• Open Access Science Articles
  • Science Sessions: The PNAS Podcast Program

Unexpected source of Fukushima-derived radiocesium to the coastal ocean of Japan

  1. Seiya Nagaob
  1. aDepartment of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA 02543;
  2. bLow Level Radioactivity Laboratory, Institute of Nature and Environmental Technology, Kanazawa University, Kanazawa 920-1192, Japan
  1. Edited by David M. Karl, University of Hawaii, Honolulu, HI, and approved August 28, 2017 (received for review May 24, 2017)

Significance

Five years after the Fukushima Dai-ichi Nuclear Power Plant accident, the highest radiocesium (137Cs) activities outside of the power plant site were observed in brackish groundwater underneath sand beaches. We hypothesize that the radiocesium was deposited on mineral surfaces in the days and weeks after the accident through wave- and tide-driven exchange of seawater through the beach face. As seawater radiocesium concentrations decreased, this radiocesium reentered the ocean via submarine groundwater discharge, at a rate on par with direct discharge from the power plant and river runoff. This new unanticipated pathway for the storage and release of radionuclides to ocean should be taken into account in the management of coastal areas where nuclear power plants are situated.

Abstract

There are 440 operational nuclear reactors in the world, with approximately one-half situated along the coastline. This includes the Fukushima Dai-ichi Nuclear Power Plant (FDNPP), which experienced multiple reactor meltdowns in March 2011 followed by the release of radioactivity to the marine environment. While surface inputs to the ocean via atmospheric deposition and rivers are usually well monitored after a nuclear accident, no study has focused on subterranean pathways. During our study period, we found the highest cesium-137 (137Cs) levels (up to 23,000 Bq?m?3) outside of the FDNPP site not in the ocean, rivers, or potable groundwater, but in groundwater beneath sand beaches over tens of kilometers away from the FDNPP. Here, we present evidence of a previously unknown, ongoing source of Fukushima-derived 137Cs to the coastal ocean. We postulate that these beach sands were contaminated in 2011 through wave- and tide-driven exchange and sorption of highly radioactive Cs from seawater. Subsequent desorption of 137Cs and fluid exchange from the beach sands was quantified using naturally occurring radium isotopes. This estimated ocean 137Cs source (0.6 TBq?y?1) is of similar magnitude as the ongoing releases of 137Cs from the FDNPP site for 2013–2016, as well as the input of Fukushima-derived dissolved 137Cs via rivers. Although this ongoing source is not at present a public health issue for Japan, the release of Cs of this type and scale needs to be considered in nuclear power plant monitoring and scenarios involving future accidents.

Footnotes

  • ?1To whom correspondence may be addressed. Email: kbuesseler{at}whoi.edu or virginie.sanial.vs{at}gmail.com.
  • Author contributions: K.O.B. and M.A.C. designed research; V.S., K.O.B., M.A.C., and S.N. performed research; V.S., K.O.B., M.A.C., and S.N. analyzed data; and V.S., K.O.B., M.A.C., and S.N. wrote the paper.

  • Conflict of interest statement: K.O.B. has served in a consulting capacity related to radionuclides in Japanese fisheries products.

  • This article is a PNAS Direct Submission.

  • This article contains supporting information online at www.danielhellerman.com/lookup/suppl/doi:10.1073/pnas.1708659114/-/DCSupplemental.

Freely available online through the PNAS open access option.

Online Impact

    <acronym id="UPyyYwe"></acronym>
    <tr id="UPyyYwe"><optgroup id="UPyyYwe"></optgroup></tr>
    <acronym id="UPyyYwe"><optgroup id="UPyyYwe"></optgroup></acronym>
    <acronym id="UPyyYwe"><small id="UPyyYwe"></small></acronym>
    <acronym id="UPyyYwe"></acronym><acronym id="UPyyYwe"></acronym>
    <acronym id="UPyyYwe"></acronym>
    <acronym id="UPyyYwe"></acronym>
    <acronym id="UPyyYwe"></acronym>
  • 8311061341 2018-02-23
  • 2679231340 2018-02-23
  • 995901339 2018-02-23
  • 6664181338 2018-02-23
  • 4692171337 2018-02-23
  • 6117421336 2018-02-23
  • 5226191335 2018-02-23
  • 8398791334 2018-02-23
  • 8369321333 2018-02-23
  • 7728251332 2018-02-23
  • 979371331 2018-02-23
  • 4548201330 2018-02-23
  • 4992161329 2018-02-23
  • 6703541328 2018-02-23
  • 8686301327 2018-02-22
  • 1879481326 2018-02-22
  • 9332351325 2018-02-22
  • 7384141324 2018-02-22
  • 8918371323 2018-02-22
  • 7638311322 2018-02-22