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

We measured the concentrations of 131I, 134Cs, and 137Cs released from the Fukushima nuclear accident in soil and rainwater samples collected March 30–31, 2011, in Ibaraki Prefecture, Kanto district, bordering Fukushima Prefecture to the south. Column experiments revealed that all 131I in rainwater samples was adsorbed onto an anion-exchange resin. However, 30% of 131I was not retained by the resin after it passed through a soil layer, suggesting that a portion of 131I became bound to organic matter from the soil. The 137Cs migration rate was estimated to be approximately 0.6 mm/y in the Kanto area, which indicates that contamination of groundwater by 137Cs is not likely to occur in rainwater infiltrating into the surface soil after the Fukushima accident.