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論文

Effect of topsoil removal and selective countermeasures on radiocesium accumulation in rice plants in Fukushima paddy field

Yang, B.*; 恩田 裕一*; 大森 良弘*; 関本 均*; 藤原 徹*; 脇山 義史*; 吉村 和也; 高橋 純子*; Sun, X.*

Science of the Total Environment, 603-604, p.49 - 56, 2017/12

 被引用回数:1 パーセンタイル:83.76(Environmental Sciences)

In this study, the effect of topsoil removal measure and fertilizer application on radiocesium uptake by rice plants was investigated over a four-year period. The results indicate that the effect of topsoil removal measure on the accumulation of radiocesium in rice plants was effective. We summarized four year's data to further confirm that potassium and nitrogen fertilizers had an opposite effect on the accumulation of radiocesium in rice plants. Increasing potassium and reducing nitrogen fertilizer conditions tended to inhibit the radiocesium uptake by rice plants.

論文

Temporal changes of radiocesium in irrigated paddy fields and its accumulation in rice plants in Fukushima

Yang, B.*; 恩田 裕一*; 脇山 義史*; 吉村 和也; 関本 均*; Ha, Y.*

Environmental Pollution, 208(Part B), p.562 - 570, 2016/01

 被引用回数:5 パーセンタイル:55.17(Environmental Sciences)

In this study, we investigated the temporal changes of radiocesium in soil, irrigation water, and rice plant in two adjacent rice paddies, with and without surface-soil-removal practice, in Fukushima Prefecture for over three years (2012 to 2014). Our results showed that radiocesium migrated into 24-28 cm soil layers and that the concentration and inventory of radiocesium in paddy soils generally decreased. The newly added radiocesium to paddies through irrigation water contributed only the maximum values of 0.15% and 0.75% of the total amount present in normal and decontaminated paddies, respectively, throughout the study period. The change trend of radiocesium concentration in suspended sediment in irrigation water exponentially decreased. Radiocesium accumulation in rice plant also decreased with time in both paddies. However, the transfer factor of radiocesium for rice plant in the decontaminated paddy increased compared with normal paddy.

論文

Behavior of accidentally released radiocesium in soil-water environment; Looking at Fukushima from a Chernobyl perspective

Konoplev, A.*; Golosov, V.*; Laptev, G.*; 難波 謙二*; 恩田 裕一*; 高瀬 つぎ子*; 脇山 義史*; 吉村 和也

Journal of Environmental Radioactivity, 151(Part 3), p.568 - 578, 2016/01

 被引用回数:27 パーセンタイル:6.18(Environmental Sciences)

Comparative analysis is provided for radiocesium wash-off parameters and Kd between suspended matter and water in rivers and surface runoff on Fukushima and Chernobyl contaminated areas for the first years after the accidents. It was found that radiocesium distribution coefficient in Fukushima rivers is essentially higher than those in Chernobyl. This can be associated with two factors: a higher RIP of samples in Fukushima and the presence of water insoluble glassy particles. It was found also that dissolved wash-off coefficients for Fukushima catchments are lower than those in Chernobyl. Particulate wash-off coefficients are comparable for Fukushima and Chernobyl. The radiocesium migration in undisturbed forest and grassland soils at Fukushima has been shown to be faster than those in Chernobyl. Investigation and analysis of radiocesium distribution in soils of Niida river catchment revealed accumulation of contaminated sediments on its floodplain.

口頭

Radiocesium wash-off associated with soil erosion from various land uses after the Fukushima Dai-ichi NPP accident

脇山 義史*; 恩田 裕一*; 吉村 和也; 加藤 弘亮*

no journal, , 

This study presents two-year observation of soil erosion and radiocesium wash-off to quantify differences in radiocesium behavior in various land uses. High erodibilities and relatively low values of radiocesium wash-off in cultivated farmlands can be attributed to the mixing of surface soil by ploughing. It was found that the total solid wash-off coefficient of radiocesium from farmlands is high and for 2 years period of time after the accident reaches 10%. Generally high precipitation in the region and steep slopes promote higher wash-off of radiocesium as compared to the Chernobyl case. Also, normalized wash-off coefficients exhibited relatively less volatility than erodibilities in thelandscapes. These results suggest that soil erosion management is crucial for mitigating risks of radiocesium.

口頭

Long-term trends of plot-scale Cs-137 wash-off on various land uses in Fukushima

脇山 義史*; 恩田 裕一*; 吉村 和也; 中村 典子*; 馬目 凌*

no journal, , 

This study shows approximately three years observation results of plot-scale Cs-137 wash-off at various land uses in Kawamata town after the accident of FDNPP. Soil erosion rate were positively correlated with vegetation cover on undisturbed soils, whereas high erosion rate were found on cultivated farmlands even with similar vegetation cover to uncultivated farmlands. Annual Cs-137 wash-off rate ranged from 0.003 to 9.3 %/year and the largest was from uncultivated farmland followed by cultivated farmlands. Decreasing trends of Cs-137 concentration were found on uncultivated farmlands, whereas no trend was found on other plots. Our results suggest that the active soil erosion results in decrease in Cs-137 concentration of sediments on uncultivated slopes, while cultivation resulted in the no trend of temporal decrease in Cs-137 concentration due to constant vertical distribution of Cs-137.

口頭

Slope-scale Cs-137 wash-off processes estimated with erosion plot observations and laser-scanning

脇山 義史*; 馬目 凌*; 恩田 裕一*; 吉村 和也

no journal, , 

本研究では、斜面スケールでの土砂移動に伴う放射性セシウムの移動プロセスを明らかにすることを目的として、福島原発により放射性セシウムが沈着した地点に土壌侵食プロットを設置して土砂およびCs-137流出量の観測を行うとともにレーザープロファイラによる地表面の地形変化を追跡し、土砂移動に伴うCs-137流出の時間変化および季節性について考察を行った。本研究結果は、放射性セシウムの移行には季節性があることを示しており、将来予測の精度向上のためには斜面スケールにおけるCs-137移動プロセスについての複数年の観測が有用であることが示唆された。

口頭

Seasonality of Cs-137 concentration of sediments eroded from a slope in Fukushima

脇山 義史*; 馬目 凌*; 恩田 裕一*; 吉村 和也

no journal, , 

This study presents a three years' Cs-137 wash-off observation and morphological surveys on a soil erosion in area affected by the accident of Fukushima nuclear power plant to describe detailed processes of Cs-137 wash-off. Cs-137 concentration varied enormously and it appeared to decrease gradually from spring to autumn and increased again after winter. Based on the photos and scan data of soil surface, the expansions of a rill from spring to summer and elevations of soil surface from winter to spring were found. Our analysis suggests that freezing and thawing cycles resulted in high Cs-137 concentration of sediments during winter, whereas expansion of rill makes decrease in Cs-137 concentration in warm seasons.

口頭

Land use controls fate and transport of radionuclides in Fukushima in the terrestial environment

恩田 裕一*; 谷口 圭輔*; 脇山 義史*; 吉村 和也; Smith, H.*; Blake, W.*; 岩上 翔*; 加藤 弘亮*

no journal, , 

An intensive field monitoring campaign has been started, immediately after the Fukushima NPP accident including detailed monitoring site in upstream (Yamakiya site), and 30 monitoring sites in downstream river sites. In this presentation, I will present the summary of four years environmental transfer studies after the Fukushima NPP accident. The detailed monitoring of activity concentration of radiocesium and their flux, which can be applicable for the fate and flux of the radionuclide transfer in humid temperate environment. We also found that land use controls most of the transport and then fate of Cs-137 in terrestrial environment.

口頭

Cesium-137 wash-off associated with soil erosion on various land uses in Fukushima

吉村 和也; 脇山 義史*; 恩田 裕一*; 高瀬 つぎ子*

no journal, , 

This study presents Cs-137 wash-off observations on various land uses including decontaminated lands in Fukushima. We established rectangle soil erosion plots on six landscape; uncultivated farmland (UFL), cultivated farmland (CFL), grassland (GL), forest (F), uncultivated and cultivated farmlands on a decontaminated land (D-UFL and D-CFL). The D-UFL and DCFL were established after the decontamination of erosion plots. Mean Cs-137 concentrations on decontaminated lands decreased down to approx. 10 to 40 % of values observed before decontamination. No significant difference in amount of eroded sediment was found between contaminated and decontaminated lands, suggesting that decontamination works decrease total Cs-137 wash-off.

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