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Ruehr, N.*; Bamberger, I.*; Duarte, A.*; 堅田 元喜; Pointner, A.*; Arneth, A.*
no journal, ,
熱波は、樹木に熱ストレスを蓄積させることで陸域の水・炭素循環に大きな影響を及ぼすが、ストレス後の回復期の樹木応答は明らかになっていない。本研究では、異なる水分環境下にあるベイマツとニセアカシアに熱波処理を繰り返し施したときの水・炭素交換過程の変化を調べた。樹木の水・炭素フラックスの大きさは、熱と乾燥処理の度合いに応じて大きく異なっていた。水分が十分にある場合は、日中および夜間の蒸散は気温と大気の蒸発要求度の増加に伴い増加した。炭素固定量は、いずれの樹種も熱処理または熱・乾燥の同時処理によって低下した。さらに、これらの処理によってベイマツの夜間呼吸量は増加する傾向が見られた。ストレスによって引き起こされた気孔閉鎖と光合成回路の損傷により、水・炭素交換速度の回復に遅れが見られた。結果として、高温イベントは乾燥イベントと相まって、ストレス期間中および期間後の樹木の水・炭素循環に強く影響することが明らかになった。これら影響は、生態系の炭素循環を予測する生物地球化学モデルに考慮する必要がある。
萩原 大樹; 小西 博巳*; 中西 貴宏; 原田 久也; 鶴田 忠彦
no journal, ,
On fluvial discharge, particulate fractions are the main carrier of radiocaesium from land to aquatic bodies such as rivers, lakes and the sea. However, within river estuaries, where there is a drastic increase in salinity, fine particles generally flocculate (in the size order of several tens 
m) before settling out and being deposited on the river bed. In this study, we investigated the sediment records and the distribution of radiocaesium within the estuary of the Odaka river in January 2014. Based on distribution of salinity, the environment of the Odaka river is divided into three areas; the freshwater area, the estuarine marine area and the brackish area between these two. Radiocaesium deposition ranged from 45 to 1070 kBq m
with the inventory of radiocaesium in the estuary being significantly greater in the brackish area relative to both the freshwater and estuarine marineareas. Particle size dependency of radiocaesium concentration in the sediments showed that the distribution with relatively higher concentration was expected in the brackish area. The possibility of flocculation in the brackish area will be discussed.
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.
恩田 裕一*; 谷口 圭輔*; Smith, H.*; Blake, W.*; 吉村 和也
no journal, ,
The monitoring started at 6 sites from June 2011. Subsequently, additional 24 monitoring sites were installed between October 2012 and January 2013. The total measured flux to the ocean of radiocesium from the Abukuma River at Iwanuma was 14 TBq for the period from August 2011 to October 2014. The transfer of radiocesium with suspended sediment declining until March 2015 and had high correlation with land cover ratio by different land use of the catchments. Also we found positive correlation with radiocesium flux and catchment landuses.