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Black Carbon (soot) as an air pollutant

Black Carbon (soot) as an air pollutant. Outline. Soot: What is it? Detection Techniques Climate Impact Physics Prior budgets INDOEX Budget evaluation Conclusions. Soot Particle from a Wood-Burning Stove. Definition of Black Carbon, soot.

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Black Carbon (soot) as an air pollutant

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  1. Black Carbon (soot) as an air pollutant

  2. Outline • Soot: What is it? • Detection Techniques • Climate Impact • Physics • Prior budgets • INDOEX • Budget evaluation • Conclusions

  3. Soot Particle from a Wood-Burning Stove

  4. Definition of Black Carbon, soot • An aerosol with strong visible light absorption of at least 5 m2/g at 550 nm fairly uniform across spectrum. • Refractory; vaporization temp near 4000 K. • Aggregate morphology. • High sp2 carbon-bond content • Insoluble in water; soluble in conc. sulfuric acid.

  5. Structure of Soot

  6. Scanning electron microscope image of particles collected in Xianghe, W of Beijing.

  7. Detection techniques for Black Carbon, soot • Subject of debate (Bond et al., JGR, 2013) • Analytical challenge – difficult to separate from organic carbon, OC. • Sunset labs uses He purge, temperature ramp, MnO2 oxidizer, and NDIR CO2 analysis. Repeat under O2 for BC (EC). • Total organic carbon more precise.

  8. From Bueno, 2011.

  9. From Bond et al., 2013. Pedro Bueno Ph.D. Dissertation, 2011.

  10. Photoacoustic Spectrometer schematic diagram.Bueno, 2011.

  11. The Single Particle Soot Photometer (SP2) utilizes the high optical power available intracavity from an Nd:YAG laser. Light-absorbing particles, mainly black or elemental carbon in atmospheric measurements, absorb energy and are heated to the point of incandescence. The energy emitted in this incandescence is measured, and a quantitative determination of the black carbon mass of the particle is made. This mass measurement is independent of the particle mixing state, and hence the SP2 is a reliable measure of the black carbon mass concentration. Since the SP2 detects single particles, the SP2 can also measure the black carbon number concentration.

  12. Climate forcing for atmospheric gases and aerosolsIPCC (2001) *Jacobson Nature, 2001.

  13. Radiative Effects (Climate Impact) of Soot • External mixture +0.27 Wm-2 • Coated core +0.54 Wm-2 • Well-mixed internally +0.78 Wm-2 (Jacobson, GRL., 2000)

  14. External vs. Internal Mixtures Sulfate & Soot mixed externally. Soot with sulfate coating (coated core). Well-mixed internally.

  15. Global Fossil Fuel Black Carbon Emissions(Cooke et al., JGR., 1999; Penner et al., 1993)

  16. Indian Today, 1996

  17. INDOEX, 1999 INDOEX Experimental Design

  18. NOAA R/V Ronald Brown

  19. Impactor Samples from Ship during INDOEX

  20. Origin of Soot? • Ratio of BC/OC near unity means origin should be fossil fuel • combustion (Novakov et al., 2001). • Low single scattering albedo, 0.81, indicates 70% from fossil • fuel combustion (Mayol-Bracero et al, 2001).

  21. Emissions InventoriesGg yr-1 Black Carbon from South AsiaHigh Estimate for 1999

  22. Estimate of BC Emissionfrom Ambient Measurements EBC = ECO*[BC]/[CO]/LBC Fort Meade, MD EBC = 90 Tg(CO)/yr * 0.0034 = 0.31 Tg(BC)/yr for N America (vs. 0.49 Tg(BC)/yr) INDOEX EBC = 87 Tg(CO)/yr * 0.0125/0.5 = 2.2 Tg(BC)/yr for South Asia (vs. 0.5 to 1Tg(BC)/yr)

  23. Source Strength Black Carbon in China Estimated annual BC emissions from China: 1300-2600 Gg/yr Inventory: 1049 Gg/yr [Streets et al., 2003] Better agreement compared to a similar study for India [Dickerson et al., 2002] Single Scattering Albedo (SSA): Morning: ~0.81, Afternoon: ~0.85

  24. Summary • Black Carbon (soot) may provide more forcing than methane. • Properties of aerosols suggest that fossil fuel combustion is main source of black carbon from South Asia. • Inventories suggest biofuels contribute substantially, and cannot support emissions above 1 Tg(BC) a-1. • Ambient measurements suggest major role for biomass burning and indicate 2-3 Tg(BC) a-1. • Combustion in S. Asia is unlike anything seen in N America or Europe. • Biomass burning generates OA that age to become darker Gustafsson Science, 2009. • A major contributor to human health and climate the world over.

  25. Black Carbon References

  26. Two-Stroke Engine • No Valves • Oil mixed with gasoline • Part of fresh charged exhausted • Fuel adulteration

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