Environmental radioactivity

Research summary

Radioactive elements can be found in the environment for several reasons. Some of the occurs naturally on Earth, while others are produced in industrial activities. Some radioactive elements, for example, C-14 are produced both by natural processes and in nuclear facilities. The occurrence of radioactive elements in the environment leads to exposure of humans to ionizing radiation. Therefore, it is important to determine the concentration of naturally occurring as well as anthropogenic radioactive elements in food and in the environment to be able to assess radiation dose and risk.

We are also studying measurement methods and models to assess radiation dose to humans following releases of radioactive elements to the environment. This applies to historical releases, as well as potential releases in the future and effects of decontamination. The group is also engaged in the Swedish national emergency preparedness. (Emergency preparedness and response) 

Research tools and resources

We make radiochemical analyses and activity measurements of radioactive elements in environmental samples by alpha and gamma spectrometry. We have also access to instruments to map radioactive fallout and to search for lost radiation sources. Measurements of radioactive elements in humans are made by whole body counting, which also can be applied in trace element studies.

Research projects

Biokinetics distribution of radionuclides in fish and shellfish and risk assessment for consumers in Sweden 

Food habits including seafood results in a 4.5 higher ingestion dose from ²¹⁰Po than for example ovo-lacto vegetarian diet. In addition, if we consider population groups with high consumption of fish and shellfish, the ingestion dose levels could increase as far as three times more than common diet. Thus, the current project aims to study the biokinetic distribution of NORM and ¹³⁷Cs in fish and shellfish to better understand the biodistribution and the radiological impact of radionuclides in fish and shellfish. Gamma spectrometry and alpha spectrometry are used to carry out the radiological determination of ¹³⁷Cs and NORM radionuclides.   

Project financing: Swedish Radiation Safety Authority (SSM2020-642). Stiftelsen Wilhelm och Martina Lundgrens Vetenskapsfond (2021-3730).

Pit lakes

The mining industry has been important for Sweden's economy for a long time due to the mineral rich bedrock. Only a few mines are active today, however, the remains of Sweden's mining history can still be seen through the many mining pits located across the country. Following mine closure, if the pit reaches below the groundwater level, it will be filled with groundwater up to the same level which creates a so-called pit lake.

Since both uranium and thorium and other naturally occurring radionuclides are present in the bedrock, they will be present in all stages of the mining process. The levels of naturally occurring radionuclides in and around the mining lakes are in most cases unknown. Furthermore, there is a lack of knowledge regarding how these radionuclides and various elements are distributed in mining lakes in different parts of the country, as well as the radiation exposure received when visiting these sites. These questions have been dealt with at our unit and a summary can be read in the PhD-thesis by Rimon Thomas (Primordial radionuclides in pit lakes in Sweden).

Project financing: Swedish Radiation Safety Authority

Wildfires

Wildfires are a recurring natural phenomenon during the dry periods of summer where soil and vegetation are one of several factors that determines the risk of the fire outbreaks. Bogs have a high amount of carbon stored in the soil and as long as the soil is moist, it forms a natural barrier that prevents wildfires from spreading across the bog. In extreme drought however, the bog itself will pose a fire hazard due to the high proportion of carbon in the soil, if a fire breaks out, large parts can therefore burn for a long time.

A radioactive isotope of cesium is found in large parts of the world in varying amounts due to previous atmospheric nuclear weapon testing and nuclear accidents such as the Chernobyl accident. Cesium is an element that is chemically similar to potassium, which is an important nutrient for plants. The plants cannot distinguish between these two elements, thus, radioactive cesium is also taken up by the vegetation. In the event of a wildfire in the bog, radioactive cesium present in the vegetation will therefore become volatile. An ongoing project is therefore looking at the relative amount of radioactive isotopes that become volatile after a wildfire by studying soil cores taken from bogs. An estimate of volatility is made by analyzing earth cores from bogs that have burned where earth cores inside and outside the burnt area are studied.

Optimization of radiochemical methods

At our unit, we are working with method optimization of the chemical separations used in the analysis of radionuclides via alpha spectrometry. Most of the available methods today require evaporation of acids to go from one type of acid to another. This is something we strive to minimize as much as possible and to minimize the volume required to perform the separations. Recent tests have shown that neutralizing an acid with a base such as NaOH, and then adding the desired acid works well in many cases. Furthermore, we have seen an increased chemical yield for water samples as we have minimized the volume of acids and reagents, however, the chemical yield and energy dissolution decrease for other types of samples that contain a higher content of interfering elements such as calcium.

Naturally occurring radioactive elements at the Kvarntorp pile

The Kvarntorp pile, consisting mainly of shale ash, and nearby pit lakes are the remains of a former oil shales industry. The aim of this project is to perform a radiological hazard assessment by measuring naturally occurring radioactive elements, such as ²³⁸U, ²³⁵U, ²³⁴U and ²¹⁰Po in soil, water and plants. The analyses have shown that the external dose rate are elevated at sites with exposed alum shale walls and on shale ash at the pile. The radiological risk to biota cannot be regarded as being of negligible concern and this work is thus ongoing. For humans, however, the effective dose to members of the public is only slightly elevated compared to the natural background radiation.

Transfer of radioactive elements in the marine environment

Bioaccumulation of radioactive elements in animals and plants will determine the radiological consequences for humans and biota following a release of radioactive elements to the environment. We are engaged in studies on transfer in the marine environment by theoretical modelling and experiments. For example, kinetic modelling of the bioaccumulation processes, measurements of concentration ratios in laboratory experiments and analyses of radioactive elements in seals.

Radiation doses and risk

In cooperation with researchers from Lund and Uppsala University, we have developed a model that sums up the contributions from external and internal exposure, likely to be incurred under various scenarios following a nuclear power plant accident. By combining this model with the lifetime attributable risk (LAR) concept, the effect of age and sex in risk estimates can be studied. The model is also applied to studies on decontamination of areas affected by fallout from a nuclear power plant release of radioactive elements.

Radioactive elements in the human body

In case of accidents or contamination at workplaces, radioactive elements can end up in the human body where they give rise to a radiation dose over time. To assess this radiation dose, it is essential to be able to measure the content of radioactive elements in the body. This is traditionally made by so called whole body counting in which specially designed detector systems are used. The access to dedicated whole body counters are, however, limited and we are therefore studying to what extent gamma cameras (used in nuclear medicine) can be used as a complement. This work includes theoretical modelling of the gamma camera response to various photon energies and geometries, as well as experimental work. The aim is to determine generic calibration factors and to increase the efficiency of the gamma camera for radioactive elements encountered in emergency situations.

List of publications

List of publications for members the group can be found by clicking on the desired researcher in the right-hand column, then you will go directly to the researcher's personal page and publication list.

Affiliations

Group Environmental radioactivity and the research is affiliated to The Institute of Clinical Sciences and SAINT (Swedish academic initiative for radiation sciences and nuclear technology).