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Trace measurements in the atmosphere
- Trace measurements in airborne dust are part of the Integrated Measuring and Information System IMIS.
- The Federal Office for Radiation Protection (BfS), the Physikalisch-Technische Bundesanstalt (PTB, National Metrology Institute of Germany) and the Deutsche Wetterdienst (DWD, Germany's National Meteorological Service) operate air samplers at 43 sampling locations for this purpose.
- Samplers allowing very high sensitivity detection of artificial radionuclides are operated at four stations.
Four of these samplers have particularly high airflow rates which means that high volume samples are collected and a sensitive detection of artificial radionuclides is possible. The stations, which additionally belong to the "sparse monitoring network" of the European Union (EU) are
- Mt. Schauinsland near Freiburg (BfS),
- Braunschweig (PTB),
- Potsdam (DWD),
- Offenbach (DWD).
The DWD has 39 additional measuring stations, where measurements of radioactivity on airborne dust are performed. Usually samples are collected over a period of one week and then analysed. In the case of noticeable events, the BfS, PTB and DWD agree upon the sampling frequency required.
In its capacity as the Coordinating Office for the field of trace analysis, the BfS reviews, summarizes and evaluates accrued data and reports these to the Federal Ministry for the Environment, Nature Conservation and Nuclear Safety (BMU).
Current measurements results
Current measurement values: Activity concentrations of artificial iodine-131 and caesium-137 at Schauinsland measuring station
In order to compare activity concentrations of artificial and natural radioactivity, the adjacent figure shows a comparison between the measured activity concentrations of artificial iodine-131 and caesium-137, and the activity concentrations of radon and beryllium-7, which occur naturally.
Presently, the activity concentrations for iodine-131 are mostly below the detection limit. Activity concentrations for caesium-137 are usually close to the detection limit or slightly above and are similar to background levels measured before the Fukushima reactor disaster.
Also caesium-137 is occasionally detected in some samples due to past fallout from nuclear weapons and the reactor disaster of Chernobyl.
Results of the trace analysis to the event in Fukushima 2011
Results of trace analysis related to the Fukushima event
The events in the Japanese nuclear power plant of Fukushima in March 2011 resulted in a release of radioactive substances into the atmosphere. These were transported in the atmosphere and were detected at distances of several thousands of kilometres by sensitive measuring instruments, despite dilution during atmospheric transport.
Activity concentrations of artificial iodine-131 and caesium-137 at Schauinsland measuring station
The adjacent figure shows the activity concentrations of artificial iodine-131 and caesium-137 compared to the activity concentration of natural radioactivity (radon and beryllium-7), measured at Schauinsland station between 21 March and 12 May 2011. During that period the sampling frequency was increased from weekly to daily sampling.
In the sample collected 24 March 2011 (measurement from 25 March 2011) iodine-131 with an activity concentration of 58 microbecquerels per cubic metre of air as well as caesium-137 were detected initially. Subsequently, the artificial nuclides iodine-131, caesium-137 as well as caesium-134 were detected in air filter samples until the middle of May.
After mid-May, the activity concentrations for iodine-131 and caesium-134 were below detection limits, the activity concentration for caesium-137 decreased further and is now at the background level measured before the reactor disaster in Fukushima.
However, caesium-137 is occasionally detected in some samples due to past from nuclear weapons and the reactor disaster of Chernobyl.
Trace analysis at four German trace analysis stations: Measurement of iodine-131 and caesium-137 in the atmosphere
The adjacent figures show the activity concentrations of iodine-131 and caesium-137 during the period from 21 March to 20 May 2011 and 11 July 2011, respectively, at the four German trace analysis stations. The values show some variability indicating that different air masses have passed over Germany repeatedly.
The values observed at the individual trace survey stations depend on the weather situation, as rain, for example, may reduce the activity concentration in the atmosphere through wash-out of radionuclides. Moreover, it can be observed that the measurement values for iodine-131 decrease faster than those for caesium-137, as iodine-131 has a considerably shorter half-life (8 days) than caesium-137 (30 years).
The measured values did not pose a health risk to humans and the environment in Germany and Europe and were several times below the measured natural radiation exposure.
The results obtained independently through different measurement methods were within a few thousandths of a becquerel per cubic metre of air for artificial radioactivity on particles.
Comparison with natural radioactivity
In Germany, the natural radiation level due to the naturally occurring noble gas radon is at a few becquerels per cubic metre of air for outdoor exposure. The values vary depending on location as the concentration of radon is influenced by the parent rock and the weather situation.
Spending 24 hours in an area with an iodine-131 activity concentration of 0.005 becquerel per cubic metre of air for example (results from the stations Braunschweig and Potsdam on 29 March 2011 were within this order of magnitude) leads to an additional radiation exposure to an adult of one billionth of a sievert. This corresponds approximately to the natural radiation exposure received when spending one minute outdoors.
State of 2017.10.30