Evaluating sulfur-impurity removal and modern carbon contamination in different preparation methods for radiocarbon dating of soil samples by accelerator mass spectrometry

Koarashi, Jun; Takeuchi, Erina; Kokubu, Yoko; Atarashi-Andoh, Mariko

Radiocarbon, 67(2), p.307 - 317, 2025/04

https://doi.org/10.1017/RDC.2024.137

Radiocarbon (C) dating of soil samples by accelerator mass spectrometry has been proven useful for studying carbon (C) cycling in terrestrial ecosystems. There are, however, two main difficulties in sample preparation for this application: contamination of samples with modern C and inhibition of graphite formation due to sulfur (S)-containing impurities. Here we evaluated these effects from three different sample preparation methods, by conducting C measurements of C-dead sample and S-rich soil samples. The preparation methods were all successful in graphite formation and C measurement for soil samples with an organic S content 6.9%. The different methods showed different percent Modern Carbon (pMC) values ranging from 0.19% to 0.64% for C-dead sample. However, the three methods had little influence on the determination of C age for samples at least younger than 12,000 yr BP. The methods examined in the present study can be used for C dating with sufficient accuracy in the application to C cycle studies.

Spatial variations in radiocesium deposition and litter-soil distribution in a mountainous forest catchment affected by the Fukushima nuclear accident

Atarashi-Andoh, Mariko; Koarashi, Jun; Tsuzuki, Katsunori; Takeuchi, Erina; Nishimura, Shusaku; Muto, Kotomi*; Matsunaga, Takeshi*

Journal of Environmental Radioactivity, 238-239, p.106725_1 - 106725_8, 2021/11

https://doi.org/10.1016/j.jenvrad.2021.106725

To understand the spatial variation in soil Cs inventory in complex mountainous topography, a whole-area investigation of Cs deposition in a broad-leaved forest catchment of a mountain stream was conducted using grid sampling. Across the catchment, organic and surface mineral soil layers were collected at 42 locations in 2013 and 6 locations in 2015. Cs deposition on the forest floor exhibited high spatial heterogeneity and altitude-dependent distribution over the catchment. The Cs retention ratio in the organic layer ranged from 6% to 82% in 2013. The Cs retention ratios had positive correlations with the material inventory in the organic layer and the elevation. The Cs retention ratios in the organic layer were less than 20% in 2015, even at the locations where the retention ratio was higher than 55% in 2013. Although there was spatial variation in the migration speed, Cs migration from the organic layer to mineral soil was almost completed within 4 y of the deposition.

Rapid analytical method of Sr in urine sample; Rapid separation of Sr by phosphate co-precipitation and extraction chromatography, followed by determination by triple quadrupole inductively coupled plasma mass spectrometry (ICP-MS/MS)

Tomita, Jumpei; Takeuchi, Erina

Applied Radiation and Isotopes, 150, p.103 - 109, 2019/08

https://doi.org/10.1016/j.apradiso.2019.05.026

A rapid analytical method for determining Sr in urine samples (1-2 L) was developed to assess the internal exposure of workers in a radiological emergency. Strontium in a urine sample was rapidly separated by phosphate co-precipitation, followed by extraction chromatography with a tandem column of Pre-filter, TRU and Sr resin, and the Sr activity was determined by ICP-MS/MS. Measurement in the MS/MS mode with an O reaction gas flow rate 1 mL min showed no tailing of Sr at m/z = 90 up to 50 mg-Sr L. The interferences of Ge, Se and Zr at m/z = 90 were successfully removed by chemical separation. This analytical method was validated by the results of the analyses of synthetic urine samples (1.2-1.6 L) containing a known amount of Sr along with 1 mg of each of Ge, Se, Sr and Zr. The turnaround time for analysis was about 10 h, and the detection limit of Sr was approximately 1 Bq per urine sample.

Case studies of radiation dose assessment in emergency situation of nuclear facilities

Kawasaki, Masatsugu; Nakajima, Junya; Yoshida, Keisuke; Kato, Saori; Nishino, Sho; Nozaki, Teo; Nakagawa, Masahiro; Tsunoda, Junichi; Sugaya, Yuki; Hasegawa, Rie; et al.

JAEA-Data/Code 2017-004, 57 Pages, 2017/03

JAEA-Data-Code-2017-004.pdf:2.34MB

In emergency situation of nuclear facilities, we need to estimate the radiation dose due to radiation and radioactivity to grasp the influence range of the accident in the early stage. Therefore, we prepare the case studies of dose assessment for public exposure dose and personal exposure dose and contribute them to emergency procedures. This document covers about accidents of nuclear facilities in Nuclear Science Research Institute and past accident of nuclear power plant, and it can be used for inheritance of techniques of emergency dose assessment.

Year-round variations in the fluvial transport load of particulate Cs in a forested catchment affected by the Fukushima Daiichi Nuclear Power Plant accident

Matsunaga, Takeshi; Nakanishi, Takahiro; Atarashi-Andoh, Mariko; Takeuchi, Erina; Muto, Kotomi; Tsuzuki, Katsunori; Nishimura, Shusaku; Koarashi, Jun; Otosaka, Shigeyoshi; Sato, Tsutomu*; et al.

Journal of Radioanalytical and Nuclear Chemistry, 310(2), p.679 - 693, 2016/11

AA2015-0821.pdf:3.78MB

https://doi.org/10.1007/s10967-016-4840-3

Particulate Cs in stream water was collected continuously for two years in order to assess the long-term trend of the Cs discharge from the forest environment. Sampling was conducted from December 2011 to December 2013 in a mountainous stream, which received the Cs from the Fukushima Daiichi Nuclear Power Plant accident. A seasonal increase in fluvial transport load of particulate Cs associated with suspended solids (SS) was observed in August and September when rainfall was abundant. The particulate Cs concentration decreased at a faster rate than the rate due to radioactive decay. This decrease might be resulted from redistribution of the easily eroded and polluted soil surface due to heavy rain events such as typhoons. These findings indicate that the particulate Cs load was subject to the inter-annual variations in rainfalls, and decreased gradually over a long period of time due to a decrease in Cs concentration in SS.

Catchment-scale distribution of radiocesium air dose rate in a mountainous deciduous forest and its relation to topography

Atarashi-Andoh, Mariko; Koarashi, Jun; Takeuchi, Erina; Tsuzuki, Katsunori; Nishimura, Shusaku; Matsunaga, Takeshi

Journal of Environmental Radioactivity, 147, p.1 - 7, 2015/09

AA2014-0585.pdf:2.18MB

https://doi.org/10.1016/j.jenvrad.2015.05.004

We collected a large amount of radiocesium air dose rate data by mountain-walking with a small -ray survey system, KURAMA-II, to create an air dose rate map of a mountainous deciduous forest that received radiocesium from the Fukushima Dai-ichi Nuclear Power Plant accident. Measurements were conducted in a small stream catchment 0.6 km in size in August and September 2013, and the relationship between air dose rates and the mountainous topography was examined. Air dose rates increased with elevation, suggesting that more radiocesium was deposited on ridges, and that it had remained there for 2.5 years with no significant migration due to soil erosion or water drainage. Slope aspect also strongly affected air dose rates. By the continuous measurement using KURAMA-II, we describe the variation in air dose rates in a mountainous area and suggest that it is important to consider topography when selecting sampling points to estimating dose rates or contaminant deposition.

Topographic heterogeneity effect on the accumulation of Fukushima-derived radiocesium on forest floor driven by biologically mediated processes

Koarashi, Jun; Atarashi-Andoh, Mariko; Takeuchi, Erina; Nishimura, Shusaku

Scientific Reports (Internet), 4, p.6853_1 - 6853_7, 2014/10

https://doi.org/10.1038/srep06853

The accident at the Fukushima Daiichi Nuclear Power Plant caused serious radiocesium (Cs) contamination of forest ecosystems located in mountainous and hilly regions with steep terrain. To understand topographic effects on the redistribution and accumulation of Cs on forest floor, we investigated the distribution of Fukushima-derived Cs in forest-floor litter layers on a steep hillslope in a Japanese deciduous forest in August 2013. Both leaf-litter materials and litter-associated Cs were accumulated in large amounts at the bottom of the hillslope. At the bottom, a significant fraction (65%) of the Cs inventory was observed to be associated with newly shed and less degraded leaf-litter materials, with estimated mean ages of 0.5-1.5 years, added via litterfall after the accident. Newly emerged leaves at the site were contaminated with Fukushima-derived Cs in May 2011 (two months after the accident) and Cs concentration in them decreased with time. However, the concentrations were still two orders of magnitude higher than the pre-accident level in 2013 and 2014. These observations are the first to show that Cs redistribution on a forested hillslope is strongly controlled by biologically mediated processes and continues to supply Cs to the bottom via litterfall at a reduced rate.

Formation of groundwater with high radium in the former mining open-pit at Ningyo-toge Environmental Engineering Center of the Japan Atomic Energy Agency

Takeuchi, Erina; Tomita, Jumpei; Ohara, Yoshiyuki

no journal, , 

no abstracts in English

Radiocesium in a mountainous forested catchment; Inventory, distribution, and fluvial discharge

Takeuchi, Erina; Atarashi-Andoh, Mariko; Nishimura, Shusaku; Nakanishi, Takahiro; Tsuzuki, Katsunori; Koarashi, Jun; Matsunaga, Takeshi

no journal, , 

no abstracts in English

Rapid determination of Sr in urine samples by extraction chromatography coupled to ICP-MS/MS

Tomita, Jumpei; Takeuchi, Erina

no journal, , 

no abstracts in English