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Cesium’s Movement in the Natural Environment

As demonstrated by the accident at the Fukushima Daiichi Nuclear Power Plant in Japan, cesium (Cs) moves in the natural environment over time, impacting cleanup operations and reoccupancy.

For example, Cs can be deposited on vegetative surfaces (i.e., grass and soil) and transported to the litter layer (e.g., dead leaves and debris above the soil) due to natural activities such as wind, precipitation and plant shedding. The Cs-soil penetration depth and time may differ depending on various factors including soil clay content, litter decomposition rate, weather and precipitation. Runoff from contamination sources to surface waters is also an important pathway for aiding in the transport of contaminants

Once introduced to aquatic environments, radionuclides begin accumulating in bottom sediments and organic matter. These levels are known to drop relatively quickly by means of flushing, burying, and radioactive decay. This process is accelerated in oceans, rivers, and lakes that are supplied by tributaries.​

Forests are known to greatly reduce the overall mobility of radionuclides. Forests (including plants and trees) act as ecological sinks with a majority of Cs residing within the first few inches of soil. Though forests are effective at limiting the spread of contamination, they are difficult to decontaminate. Therefore, presence of nearby forests may influence decisions when considering decontamination of non-forested areas, especially when adjacent to populated or recreational areas. While forests act as a sink for radionuclides, they can also be a source of further radionuclide releases, such as during a forest fire.​

EPA has studied Cesium’s interactions with the natural environment at the bench, pilot and field-scale.

Related Research Products

  • Journal Article: Cesium Emissions from Laboratory Fires
  • Journal Article: Characterizing cesium sorption in freshwater settings using fluvial sediments and characteristic water chemistries
  • Journal Article: Radiological Dispersal Device Outdoor Simulation Test: Cesium Chloride Particle Characteristics

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Last updated on May 6, 2025
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