Spectrocolorimetric, geochemical and radiocesium properties of source material and sediment collected after the 2019 typhoons in Fukushima coastal rivers (Japan)

Spectrocolorimetric properties analysed with a portable diffuse reflectance spectrophotometer (Konica Minolta CM-700d) and geochemical contents obtained with an energy dispersive X-ray fluorescence spectrometer (ED-XRF Epsilon 4) were analysed in potential source material that may supply sediment to coastal rivers draining the main Fukushima radioactive pollution plume (Japan). Three potential source materials (n=57) were considered (cropland soils ready for cultivation after the completion of the local decontamination programme; forest soils and subsurface material originating from landslides and channel bank collapse). Recent sediment lag deposits (mud drapes deposited on channel-bed sand; n=24) were collected along the main rivers draining the Mano and Niida catchments (Fukushima Prefecture, Japan) on the 29th and 30th of October 2019 after the 2019 typhoon season including typhoon Hagibis. In addition to spectrolorimetric and geochemical properties, radiocesium (Cs-137) concentrations were analysed by gamma spectrometry using Germanium Hyperpure detectors in all source and sediment samples (n=81).