Transfer of cesium 137 from riparian forest to a headwater stream ecosystem in Fukushima, Japan

Abstract

We elucidated cesium 137 (137Cs) transfer from riparian forest to a headwater stream ecosystem through input of leaves contaminated by radionuclides due to the Fukushima Daiichi Nuclear Power Plant (NPP) Accident. In riparian zone of Kawamata-machi, Fukushima, living leaves of konara (Quercus serrata) were collected from crowns in 2013 and senescent leaves of that were collected from forest floor in November 2012 and 2013, respectively. In March 2013 and 2014, we collected senescent ones, which include konara leaves, deposited in a headwater stream running off the riparian zone. The comparison of 137Cs concentration showed that living leaves of konara contained higher 137Cs than fresh senescent ones. The 137Cs concentrations of fresh senescent leaves in the forest floor were larger than those of senescent ones deposited in the headwater stream. Therefore, we consider that 137Cs in the leaves was released to headwater stream while they were deposited in there. There was little change in 137Cs concentration of senescent leaves on forest floor and in the stream between 2 and 3 years after the FDNPP Accident, suggesting that 137Cs transfer from leaves to headwater stream ecosystems continues for a prolonged period.