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Nitrous Oxide: Stratospheric Isotopic Composition and Tropospheric Impact

Nitrous Oxide: Stratospheric Isotopic Composition and Tropospheric Impact . Y. L. Yung, J. Weibel* and R. L. Shia Divisions of Geological and Planetary Sciences California Institute of Technology, CA * Chemistry Department, Shenandoah University, Winchester, VA.

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Nitrous Oxide: Stratospheric Isotopic Composition and Tropospheric Impact

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  1. Nitrous Oxide: Stratospheric Isotopic Composition and Tropospheric Impact Y. L. Yung, J. Weibel* and R. L. Shia Divisions of Geological and Planetary Sciences California Institute of Technology, CA *Chemistry Department, Shenandoah University, Winchester, VA

  2. 14N14N16O (446) _ 14N15N16O (456) --N 15N14N16O (546) --N 14N14N18O (448) --18O (δ15N = ½ [δN + δN]) # Source: natural -- land -- ocean anthropogenic -- agriculture, fossil fuels & industry, biomass burning,… # Sink: (stratosphere) -- photolysis and chemistry (~160-220 nm) N2O continues to increase in the atmosphere. However, contribution of each source is not well-quantified.

  3. Kim and Craig 1993

  4. Liang and Yung 2007 JGR112(D13): D13307

  5. Liang and Yung 2007 JGR112(D13): D13307

  6. ISI 2008 Liang and Yung, Isotopic Constraints on the Global Budget and Trend of Atmospheric Nitrous Oxide Method – a simple box model F_sink Available measurements: 1. N2O trend 2. 18O 3. 15N ( and ) Troposphere F_ocean F_land F_anthro. (1) Ocean source = prescribed isotopic composition. (2) The isotopic composition of anthropogenic source = land source (3) Solve the mean isotopic composition of land for PRE. (4) Magnitude of the natural and anthropogenic sources are deduced. (5) The strength of STE does not vary. (6) The lifetimes do not vary with time.

  7. x: Machida et al. [1995] +: Bernard et al. [2006]

  8. Time evolution of δ18O(N2O) and δ15N (N2O) x: Sower et al. [2002]

  9. Sources and sinks OC -- ocean LD -- land AN -- anthropogenic Total = OC+LD+AN SK -- sink TD -- trend

  10. Park et al. 2010, Cape Grimm

  11. Source of N2O (IPCC vs. Model) IPCC2007 AR4 IPCC2007 AR4 range Model result 0 1 2 3 4 5 6 7 8 9 10 (Tg N yr-1) Natural sources Soils (natural vegetation) Oceans Atmospheric chemistry Anthropogenic sources AG+ HE+ ADa FF+ BB+ RE b • a. AG: Agriculture. HE: Human excreta. AD: Atmospheric deposition. • FF: Fossil fuel combustion & industrial processes. BB: Biomass and biofuel burning. • RE: Rivers, estuaries, coastal zones.

  12. Conclusion • Better measurements are needed as present data have large errors • Seasonal Cycle Use the Caltech/JPL 2-D and MOZART/CAM-CHEM 3-D models for better estimates

  13. Thanks M. C. Liang K. Boering Yung’s group NSF

  14. Backup slides

  15. FF+BB+RE ocean 1700 1970 2003 land

  16. Secular changes 1970-2003 A.D. Bernard et al. 2006 1700-2003 A.D. Bernard et a 2006 1990-2003 A.D. Rockmann and Levin 2005  = [(t1) - (t2)] / [N2O(t1) - N2O(t2)]

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