Skip to main content
DeutschDE
European Commission logo print header

Laboratory studies And Modelling Of heterogeneous Chemistry in the Stratosphere

Ziel

This research project is a joint laboratory and modelling study of heterogeneous chemical processes which take place on stratospheric sulphuric acid aerosol (SAA) and which influence the partitioning of hydrogen, halogen and nitrogen species in the lower stratosphere over middle to high latitudes. The main goals of the project are to illucidate: A. Fundamental physico-chemical properties of the stratospheric sulphate aerosol:
- Chemical speciation and oxidative capacity (neutral and ionic components)
- Diffusion coefficients
- Uptake coefficients (sticking coefficients)
- Henry's law constants
- Solvent effect on UV spectra and photolysis products of dissolved trace gases.
B. Chemical reactions in or on the sulphate aerosol:
- Conversion of NO3 radicals which may result in a nighttime production of H2O2
- Reaction of ClOOCl with halogen ions which may convert HCl into ClO and OH
- Oxidation of ClO and BrO to higher halogen oxides.
- Reaction of ClONO2 with H2O2 to form ClOOH
- Reactions of N2O5, BrONO2, BrCl, etc.
- Calculation of spectroscopic and thermodynamic parameters for chemical compounds and reactions not easily accessible to laboratory studies. C. The impact of heterogeneous chemical reactions on stratospheric ozone depletion by modelling:
- Parameterisation of (new) heterogeneous chemical reactions for use in models of the stratosphere.
- Sensitivity tests of the individual reactions studied in the laboratories by the use of 2D- and trajectory models of the stratosphere

All laboratory investigators in the project will use a common reaction medium of a composition close to that
of the stratospheric aerosol at mid-latitude, i.e. 60-80 wt % sulphuric acid in water with trace constituents added
in the right proportions. The surface of the laboratory SAA mimics will be characterized by X-ray diffraction
and FTIR studies of the same sample; the unique FTIR signature will then be used by all participating
laboratories to characterize the substrate. The X-ray diffraction give information of structure andories to
morphology, the FTIR spectra give information on dangling OH bonds on the surface which may act as
adsorption sites for trace gases. Amorphous samples can be discriminated from crystalline ones and the influence
of the minor constituents on the structure as well as the crystallite or particle size can be estimated. In addition
to the surface characterisation, the uptake of trace gases on the SAA mimics will be measured by the use of
mass spectrometry whereby the mass accommodation coefficients can be determined. The bulk physico-chemical
properties of the SAA mimics will be studied by other spectroscopic techniques like NMR, Raman and UV-VIS.
The latter two techniques are for obtaining detailed information on the chemical speciation in the SAA mimics.
Diffusion processes in the SAA mimics and diffusion coefficients of H2O and trace species (e.g. HCl, HBr and
HNO3) at relevant temperatures will be studied by the NMR technique.
A 2-D model and a trajectory model will be used to study effects of new chemical reactions that are investigated
in the laboratories within this project. The photochemical scheme and a microphysical module are common for
the two models. The trajectory model will be used for extensive tests of reactions and parameterisations,
whereas the 2-D model will be applied for a selected and limited set of cases.

Wissenschaftliches Gebiet

Programm/Programme

Thema/Themen

Aufforderung zur Vorschlagseinreichung

Data not available

Finanzierungsplan

CSC - Cost-sharing contracts

Koordinator

Alfred-Wegener-Institut für Polar- und Meeresforschung
EU-Beitrag
Keine Daten
Adresse
12,Am Handelshafen
27515 Bremerhaven
Deutschland

Auf der Karte ansehen
Gesamtkosten
Keine Daten

Beteiligte (7)

Diese Seite teilen

Herunterladen

Letzte Aktualisierung: 8 Oktober 1998

Mein Booklet

Permalink: https://cordis.europa.eu/project/id/ENV4950046/de

European Union, 2024