SAMPLER: Sampling device for the measurement of peroxy radicals in laboratory and field experiments

• Unité de recherche: PCRD EU
• Numéro de projet: 97.0376
• Titre du projet anglais: SAMPLER: Sampling device for the measurement of peroxy radicals in laboratory and field experiments

Mots-clé (Anglais)

Sampling measurement of peroxy radicals

Autre Numéro de projet (Anglais)

EU project number: ENV4-CT97-0389

Programme de recherche (Anglais)

EU-programme: 4. Frame Research Programme - 3.1 Environment

Description succincte (Anglais)

See abstract

Autres indications (Anglais)

Full name of research-institution/enterprise:
EPF Lausanne
Département de Génie Rural
Laboratoire de Pollution Air-Sol / LPAS

Partenaires et organisations internationales (Anglais)

BUGH Wuppertal, Forschungszentrum Jülich, CEAM Valencia

Résumé des résultats (Abstract) (Anglais)

The task of the EPF Lausanne in the project SAMPLER is to model smog chamber experiments in order to evaluate a new method for measuring RO2 radicals (sampling of RO2 radicals in a cyrosampler and later analysing the samples by ESR spectroscopy).
Because current lumped mechanisms are not sufficiently detailed for this task, the program CHEMATA (CHEmical Mechanism Adaptation to Tropospheric Applications) was designed. CHEMATA can generate extended mechanisms which describe the chemical behaviour of the investigated hydrocarbons and of all resulting products in great detail. The only needed input data are structure reactivity relationships, available experimental values and the chemical structures of VOC compounds. The program transfers the chemical structures into number codes which are used to calculate all rate constants and products of the VOC reactions. Because CHEMATA enables also a lumping of VOC species it will not only be very helpful to laboratory experimentalists but also to 3D modellers who want to create, adapt or update chemical mechanisms for use in 3D models.
Experiments with VOC/HCHO/NOX/air mixtures (VOC = HCHO, ethene, n-butane or iso-butane) were performed in the EUPHORE smogchamber of Valencia, Spain. HCHO which is photolysed by the sun light acts as the radical source in the system. By comparing the simulation results to the measurements we found that in all simulations the calculated ozone values are higher than the measured ones. This is probably caused by an unknown ozone loss process in the chamber, likely by wall reactions. Because of the very low humidity of about 0.01%, ozone is not an important source for radicals; therefore the overestimation of ozone does not affect the simulated peroxy radical mixing ratios.
In the ethene experiment too high simulated HCHO must cause too high calculated HO2 concentrations. In all other experiments calculated and measured HO2 values agree within a range of about 20%. In most of the cases the agreement for the organic peroxy radicals is even better. Only in the case of iso-butane and in the first hour after starting the experiment larger differences between simulation and measurements were found. Considering the uncertainties in the kinetic data on which the calculations are based, an even better agreement could not be expected.

Références bases de données (Anglais)

Swiss Database: Euro-DB of the
State Secretariat for Education and Research
Hallwylstrasse 4
CH-3003 Berne, Switzerland
Tel. [phone]
Swiss Project-Number: 97.0376