STACCATO: Influence of stratosphere-troposphere exchange in a changing climate on atmospheric transport and oxidation capacity

• Unité de recherche: PCRD EU
• Numéro de projet: 99.0582-1
• Titre du projet anglais: STACCATO: Influence of stratosphere-troposphere exchange in a changing climate on atmospheric transport and oxidation capacity

Mots-clé (Anglais)

Be-7; Be-10; Pb-210; Be-10/Be-7 ratio; Jungfraujoch; accelerator mass spectrometry (AMS)

Autre Numéro de projet (Anglais)

EU project number: EVK2-1999-00050

Programme de recherche (Anglais)

EU-programme: 5. Frame Research Programme - 1.4a.2 Global change, climate and biodiversity

Description succincte (Anglais)

See abstract

Partenaires et organisations internationales (Anglais)

Coordinator: LMU, München (D)

Résumé des résultats (Abstract) (Anglais)

The particle bound atmospheric concentrations of the cosmogenic radionuclides 7Be and 10Be have been measured on dust filters at the high-alpine stations Jungfraujoch (3580 m asl), Switzerland.
Particle bound 7Be and 10Be are collected on glass fiber filters at the Jungfraujoch with a time resolution of 48 h by the NABEL network [1]. An automatic high volume aerosol sampler, which filters about 1100 cubic meters of air per day, was used.
The respective filters were measured for its 7Be activity (T1/2 = 53.12 d) using its characteristic g-radiation (Eg: 478 keV, Ig: 10.52%) in a well-type Ge-detector. Measurement times were 34 h for each sample.
In addition, the 210Pb activity (T1/2 = 22.3 a) was determined in the same measurement in these filters. 210Pb has a characteristic g-line at 46.5 keV with an emission probability of 4.5%.
The 10Be content of the filters was measured using the method of accelerator mass spectrometry (AMS) AMS is the only available tool for measuring 10Be activities of nBq/m3 in a reasonable time. The AMS facility of the Paul Scherrer Institute at the Institute of Particle Physics of the ETH Zurich performed 10Be measurements for STACCATO.
After the non-destructive determination of 7Be, 10Be was separated from the filters by a chemical procedure. The filters were leached with nitric acid (17 wt.-%), followed by a cation exchange technique, precipitation of beryllium hydroxide, formation of beryllium nitrate and its decomposition to beryllium oxide. The effective reduction of boron during sample preparation of glass fiber filters was the most important task. Changes in the chemical procedure during the project period led to much purer samples making any boron correction negligible and lowered the statistical errors by a factor of about 2.7.
The amount of 10Be collected on a filter is measured via the corresponding isotopic ratio 10Be/9Be, where a well-known mass of 9Be is added to the filter for sample preparation (normally 1 mg of spike material). The samples are measured together with standards (material of known 10Be/9Be), chemistry blanks (new filter material which has followed all sample preparation steps), and blanks (from pure 9Be, spike material alone). The samples are corrected for background (deduced from the ratio of the blank) and normalized using the results for the standard material. The 10Be data were corrected for losses during sample preparation using the leaching efficiency information.

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: 99.0582-1