Prediction of groundwater contamination with 137Cs and 131I from the Fukushima nuclear accident in the Kanto district

Ohta, Tomoko; Mahara, Yasunori; Kubota, Takumi; Fukutani, Satoshi; Fujiwara, Keiko; Takamiya, Koichi; Yoshinaga, Hisao; Mizuochi, Hiroyuki; Igarashi, Toshifumi

doi:10.1016/j.jenvrad.2011.11.017

Cited by 40 publications

(24 citation statements)

References 5 publications

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“…Though most of the atmospheric fallout was believed to be over the ocean (Yoshida and Kanda, 2012), fallout over land presumably led to Cs enrichment in river runoff and potential contamination of surficial aquifers. From column experiments using ion exchange media and local soils, Ohta et al (2012) found that the 137 Cs migration rate was only 0.6 mm yr −1 , suggesting that rain-derived Fukishima Cs will not likely lead to contamination of the local aquifers in the near term. At the FNPP site, however, cracks in reactor foundations combined with potentially inefficient methods for collecting cooling water most certainly led to direct radionuclide inputs to the local aquifer with the potential for transport to the coastal ocean via submarine groundwater discharge (SGD) (Taniguchi, 2002).…”

Section: Discussionmentioning

confidence: 99%

Radium-based estimates of cesium isotope transport and total direct ocean discharges from the Fukushima Nuclear Power Plant accident

et al. 2013

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Radium has four naturally occurring isotopes that have proven useful in constraining water mass source, age, and mixing rates in the coastal and open ocean. In this study, we used radium isotopes to determine the fate and flux of runoff-derived cesium from the Fukushima Dai-ichi Nuclear Power Plant (FNPP). During a June 2011 cruise, the highest cesium (Cs) concentrations were found along the eastern shelf of northern Japan, from Fukushima south, to the edge of the Kuroshio Current, and in an eddy ~ 130 km from the FNPP site. Locations with the highest cesium also had some of the highest radium activities, suggesting much of the direct ocean discharges of Cs remained in the coastal zone 2–3 months after the accident. We used a short-lived Ra isotope (²²³Ra, t_1/2 = 11.4 d) to derive an average water mass age (T_r) in the coastal zone of 32 days. To ground-truth the Ra age model, we conducted a direct, station-by-station comparison of water mass ages with a numerical oceanographic model and found them to be in excellent agreement (model avg. T_r = 27 days). From these independent T_r values and the inventory of Cs within the water column at the time of our cruise, we were able to calculate an offshore ¹³⁴Cs flux of 3.9–4.6 × 10¹³ Bq d⁻¹. Radium-228 (t_1/2 = 5.75 yr) was used to derive a vertical eddy diffusivity (K_z) of 0.7 m² d⁻¹ (0.1 cm² s⁻¹); from this K_z and ¹³⁴Cs inventory, we estimated a ¹³⁴Cs flux across the pycnocline of 1.8 × 10⁴ Bq d⁻¹ for the same time period. On average, our results show that horizontal mixing loss of Cs from the coastal zone was ~ 10⁹ greater than vertical exchange below the surface mixed layer. Finally, a mixing/dilution model that utilized our Ra-based and oceanographic model water mass ages produced a direct ocean discharge of ¹³⁴Cs from the FNPP of 11–16 PBq at the time of the peak release in early April 2011. Our results can be used to calculate discharge of other water-soluble radionuclides that were released to the ocean directly from the Fukushima NPP

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Section: Discussionmentioning

confidence: 99%

Radium-based estimates of cesium isotope transport and total direct ocean discharges from the Fukushima Nuclear Power Plant accident

et al. 2013

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“…The middle layer (20-30 m above sea level) consists of sandy loam while the overlying (0-20 m above sea level) are mainly of sandstone (Saeki, 1967;Marui, 2015). Such local lithology suggests that the migration of 129 I and 137 Cs into a deeper soil layer (>5 cm) is restricted due to their strong affinities for humic substances and clay minerals, respectively (Ohta et al, 2012;Tanaka et al, 2012;Saito et al, 2014). Nevertheless, water-leaching experiments on soil have shown that less than 1 % of 137 Cs and about 10 % of 131 I can be dissolved into the aqueous phase at any pH .…”

Section: Radionuclides In Groundwater In the Unconfined Aquifermentioning

confidence: 99%

“…from the local and worldwide environments. Among these studies some have focused on the migration of radiocesium ( 134 Cs and 137 Cs) and radioiodine ( 131 I) in the soil layer (Ohta et al, 2012;Tanaka et al, 2012;Saito et al, 2014). It has been argued that the migration rates of 137 Cs are so low that contamination of groundwater by 137 Cs is not likely to occur in rainwater infiltrating into the surface soil after the Fukushima accident (Ohta et al, 2012).…”

Section: Introductionmentioning

confidence: 99%

<sup>129</sup>I and <sup>137</sup>Cs in groundwater in the vicinity of Fukushima Dai-ichi nuclear power plant

Zhang

Freeman

et al. 2016

Geochem. J.

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This paper reports iodine ( 127 I and 129 I) and cesium ( 137 Cs) isotope concentrations in groundwater of confined and unconfined aquifers in the vicinity of the Fukushima Dai-ichi nuclear power plant (FDNPP). 127 I and 129 I concentrations range from 2-13 µg/L and 5×10 7 -8×10 10 atom/L respectively, resulting in 129 I/ 127 I atomic ratios from 5×10 -9 to 2×10 -6 . In all samples, 137 Cs concentrations were below detection limit. The deep-sealed groundwater from the confined aquifer did not contain significant quantities of Fukushima-derived 129 I compared to the groundwater in the unconfined aquifer. The minimal 129 I/ 137 Cs activity ratios in the groundwater are more than 2-500 times higher than the FDNPP source ratio. These data can be explained by rainwater infiltrating through the surface soils, with the more watersoluble 129 I preferentially extracted into the aqueous phase and the 137 Cs preferentially retained in the soil.

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“…On March 15-17 and 21-23, deposition increased in the areas surrounding Fukushima prefecture because north-easterly, easterly, and south-easterly winds under a lowpressure system transported the radionuclides from the Fukushima NPP, and subsequent precipitation associated with the same system washed radioactive materials out of the radioactivity plume, thereby effectively depositing them on land [1][2][3][4][5]. In addition to the radioactive plume that covered the Fukushima Prefecture, two other large plumes suffered severe radioactive contamination over north Japan.…”

Section: Introductionmentioning

confidence: 99%

Speciation of 137Cs and 129I in Soil After the Fukushima NPP Accident

Ohta

Mahara

Fukutani

et al. 2016

Radiological Issues for Fukushima’s Revitalized Future

Self Cite

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We evaluated the migration of radionuclides ( 131 I, 129 I, 134 Cs, 136 Cs, 137 Cs, and 132 Te) in the surface soil after the Fukushima nuclear accident. The radionuclides in the soil collected late March in 2011 were barely leached with ultrapure water, indicating that these are insoluble. We observed the chemical behavior of 137 Cs and 129 I in soil: (1) 137 Cs was predominantly adsorbed within a depth of 2.5 cm from the ground surface; (2) 137 Cs was hardly released from soil by the water leaching experiments that lasted for 270 days; (3) approximately, more than 90 % of 137 Cs was adsorbed on organic matters and the residual fractions, while 129 I was mainly fixed on the Fe-Mn oxide and organically bounded fraction. Therefore, we conclude that 137 Cs and 129 I in soil seldom leach into the soil water and migrate downward because of the irreversible adsorption. The shallow groundwater which residence time is short.

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Prediction of groundwater contamination with 137Cs and 131I from the Fukushima nuclear accident in the Kanto district

Cited by 40 publications

References 5 publications

Radium-based estimates of cesium isotope transport and total direct ocean discharges from the Fukushima Nuclear Power Plant accident

Radium-based estimates of cesium isotope transport and total direct ocean discharges from the Fukushima Nuclear Power Plant accident

<sup>129</sup>I and <sup>137</sup>Cs in groundwater in the vicinity of Fukushima Dai-ichi nuclear power plant

Speciation of 137Cs and 129I in Soil After the Fukushima NPP Accident

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