Atmospheric behavior, deposition, and budget of radioactive materials from the Fukushima Daiichi nuclear power plant in March 2011

TLDR

Accurate estimation of airborne emissions is critical because radioactivity budgets are highly sensitive to temporal emission patterns, and uncertainties in emission, transport, and deposition processes can cause discrepancies in modeled deposition. The study aims to understand the atmospheric behavior of iodine‑131 and cesium‑137 released from Fukushima by simulating their transport and deposition. A chemical transport model was employed to simulate the transport and deposition of iodine‑131 and cesium‑137. The model reproduced observed deposition patterns across 15 prefectures, though with some discrepancies, and the budget analysis showed that about 13 % of iodine‑131 and 22 % of cesium‑137 were deposited on land, with the remainder falling in the ocean or leaving the domain.

Abstract

[1] To understand the atmospheric behavior of radioactive materials emitted from the Fukushima Daiichi nuclear power plant after the nuclear accident that accompanied the great Tohoku earthquake and tsunami on 11 March 2011, we simulated the transport and deposition of iodine-131 and cesium-137 using a chemical transport model. The model roughly reproduced the observed temporal and spatial variations of deposition rates over 15 Japanese prefectures (60−400 km from the plant), including Tokyo, although there were some discrepancies between the simulated and observed rates. These discrepancies were likely due to uncertainties in the simulation of emission, transport, and deposition processes in the model. A budget analysis indicated that approximately 13% of iodine-131 and 22% of cesium-137 were deposited over land in Japan, and the rest was deposited over the ocean or transported out of the model domain (700 × 700 km2). Radioactivity budgets are sensitive to temporal emission patterns. Accurate estimation of emissions to the air is important for estimation of the atmospheric behavior of radionuclides and their subsequent behavior in land water, soil, vegetation, and the ocean.