Spatial and temporal changes of Cs concentrations derived from nuclear power plant accident in river waters in eastern Fukushima, Japan during 2012-2014.

Concentrations of Cs measured in water collected from seven rivers under base-flow conditions in eastern Fukushima Prefecture in 2014 were combined with previously reported data for the same sampling points from 2012 to 2013. Dissolved Cs concentrations at the sampling points were strongly correlated with the Cs inventories of the corresponding catchment areas. The ratios of the dissolved Cs concentrations to the Cs inventories have declined exponentially since the 2011 Fukushima nuclear power plant accident with an effective decreasing coefficient of 0.40 y (effective half-time of 1.7 y), within the range reported in European rivers following the Chernobyl accident. [ABSTRACT FROM AUTHOR]