Initial radiocesium deposition on forest ecosystems surrounding the Tokyo metropolitan area due to the Fukushima Daiichi Nuclear Power Plant accident

Abstract

Abstract:The Fukushima Daiichi Nuclear Power Plant accident in 2011 resulted in releases of enormous amounts of radionuclides into the atmosphere. The radionuclides were deposited over a large forested area in the Tohoku and Kanto regions. There were few reports about the initial depositions of radionuclides on forest ecosystems during the main emission period. We investigated the initial radiocesium deposition at various forest sites. The deposition of radiocesium by bulk precipitation during the initial few months (approximately until the end of May just after the accident) ranged from 4.4-42.1 kBq m -2 while that by throughfall ranged from 2.1-36.6 kBq m -2. The ratio of radiocesium deposition by throughfall to that by bulk precipitation (D TF /D BP ) ranged from 0.13-0.66 during the first sampling period (approximately until the end of March just after the accident). In the following sampling periods, the radiocesium input by bulk precipitation decreased rapidly and became undetectable. The D TF /D BP ratios in these periods increased and then generally exceeded 1.0, meaning that the forest canopies gradually released the entrapped radiocesium. Atmospheric radiocesium inputs to forest ecosystems were strongly influenced by the forest canopy interception and temporal retention.

Meta-analysis of radiocesium contamination data in Japanese cedar and cypress forests over the period 2011–2017

“…throughfall) and, on the longer term, the contribution of litterfall driven by tree phenology or natural damage events (e.g. Kato and Onda, 2014;Teramage et al, 2014a;Loffredo et al, 2014Loffredo et al, , 2015Itoh et al, 2015;Endo et al, 2015;Okada et al, 2015;Kato et al, 2017Kato et al, , 2019Yoshihara et al, 2016;Nishikiori et al, 2019). These two bio-physical mechanisms gradually transfered the major part of intercepted radiocesium to the forest floor, i.e.…”

Strategic roadmap to assess forest vulnerability under air pollution and climate change

“…In exposed areas, forest ecosystems are released from pressure by human existence, resulting in creation of ecological niches and expansion of populations of some species (Deryabina et al, 2015; Lyons et al, 2020; Perino et al, 2019). Through intensive monitoring, it was confirmed that the overall dynamics of 137 Cs within forest ecosystems were similar between Chernobyl and Fukushima: tree canopies captured the deposition of 137 Cs and 137 Cs migrated from the canopy to the soil surface via water and litter fall, and most of it stays in the top layers of soil (Itoh et al, 2015; Kato et al, 2019; Suchara et al, 2016). However, the migration velocity and distribution patterns of 137 Cs within forests and tree bodies differ substantially among forests and trees (Imamura et al, 2017; Ohashi et al, 2017).…”