Naturally produced organohalogens; Atmospheric simulation experiments on halogen activation in aerosol smog chamber facilities with sea salt and secondary organic aerosol (HALOSOA)

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Zusammenfassung (deutsch)Mixing of continental and marine air masses causes an interaction of activated halogens with humic compounds from soil and humic-like substances (HULIS), detected only recently as an ubiquitous aerosol constituent – the well-known secondary organic aerosol (SOA) from gas-to-particle conversion of mainly natural hydrocarbons. The halides from sea-spray are oxidized to halogenating compounds by photochemical, heterogeneous interactions involving ozone, OH radicals and other photooxidants, where reactive oxides of nitrogen (NO, NO2, NO3, N2O5) and acids play a decisive role. The resulting activated halogens (X, X2, XY, XO, HOX, XNO, XNO2 XONO2 with halogens X, Y = Cl, Br and I) may form organohalogen compounds, some of which are gaseous and some of which remain in the particles. The goal of the present study is to simulate this environmental situation (covering the full range from salt lakes and volcanic plumes via marine boundary layer to arctic conditions) in aerosol smog chamber experiments and to investigate it by a large variety of techniques, observing the activated halogens by the radical clock from time profiles of specific indicators and by direct, differential optical and cavity enhanced absorption spectroscopy (DOAS and CEAS), and detecting halogenated organics in gas and particle phase by specific techniques, such as GC-ECD, GC-HID, GC-MS, TPP-MS, direct aerosol-MS, ion chromatography and HPLC-DAD (including ICR-FTMS, AMS and CIMS from external collaborators and guests in campaigns). The contributions of Cl, Br and I to these geochemical cycles are settled by various supporting experiments, not to mention mandatory model calculations of the observations in the chamber experiments to be extrapolated to the boundary layer of the troposphere.