build
Comparability with other Programs
Performance Requirements Linked to Program Goals
Data of Known and Documented Quality
QA/QC Tools Systems to Improve Efficiency
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How Intercomparison Studies Help

• Comparability of Data (bias)
• within current project schedule
• year-to-year
• other programs?
• Alerts program/project/method/lab issues
• Individual Lab Performance (esp. CRMs)
• Data of Known and Documented Quality
• CBDA since March 2000 (6 years!)

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Intercomparison Study Schedule
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Intercomparison Study 2

• 4 laboratories plus the referee lab
• samples shipped 11/17, results back 01/15,
  draft report 03/06

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Evaluation of Laboratory Results
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THg in Water Results
QA group and lab E are investigating
systematically low-bias results to assess
significance and causes
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MMHg in Water Results
Difference between reference value and all lab
results was less than 3 times the MDL (0.020 ng/L)
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THg in Sediment Results
All laboratories employed different analytical
methods, however results indicate good
comparability of data
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MMHg in Sediment Results
Significant high-bias in lab C results likely due
to artifact resulting from distillation method.
Other labs use extraction method.
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THg in Tissue Results
Lab A good very close to very good Lab D and
lab E do not perform THg tissue analysis for
this project
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MMHg in Tissue Results
Study results indicate good comparison of MMHg in
tissue results across all participating labs
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Closing Remarks

• The MMHg in sediment results submitted by lab C
  highlight the potential problem associated with
  the distillation of sediment sampleshigh-bias
  resulting from the methylmercury artifact.
  Projects using this method should have a specific
  plan for assessing if this method is appropriate
  to meeting project objectives (the QA group can
  help).
• One intercomparison study with only one sample
  per analyte/matrix combination is not
  statistically significant.
• Based on the results of this intercomparison
  study, comparability of data generated by
  laboratories is good across all matrix/analyte
  combinations.

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Contact Information
Beverly H. van Buuren QA Manager beverly_at_vanbuuren
consulting.com Van Buuren Consulting, LLC 4320
Baker Avenue Northwest Seattle, WA 98107 (206)
781-1692
Other projects were working on Surface Water
Ambient Monitoring Program Training classes for
Monitoring Design and QA/QC Holding Time Study on
Low-level Nutrients Appropriate QA/QC for
Physical Habitat and Bioassessment
Studies Intercomparison for Pyrethroids in
Sediment QA/QC for Citizen Monitoring QAPP Review
for the SWRCB DFA SWRCB OIT CIWQS Database
Expert Software System to draft QAPPs
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Milestone DMA-80 Hg Analyzer

• Commercially available automated mercury analyzer
• Uses thermal decomposition of sample followed by
  amalgamation onto gold trap and atomic absorption
  spectrophotometry (AAS)
• Used for total mercury analysis of tissues and
  sediments
• EPA Method 7473 was developed to cover analysis
  of THg using this instrument

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QA Considerations for the DMA-80

• Currently 3 laboratories participating in the
  program use this analyzer
• EPA Method 7473 is vague regarding important
  practical details (such as how to perform matrix
  spikes)
• Other QC parameters such as instrument
  calibration and accounting for carryover
  contamination must be detailed so they conform to
  the QC requirements of the CBDA Mercury Program
• Important to address QC issues without losing
  benefit of analysis with this instrument (savings
  in time/labor)

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Resolution of QC questions for DMA-80

• Spoke with Milestone applications chemist, Dr.
  Skip Kingston, and Wes Heim (MLML) to resolve
  questions and develop QA policies
• Calibration will consist of 10-point primary
  calibration performed every 2 weeks and 5-point
  daily calibration performed before an analytical
  run
• Matrix spikes can be performed by addition of
  standard directly to sample boat

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Resolution of QC questions for DMA-80

• Carryover contamination can occur after running
  greater than 250ng of Hg through the analytical
  system
• Results will be reviewed after analysis to
  identify potential carryover

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Evaluation of Laboratory Results

• Performance is evaluated through the use of
  z-scores
• ?lab the mean of the three values reported by
  the participating laboratory
• xref the reference value established for the
  study
• ?ref 0.05 xref to evaluate results 10 from
  the reference value