Sinking velocity of particulate radiocesium in the northwestern North Pacific

Abstract

Sinking particles (SP) were collected by time series sediment traps at two depths in the northwestern Pacific before and after the Fukushima Daiichi Nuclear Power Plant accident, and accident-derived particulate radiocesium was measured. Radiocesium (137Cs) was first detected at 500m (4810m) about 2weeks (1month) after the accident. 137Cs of SP collected over 1year revealed that the time lag between two depths was larger than that for the first 137Cs detection (about 2weeks). We estimated the transient sinking velocity (SV) from the cumulative temporal 137Cs flux and the time lags at the two depths. Although the SV of SP collected in very early period was large, the estimated SV of most particulate 137Cs (about 80%) was about 50md-1. Based on comparison of 137Cs concentration in total SP with that in SP without organic materials, we suspect that most of the 137Cs was likely incorporated into aluminosilicates. © 2014. American Geophysical Union. All Rights Reserved.