Sampling device for the measurment of peroxy radicals in atmospheri c systems

Projektinformationen

ID Finanzhilfevereinbarung: ENV4970389

Projekt abgeschlossen

Startdatum 1 November 1997

Enddatum 29 Februar 2000

Finanziert unter

• Specific programme of research and technological development in the field of environment and climate, 1994-1998

Gesamtkosten

Keine Daten

EU-Beitrag

Keine Daten

Koordiniert durch

BERGISCHE UNIVERSITAET GESAMTHOCHSCHULE WUPPERTAL
Germany

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Verwertbare Ergebnisse

Development of a new computer software for chemical modelling of smog chamber experiments

Within the present project, a completely new tool for chemical modelling was developed. The simulation program CHEMATA uses experimentally obtained kinetic and mechanistic data of tropospheric VOC oxidation as well as structure-activity relationships for the construction of a chemical mechanism, for the description of smog chamber experiments. The advantage of this new modelling tool compared to currently established mechanisms for tropospheric chemistry is that the program is individually configured for the problem to be solved. Therefore, only the necessary reaction steps are included, which significantly increases the performance of the model.

Development of a sampling, facility for the in situ measurement of peroxy radicals in the European photoreactor EUPHORE

The technique for the sensitive detection of H02, ER02, NO3 and NO2 concentration-time profiles is the trapping of the trace species by matrix isolation (M1) and analysis of the samples by electron spin resonance (ESR). Ambient air enters the sampling device through a nozzle. The radicals are trapped on a cold finger in a polycrystalline ice matrix at 77K. The matrix is formed by adding heavy water vapOLir to the air jet during sample collection through a stainless steel frit mounted coaxial behind the nozzle. The pressure in the vacuum chamber is kept below 0.1 mbar by a cryopump. The sampling interval is between 15 and 30 min and the sampling efficiency is => 95%. The cryosampler is designed to collect 16 samples on 16 gold-plated copper fingers during the measuring period. Specification and quantification of the radicals is achieved by ESR spectroscopy. In order to reach an optimum signal to noise ratio the number of scans for each individual sample was 100. The spectra are analyzed with a numerical procedure. The detection limit is 3 ppt for H02, R02 and NO2 and 2 ppt for N03. The accuracy of the method estimated from absolute calibration is 5 + -%.