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GAWP.111715

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GAWP.111715

  1. 1. Optical Dissolved Oxygen: Fundamentals and Applications GAWP – Athens, GA Scott Kindelberger 17 November 2015
  2. 2. A Brief History ©2015 YSI Inc. All Rights Reserved. • Winkler Titration (1888) • Slow, highly subjective result • Sample transport to lab • Toxic glassware cleaning reagent
  3. 3. A Brief History ©2015 YSI Inc. All Rights Reserved. • Electrochemical (1956) • Most widely used method
  4. 4. A Brief History ©2015 YSI Inc. All Rights Reserved. • Optical (Luminescence Lifetime) • Method optimized for environmental monitoring (YSI, 2006) • Theoretical (1939) • Practical (1984)
  5. 5. ©2015 YSI Inc. All Rights Reserved. • Oxygen diffuses across membrane, and is consumed at the electrode A Little Deeper: Electrochemical DO • This generates a small current More oxygen = More Current = Higher Signal Oxygen (mg/L) Current(mA)
  6. 6. The Problem with Membranes… ©2015 YSI Inc. All Rights Reserved. • Electrolytes + Membranes • 1-4 week lifetime • Easily damaged (3/1000 inch thick) • Large calibration drifts
  7. 7. The Problem with Membranes… ©2015 YSI Inc. All Rights Reserved.
  8. 8. Light at the End of the Tunnel… ©2015 YSI Inc. All Rights Reserved. • No electrolytes, membranes • 1-2 year lifetime ($200) • Thermal / Physical shock resistant calibration • Calibration stability on order of months • Screw-on cap
  9. 9. So What’s the Big Deal? ©2015 YSI Inc. All Rights Reserved. • Durable, can be wiped • Essential in high fouling environments • RELIABLE long-term data
  10. 10. 4 day deployment, July 2010 Water Temp 82 °F 6 day deployment, Jan 2013 Water Temp 54 °F Biofouling Issues
  11. 11. Other Deployments ©2015 YSI Inc. All Rights Reserved. Hydroelectric Monitoring Wells High-fouling
  12. 12. So What’s the Big Deal? ©2015 YSI Inc. All Rights Reserved. • Equal or Higher Accuracy • Work BETTER at low DO • Impervious H2S • +/- 1.0%, or 0.1mg/L • 0 – 500% Range
  13. 13. Calibration / Check • Water-saturated air • Semi-closed environment • Wait 15 minutes, calibrate • Saturate with airstone • Reading should be ~100%
  14. 14. Drawbacks.. ©2015 YSI Inc. All Rights Reserved. • Expense.. About 2x as membrane • Equilibration times • High turbidities..
  15. 15. Method Certifications.. ©2015 YSI Inc. All Rights Reserved. • US-EPA : 1002-8-2009 • ASTM (International): D888-09 • Standard Methods: 4500-O-G • CFR: 40 CFR 136
  16. 16. • Thank you for your time and attention! • Questions?

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