# Variation in Atmospheric 137Cs and the Carriers in Aerosol Samples Obtained from a Heavily Contaminated Area of Fukushima Prefecture

## TL;DR

A study in Fukushima found that atmospheric cesium-137 levels still fluctuate a decade after the nuclear accident, with carbon and aluminum particles carrying the radioactive isotope.

## Contribution

The study identifies specific particle types and environmental factors influencing cesium-137 fluctuations in heavily contaminated areas.

## Key findings

- Atmospheric 137Cs carriers in May included 68% aluminum particles and 88% carbonaceous particles in September.
- Bacteria and spores showed a linear relationship with 137Cs distribution in September aerosol samples.
- Temperature and precipitation were key factors affecting 137Cs distribution and its carriers.

## Abstract

Even a decade after the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident on 11 March 2011, fluctuations in atmospheric 137Cs were still observed, and explanations for the fluctuations and their carriers remained elusive. In this study, small fluctuations within 0.0002 Bq∙m−3 were still detected in aerosol samples obtained from January to April, and slightly higher levels of atmospheric 137Cs were observed from May to September in a heavily contaminated area of Fukushima prefecture. Specifically, it is demonstrated that the 137Cs carriers in the aerosol samples were a combination of carbon-containing particles and aluminum-containing particles (Al particles dominated, with the percentage being 68%) in early May, whereas the main 137Cs carriers were carbonaceous particles, with the average percentage being 88% in September and at the end of May, using fluorescent upright microscope and scanning electron microscope equipped with an energy-dispersive X-ray spectrometer quantitatively. Additionally, small particles (less than 2 μm) and medium particles (2–8 μm) of carbonaceous particles had a higher level in the aerosol samples of May and September. Specifically, bacteria (1–1.8 μm) and spores (1.8–10 μm) had a linear relationship with the distribution of atmospheric 137Cs in the aerosol samples of September. In addition, temperature and precipitation were the main impact factors affecting the distribution of 137Cs and their carriers. This observation further suggests that there is still a need for long-term monitoring of atmospheric 137Cs.