Navigation and service

Ionising radiation

Environmental Radioactivity - Medicine - Occupational Radiation Protection - Nuclear Hazards Defence

Ionisierende Strahlung

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, the Physikalisch-Technische Bundesanstalt and the Deutsche Wetterdienst operate air samplers at 43 sampling locations for this purpose.
  • Samplers allowing very high sensitivity detection of artificial radionuclides are operated at four stations.

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, Germany’s National Metrology Institute) and the Deutsche Wetterdienst (DWD, Germany's National Meteorological Service) operate air samplers at 43 sampling locations for this purpose.

Four of these samplers have a particularly high airflow which means that high volume samples are collected and a very sensitive detection of artificial radionuclides is possible. These stations, which 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 monitoring stations, where measurements of radioactivity on airborne dust are performed. Usually air samples are collected over a period of one week and then analysed in the laboratory. In the case of noticeable events, the BfS, PTB and DWD agree upon an increased sampling frequency if 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 data: Activity concentrations of artificial iodine-131 and caesium-137 at Schauinsland monitoring station

Time series of the activity concentrations of natural radioactivity Time series of the activity concentrations of natural radioactivityTime series of the activity concentrations of natural radioactivity (radon and beryllium-7) and the artificial radionuclides iodine-131 and caesium-137 at Schauinsland station. The graph is updated weekly.

In order to compare activity concentrations of artificial and natural radioactivity, the adjacent figure compares the measured activity concentrations of artificial iodine-131 and caesium-137 with 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.

Caesium-137 is also occasionally detected in some samples, due to past fallout from nuclear weapons and the reactor disaster at 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 the 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 monitoring instrument, despite dilution during atmospheric transport.

Time series of the activity concentrations Fukushima Time series of the activity concentrationsTime series of the activity concentrations of the artificial radionuclides iodine-131 and caesium-137 compared to natural radioactivity (radon and beryllium-7) at Schauinsland station during the period from 21 March to 12 May 2011.

Activity concentrations of artificial iodine-131 and caesium-137 at Schauinsland monitoring 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 radionuclides 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 levels measured before the reactor disaster in Fukushima.

However, caesium-137 is occasionally still detected in some samples due to fall-out from nuclear weapons and the past reactor disaster at Chernobyl.

Trace measurements iodine to Fukushima Trace measurements iodine to FukushimaTime series of the activity concentration of iodine-131 at four German trace analysis stations during the period from 21 March to 20 May 2011.

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 successively.

The activity concentrations measured at the individual stations depend on the weather conditions, as rain, for example, may reduce the activity concentration in the atmosphere through wash-out of radionuclides. Moreover, it can be observed that the measured 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).

Trace measurements caesium to Fukushima Trace measurements caesium to FukushimaTime series of the activity concentration of caesium-137 at four German trace survey stations during the period from 21 March to 11 July 2011.

Assessment

The measured acitivity concentrations 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 were around 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 host 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 while spending one minute outdoors.

State of 2018.08.06

How do you rate this article?

© Bundesamt für Strahlenschutz