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Atmospheric Chemistry at

Atmospheric Chemistry at. Ole John Nielsen Department of Chemistry, University of Copenhagen. Outline. Who am I? What are the concerns on atmospheric emissions? How do we study atmospheric chemistry? Cases: CFC alternatives Trifluoroacetic acid (TFA) CF 3 COOH

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Atmospheric Chemistry at

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  1. Atmospheric Chemistry at Ole John Nielsen Department of Chemistry, University of Copenhagen

  2. Outline • Who am I? • What are the concerns on atmospheric emissions? • How do we study atmospheric chemistry? • Cases: • CFC alternatives • Trifluoroacetic acid (TFA) CF3COOH • Perfluoro organic acids (PFOAs) • Alternatives to the CFC alternatives • Conclusions

  3. 5.5M people 43000 km2 1009M people 3287000 km2

  4. Why/How did I become interested inAtmospheric Environmental Chemistry? 1954 Born 1973 Began at UoC (chemistry and physics) 1974 Important Atmospheric Year 1978 M.Sc. and on to do a PhD at Risø Nat. Lab. 1978-95 Risø National Laboratory 1995-96 Ford Research Center Aachen, Germany 1996-99 Risø National Laboratory 1999-? Professor at UoC 2007 Nobel Peace Prize together with Al Gore and 2500 scientists Gas phase kinetics and reaction mechanisms - relevant to the atmosphere IPCC – Intergovernmental Panel of Climate Change – India?

  5. Mr. Jens Sehested Mrs. Trine Møgelberg Mrs. Merete Bilde Mrs. Lene Christensen Mr. Jesper Platz Mrs. Anne Toft Mr. Mads Andersen Mrs. Meshkat Javadi Tim Wallington (Ford) Mike Hurley (Ford) Jim Ball (Ford) John Owens (3M) Rajiv Singh (Honeywell) Bob Waterland (Dupont) Scott Mabury (Toronto) Brian Scott (CanEnv) Acknowledgements

  6. What are the Concerns on Atmospheric Emissions ? 1. Radiation Forcing/Global Warming/Climate Change • (global) 2. Stratospheric Ozone Depletion (CFCs) • (global) 3. Tropospheric Oxidant Formation • (local-regional-global) 4. Harmful emissions and/or Harmful Degradation Products • (local-regional-global) • Example: 1984 Bhopal accident, methyl isocyante • What do we need to know about a compound in order to quantify the environmental impacts ? • "Guilty - until proven innocent" • We (the people of the Earth) have been extremely lucky (CFCs)

  7. We need to know the atmospheric chemistry

  8. And that is the research that we do: • Atmospheric Science (Chemistry) Research Investigations of chemical/physical processes We use the lab and/or the field and/or modelling to provide a better understanding of atmospheric processes and composition. • Will lead to better quantification of environmental impact • May not lead to a better environment

  9. Laser Photolysis 1 liter stainless steel UV/VIS-absorption pm or diode array microsec. resolution Kinetics Continuous photolysis 100 liter Quartz FTIR spectroscopy 26 m and 0.25 cm-1 min. resolution Kinetics and Products How ? Initiation Container Detection

  10. How ? laser

  11. What problems are we interested in? • How and why are compounds degraded or transformed in the atmosphere in certain ways? • CFC alternatives • Trifluoroacetic acid (TFA) CF3COOH • Perfluoro organic acids (PFOAs) • Alternatives to the CFC alternatives • Biofuels for transportation • Greenhouse gases in general • Formation of cloud condensation nuclei

  12. What was the issue in 1974? • Ask: “What happens with …..?” – and get the Nobel Prize (the real one) • Rowland and Molina asked themselves What happens to CFCs in the atmosphere? CF2Cl2 does not react in the troposphere but is photolyzed in the stratosphere: CF2Cl2 + hν→ CF2Cl + Cl - and so what?

  13. What was the problem? 1974? 1985? CFC-11 CFCl3 Cl + O3→ ClO + O2 ClO + O → Cl +O2 -------------------------- O + O3→O2 + O2 CFC-12 CF2Cl2 What did the chemists have to do to protect the ozone?

  14. What did the chemists have to do to protect the ozone? Make similar compounds with shorter lifetimes or make similar compounds with no Cl or both • HCFC: Hydrochlorofluorocarbons: CHClF2 • HFC: Hydrofluorocarbons: CF3CFH2 • HFE:Hydrofluoroethers: CF3OCF2H CHClF2 + OH → H2O + CClF2 → ……….

  15. Better in every way – But

  16. CFC alternatives - Conclusions • 25 papers with the title ”Atmospheric Chemistry of……” • last one in 1998 – we thought ! • The new compounds did not destroy ozone • The new compounds did not produce ozone in the troposphere • The new compounds were more acceptable as green house gases – good enough? • Some of the new compounds produced TFA

  17. TFA (CF3COOH) IN THE ENVIRONMENTWhy are we interested ? • pKa = 0.23 • Solubility > 10000 g/L • Henry´s law constant 0.112 atm cm3/mole • kOH = (1.7±0.5)x10-13 cm3molecule-1s-1 (68d) • Other Sinks ? Bacteria ? No real sinks! • Phytotoxic • Atmospheric sources e.g.: • CF3CFH2, CF3CCl2H, CF3CFClH • Analysis: Derivatization and GC-MS

  18. Objective 1 • Compare the levels of TFA calculated to arise from known sources with those observed in the environment.

  19. CF3COOH - KNOWN SOURCES

  20. CF3COOH - CONCENTRATIONS • TFA found in oceans, rivers, lakes, fog, snow, rainwater and air samples (U.S., Germany, Israel, Ireland, France, Switzerland, Austria, Russia, South Africa, and Finland) • TFA in rainwater in Bayreuth 1995 was 100 ng/L • Jordan, A.; Frank, H., Environ. Sci. Tech., 1999, 33, 522. • Fog and rain 36 samples in 1994-1996 in California and Nevada contained 31-3779 ng/L TFA • Wujcik, C. E.; Zehavi, D.; Seiber, J. N., Chemosphere, 1998, 36, 1233. • TFA in ocean water (Pacific, Atlantic, Arctic) 20-250 ng/L • Wujcik, C. E.; Zehavi, D.; Seiber, J. N., Chemosphere, 1998, 36, 1233. • Scott, B. F. et al. at the Atmospheric Reactive Substances Symposium, April, 1999. • No variation with depth down to 3000m (300years) • Scott, B. F. et al. at the Atmospheric Reactive Substances Symposium, April, 1999.

  21. CF3COOH - BURDEN • TFA in ocean water (Pacific, Atlantic, Arctic) 20-250 ng/L • Wujcik, C. E.; Zehavi, D.; Seiber, J. N., Chemosphere, 1998, 36, 1233. • Scott, B. F. et al. at the Atmospheric Reactive Substances Symposium, April, 1999. • The oceans: 1.4x1021 L • The oceans contain (0.3-3.5)x108 tonnes of TFA

  22. CF3COOH - DILEMMA • The oceans contain (0.3-3.5)x108 tonnes • TFA flux of 3080 tonnes/yr • 10000-100000 years to give current TFA levels • But – we have only used these compounds for 50 years? • Possible conclusions: • concentration measurements are all wrong ? • Under-estimated the sources ? Unknow sources ? • Or both ?

  23. Objective 2 • Have there been old/natural sources of TFA ?

  24. Old Groundwater

  25. Old Ice

  26. Conclusions • TFA is not a natural component of the freshwater hydrosphere ! • TFA from underwater volcanic activity ? • Sources of TFA in ocean water need to be determined !

  27. Long chain perfluorinated acids (PFCAs/PFAs) observed in fauna in urban and remote locations PFOA (perfluorooctanoic acid) C7F15C(O)OH PFNA (perfluorononanoic acid) C8F17C(O)OH PFDA (perfluorodecanoic acid) C9F19C(O)OH PFUA (perfluoroundecanoic acid) C10F21C(O)OH PERSISTENCE ! – ASK ME ABOUT IT

  28. Contamination Profile - Polar Bears (Sanikiluaq Isl.) Box plots show the outliers, 10th, 25th, median, 75th and 90th centile. We’re 0.0001% PFOS ! <0.5 n.d. Martin et al. 2004

  29. C10F21C(O)OH

  30. Where do long chain Perfluorocarboxylicacids (PFCAs), CnF2n+1COOH come from? No natural sources. Water-soluble PFCA salts used in fluoropolymer processing. Not released in significant quantities. Presence of PFCAs in remote areas and in foxes suggests atmospheric source.

  31. PolyfluoroAlcohols are highly volatile!!! Observed in the atmosphere 8:2 FTOH = 212 Pa HC data from Daubert & Danner; FTOH data from Lei et al, J Chem Eng Data and Stock et al, ES&T, both in press.

  32. FTOH based coatings heavily used in consumer products; 5x106 kg/yr 40% in North America 80% are in polymers* *TRP Presentation to USEPA OPPT. Nov 25, 2002 US Public Docket AR226-1141

  33. Research Question: Does atmospheric oxidation of FTOHs contribute significantly to PFCA burden in remote locations? • Three necessary conditions: • FTOH survive long enough for atmospheric transport • FTOH degrade to give PFCAs • Magnitude of PFCA formation must be significant Use a FTIR Smog chamber

  34. UV irradiation of FTOH/reference/CH3ONO/NO/air mixtures FTOH = 4:2 FTOH, 6:2 FTOH, or 8:2 FTOH reference = C2H2 or C2H4 CH3ONO  CH3O + NO CH3O + O2 HCHO + HO2 HO2 + NO  OH + NO2 OH + FTOH  products (1) OH + reference  products (2)

  35. OH + FTOH  products (1) OH + reference  products (2) Integration gives: FTOH and reference have equal exposure to OH radicals, hence:

  36. No discernable difference in reactivity of OH radicals towards 4:2, 6:2, and 8:2 FTOH OH + CnF2n+1CH2CH2OH → products (10) OH + C2H2 → products (11) OH + C2H4 → products (12) Linear fits give k10/k11 = 1.18±0.15 and k10/k12 = 0.131±0.018. Using k11 = 8.5 x 10-13 and k12 = 8.66 x 10-12 gives k10 = (1.00±0.13) x 10-12 and (1.13±0.16) x 10-12 cm3 molecule-1 s-1. Final value, k10 = (1.07±0.22) x 10-12 cm3 molecule-1 s-1.

  37. FTOH Lifetime Estimate Assuming: atmospheric lifetime* for CH3CCl3 = 5.7 years k(CH3CCl3 + OH) = 1.0 x 10-14 cm3 molecule-1 s-1 then atmospheric lifetime* of CF3(CF2)nCH2CH2OH  (1.0x10-14)/(1.1x10-12) x 5.7 x 365  20 days. * with respect to reaction with OH radicals

  38. Other loss mechanisms? Photolysis – is negligible Rainout – estimated to be negligible Dry deposition – lifetime estimated to be 8 years Homogeneous reactions other than with OH - unlikely Atmospheric lifetime determined by reaction with OH and is approximately 20 days.

  39. 20 days… Long Enough for Long Range Transport? Assuming 5m/s winds and a 20d lifetime, FTOHs could be transported over 8500 km Copenhagen to Detroit = 6500 km

  40. Does atmospheric oxidation of FTOHs contribute significantly to PFCA burden in remote locations? Three necessary conditions: (1) Do FTOHs survive atmospheric transport? YES (2) Do FTOHs degrade to give PFCAs? (3) Magnitude of PFCA formation must be significant

  41. FTIR study of 4:2 FTOH oxidation CF3(CF2)3CH2CHO is the major primary product from Cl atom and OH radical initiated oxidation of 4:2 FTOH

  42. CnF2n+1CH2CH2OH + OH  CnF2n+1CH2C(•)HOH + H2O CnF2n+1CH2C(•)HOH + O2 CnF2n+1CH2CHO + HO2 CnF2n+1CH2CHOis reactive … Gives secondary products … Secondary products: C4F 9CHO, C4F9CH2COOH C4F9C(O)OOH Secondary products are reactive …

  43. Tertiary products include: COF2, CF3OH C4F9COOH Conclusion of FTIR experiments: simulated atmospheric oxidation of 4:2 FTOH (in absence of NOx) gives a small (few %) yield of C4F9COOH

  44. FTIR data shows that in gas phase: in absence of NOx 4:2 FTOH   C4F9CHO C4F9COOH in presence of NOx 4:2 FTOH   C4F9CHO C4F9COOH Likely explanation, presence of HO2 radicals in absence of NOx because: HO2 + NO → OH + NO2 is a very fast reaction Well established that CH3C(O)O2 + HO2 gives acetic acid and peracetic acid, , presumably CxF2x+1C(O)O2 + HO2 reaction gives CxF2x+1COOH and CxF2x+1COOOH. Product study of CxF2x+1C(O)O2 + HO2 (x=1-4) to test this idea.

  45. IR spectra obtained before (A) and after (B) 55 s of irradiation of a mixture of 18.8 mTorr C2F5C(O)H, 218 mTorr Cl2 and 2.8 Torr H2 in 700 Torr of air. The consumption of C2F5C(O)H was 63%.

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