Observations of atmospheric variability and soil exhalation rate of radon-222 at a Russian forest site - Technical approach and deployment for boundary layer studies

• Published in: Tellus B: Chemical and Physical Meteorology
• Main Authors: Levin, Ingeborg, Born, M, Cuntz, Matthias, Langendörfer, U, Mantsch, S, Naegler, T, Schmidt, M, Varlagin, A, Verclas, S, Wagenbach, D
• Other Authors: Institut für Umweltphysik Heidelberg, Universität Heidelberg Heidelberg = Heidelberg University, Philipps Universität Marburg = Philipps University of Marburg, Svertsov Institute for Evolutionary and Ecological Problems, RAS, Partenaires INRAE
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2002
• Subjects: atmospheric; adioactive disequilibrium; spectroscopy; [SDV]Life Sciences [q-bio]; taiga
• Online Access: https://hal.inrae.fr/hal-02677624; https://hal.inrae.fr/hal-02677624/document; https://hal.inrae.fr/hal-02677624/file/2002_Levin_Tellus%20Series%20B%20Chemical%20and%20Physical%20Meteorology_1.pdf; https://doi.org/10.3402/tellusb.v54i5.16681

International audience A monitor for continuous observations of the atmospheric Rn-222 daughter activity has been improved and successfully implemented in a field study in the European Taiga (Fyodorovskoye Forest Reserve). The alpha-activity of the short-lived Rn-222 and Rn-220 (Pb-212) decay products, which are attached to aerosols, is accumulated on a quartz aerosol filter and assayed on line by alpha-spectroscopy. The alpha-activity from the Pb-212 daughters is determined by spectroscopy and corrected for. This monitor is suitable to measure Rn-222 activities at hourly resolution down to 0.5 Bq m(-3) with an uncertainty well below +/-20%. The prototype of this monitor is run in Heidelberg on the roof of the Institute's building about 20 m above ground. For this site, the atmospheric radioactive disequilibrium was determined between the Rn-222 daughter Po-214 and Rn-222, which has to be known in order to derive the atmospheric Rn-222 activity with the static filter method. We derived a mean disequilibrium Po-214/Rn-222 = 0.704 +/- 0.081 for various meteorological conditions through parallel Rn-222 gas measurements with a slow pulse ionisation chamber. At the Russian field site, continuous activity observations were performed from July 1998 until July 2000 with half a year's interruption in summer/fall 1999. During intensive campaigns, a second monitor was installed at Fyodorovskoye at 15.6 m (July/August 1998), and at 1.8 m (July/August 1999 and October 1999) above ground. As expected, pronounced diurnal cycles of the Rn-222 daughter activity were observed at all sites, particularly during summer when the vertical mixing conditions in the atmospheric surface layer vary strongly between day and night. The lower envelope of the continuous measurements at Fyodorovskoye and at Heidelberg changes on synoptic timescales by a factor of 4-10 due to long-range transport changes between continental to more maritime situations. Generally, the Rn-222 activity at 26.3 m height at Fyodorovskoye is lower by a factor of 2-3 ...