Radiation in the environment: Application and Evaluation

Tracing radionuclides in the environment…

There are a number of radionuclides with different origins and physico-chemical properties on the earth. Some already existed 4,600 million years ago when the earth was born (lithogenic radionuclides), while others were produced by interactions of cosmic rays with the nuclei in the atoms of the atmosphere (cosmogenic radionuclides). Human activities have also produced another type of radionuclides, which were accidentally released into the environment (anthropogenic radionuclides). All of these are called “environmental radionuclides”.
Our group is focusing on environmental radionuclides contained in various components like trees, litter as well as soils in forest sites worldwide as natural radiotracers, to elucidate changes in the environment.
For example, we could identify soil homogeneity using lithogenic and long-lived nuclides, 40K (109 years in half-life) and 226Ra (1600 years in half-life), and estimated apparent burial rates using 210Pb and 137Cs emitted from combustion of fossil fuels and accidents of nuclear power facilities in the past, respectively. The latter nuclides are good tracers to assess the degree of (natural and artificial) turbation. The nuclide 210Pb, a progeny of 238U, is used to trace emission sources of atmospheric pollutant lead through investigating its isotope ratio to total lead (210Pb/Pb) in soil.
A natural radionuclide, radon (222Rn), a gaseous progeny of 238U, is known as a carcinogen damaging human health in internal exposure. Inhaling 222Rn has serious effects on the human body, especially on the respiratory tract including the lungs. In contrast, 222Rn is a good tracer for elucidating transportation mechanisms of air and water (water vapor) in soil. Carbon dioxide contains ultra-trace amounts of radiocarbon (14C) as well as stable ones (12C and13C) which is useful for elucidating soil air dynamics in forest sites.

  • Hokkaido University Campus(2013.3)

  • Soil profile(Tomakomai Experimental Forest, Hokkaido Univ. 2011.5)

  • Gamma Radiation Survey
    (Norway 2010.9)

  • Ceiba tree(Northern Peru 2004.3)

  • Collecting Soil air CO2
    (Slovenia 2013.9)

  • Radon Intercomparison
    (Czech Republic 2013.9)

  • Hrubý Jeseník
    (Czech Republic 2013.9)

  • Gorišnica(Slovenia 2013.9)