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Sources of Chlorine Radicals in the Marine Boundary Layer

This study investigates the sources of chlorine radicals in the polluted marine boundary layer through in-situ measurements of ClNO2 and Cl2. It explores the potential effects of Cl atoms on ozone, VOCs, and mercury levels. The findings suggest substantial inland production of Cl atom precursors, which are then transported to marine environments. The study emphasizes the importance of considering ClNO2 as a Cl atom precursor alongside Cl2.

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Sources of Chlorine Radicals in the Marine Boundary Layer

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  1. Chlorine Radical Sources in the Polluted Marine Boundary Layer: Insights from in situ measurements of ClNO2 and Cl2 Joel Thornton and Theran Riedel Department of Atmospheric Sciences Department of Chemistry University of Washington Seattle, WA

  2. Atomic Chlorine • Atomic Cl has a large oxidizing potential (10-100x OH) • Cl atoms have potential to substantially affect O3, VOC, and Hg levels. • Cl atom sources are uncertain, but Cl2 has typically been considered the major Cl atom source in polluted regions • Pechtl and von Glasow. GRL, 2007 • Knipping and Dabdub. ES&T, 2003 • Spicer et al. Nature 394, 1998.

  3. Atomic chlorine production ? HOCl H+, Cl- Cl2 ClNO2 Cl- OH N2O5 Cl HCl BrCl H+, Cl- HOBr

  4. Expected ClNO2 production ClNO2 Production: log(g Cl/year) From: Thornton, et al. Nature 464, 2010

  5. CalNex observations Los Angeles, CA ClNO2 pptv

  6. Expected Cl2 levels • Spicer et al. at Long Island, NY, June 1996. • Finley and Saltzman at La Jolla, CA, January 2006. From: Spicer et al. Nature 394, 1998. AND Finley and Saltzman. JGR 113, 2008.

  7. CalNex observations

  8. Inland production and plume transport/interception? Santa Monica Bay

  9. ClNO2 and Cl2 correlations UTC DOY

  10. Cl atom production: ClNO2 vs. Cl2

  11. Thoughts • Our observations consistent with substantial inland production of Cl atom precursors transported to marine environments along with continued production off shore. • ClNO2 should be considered a Cl atom precursor with at least similar importance to Cl2. • Measurements of N2O5 and aerosol composition, mixing, play important roles given the heterogeneous reaction mechanism at work.

  12. Opportunities for Collaboration & Future Analyses • ClNO2 production efficiencies • ClNO2 yield predictions • Utilize HCl measurements • Hydrocarbon evidence of Cl atom chemistry • Utilize PTRMS and GC-FID VOC data • ClNO2 as a fraction of NOy • Box modeling Cl activation and Cl atom chemistry

  13. The End Funding: NASA NESSF NNX-10AN48H,

  14. ClNO2 as a fraction of NOy

  15. Finley and Satlzman. JGR 113, 2008

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