1 / 24

What is Elemental Carbon and How Do Definitions Differ for Different Applications?

What is Elemental Carbon and How Do Definitions Differ for Different Applications?. Bob Cary and David Smith. Speciation of Carbon Aerosol. Organic – Elemental – Inorganic Sources : OC – Many EC – Pyrolysis of OC’s. Analysis of Ambient Carbon Aerosols. HOW -??? WHAT

chungs
Download Presentation

What is Elemental Carbon and How Do Definitions Differ for Different Applications?

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. What is Elemental Carbon and How Do Definitions Differ for Different Applications? Bob Cary and David Smith Sunset Lab OCEC

  2. Speciation of Carbon Aerosol • Organic – Elemental – Inorganic • Sources: OC – Many EC – Pyrolysis of OC’s Sunset Lab OCEC

  3. Analysis of Ambient Carbon Aerosols • HOW -??? • WHAT -Elemental Carbon -Organic Carbon -Inorganic Carbonate Carbon • WHY -Health -Visibility -Source Tracer -Climate Effects Sunset Lab OCEC

  4. Carbonate and Organic Carbon • Inorganic Carbonate Carbon -e.g. CaCO3 (limestone dust – most common) • Organic Carbon -Nearly all remaining carbon -Primary-Secondary-Condensed Vapor -Wide Range of Chemical and Physical Characteristics Sunset Lab OCEC

  5. EC Aerosol Species(BC, Graphitic Carbon; NOT Soot) • Elemental Carbon -Extended Aromatic Rings of Carbon Atoms -Black (absorbs all visible light radiation) (Degenerate Resonance Pi-bond electrons in conductance bands; Metal-like) -Refractory (does not melt or sublime, even at high temperatures; >2000 C) - Insoluble and Chemically inert at normal temperatures Sunset Lab OCEC

  6. Idealized EC Structure Sunset Lab OCEC

  7. STM of Graphitic Carbon Sunset Lab OCEC

  8. STM of Graphitic Carbon Sunset Lab OCEC

  9. Fractal Structure of EC Sunset Lab OCEC

  10. Soot Representationfrom Akhter, Chughtal and Smith, Applied Spectroscopy, 1985 Sunset Lab OCEC

  11. Formation of EC • EC created by Pyrolysis of OC • Thermal Energy breaks bonds creating atoms and molecule fragments • Usually exist as Radicals • Subsequent collisions can cause recombination to form new bonds • Extended C-C bonds build aromatics • Small atoms or fragments diffuse away quickly; e.g., H2 or H-radicals Sunset Lab OCEC

  12. Quantitative Measurement of EC • DIRECT • DIFFERENCE Sunset Lab OCEC

  13. Direct Measure of EC • Using Optical Properties and Spectroscopic Techniques i.e., Absorbance of Electromagnetic Radiation Sunset Lab OCEC

  14. Abs. Coeff. Vs. Size e.g., from Horvath, Fuller, Taha Sunset Lab OCEC

  15. Absorbance by EC • Depends on wavelength • Depends on size of particle • Depends on morphology of particle (e.g., small monomeric clusters or fractals or agglomerated fractals) Sunset Lab OCEC

  16. Difference Measure of EC by Removal of OC from TC • Remove OC by Solvent of Chemical Means • Remove OC by Thermal Methods • Combinations of Above e.g., heat in oxygen atmosphere Finally Do some Type of Direct Measurement Sunset Lab OCEC

  17. T/O Analysis of Diesel \------------- He ------------\----------- Ox ---------------\ T = 870 C  Int. Calib. Std. Laser Transmission. OC/EC Split Pt. FID response to Carbon Note: Very Little Pyrolysis Note: Small OC4 Peak Note: EC Peak Location Sunset Lab OCEC

  18. T/O Analysis of Ambient( wood smoke and metal oxides) \-------------- He ----------------------\--------------- Ox ---------------------------\ n.b., Sample Very Dark at Start EC/OC Split Pt. Absorbance ------------------------------------------------------------------------------------------- -------------------------------------------------------------------------------------------------- Note: Location of EC Peaks Note: Abs Increase at OC4 [Fe] = 7.8 ug/sq cm Sunset Lab OCEC

  19. Sample with OC and Carbonate Carbon \------------------ He -----------------\--------------------- Ox ---------------------\ Cal. Pk. CC Note: Sharp OC4 Peak Sunset Lab OCEC

  20. T/O of Pure OrganicEDTA \------------------- He -------------\----------------- Ox -----------------\ Cal. Pk. Sunset Lab OCEC

  21. Further Pre-Treatments • Solvent Extractions (organic or water) • Chemical Pre-Treatments • Other Thermal-Treatments Sunset Lab OCEC

  22. Pre-Treatment with Oxygen followed by Full Thermal-Optical Analysis Residual then Analyzed with TOA \------- He -----------\---------- Ox --------------\ 870 C \-----------------He and Oxygen -------------\ Cal Pk. 530 C  Cal. Pk Sunset Lab OCEC

  23. SUMMARY • There are Chemical and Physical Definitions of EC • These Properties may differ for small particles compared with bulk material • Analytical Methods should try to be consistent with these definitions Sunset Lab OCEC

  24. Further Research on EC • Can Additional Pre-treatments Help? • Do the Physical or Chemical Properties Change? - From Source to final Collection or Measurement? - During Analysis itself? Sunset Lab OCEC

More Related