Scientists trace the path of radioactive cesium in the ecosystem of
Fukushima

Date:
January 20, 2022
Source:
National Institute for Environmental Studies
Summary:
In 2011, the nuclear accident at Fukushima, Japan, resulted in the
deposit of radioactive cesium (radiocesium) into habitats in the
vicinity. A decade after the accident, researchers have collated the
complicated dynamics of radiocesium within forest-stream ecosystems.

Understanding radiocesium flow in the environment could help
mitigate contamination and inform future containment strategies.



FULL STORY ==========================================================================
In the aftermath of the Fukushima nuclear accident, the Japanese
government performed intensive decontamination in the human-occupied
parts of the affected area by removing soil surface layers. But a major affected region consists of dense, uninhabited forests, where such decontamination strategies are not feasible. So, finding ways to avoid
the spread of radioactive contaminants like radiocesium to areas of human activity that lie downstream to these contaminated forests is crucial.


==========================================================================
The first step to this is to understand the dynamics of radiocesium flow through forest-stream ecosystems. In the decade since the accident, a
vast body of research has been dedicated to doing just that. Scientists
from the National Institute of Environmental Studies, Japan, sifted
through the data and detangled the threads of individual radiocesium
transport processes in forest- stream ecosystems. "We identified that radiocesium accumulates primarily in the organic soil layer in forests
and in stagnant water in streams, thereby making them potent sources
for contaminating organisms. Contamination management in these habitats
is crucial to provisioning services in forest-stream ecosystems," says
Dr. Masaru Sakai, who led the study. The findings of this study was
made available online on 6 July 2021 and published in volume 288 of the
journal Environmental Pollution on 1st November 2021.

The research team reviewed a broad range of scientific research on
radiocesium in forests and streams to identify regions of radiocesium accumulation and storage. After the accident, radiocesium was primarily deposited onto the forest canopy and forest floor. This radiocesium
reaches the earth eventually - - through rainfall and falling leaves --
where it builds up in the upper layers of the soil. Biological activities,
such as those of detritivores (insects and fungi that live off leaf debris etc.) ensure that radiocesium is circulated through the upper layers
of the soil and subsequently incorporated into plants and fungi. This
allows radiocesium to enter the food web, eventually making its way
into higher organisms. Radiocesium is chemically similar to potassium,
an essential mineral in living organisms, contributing to its uptake
in plants and animals. "Fertilizing" contaminated areas with an excess
of potassium provides an effective strategy to suppress the biological absorption of radiocesium.

Streams and water bodies in the surrounding area get their share of
radiocesium from runoff and fallen leaves. Most radiocesium in streams is likely to be captured by the clay minerals on stream beds, but a small
part dissolves in the water. Unfortunately, there is little information
on the relationship between dissolved radiocesium and aquatic organisms,
like fish, which could be important to the formulation of contamination management strategies.

Radiocesium in streams also accumulates in headwater valleys,pools,
and other areas of stagnant water. Constructions such as reservoir dams
provide a way to effectively trap radiocesium but steady leaching from
the reservoir sediments causes re-contamination downstream.

This complicated web of radiocesium transport is hard to trace, making
the development of a one-stop solution to radiocesium contamination
impossible. Dr.

Sakai and team recommend interdisciplinary studies to accelerate a full understanding of radiocesium pathways in forest-stream ecosystems so that measures can be developed to reduce future contamination. "This review can serve as basal knowledge for exploring future contamination management strategies. The tangled radiocesium pathways documented here may also
imply the difficulties of creating successful radiation contamination management strategies after unwished-for nuclear accidents," explains
Dr. Sakai.

Nuclear power is often touted as a solution to the energy crisis, but it
is important to plan response measures to unpredictable contamination
events. To address the essential need for clean energy in view of the
climate crisis, contamination management in societies depending on
nuclear power is integral.

Fully understanding the behavior of radiocesium in ecosystems can not
only lead to the successful management of existing contamination but
can also ensure the swift containment of potential future accidents.

========================================================================== Story Source: Materials provided by National_Institute_for_Environmental_Studies. Note: Content may be edited
for style and length.


========================================================================== Journal Reference:
1. Masaru Sakai, Hideki Tsuji, Yumiko Ishii, Hirokazu Ozaki, Seiichi
Takechi, Jaeick Jo, Masanori Tamaoki, Seiji Hayashi, Takashi Gomi.

Untangling radiocesium dynamics of forest-stream ecosystems:
A review of Fukushima studies in the decade after the
accident. Environmental Pollution, 2021; 288: 117744 DOI:
10.1016/j.envpol.2021.117744 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/01/220120091213.htm

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