Low levels of .sup.134Cs in suspended solids in rivers discharging into the Sea of Japan

We investigated radiocesium concentrations in the suspended solids (SS) of two large rivers discharging into the Sea of Japan. Higher .sup.134Cs concentrations in SS sampled from upstream area in 2013 (711 Bq/kg-SS) reflected the larger effect of radioactive depositions in western Fukushima Prefecture. However, smaller but less variable concentrations in downstream areas (< 100 Bq/kg-SS) indicated a continual supply of .sup.134Cs-contaminated SS from 2013 to 2017. The particulate .sup.134Cs concentrations in normal flow conditions were at approximately similar levels with those in coastal waters (< ~1 mBq/L), suggesting that the impact of SS on the Sea of Japan was negligible after 2013.