Radioactivity in the air
Air is one of the most important pathways by which radioactivity can disperse in the environment. This is because air currents can transport radioactive particles over long distances. Therefore, the measurement of radioactivity in air is one of the most important tasks we perform in environmental monitoring. Radioactive particles in the air are collected at ten locations throughout Austria (see graphic).
Most radioactive substances in the air are bound to droplets or particles (aerosols). During sampling, air is sucked through a filter. The droplets and particles remain on the filter and are collected. At some sites, additional special collection devices are operated (Vienna, Linz and Innsbruck) in order to also detect gaseous radionuclides, such as radioactive iodine.
The air filters are vacuumed over a period of one week. After that, the air filters are exchanged and sent to our radioactivity measurement laboratories. The filters are pressed into appropriate measuring containers and a measurement on highly sensitive detectors follows. Our experts evaluate the measurement results and immediately report any unusual readings to the responsible federal ministries. In 2020, a total of 782 samples were collected and analyzed for air monitoring.
Nuclides are a type of atoms. Radioactive nuclides are also called radionuclide. In the air, mainly natural radionuclides are detected. These are formed from the radioactive noble gas radon or are produced in the atmosphere by radiation from outer space (cosmogenic radionuclides).
Radionuclides - Klagenfurt: Beryllium-7
The most important cosmogenic radionuclide is beryllium-7. The following figure shows an example of the variation of the beryllium-7 content in the air in Klagenfurt over the last years. The fluctuation at the different seasons is mainly related to the weather.
Radionuclides - Klagenfurt: Cesium-137
In addition to the natural radionuclides, the artificial radionuclide caesium-137 is also regularly detected in the air. Cesium-137 was released in 1986 during the Chernobyl reactor accident and is still detectable today. The following figure shows an example of the course of the caesium-137 content in the air for Klagenfurt. In addition to a steady decrease, the curve also shows a seasonal fluctuation. The higher values in the winter months are caused by the weather, due to a lower exchange between the air layers.
Radionuclides - Klagenfurt: Beryllium -7 and Cesium -137 in comparison
In direct comparison, the amount of artificial radioactivity is far below the natural one. For example, the activity of cesium-137 (artificial) is hundreds to tens of thousands of times lower than beryllium-7 (natural), depending on the season (see graph below).
Monitoring and cooperation
By monitoring the air and prescipitation, we can also detect minor increases in radioactivity in the environment and report them immediately to the responsible federal ministry. If conspicuous measured values occur, these are exchanged within the European and international framework via the EU and the IAEA and the population is informed. In addition, the radioactivity laboratories worldwide are also in direct contact with each other and exchange information.
More details on environmental and food monitoring in Austria from 2017 to 2019, as well as 2020, can be found in our joint report with the Ministries of Climate Protection and Health. You can find the report at the bottom of this page under Downloads.
Radioactivity in wood fuels and their ashes
Harmful substances such as heavy metals and radioactive substances can accumulate in wood ashes, and the amount can vary greatly. For radioactive substances, the accumulation is highest in wood pellet ash. For this reason, among others, wood pellet ash should not be used for fertilizing the garden.
Wood is a relatively quickly renewable resource and is considered an environmentally friendly,CO2-neutralfuel. The combustion process produces only ash as a waste product. For the respective wood fuel (wood pellets, wood chips, logs and wood briquettes), there are specially designed combustion systems that are optimally adapted to the product used.
Heating with wood pellets is subsidized by the federal government, the states and the municipalities. In recent years, more and more households are heating with pellet boilers. Nationwide, there are more pellet boilers than other biomass boilers . In Austria, only by-products of the sawmill industry and no bark are used for pellet production. During heating, the organic component of the wood is burned, while the mineral, non-combustible component remains as ash. Plant ashes from biomass furnaces can be valuable secondary raw materials. Their possible use on agricultural and forestry land is described in more detail in the "Guideline for the proper use of plant ashes". You can find this at the end of this page under Downloads.
Caesium and strontium in wood ashes
Due to the Chernobyl reactor accident (1986), among other things, radioactive cesium and strontium were distributed over several European countries, including Austria. These radioactive substances are absorbed by vegetation. Due to their half-life of about 30 years, radioactive caesium and strontium can still be detected in plants (e.g. trees) and wild animals in the affected areas. If wood from these regions is used for heating, radioactive cesium and strontium may accumulate in the ashes.
The radioactivity in the wood itself is harmless from a radiation protection point of view and therefore poses no health risk to the population. However, the accumulation of radioactive substances in the wood ashes produced varies greatly and can be relevant from a radiation protection point of view.
AGES monitoring project for radioactivity monitoring in wood fuels
As early as 1998, the Austrian Federal Environment Agency, together with the Federal Institute for Foodstuffs Investigation (now AGES), reported on the caesium content in Austrian wood ashes. (Report) Since little current data was available for Austria, we conducted a monitoring project for radioactivity monitoring of wood fuels (according to § 125 Radiation Protection Act 2020) in 2020/21. The main focus was on wood pellet samples because their ash content is the lowest compared to the ash content of other wood fuels. As a result, the accumulation of radioactive substances in wood pellet ash is higher.
Based on our project results, an estimation of the radiation exposure (= dose) when using wood pellet ash for vegetable fertilization in the garden was carried out. It was assumed that a one-centimeter-thick layer of ash is used for fertilization per year and that half of the vegetables consumed annually come from one's own garden. The highest measured radioactivity levels were used for the calculation. In this case, the annual dose is 0.2 millisievert (abbreviation: mSv). As the following graph shows, this is a very low value compared to other radiation exposures.
Nevertheless, from our point of view, it is not recommended to scatter the wood pellet ashes in the garden or even on a vegetable patch. This is because the ashes contain not only radioactive substances but also non-combustible and potentially harmful minerals, salts, heavy metals and organic pollutants.
The disposal of ashes in private households is regulated differently in each federal state and often also in each municipality. In most of Austria, it is mandatory to dispose of the cooled ash in the residual waste.
Detailed technical information on the project can be found in the final report, which can be downloaded under Downloads.
Last updated: 26.01.2022