1. Radiocesium leaching from litter during rainstorms in the Fukushima broadleaf forest.
- Author
-
Sakakibara K, Iwagami S, Tsujimura M, Konuma R, Sato Y, and Onda Y
- Subjects
- Forests, Trees, Fukushima Nuclear Accident, Radiation Monitoring, Soil Pollutants, Radioactive analysis
- Abstract
Forests are important sources of dissolved radiocesium (
137 Cs) discharge downstream. To improve understanding of dissolved137 Cs discharge processes during rainstorms, we investigated the relationship between rainfall-runoff hydrological processes and the discharge of137 Cs leached from litter. Leaching tests were conducted with broadleaf litter collected in the area where saturated overland flow was generated during rainstorms in a broadleaf-tree-dominated forest. According to the leaching test results, the137 Cs leaching rate was higher in the early stage of the test and decreased afterward. There was no significant difference in the overall results between the agitation and non-agitation cases. The137 Cs leaching rate from litter after the 24-h test was up to 33.7%. A large proportion of the original137 Cs activity was present even after the tests, as leaching from litter during rainstorms in the headwater area could be an additional source of dissolved137 Cs in the stream water. If mixing of137 Cs originating from groundwater, soil water, and rainfall with the hydrological processes is assumed, differences between the observed and estimated137 Cs in the surface runoff water became larger under high flow conditions. This analysis indicates additional137 Cs loading on surface runoff water during rainstorms, where saturated surface area can expand as the surface runoff rate increases. Contact area between surface runoff and litter accumulated on the forest floor should increase and accelerate137 Cs leaching from the litter. Therefore,137 Cs leaching in the saturated surface area that is temporarily formed during rainstorms can play a principal role in dissolved137 Cs discharge during rainfall-runoff events. Contaminated litter in the temporally saturated region of forested headwaters is an important factor contributing to elevated levels of dissolved137 Cs during rainstorms in the Fukushima area., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier B.V. All rights reserved.)- Published
- 2021
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