Calculations for ambient dose equivalent rates in nine forests in eastern Japan from Cs and Cs radioactivity measurements

Malins, A.; Imamura, Naohiro*; Niizato, Tadafumi; Takahashi, Junko*; Kim, M.; Sakuma, Kazuyuki; Shinomiya, Yoshiki*; Miura, Satoru*; Machida, Masahiko

Journal of Environmental Radioactivity, 226, p.106456_1 - 106456_12, 2021/01

https://doi.org/10.1016/j.jenvrad.2020.106456

Radiocarbon-based estimation of soil carbon turnover in a cool-temperate beech forest

Koarashi, Jun; Atarashi-Andoh, Mariko; Ishizuka, Shigehiro*; Saito, Takeshi*; Hirai, Keizo*; Miura, Satoru*

Proceedings of International Symposium on Application of a Closed Experimental System to Modeling of C Transfer in the Environment, p.72 - 76, 2008/00

Recent debate has emphasized that our capacity to predict the response of soil organic carbon (SOC) to climate change depends on a clear understanding of the heterogeneity in SOC biodegradability. We collected soil samples from the Appi forest meteorology research site dominated by Japanese beech, separated the soil samples into three SOC fractions with a chemical method, and determined their radiocarbon isotope ratios using an accelerator mass spectrometry. The radiocarbon signatures allow us to estimate their turnover times (TTs), quantifying the rates of SOC decomposition. According to the estimated TTs, the SOC was distinguished into six SOC pools with distinct TTs of several years to 1000 years. The annual SOC decomposition rate was summed up to 0.47 kgC m y, about a half of which was from the fastest-cycling pool (litter). Approximately 5% of SOC gave the over-millennium TTs, suggesting that this pool plays a role of a long-term carbon sequestration in the carbon cycle.

Radiocarbon-based estimation of soil carbon turnover and its potential response to global warming

Koarashi, Jun; Atarashi-Andoh, Mariko; Ishizuka, Shigehiro*; Saito, Takeshi*; Hirai, Keizo*; Miura, Satoru*

no journal, , 

no abstracts in English

Investigation on distribution of radioactive substances in Fukushima, 9; Analysis of temporal changes in ambient dose equivalent rates in forests over 6 years following the FDNPP accident

Malins, A.; Imamura, Naohiro*; Niizato, Tadafumi; Kim, M.; Sakuma, Kazuyuki; Shinomiya, Yoshiki*; Miura, Satoru*; Machida, Masahiko

no journal, , 

We analyzed changes in ambient dose equivalent rates (*(10)) between 2011 and 2017 in forests in Fukushima Prefecture. PHITS was used to calculate the effects of changes in the distribution of Cs and Cs within forests on *(10). The transfer of radiocesium from the crowns of evergreen coniferous trees to the forest floor appeared to cause slower decreases in *(10) at 1 m height in early years than expected by the rate of Cs and Cs decay.

Dynamics of radiocaesium in forests deposited by the Fukushima Daiichi Nuclear Power Plant accident; Long-term monitoring and modelling approaches

Hashimoto, Shoji*; Tanaka, Taku*; Komatsu, Masabumi*; Gonze, M.-A.*; Sakashita, Wataru*; Kurikami, Hiroshi; Nishina, Kazuya*; Ota, Masakazu; Ohashi, Shinta*; Calmon, P.*; et al.

no journal, , 

We applied modelling approaches to evaluate the past and future dynamics of Cs in forests. In the model inter-comparison exercise using Fukushima data, six models with diverse model structures, processes, parameters and numerical approaches joined this exercise and the performance and uncertainties of the state-of-the-art models were explored. The inter-comparison revealed that, after appropriate calibration, the models reproduced the observed data reliably and the ranges of calculated trajectories were narrow in the early phase after the fallout. However, the envelope of the calculated model end points enlarged in long-term simulations over 50 years after the fallout. The model-inter comparison exercise emphasizes the importance of decadal data for various forest types and repetitive verification/validation processes using holistic, long-term data to improve the models and to update the forecasting capacity of the models.