Importance of desorption process from Abukuma River's suspended particles in increasing dissolved 137Cs in coastal water during river-flood caused by typhoons

Desorption of radiocesium (137Cs) from riverine particles into seawater strongly influences 137Cs concentrations in coastal seawater. This process is important for quantifying the input radionuclides to marine environments. Here we quantify particulate flux Abukuma River, Japan, during typhoon Hagibis and following typhoons 2019 estimate resulting increased dissolved levels Particulate export flux, 1.1 × 1012 Bq, River 4-day period (12–15 October 2019) equaled two-thirds annual 2012–2015, high Fukushima Daiichi Nuclear Power Plant accident. The desorbed fraction was 0.061–0.12 1012Bq, its daily surrounding (1.5–3.0 1010 Bq/d) one two orders magnitude greater than estimated pre-typhoon (1.3× 108–1.0 109 Bq/d). Simulated results suggest that massive influx subsequent desorption by an order magnitude, 3.3 mBq/L (pre-typhoon level) 45–126 mBq/L. found pathway opens up new scenarios involving radionuclide dynamics boundary area river-sea system.