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FOR NOTES / ADDITIONAL MATERIAL not to be covered in 40 min

This material explores the complexities of light stable isotope abundances and the variability in quality assurance and control across different labs, emphasizing that not all facilities provide the same level of data integrity. Key factors affecting carbon isotope values include moisture stress, salinity, light levels, canopy height, and lifespan of plants. It also highlights technological advances such as Tunable Diode Laser Absorption Spectroscopy (TDLAS) and Mass Spectrometry (MC-ICP-MS), and their applications in research, including DNA studies and microbial analysis.

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FOR NOTES / ADDITIONAL MATERIAL not to be covered in 40 min

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  1. FOR NOTES / ADDITIONAL MATERIAL not to be covered in 40 min

  2. Stable Isotope Standards (d=0)

  3. Light Stable Isotope Abundances

  4. NOTE: All labs do not provide the same QA/QC! NIST 1575 Pine run by 15 different labs Source: Jeff Owen, 2004

  5. d13C values of plants are affected by / reflect: • moisture stress (e.g., Rundel and Sharifi, 1993, Stewart et al. 1995) • salinty (e.g., Guy et al. 1980) • light level (e.g., Ehleringer et al. 1986) • height in the canopy (e.g., Leavitt and Long 1982, McDowell et al. 2005) • lifespan (e.g., Ehleringer et al. 1993)

  6. … because • When stomates relatively closed, ci low and Δ approaches 4.4 ‰; • if wide open, Δ  27‰ source unknown (oops)

  7. Part 3: Advances in technology • TDL • MC-ICP-MS (for iron) • SIP (DNA studies) • SIMS • NMR • PLFA (microbial)

  8. The math for a Keeling plot Cz = Ca – Cb Czdz = Cada – Cbdb Czdz = Cada – [(Ca-Cz)*db] Czdz = Cada – Cadb + Cz db Czdz = Ca(da – db) + Czdb Czdz – Czdb = Ca(da – db) Cz(dz – db) = Ca(da – db) dz – db = [Ca(da – db) ]/Cz dz = db + [Ca(da – db) ]/Cz A linear relationship; the intercept is the isotopic composition of the “source”

  9. A Keeling plot integrates spatially Tu & Dawson, 2004

  10. TDLAS = Tunable Diode Laser Absorption Spectroscopy A laser based system for measuring the mole fraction of a specific gas molecule Raw materials: Lead, Selenium, Sulfur End Product: About the size of a pencil eraser! Bowling et al. (2003)

  11. Tunable diode laser absorption spectroscopy • fast-response analyzer for carbon isotopes of CO2 • very narrow wavelength infrared absorption • 4.3594 (12CO2) and 4.3582 mm (13CO2) • 1 kW and liquid nitrogen required • operates at field site Bowling et al. (2003)

  12. TDL used in an Eddy Covariance System

  13. SIP: Principle • Add a 13C-labeled compound (15N, 2H) • Incubate • Extract and separate an informative biomolecule • Lipids (PLFA) • Nucleic acids (DNA or RNA) • Proteins (not yet used) • Analyze biomolecule

  14. Principles of SIMS

  15. Depth Profile of δ13C through an AOM Aggregate Orphan et al. (2001) Science 293:484.

  16. 13C-PLFA: who is eating what Brant et al. 2006 SBB

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