First isolation and analysis of caesium-bearing microparticles from marine samples in the Pacific coastal area near Fukushima Prefecture

Abstract

A part of the radiocaesium from the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident was emitted as glassy, water-resistant caesium-bearing microparticles (CsMPs). Here, we isolated and investigated seven CsMPs from marine particulate matter and sediment. From the elemental composition, the 134Cs/137Cs activity ratio, and the 137Cs activity per unit volume results, we inferred that the five CsMPs collected from particulate matter were emitted from Unit 2 of the FDNPP, whereas the two CsMPs collected from marine sediment were possibly emitted from Unit 3, as suggested by (i) the presence of calcium and absence of zinc and (ii) the direction of the atmospheric plume during the radionuclide emission event from Unit 3. The presence of CsMPs can cause overestimation of the solid–water distribution coefficient of Cs in marine sediments and particulate matter and a high apparent radiocaesium concentration factor for marine biota. CsMPs emitted from Unit 2, which were collected from the estuary of a river that flowed through a highly contaminated area, may have been deposited on land and then transported by the river. By contrast, CsMPs emitted from Unit 3 were possibly transported eastward by the wind and deposited directly onto the ocean surface.

The Discovery of Radiocesium-bearing Microparticles Directly Delivered to a Person in Tokyo as a Result of the Fukushima Daiichi Nuclear Disaster

“…An approximately 1-mm 2 area surrounding high-radioactivity spots of the Kapton tape was cut. According to previous studies (Higaki et al 2017;Kurihara et al 2020;Miura et al 2018Miura et al , 2021, high spots indicate the presence of CsMPs. If high-radioactivity spots remained on the non-woven fabric fragment, the fragment was treated again by ultrasonication.…”

Improved Radio-Cesium Detection Using Quantitative Real-Time Autoradiography

“…Moreover, CsMPs can be transported (e.g., as dust in the air, by flowing water, etc. ), resulting in an unpredictable, changing radio-Cs distribution in the environment. − Given the existence of CsMPs and their potential long-term impact on the environment and human health, it is essential to detect, evaluate, and differentiate the varying forms of radio-Cs (micro-particle or bulk) found in samples.…”

Radiocesium-bearing microparticles cause a large variation in 137Cs activity concentration in the aquatic insect Stenopsyche marmorata (Tricoptera: Stenopsychidae) in the Ota River, Fukushima, Japan

“…The total radioactivity of other bulk samples was larger in periphyton (17-220 Bq), CPOM (47-285 Bq), and SS (3-54 Bq) than that of caddisfly due to the larger sample weight for periphyton and CPOM samples, and the higher 137 Cs activity concentration in SS samples, resulting in a small CsMP radioactivity fraction and a small effect of CsMPs on 137 Cs activity concentration. Thus, it should be noted that the inclusion of CsMPs could substantially increase the measured value of 137 Cs activity concentration, especially for samples with low total radioactivity, such as small insects or plankton samples [10].…”

“…The total RCs deposited on land is 3-6 PBq [8], but the ratio of RCs abundance in CsMPs to water-soluble RCs is unknown. CsMPs are important for understanding and predicting the fate of RCs in the environment and their uptake by organisms [9,10]. After CsMPs were first reported by Adachi et al [11], subsequent studies revealed two types of CsMPs: Type A and Type B particles [12].…”

“…Type-A particles have been found in suspended solids (SS) in the water of the Kuchibuto River in Fukushima Prefecture [18]. Miura et al [10] also reported Type-A particles in various marine samples, such as SS and plankton net samples, which were probably transported from rivers. Therefore, CsMPs in aquatic environments may be taken up by aquatic organisms, such as aquatic insects and fish, and the radiological risk of CsMPs to aquatic organisms because of their intense radioactivity is concerning.…”