1 / 23

THE SIZE & COMPOSITION DEPENDENCE OF NITRIC ACID REACTIVE UPTAKE

THE SIZE & COMPOSITION DEPENDENCE OF NITRIC ACID REACTIVE UPTAKE ONTO MARINE AEROSOL NANO-DROPLETS. Thomas D. Saul, Michael P. Tolocka, and Murray V. Johnston. University of Delaware - Department of Chemistry and Biochemistry. 22nd Annual AAAR Conference - Platform Session #10

marvin
Download Presentation

THE SIZE & COMPOSITION DEPENDENCE OF NITRIC ACID REACTIVE UPTAKE

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. THE SIZE & COMPOSITION DEPENDENCE OF NITRIC ACID REACTIVE UPTAKE ONTO MARINE AEROSOL NANO-DROPLETS Thomas D. Saul, Michael P. Tolocka, and Murray V. Johnston University of Delaware - Department of Chemistry and Biochemistry 22nd Annual AAAR Conference - Platform Session #10 Thursday, October 23rd, 2003

  2. HNO3 (g) + NaCl (s) NaNO3 (s) + HCl (g) (1) N2O5 (g) + NaCl (s) NaNO3 (s) + ClNO2(g) (2) ClONO2 (g) + NaCl (s) NaNO3(s)+ Cl2 (g) (3) Halogen Deficit in Marine Aerosols

  3. Coastal Ecosystem’s Nitrogen Balance HOCl HO2 h O CH4 ClO Cl HCl (g) O3 OH h h NO2 ClONO2 HNO3 (g) + NaCl (aq) NaNO3 (aq) + HCl (g) (1) Escape to the mid-latitude Lower Stratosphere Wet or dry deposition Simplified schematic of the ClOx ozone depletion cycle

  4. Goals of this Research: ·Employ SP-TOF-MS to investigate the heterogeneous kinetics of Cl- to NO3- conversion. ·Facilitate experimentation above the deliquescent RH of NaCl nano-particles (>75% RH). ·Determine reaction rate constants and uptake coefficients. ·Apply a resistance model of gas-droplet interactions to depict physical mechanistic dependencies. ·Better understand how anthropogenic emissions influence the composition of sea-salt aerosols.

  5. Single Particle Mass Spectrometer

  6. NO2- O- NO3- .08 .07 Na- 37 Cl- 35 Cl- .06 NO- .05 NaCl- Relative Abundance .04 1 .03 .8 .6 .02 .4 Mass Fraction NO3 .01 .2 0 0 10 15 20 25 30 35 40 45 50 55 60 65 70 m/Z SP-TOF-MS - Response to Standard Aerosols

  7. - Cl X Relative Ion Response (RIR) 1.0 0.8 0.6 0.4 0.2 0.0 0.0 0.2 0.4 0.6 0.8 1.0 SCl/(SCl+SNO3)

  8. Nitric Acid Generation, Dilution and Detection

  9. RDMA - size selection Humid air  Relative humidity and aerosol deliquescence

  10.  HNO3(g)  Reaction Chamber NaCl aerosol droplets

  11. Experimental Design: Aerosol kinetics through SP-TOF-MS. ~3 Torr ~5 x 10-7 Torr

  12. Monitoring Chloride Concentration / Conversion ·The molar concentration of Chloride in a single aerosol droplet can be monitored: (4) ·The time-dependent rate of chloride ion loss (moles/liter-sec) in a droplet is given by: (5)

  13. ~8M NaCl 100nm droplets First order exponential loss of [Cl-] vs. time HNO3 (g) + NaCl (aq) NaNO3 (aq) + HCl (g) 0.0 -0.2 -0.4 ln([Cl]/[Cl]0) -0.6 [HNO3] ppb -0.8 378 189 95 -1.0 63 -1.2 -6 -6 -6 -6 -5 -5 0.0 2.0x10 4.0x10 6.0x10 8.0x10 1.0x10 1.2x10 x t P HNO3

  14. Dependence of Pseudo-first order rate constants (kobs) with HNO3 concentration.

  15. Net Collisional Uptake Probability (gnet): (6) net g [HNO ], ppb k 3 obs 0 ~100 nm droplets _ -2 -3 378 3.73 x 10 6.9 x 10 _ -2 -3 189 1.18 x 10 4.4 x 10 _ -3 -3 95 5.20 x 10 3.9 x 10 _ -3 -3 63 3.04 x 10 4.5 x 10  g -3 4.9 x 10 Ave 0

  16. Published Reactive Uptake Coefficients & This Work g0 Laboratory Technique Sample Type HNO3 concentration [molecules/cm3] 3 x 1012 to 3.5 x 1013 Beichert and Finlayson-Pitts MS Knudsen Cell Single crystals; Ground powders 1.4 x 10-2 5 x 1011 to 7 x 1013 Flow Tube Davies and Cox Ground powders 0.8 to 9 x 10-4 Ground powders Single crystals Ghosal and Hemminger XPS/UHV Predicted model 1.1 x 10-3 8 x 109to 4 x 1010 5.9 x 10-2 Recrystallized NaCl Zangmeister and Pemberton Raman Spectroscopy Single crystals Ghosal and Hemminger XPS/UHV 8 x 1012 to 9 x 1013 5 x 10-3 Flow Tube Tolocka, Saul, and Johnston 1 x 1012 to 1 x 1013 4.9 x 10-3 100nm NaCl Aerosols/droplets

  17. Resistance Model of Gas-Droplet Interactions ·Net Collisional Uptake Probability: gnet = net rate of uptake of the gas normalized to the rate of gas-surface collisions. Gas Phase Liquid FAST FAST Liquid-phase diffusion Transfer across interface Gas-phase diffusion Chemical reaction FAST Adapted from Finlayson-Pitts, Chemistry of the Upper & Lower Atmosphere. 2000

  18. ·Mechanisms that Limit Uptake Kinetic expression Uptake expression Surface Reaction Reaction in a surface layer Reaction throughout droplet

  19. ddrop = 100nm ddrop = 200nm HNO3 HNO3 HNO3 HNO3 Na+ Cl- Na+ Cl- Cl- Na+ Cl- Na+ Cl- Na+ Cl- Na+ Cl- Na + Cl- Na+ Cl- Na+ Cl- Na+Na+ Cl- Na+ Cl- Cl- Na+ Cl- Na+ Cl-Cl- Na+ Cl Na+ Cl- Na+ Cl- Cl- Na+ Cl- Na+ Na+ Cl- Na+ Cl- Cl- Na+ Cl- Na+ Cl- Cl- Na+ Cl- Na+ Cl- Na+ Cl- Cl- Na+ Cl- Na+Na+ Cl- Na+ Cl- Cl- Na+ Cl Na+ Cl- Na+ Cl- Na+ Cl- HNO3 HNO3 Cl- Na+ Cl- Na+ Cl- Na+ Cl- Cl- Na+ Cl- Na+ Na+ Cl- Na+ Cl- Cl- Na+ Cl- Na+ Cl- HNO3 HNO3 HNO3 HNO3 HNO3 HNO3 HNO3 HNO3 HNO3 HNO3 HNO3 HNO3 HNO3 HNO3 HNO3

  20. Laboratory Techniques ·Single-particle mass spectra quantitatively depict the chemical composition of individual particles. ·Kinetic experiments can be performed for significant reactions that may occur in the marine boundary layer. Size-Dependence Conclusions Heterogeneous Reactions ·A resistive model of gas-liquid interactions can help understand the mechanism of uptake. ·The reactive uptake of HNO3(g) onto NaCl (aq) appears to be limited by a UNDER REVIEW. * Note: the reactant and product both traverse the gas-liquid interface

  21. HNO3 HNO3 HNO3 HNO3 HNO3 HNO3 HNO3 HNO3 HNO3 HNO3 HNO3 HNO3 HNO3 HNO3 HNO3 HNO3 HNO3 HNO3 HNO3 HNO3 CH2CH3 CH2CH3 CH2CH3 Na+ Cl- Na+ Cl- Cl- Na+ Cl- Na+ Cl- Na+ Cl- Na+ Cl- Na + Cl- Na+ Cl- Na+ Cl- Na+Na+ Cl- Na+ Cl- Cl- Na+ Cl- Na+ Cl-Cl- Na+ Cl Na+ Cl- Na+ Cl- Cl- Na+ Cl- Na+ Na+ Cl- Na+ Cl- Cl- Na+ Cl- Na+ Cl- Cl- Na+ Cl- Na+ Cl- Na+ Cl- Cl- Na+ Cl- Na+Na+ Cl- Na+ Cl- Cl- Na+ Cl Na+ Cl- Na+ Cl- Na+ Cl- CH2CH3 CH2CH3 Cl- Na+ Cl- Na+ Cl- Na+ Cl- Cl- Na+ Cl- Na+ Na+ Cl- Na+ Cl- Cl- Na+ Cl- Na+ Cl- CH2CH3 CH2CH3 CH2CH3 CH2CH3 CH2CH3 CH2CH3 CH2CH3 CH2CH3 HNO3 CH2CH3 CH2CH3 CH2CH3 Current Work Surfactants - decomposition of marine organisms releases hydrocarbons. Sea spray can consist of an aqueous salt core and an organic monolayer surface. CH2CH3 CH2CH3 CH2CH3 CH2CH3 CH2CH3 CH2CH3 CH2CH3 CH2CH3 CH2CH3 CH2CH3 CH2CH3 CH2CH3 CH2CH3 CH2CH3 CH2CH3 CH2CH3 CH2CH3 CH2CH3 CH2CH3 CH2CH3 CH2CH3 CH2CH3 CH2CH3 CH2CH3 • Will organic compounds on the surface of the droplets influence the kinetics of chloride to nitrate conversion? • Will saturated and/or unsaturated hydrocarbons inhibit gnet? Stay tuned…...

  22. ¤ Dr. Doug Worsnop • Aerodyne National Science Foundation CHE-0098831 Acknowledgements University of Delaware ¤ Dr. Murray Johnston ¤ Mr. Berk öktem ¤ Dr. Michael Tolocka ¤ Mr. Derek Lake • UNC-Chapel Hill • ¤ Professor Tomas Baer

  23. Gas-phase diffusion Dg = Diffusion coefficient (gas phase) dd = diameter of NaCl droplet Transfer across interface: stick or bounce off Solubility and diffusion into bulk Dl = Diffusion coefficient (liquid phase) Reaction in aqueous-phase k = irreversible first order rate contstant (s-1)

More Related