Distinct food-web transfers of Cs to fish in river and lake ecosystems: A case study focusing on masu salmon in the Fukushima evacuation zone.

This study was conducted to elucidate the spatial and size variations, and food-web transfer of Cs in freshwater fish in the upper reaches of the Ukedo River system, a highly contaminated river system flowing through the Fukushima evacuation zone. Fish collection and environmental surveys were conducted in the summer of 2020 at five forest rivers and at the Ogaki Dam reservoir (an artificial lake) with different air dose rates (mean 0.20-3.

Variability in radiocesium activity concentration in growing hardwood shoots in Fukushima, Japan.

The radiocesium contamination caused by the Fukushima Daiichi Nuclear Power Plant accident has made it difficult to use coppice woods as bed logs for mushroom cultivation. Evaluating the variability in the radiocesium activity concentration of logs is necessary in order to predict how many coppice woodlands are available for producing mushroom bed logs. To clarify the variability in radiocesium activity concentrations and to estimate the sample size required to estimate these concentrations with sufficient accuracy, we modeled the log-transformed radiocesium activity concentrations in growing shoots of hardwoods.

Factors controlling dissolved Cs activities in coastal waters on the eastern and western sides of Honshu, Japan.

The distributions of dissolved Cs in river, nearshore, and offshore waters on the east and west coasts of the Japanese island of Honshu were studied in 2018-2021, 7-10 years after the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident. On the east side along the north western North Pacific (Fukushima Prefecture), estuarine processes, including desorption from riverine particles and dissolution into pore water from riverine particles that had settled to the seafloor, contributed to the maintenance of high dissolved Cs activities in nearshore and offshore waters. A survey and mass-balance calculation in a semi-enclosed estuarine area, the Matsukawa-ura, in the northern part of Fukushima, provided convincing evidence that rivers contributed to the influx of Cs to coastal waters.

Speciation of cesium in tree tissues and its implication for uptake and translocation of radiocesium in tree bodies.

Since the Chernobyl and Fukushima nuclear power plant accidents, extensive research has focused on the distribution and cycle of radiocesium in forest systems. Nevertheless, direct chemical speciation analyses of Cs by spectroscopic methods are limited by the low abundances of stable Cs as well as radiocesium in trees. In this study, we investigated coordination structures of Cs in Cs-doped bark, sapwood, heartwood, needle, and branch samples of trees collected in Fukushima by extended X-ray absorption fine structure (EXAFS) spectroscopy.

Relationship between the activity concentration of Cs in the growing shoots of Quercus serrata and soil Cs, exchangeable cations, and pH in Fukushima, Japan.

Incorporation of radiocesium by plants via root uptake appears to be affected by some of the exchangeable cations in the soil and/or pH of the soil. However, few studies have examined the relationship between Cs in trees and soil properties in the area surrounding the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) after the accident in March 2011. To elucidate the relationships between the root uptake of Cs by deciduous broadleaved trees and soil properties, we measured the activity concentration of Cs in the growing shoots of coppiced konara oak (Quercus serrata) grown after the FDNPP accident and the amounts of total Cs; exchangeable (ex-) Cs, ex-K, ex-Mg, and ex-Ca; and pH (HO) in soils collected from 34 forest stands in Fukushima between December 2016 and May 2017.

Web-building spider Nephila clavata (Nephilidae: Arachnida) can represent Cs contamination of arthropod communities and bioavailable Cs in forest soils at Fukushima, Japan.

Large areas of Fukushima's forests were contaminated with radiocesium (Cs) after the Fukushima Dai-ichi Nuclear Power Plant accident. Most of the contaminated forests have not been decontaminated, and bioavailable Cs is likely to circulate within the forest environment's food web. Nephila clavata (Nephilidae: Arachnida) is a top predator in the forest arthropod community, and this web-building spider potentially consumes many arthropod species presented in the grazing and detrital food chains.

Evaluation of radiocesium concentrations in new leaves of wild plants two years after the Fukushima Dai-ichi Nuclear Power Plant accident.

Radiocesium ((137)Cs) transfer to plants immediately after the Fukushima Dai-ichi Nuclear Power Plant accident was investigated by collecting newly emerged leaf and soil samples between May 2011 and November 2012 from 20 sites in the Fukushima prefecture. Radiocesium concentrations in leaf and soil samples were measured to calculate concentration ratios (CR). Woody plants exhibited high CR values because (137)Cs deposited on stems and/or leaves were transferred to newly emerging tissues.

Inferring the chemical form of 137Cs deposited by the Fukushima Dai-ichi Nuclear Power Plant accident by measuring (137)Cs incorporated into needle leaves and male cones of Japanese cedar trees.

We hypothesized that the water-soluble (ionic) and water-insoluble (stable) radiocesium from the initial fallout of the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident was distributed in various proportions in the surrounding areas and that this distribution was reflected in the trees that suffered deposition from the initial fallout. This study attempted to evaluate local variations in the chemical form of (137)Cs derived from the initial fallout of the FDNPP accident and whether its chemical form affected the radiocesium concentration in the tissues currently growing in trees, even after the initial fallout ceased. For these estimations, the ratio between the (137)Cs concentration in Cryptomeria japonica needle leaves in the tree crown, which existed before the FDNPP accident and subsequently directly exposed to the initial fallout ((137)Cs pre-accident N), and the amount of (137)Cs in the initial fallout itself ((137)Cs fallout) was determined ((137)Cs pre-accident N/(137)Cs fallout) at 66 sites.

Radiocesium accumulation properties of Chengiopanax sciadophylloides.

Through the assessments of radioactive contamination after the Fukushima Dai-ichi Nuclear Power Plant (F1NPP) accident, it has been reported that some sprouts of Chengiopanax sciadophylloides (Franch. et Sav.) at the site contained radiocesium (((134),)(137)Cs) at higher concentrations than the other plants.

Relationship between radiocesium contamination and the contents of various elements in the web spider Nephila clavata (Nephilidae: Arachnida).

The accident at the Fukushima Dai-ichi nuclear power plant seriously contaminated a large area in northeast Japan with a large amount of radioactive material. Consequently, various organisms, including arthropods, in the ecosystem have been contaminated with radiocesium ((137)Cs) through the food chain. We previously showed that the web spider Nephila clavata was contaminated with (137)Cs and that the level of contamination, which varied among spider individuals, was independent of the amount of prey consumed.

Radiocesium distribution in sugi (Cryptomeria japonica) in eastern Japan: translocation from needles to pollen.

We assessed the radiocesium contamination of sugi (Cryptomeria japonica) forests in eastern Japan from November 2012 to February 2013, including 80 sites in Fukushima and 35 sites in other regions (Tohoku and Kanto-Koshinetsu), by measuring the (137)Cs concentrations in needles of different ages, male flowers, and pollen. Over a wide geographic area, needles that were present at the time of the Fukushima Dai-ichi Nuclear Power Plant accident contained much higher (137)Cs concentrations than needles that emerged after the accident. This result, together with visual analysis of (137)Cs distribution using autoradiography, indicated that some of the (137)Cs derived from direct fallout remained on the surface of the older needles.

Radiocesium contamination of the web spider Nephila clavata (Nephilidae: Arachnida) 1.5 years after the Fukushima Dai-ichi Nuclear Power Plant accident.

We measured the concentrations of radiocesium ((134)Cs and (137)Cs) in a large web spider, Nephila clavata L. Koch (Nephilidae: Arachnida), collected at three sites at different distances from the Fukushima Dai-ichi Nuclear Power Plant about 1.5 y after the accident in March 2011.