Relative importance of Asian-dust-derived micas estimated from oxygen isotopic analysis of fine quartz on specific retention of radiocesium in Andosols in Tohoku Region, Japan

Andosols are the soil type that potentially has the highest radiocesium (RCs) transfer risk due to their deficiency in micaceous minerals (micas) that can strongly retain RCs in their interlayer sites. However, an exogeneous source of micas as a component of Asian dust may have contributed largely to increase the RCs retention ability for Andosols in Tohoku Region, Japan. We investigated 29 pasture soils with andic soil properties that were collected at various places across this region to clarify the provenance of micas whether they originated from Asian dust or local lithological materials. Mica content in bulk size fraction (&lt;2.0 mm) positively and strongly correlated with the factor related to felsic elemental composition obtained by principal component analysis (<i>r</i> = 0.90, <i>p</i> &lt; 0.01). Fine micas in the &lt;20 µm fraction (Mica_&lt;20 µm) accounted for a large fraction (72 ± 16%) of the total mica contents and positively correlated with the content of fine quartz derived from Asian dust (Qz_{ad_&lt;20 µm}) (<i>r</i> = 0.86, <i>p</i> &lt; 0.01), which were distinguished from fine quartz derived from igneous bedrock materials (Qz_{ig_&lt;20 µm}) by using the δ¹⁸O values for quartz isolated from the &lt;20 µm fraction. Furthermore, Mica_&lt;20 µm correlated positively with radiocesium interception potential (RIP) of this fraction. These results for the first time demonstrated the importance of Asian-dust-derived micas relative to those from another local sources on the RCs retention abilities in Andosols in Tohoku, Japan.