Temporal variation of cesium isotope concentrations and atom ratios in zooplankton in the Pacific off the east coast of Japan

Abstract

After the Fukushima Daiichi Nuclear Power Plant accident in March 2011, concentrations of cesium isotopes (133Cs, 134Cs, and 137Cs) were measured in zooplankton collected in the Pacific off the east coast of Japan from May 2012 to February 2015. The time series of the data exhibited sporadic 137Cs concentration peaks in zooplankton. In addition, the atom ratio of 137Cs/133Cs in zooplankton was consistently high compared to that in ambient seawater throughout the sampling period. These phenomena cannot be explained fully by the bioaccumulation of 137Cs in zooplankton via ambient seawater intake, the inclusion of resuspended sediment in the plankton sample, or the taxonomic composition of the plankton. Autoradiography revealed highly radioactive particles within zooplankton samples, which could be the main factor underlying the sporadic appearance of high 137Cs concentrations in zooplankton as well as the higher ratio of 137Cs/133Cs in zooplankton than in seawater.

Decline in radiocesium in seafloor sediments off Fukushima and nearby prefectures

“…So-called Cs balls, which are particles with a diameter of a few micrometers containing extremely high 137 Cs concentrations (0.66-3.27 Bq/particle), were released into the air by the accident (Adachi et al 2013). Recently, Ikenoue et al (2017) have hypothesized that consistently high but variable concentrations of 137 Cs in zooplankton collected from the waters off Fukushima and nearby prefectures, compared with concentrations in the ambient seawater, are mainly attributable to the presence of 137 Cs-enriched particles. Although Cs balls or 137 Cs-enriched particles have not yet been reported in marine sediments, it is possible that the concentration variability in sediments might be at least partially due to the presence of such particles.…”

Contribution of 137Cs-enriched particles to radiocesium concentrations in seafloor sediment: Reconnaissance experiment

“…Radiocesium-bearing microparticles (CsMPs) have been found since the FDNPP accident in a variety of samples, including aerosols, soil, river water, forest leaves, vegetables, and oceanic zooplankton [ 7 – 16 ]. In addition to mineralogical and chemical analyses, techniques employed in these studies have included use of an imaging plate, which is well suited for identification of heterogeneously located radioactive particles.…”

“…In addition to mineralogical and chemical analyses, techniques employed in these studies have included use of an imaging plate, which is well suited for identification of heterogeneously located radioactive particles. Ikenoue et al [ 7 ] have suggested that the presence of highly radioactive particles probably explains the consistently higher 137 Cs/ 133 Cs ratios in oceanic zooplankton than in seawater. It is thus possible that the variability of radiocesium concentrations in seafloor sediments is due to the presence of heterogeneously distributed radioactive particles.…”

Celastrol Alleviates Gamma Irradiation-Induced Damage by Modulating Diverse Inflammatory Mediators

“…Free radicals further result in oxidation, DNA damage, and inflammation in the body [1,3,4]. Currently, the probability of radiation exposure in human beings is increased due to the wide use of nuclear energy in modern society, which makes the development of effective radioprotective agents an urgent task [5][6][7].Celastrol, also known as tripterine, is a pentacyclic triterpenoid that belongs to the family of quinone methides [8][9][10][11][12][13][14][15]. It is a natural compound extracted from the root of Chinese medicinal plants Tripterygium wilfordii (Thunder god vine) and Celastrus regelii.…”

“…Free radicals further result in oxidation, DNA damage, and inflammation in the body [1,3,4]. Currently, the probability of radiation exposure in human beings is increased due to the wide use of nuclear energy in modern society, which makes the development of effective radioprotective agents an urgent task [5][6][7].…”