Naturally produced organohalogens; Atmospheric simulation experiments on halogen activation in aerosol smog chamber facilities with sea salt and secondary organic aerosol (HALOSOA)
Hydrogeologie, Hydrologie, Limnologie, Siedlungswasserwirtschaft, Wasserchemie, Integrierte Wasserressourcen-Bewirtschaftung
Mineralogie, Petrologie und Geochemie
Zusammenfassung der Projektergebnisse
The installation of an aerosol smog chamber, made of FEP-Teflon film, with an inserted FEP-Teflon sheet for exposure of salt samples in a refrigerated laboratory with a solar simulator provides a unique facility for atmospheric research. The facility was shared with partners of the research unit with external partners providing optical detection methods for BrO, ClO, OClO, IO, atomic I, I2, IONO2, BrONO2 and chemical ionization mass spectrometry for numerous reactive halogen substances, enabling us to study photochemical halogen activation from simulated salt pans and from aerosol (doped salt samples and aerosol droplets). Ozone depletions above simulated salt pans and in the presence of deliquescent salt aerosol were observed to be catalyzed by bromide, leading to bromine explosions observed for the first time in laboratory experiments. The ultrasonic nebulizer was found to produce HONO during the production of the aerosol as an unexpected interference. BrO radicals were observed to occur simultaneously with the depletions and to be largely dependent on NOx, the relative humidity and on the level of bromide in the quasi-liquid layer of the salt pan/the aerosol droplets. ClO radicals and OClO were observed in addition. Time profiles of OH radicals and atomic Cl and Br were determined by gas chromatographic monitoring of a test mixture of hydrocarbons (toluene and alkanes) by these radical species. The aerosol experiments were accompanied by model calculations. The presence of secondary organic aerosol (SOA) was observed to diminish the halogen activation above the salt pan and in the presence of photoactivated salt aerosol droplets, and uptake coefficients of reactive bromine species on three types of SOA (from catechol, guaiacol and α-pinene) were determined. The role of iron-(III) ions and hematite was investigated by photochemical experiments with a iron-doped salt pan and with salt aerosol, containing dissolved iron(III) or suspended hematite particles. Photo-Fenton reactions were found to activate Cl and Br efficiently in a catalytic cycle, and the source strengths per square cm of aerosol surface were quantified. An estimate of the global impact will require model calculations. Kinetic isotope effects of the reactions of OH and Cl with methane and methyl chloride were determined by gas-phase chamber experiments.
Projektbezogene Publikationen (Auswahl)
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Physico-chemical characterization of SOA derived from catechol and guaiacol – a model substance for the aromatic fraction of atmospheric HULIS, Atmos. Chem. Phys., 11, 1-1
Ofner, J., Krüger, H.-U., Grothe, H., Schmitt-Kopplin, Ph., Whitmore, K., and Zetzsch, C.
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Halogenation processes of secondary organic aerosol and implications on halogen release mechanisms, Atmos. Chem. Phys., 12, 5787-5806
Ofner, J., Balzer, N., Buxmann, J.-C., Grothe, H., Schmitt-Kopplin, Ph., Platt, U., and Zetzsch, C.
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Observations of bromine explosions in smog chamber experiments above a model salt pan, Int. J. Chem. Kinet., 44, 312– 326
Buxmann, J.-C., Balzer, N., Bleicher, S., Platt, U., and Zetzsch, C.
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Halogen-induced organic aerosol (XOA): A study on ultra-fine particle formation and time-resolved chemical characterization, Faraday Discuss., 165, 135-149
Ofner, J., Kamilli, K.A., Held, A., Lendl, B. and Zetzsch, C.
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A new purge and trap headspace technique to analyse low volatile compounds from fluid inclusions of rocks and minerals, Chem.Geol. 358, 148–155, 2014
Mulder, I., Huber, S.G., Krause, T., Zetzsch, C. , Kotte, K., Dultz, S., and Schöler, H.F.
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An instrument for measurements of BrO with LED-based cavity-enhanced differential optical absorption spectroscopy, Atmos. Meas. Tech., 7, 199-214
Hoch, D. J., Buxmann, J.-C., Sihler, H., Pöhler, D., Zetzsch, C., and Platt, U.
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The influence of nitrogen oxides on the activation of bromide and chloride in salt aerosol, Atmos. Chem. Phys. Discuss., 14, 10135-10166
Bleicher, S., Buxmann, J.-C., Sander, R., Riedel, T.P., Thornton, J. A., Platt, U., and Zetzsch, C.
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Consumption of reactive halogen species from sea-salt aerosol by secondary organic aerosol: slowing down the bromine explosion, Environ. Chem. 12, 476-488
Buxmann, J., Bleicher, S., Platt, U., von Glasow, R., Sommariva, R., Held, A., and Zetzsch, C.
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Iron (III)-induced activation of chloride from artificial sea-salt aerosol, Environ. Chem. 12, 461-475
Wittmer, J., Bleicher, S., Ofner, J., and Zetzsch, C.
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Iron(III)-induced activation of chloride and bromide from modeled salt pans, J. Phys. Chem. A, 119, 4373–4385
Wittmer, J., Bleicher, S., and Zetzsch C.
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New particle formation above a simulated salt lake in aerosol chamber experiments, Environmental Chemistry, 12, 489-503
Kamilli, K.A., Ofner, J., Lendl, B., Schmitt-Kopplin, Ph., and Held, A.
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Photochemical activation of chlorine by iron-oxide aerosol, J. Atm. Chem.
Wittmer, J., and Zetzsch, C.
