Das Projekt "Entwicklung von Modellen fuer die Aerosol- und Wolkenchemie der Troposphaere" wird vom Umweltbundesamt gefördert und von Leibniz-Institut für Troposphärenforschung e.V. durchgeführt. The proposed project is devoted to the development of adequate physico-chemical models for the description of heterogeneous and aqueous phase chemical processes taking place in the troposphere. The systems to be described by the model will be limited to aqueous phase systems, ie the droplets of clouds, fog and rain and the aqueous (wet) aerosol. The model development to be performed in the project will be limited to the so-called 'tropospheric aqueous phase' which includes the aqueous particles dispersed in air. Reactions occuring on solids (ie direct gas-solid interactions) will not be treated in the project. The objectives of this proposal are: 1) To develop an extensive aqueous phase chemical mechanism, including all relevant processes, that will be based on an evaluation of current scientific knowledge ('the overall mechanism'). In particular, the model will include an extended description of organic chemistry and radical processes, 2) To apply tools of sensitivity analysis to the above mechanism in order to check which processes are of the highest importance and also which classes of reaction do not contribute significantly to chemical conversions in the tropospheric aqueous phase, 3) To couple the overall aqueous phase mechanism with an existing and well accepted gas phase chemical RADM2 mechanism, 4) To develop a kinetic description of transport in the aqueous phase, the gas phase and a cross the gas/liquid interface and to use this description in the model, 5) To include heterogeneous gas/aqueous processes in the model and to describe them adequately, 6) To develop a reduced chemical mechanism which may in the future be applied in larger (global) models, 7) To couple the model to a simple description of cloud dynamics for a stratocumulus cloud and to couple the model to a simple wet aerosol model, 8) To introduce into the model emission scenarios which are typical for Europe, ie a marine, a continental polluted and a continental rural scenario, 9) To perform a limited set of laboratory studies on reaction kinetics and uptake coefficients on systems which are of central importance for the overall model but for which data either do not exist or are inconclusive
Das Projekt "Entfernung und Interkonversionen von Oxidantien in der atmosphaerisch-waessrigen Phase, Teil 2" wird vom Umweltbundesamt gefördert und von Universität-Gesamthochschule Essen, Fachbereich 8 Chemie, Institut für Physikalische und Theoretische Chemie durchgeführt. The processes to be studied are expected to influence the oxidizing capacity of the troposphere by 1) phase transfer of organic compounds from the gas phase and 2) aqueous phase reactions of primary and secondary oxidants. The following organic key substance groups (KSG 1-5) have been chosen: 1) KSG 1: oxidation products of sulphur containing organics, 2) KSG 2: aldehydes and their condensation products with S(IV), 3) KSG 3: substituted aromatics, 4) KSG 4: isoprene and terpenes and 5) KSG 5: products from isoprene/terpene degradation. The tasks of this project are: 1) To quantify the reaction kinetics of strongly oxidizing radicals such as OH, HO2, O3, NO3, SO4- and C12- with the key organic substances listed above with complementary techniques (pulse radiolysis/time resolved UV-absorption and laser flash photolysis/time resolved Vis absorption) to study the influence of TMI (FE, MN) in ozone reactions additionally. 2) To identify intermediates which are formed in aqueous phase free radical reactions by the complementary techniques of time resolved laser photolysis/long path diode array absorption spectroscopy and time-resolved electron spin resonance. 3) To determine accommodation and uptake coefficients of important gasphase organic species for each of the key substance groups. 4) To perform product studies in steady-state photolysis experiments in order to identify the most important stable degradation products for the most important constituents of each group as listet earlier. The project is expected to provide a number of rate data concerning phase transfer and reactivity. The use of these data as input-parameters in advanced tropospheric multiphase models is expected to significantly improve our understanding of the complex tropospheric chemistry system.
Das Projekt "Entfernung und Interkonversionen von Oxidantien in der atmosphaerisch-waessrigen Phase" wird vom Umweltbundesamt gefördert und von Universität-Gesamthochschule Essen, Fachbereich 8 Chemie, Institut für Physikalische und Theoretische Chemie durchgeführt. This project is concerned with laboratory studies of the phase transfer and the aqueous phase chemistry of tropospheric oxidants. The accomodation coefficients of important gas phase oxidants like ozone and methylhydroperoxide into water droplets will be determined. The influence of ozone on atmospheric aqueous phase chemistry will be studied with respect to: 1) The oxidation of S (IV) in the presence of transition metal ions (eg Fe, Mn, Cu, V, Co) and 2) its reactions with transition metal ions TMI's and the role of the resulting intermediates. Elementary reactions of the radical anions SO-4 and SO-5 which are key intermediates in the atmospheric aqueous phase oxidation of S (IV) will be studied with respect to potential loss mechanisms in reactions with TMI's like Fe (II), Mn (II), and organic cloudwater constituents like HCHO, CHOOH, etc. Moreover, this project addresses the reactivity of organic peroxy radicals which are either formed by direct uptake from the gas phase or in reactions of radical oxidants with organic compounds within the aqueous phase. It is expected to obtain a number of rate data concerning phase transfer and reactivity, which could improve the understanding of the complex tropospheric chemistry system.
Das Projekt "Untersuchungen zum Verteilungsverhalten von organischen Stoffen zwischen waessriger Phase und Festphasenoberflaeche in Anwesenheit von Tensiden" wird vom Umweltbundesamt gefördert und von Universität Bayreuth, Fakultät für Biologie, Chemie und Geowissenschaften, Fachgruppe Geowissenschaften, Lehrstuhl für Hydrologie durchgeführt. Unser Ziel ist es, eine Grundlage fuer die Entwicklung eines Modells zu bilden, das den Prozess der Adsolubilisierung von hydrophoben Stoffen, insbesondere in Hinblick auf den Einsatz von Tensiden im Umweltbreich, beschreibt. Unsere bisherigen Untersuchungen zeigen, dass der Verlauf der Tensidadsorptionsisotherme eine wichtige Eingangsgroesse fuer ein solches Modell ist. Der Verlauf gibt Auskunft ueber die Tensidbelegung der Festphasenoberflaeche und wird von den Einflussfaktoren: Temperatur, Art der Oberflaeche, Art des Tensides und Zusammensetzung der Loesung determiniert. Von diesen Faktoren haben wir die Zusammensetzung der Loesung in bezug auf pH-Wert und die Ionenstaerke variiert, da diese Parameter einerseits die Eigenschaften der Festphasenoberflaeche veraendern andererseits auch die Wechselwirkung der Tensidmolekuele untereinander. Wir wollen unsere bisherigen Erkenntnisse erweitern und uns in der Fortsetzung des Projektes auf den Einfluss der Art des Tensides und der Arte der hydorphoben Verbindung konzentrieren. Ein weiteres Anliegen von uns ist es, die Uebertragbarkeit der Ergebnisse von unserem Modellsystem auf natuerliche Systeme zu ueberpruefen.