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

5. 14 N 14 N 16 O (446) _ 14 N 15 N 16 O (456) -- N  15 N 14 N 16 O (546) -- N  14 N 14 N 18 O (448) -- 18 O (δ 15 N = ½ [δN  + δN  ]) # Source: natural -- land -- ocean anthropogenic -- agriculture, fossil fuels & industry, biomass burning,… # Sink : (stratosphere) -- photolysis and chemistry (~160-220 nm) N 2 O continues to increase in the atmosphere. However, contribution of each source is not well-quantified.

6. Kim and Craig 1993

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

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

9. (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. Troposphere F_oceanF_landF_anthro. F_sink ISI 2008Liang and Yung, Isotopic Constraints on the Global Budget and Trend of Atmospheric Nitrous Oxide Available measurements: 1. N 2 O trend 2.  18 O 3.  15 N (  and  )

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

11. x: Sower et al. [2002] Time evolution of δ 18 O(N 2 O) and δ 15 N (N 2 O)

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

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

14. Secular changes  = [  (t1) -  (t2)] / [N 2 O(t1) - N 2 O(t2)] 1700-2003 A.D. Bernard et a 2006 1970-2003 A.D. Bernard et al. 2006 1990-2003 A.D. Rockmann and Levin 2005

15. Models

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

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