29 results on '"Onda, Yuichi"'
Search Results
2. Mode of Atmospheric Deposition in Forests Demonstrates Notable Differences in Initial Radiocesium Behavior
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Anderson, Donovan, Kato, Hiroaki, and Onda, Yuichi
- Abstract
The March 2011 Fukushima Dai-ichi Nuclear Power Plant accident in Japan released 520 PBq of radionuclides compared to a total release of 5300 PBq from the Chornobyl Nuclear Power Plant accident. Both nuclear accidents resulted in deposition of radiocesium throughout the northern hemisphere, and a plethora of studies have been performed regarding radiocesium (137Cs) behavior. However, few studies have assessed the impact of precipitation on 137Cs deposition in forests. Wide-scale environmental measurements from 2011 and 2016 were used to determine the differences in 137Cs deposition because of precipitation following the Fukushima accident. In areas where wet deposition processes were dominant, dense forests generally had lower ambient dose rates and levels of contamination on forest floors than other stands with fewer stems per hectare in 2011. Similar tendencies were not observed in areas that were primarily subject to dry deposition nor were any trends observed in 2016. 137Cs was retained in dense forest canopies for an extended period regardless of the deposition mode. Additionally, it was found that the initial retention of radionuclides by forest canopies is in general higher for areas with predominantly dry deposition. Incorporation of radiocesium into wood tissues was the same for both wet and dry deposition.
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- 2022
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3. Transport and Redistribution of Radiocesium in Fukushima Fallout through Rivers.
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Taniguchi, Keisuke, Onda, Yuichi, Smith, Hugh G., Blake, William, Yoshimura, Kazuya, Yamashiki, Yosuke, Kuramoto, Takayuki, and Saito, Kimiaki
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- 2019
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4. A watershed-scale evapotranspiration model considering forest type, stand parameters, and climate factors.
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Inokoshi, Shodai, Gomi, Takashi, Chiu, Chen-Wei, Onda, Yuichi, Hashimoto, Asahi, Zhang, Yupan, and Saitoh, Taku M.
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BROADLEAF forests ,CONIFEROUS forests ,DECIDUOUS forests ,TEMPERATE forests ,EVAPOTRANSPIRATION ,THROUGHFALL - Abstract
[Display omitted] • A simple evapotranspiration model was developed for coniferous and deciduous forests in temperate climates. • The model consists of wet and dry canopy evaporation submodels, the former of which considers both rainfall and snowfall. • Estimated evapotranspiration values agreed with those observed using the eddy covariance method. • The model is applicable to a wide range of forested landscapes including multiple forest types and stand parameters, with rain and snow as precipitation input. We developed a model to estimate evapotranspiration (ET) for temperate coniferous and broadleaf forests that considers stand structure (density and height) and meteorological data (precipitation, air temperature, solar radiation, and vapor pressure deficit) as input. We used globally available data from 65 publications, as well as 37 datasets from sources such as FLUXNET, that were collected mainly from temperate climates. The wet canopy evaporation (E wet) submodel consisted of a nonlinear function to determine the ratio of interception loss to precipitation from stand density for coniferous forests or stand height for broadleaf forests. The parameters of the E wet submodel were determined separately for rainfall and snowfall. The dry canopy evaporation (E dry) submodel consisted of a simplified Penman–Monteith equation, including a nonlinear function to determine the reference surface conductance from stand height. We tested the prediction ability of the model using data from three locations covered by evergreen coniferous (ET, 13–83 mm/month) and deciduous coniferous forests (24–104 mm/month) in central Japan, and a deciduous broadleaf forest (1–59 mm/month) in northern Wisconsin, USA, for a mixture of rain and snow. Our model reproduced seasonal ET patterns, with mean absolute errors of 10 ± 5, 12 ± 7, and 6 ± 9 mm/month for the evergreen coniferous, deciduous coniferous, and deciduous broadleaf forests, respectively. The model is applicable to ET estimation over watershed-scale areas with heterogeneous biotic (forest condition) and abiotic (meteorological) factors in landscapes with complex topography. [ABSTRACT FROM AUTHOR]
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- 2023
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5. Changes in air dose rates due to soil moisture content in the Fukushima prefecture forests.
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Nakanishi, Miyu, Onda, Yuichi, Takahashi, Junko, Kato, Hiroaki, Iida, Hikaru, and Takada, Momo
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SOIL moisture ,SOIL air ,NUCLEAR power plant accidents ,RAINFALL - Abstract
Radionuclides released and deposited because of the 2011 Fukushima Dai-ichi Nuclear Power Plant accident caused an increase in air dose rates in Fukushima Prefecture forests. Although an increase in air dose rates during rainfall was previously reported, the air dose rates in the Fukushima forests decreased during rainfall. This study aimed to develop a method to estimate rainfall-related changes in air dose rates, even in the absence of soil moisture data, in Namie-Town and Kawauchi-Village, Futaba-gun, Fukushima Prefecture. Moreover, we examined the relationship between preceding rainfall (Rw) and soil moisture content. The air dose rate was estimated by calculating the Rw in Namie-Town from May to July 2020. We found that the air dose rates decreased with increasing soil moisture content. The soil moisture content was estimated from Rw by combining short-term and long-term effective rainfall using half-live values of 2 h and 7 d and considering the hysteresis of water absorption and drainage processes. Furthermore, the soil moisture content and air dose rate estimations showed a good agreement with coefficient of determination (R
2 ) scores >0.70 and >0.65, respectively. The same method was tested to estimate the air dose rates in Kawauchi-Village from May to July 2019. At the Kawauchi site, variation in estimated value is relatively large due to the presence of water repellency in dry conditions, and the amount of137 Cs inventory was low, so estimating air dose from rainfall remained a challenge. In conclusion, rainfall data were successfully used to estimate soil moisture and air dose rates in areas with high137 Cs inventories. This leads to the possibility of removing the influence of rainfall on measured air dose rate data and could contribute to the improvement of methods currently used to estimate the external air dose rates for humans, animals, and terrestrial forest plants. [Display omitted] • Soil moisture content and air dose rate were estimated using effective rainfall. • Air dose rate changes were estimated using measured soil moisture content changes. • Magnitude of soil shielding effect was elevated by preceding rainfall. • This method might reveal influences besides rainfall on air dose rate changes. [ABSTRACT FROM AUTHOR]- Published
- 2023
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6. Transport and Redistribution of Radiocesium in Fukushima Fallout through Rivers
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Taniguchi, Keisuke, Onda, Yuichi, Smith, Hugh G., Blake, William, Yoshimura, Kazuya, Yamashiki, Yosuke, Kuramoto, Takayuki, and Saito, Kimiaki
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The Fukushima Daiichi Nuclear Power Plant (FDNPP) accident released the most significant quantity of radiocesium into the environment since Chernobyl, and detailed measurements over the initial 5 years provide new insights into fluvial redistribution of radiocesium. We found that the high initial activity concentration of 137Cs-bearing suspended sediment in rivers was followed by a steep exponential decline (λ1) which extended to approximately 1 year after the accident, while the rate of initial decline in radiocesium activity concentration in water was an order of magnitude higher than rates measured after Chernobyl. Fluvial transport of 137Cs to the ocean from the Abukuma river totaled 12 TBq between June 2011 and August 2015 and almost all this radiocesium (96.5%) was transported in the particulate form. The primary sources of 137Cs were paddy fields, farmland, and urban areas [plaque-forming unit (PFU)], discharging 85% of the exported 137Cs from 38% of the watershed area. After 1 year, activity concentrations were lower and exhibited a more gradual secondary decline (λ2) which was associated with reduced radiocesium losses from PFU areas, while forest areas continue to represent more stable contaminant stores.
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- 2019
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7. Plutonium isotopic signatures in soils and their variation (2011-2014) in sediment transiting a coastal river in the Fukushima Prefecture, Japan.
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Jaegler, Hugo, Pointurier, Fabien, Onda, Yuichi, Hubert, Amélie, Laceby, J. Patrick, Cirella, Maëva, and Evrard, Olivier
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FUKUSHIMA Nuclear Accident, Fukushima, Japan, 2011 ,PLUTONIUM ,ISOTOPIC analysis ,EMISSION control ,RADIOISOTOPES - Abstract
The Fukushima Daiichi Nuclear Power Plant (FDNPP) accident resulted in a significant release of radionuclides that were deposited on soils in Northeastern Japan. Plutonium was detected at trace levels in soils and sediments collected around the FDNPP. However, little is known regarding the spatial-temporal variation of plutonium in sediment transiting rivers in the region. In this study, plutonium isotopic compositions were first measured in soils (n = 5) in order to investigate the initial plutonium deposition. Then, plutonium isotopic compositions were measured on flood sediment deposits (n = 12) collected after major typhoon events in 2011, 2013 and 2014. After a thorough radiochemical purification, isotopic ratios ( 240 Pu/ 239 Pu, 241 Pu/ 239 Pu and 242 Pu/ 239 Pu) were measured with a Multi-Collector Inductively Coupled Mass Spectrometer (MC ICP-MS), providing discrimination between plutonium derived from global fallout, from atmospheric nuclear weapon tests, and plutonium derived from the FDNPP accident. Results demonstrate that soils with the most Fukushima-derived plutonium were in the main radiocaesium plume and that there was a variable mixture of plutonium sources in the flood sediment samples. Plutonium concentrations and isotopic ratios generally decreased between 2011 and 2014, reflecting the progressive erosion and transport of contaminated sediment in this coastal river during flood events. Exceptions to this general trend were attributed to the occurrence of decontamination works or the remobilisation of contaminated material during typhoons. The different plutonium concentrations and isotopic ratios obtained on three aliquots of a single sample suggest that the Fukushima-derived plutonium was likely borne by discrete plutonium-containing particles. In the future, these particles should be isolated and further characterized in order to better understand the fate of this long-lived radionuclide in the environment. [ABSTRACT FROM AUTHOR]
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- 2018
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8. Radiocesium concentrations in soil and leaf after decontamination practices in a forest plantation highly polluted by the Fukushima accident.
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López-Vicente, Manuel, Onda, Yuichi, Takahashi, Junko, Kato, Hiroaki, Chayama, Shinya, and Hisadome, Keigo
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CESIUM content of soils ,RADIOACTIVE decontamination ,TREE farms ,FUKUSHIMA Nuclear Accident, Fukushima, Japan, 2011 ,RADIATION doses - Abstract
Owing to the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident a vast amount of radiocesium was released polluting the land. Afterwards, a variety of decontamination practices has been done, reducing the ambient dose rates. In this study we evaluated the effectiveness of eight forest decontamination practices by means of monitoring the radiocesium ( 137 Cs) concentration in soil and leaf samples, and the daily discharge rates in ten plots during 27 months (May 2013–July 2015). A forest plantation located 16 km southwest to the FDNPP and within the exclusion area was selected. Radiocesium concentrations were analysed using a germanium gamma ray detector. The differences in radiocesium activities between the different plots were statistically significant (p < 0.05) and four homogeneous groups were distinguished. Tree thinning and litter removal greatly reduced the radioactivity and the two plots devoted to these practices presented the highest discharge rates of 137 Cs (Th + LR; 350–380 Bq/m 2 day), followed by the two Th plots (163–174 Bq/m 2 day). The clearcutting with LR and the LR plots (104 and 92 Bq/m 2 day) also had higher rates than those rates in the control plots (51 Bq/m 2 day). We only observed low rates in the two plots with matting (19–25 Bq/m 2 day). The temporal variability was explained by (i) the different rainfall depths registered during the measurement intervals (accumulated precipitation from 14 to 361 mm); and (ii) the fluctuations of the total surface coverage. The decrease trend in radiocesium concentration was high in 2013, moderate in 2014 and low in 2015 owing to the vegetation recovery after the countermeasures, thus reducing the possibility of the second pollution of the neighbouring areas. The average proportions of contribution of 137 Cs discharge by soil and leaf fraction were 96.6% and 3.4%. [ABSTRACT FROM AUTHOR]
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- 2018
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9. Discovery of Novel Pyrazole-Based Selective Aldosterone Synthase (CYP11B2) Inhibitors: A New Template to Coordinate the Heme-Iron Motif of CYP11B2.
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Sakakibara, Ryo, Sasaki, Wataru, Onda, Yuichi, Yamaguchi, Minami, Ushirogochi, Hideki, Hiraga, Yuki, Sato, Kanako, Nishio, Masashi, Egi, Yasuhiro, Takedomi, Kei, Shimizu, Hidetoshi, Ohbora, Tomoko, and Akahoshi, Fumihiko
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- 2018
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10. Vertical distribution and temporal dynamics of dissolved 137Cs concentrations in soil water after the Fukushima Dai-ichi Nuclear Power Plant accident.
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Iwagami, Sho, Onda, Yuichi, Tsujimura, Maki, Hada, Manami, and Pun, Ishwar
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NUCLEAR power plant accidents ,SOIL moisture ,TSUNAMI damage ,EARTHQUAKE damage - Abstract
Radiocesium ( 137 Cs) migration from headwater forested areas to downstream rivers has been investigated in many studies since the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident, which was triggered by a catastrophic earthquake and tsunami on 11 March 2011. The accident resulted in the release of a huge amount of radioactivity and its subsequent deposition in the environment. A large part of the radiocesium released has been shown to remain in the forest. The dissolved 137 Cs concentration and its temporal dynamics in river water, stream water, and groundwater have been reported, but reports of dissolved 137 Cs concentration in soil water remain sparse. In this study, soil water was sampled, and the dissolved 137 Cs concentrations were measured at five locations with different land-use types (mature/young cedar forest, broadleaf forest, meadow land, and pasture land) in Yamakiya District, located 35 km northwest of FDNPP from July 2011 to October 2012. Soil water samples were collected by suction lysimeters installed at three different depths at each site. Dissolved 137 Cs concentrations were analyzed using a germanium gamma ray detector. The dissolved 137 Cs concentrations in soil water were high, with a maximum value of 2.5 Bq/L in July 2011, and declined to less than 0.32 Bq/L by 2012. The declining trend of dissolved 137 Cs concentrations in soil water was fitted to a two-component exponential model. The rate of decline in dissolved 137 Cs concentrations in soil water ( k 1 ) showed a good correlation with the radiocesium interception potential (RIP) of topsoil (0–5 cm) at the same site. Accounting for the difference of 137 Cs deposition density, we found that normalized dissolved 137 Cs concentrations of soil water in forest (mature/young cedar forest and broadleaf forest) were higher than those in grassland (meadow land and pasture land). [ABSTRACT FROM AUTHOR]
- Published
- 2017
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11. Estimation of throughfall with changing stand structures for Japanese cypress and cedar plantations.
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Sun, Xinchao, Onda, Yuichi, Kato, Hiroaki, Gomi, Takashi, and Liu, Xueyan
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THROUGHFALL ,CYPRESS ,CEDAR ,WATERSHEDS ,FOREST management - Abstract
Throughfall ( TF ) is a critical component of the hydrological and biogeochemical cycles and is greatly influenced by stand structures in forested watersheds. Previous studies have examined the relationships between TF and stand structures for different species and regions. However, there remains acknowledged difficulty in estimation of TF with changing stand structures due to forest management (e.g., thinning) for specific species and regions. This study conducted intensive thinning with 43–50% stem removal at seven experimental plots with various structures (e.g., stand density, canopy cover and basal area) across Japan that were covered by Japanese cypress ( Chamaecyparis obtusa Endl.) and cedar ( Cryptomeria japonica D. Don) plantations. TF was measured by a set of 20 tipping-bucket rain gauges placed in a lattice-like pattern within the plots before and after thinning. Results showed that during the study periods, thinning caused an increase in the mean TF rate from 63.2 ± 7.0% to 75.4 ± 6.0%. The TF rate was significantly negatively correlated with stand density, canopy cover, and basal area on a stand scale. Additionally, the slope ( a TF ) of event-based linear TF - P g (gross rainfall) equation was significantly higher in post-thinning (0.782 ± 0.077) than that in pre-thinning (0.663 ± 0.078), whereas it’s intercept ( b TF ) showed no significant difference (−0.707 ± 0.810 mm in pre-thinning and −0.441 ± 0.607 mm in post-thinning). The a TF significantly decreased with increasing stand density and canopy cover, whereas the b TF was not significantly correlated with any forest-structure variables. Further, the TF rate and a TF were estimated, respectively, by their related stand-structural variables in multiple regression models with high determination coefficients and moderate relative errors. The b TF was assumed to be a constant and its mean value obtained from all the experimental plots in each (pre- and post-thinning) period. Thus, the models of stand-scale TF rate and event-based TF amount were developed with input of commonly forest inventories. These models were validated by using the dataset of this study and earlier publications for Japanese cedar and cypress plantations, and showed good fit between the estimated and measured values. These models are practical tools that can be readily used for assessing the changes in TF with changing stand structures at both stand and event-based scales, and have also potential implications in evaluating the spatial TF patterns at catchment scale and exploiting similar models in other species and regions. [ABSTRACT FROM AUTHOR]
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- 2017
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12. Conformation-Based Design and Synthesis of Apratoxin A Mimetics Modified at the α,β-Unsaturated Thiazoline Moiety.
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Onda, Yuichi, Masuda, Yuichi, Yoshida, Masahito, and Doi, Takayuki
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- 2017
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13. Determining the initial Fukushima reactor accident-derived cesium-137 fallout in forested areas of municipalities in Fukushima Prefecture
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Kato, Hiroaki and Onda, Yuichi
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ABSTRACTThis study determined the initial distribution of Fukushima reactor-derived radiocesium fallout in forest areas of Fukushima Prefecture based on analysis of airborne monitoring surveys by the Japanese Ministry of Education, Culture, Sports, Science and Technology (MEXT). The results of the fifth airborne monitoring surveys were compared with the third airborne survey data in order to correct for variation of deposition density due to multiple factors such as weathering processes and measurement uncertainties between two surveys. Finally, the results of the third and the corrected fifth airborne surveys were combined to reconstruct the initial radiocesium fallout map over the whole Fukushima Prefecture area following the Fukushima reactor accident. Our calculation results showed that forest areas accumulated 72% of the total atmospheric input of 137Cs to the land of Fukushima Prefecture. The deposition density in forest areas showed significant variability among municipalities. Nevertheless, forest areas accumulated a large percentage of atmospherically deposited radiocesium in many municipalities. Statistical analysis of the variability in 137Cs deposition density indicated that deposition density varied significantly, even within a municipality. Furthermore, the inconsistency in the probability distributions of measured deposition density among municipalities makes it difficult to obtain a representative initial radiocesium fallout input following the accident. To reduce uncertainty in environmental parameters related to radiocesium transfer in forest environments, we strongly recommend that the deposition density of initial 137Cs fallout at each location is determined by in-situ sampling survey and using the reconstructed 137Cs fallout map presented in this study.
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- 2018
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14. Temporal changes of radiocesium in irrigated paddy fields and its accumulation in rice plants in Fukushima.
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Yang, Baolu, Onda, Yuichi, Wakiyama, Yoshifumi, Yoshimura, Kazuya, Sekimoto, Hitoshi, and Ha, Yiming
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CESIUM ,PADDY fields ,BIOACCUMULATION ,EFFECT of radiation on plants ,RICE ,PLANTING ,METAL content of soils - Abstract
About half of the total paddy field area, which is the dominant agricultural land in Fukushima Prefecture, was contaminated by radiocesium released by the Fukushima Daiichi Nuclear Power Plant accident. 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, in Fukushima Prefecture for over three years (2012–2014) after the nuclear accident. Our results showed that radiocesium migrated into 24–28 cm soil layers and that the activity concentration of radiocesium in paddy soils showed a significant reduction in 2014. The newly added radiocesium to paddies through irrigation water contributed only a maximum value of 0.15% and 0.75% of the total amount present in control and decontaminated paddies, respectively, throughout the study period. The radiocesium activity concentration in suspended sediment in irrigation water exponentially decreased, and the effective half-lives (T eff ) for 137 Cs and 134 Cs were 1.3 and 0.9 years, respectively. Additionally, the average suspended sediment concentration in irrigation water increased between 2012 and 2014, suggesting that enhanced soil erosion had occurred in the surrounding environment. Radiocesium accumulation in rice plant also decreased with time in both paddies. However, the concentration ratio of radiocesium for rice plant in the decontaminated paddy increased compared with control paddy, despite approximately 96% of fallout radiocesium removed in paddy soil. Further analysis is required to clarify the reasons of high concentration ratio of radiocesium for rice plant in the decontaminated paddy. [ABSTRACT FROM AUTHOR]
- Published
- 2016
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15. Soil removal as a decontamination practice and radiocesium accumulation in tadpoles in rice paddies at Fukushima.
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Sakai, Masaru, Gomi, Takashi, Nunokawa, Masanori, Wakahara, Taeko, and Onda, Yuichi
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BIOACCUMULATION ,CESIUM ,TADPOLES ,RANIDAE ,PHYSIOLOGICAL effects of radioisotopes ,RADIOACTIVE decontamination ,PADDY fields ,INVERTEBRATES - Abstract
We investigated the biological accumulation of radiocesium in tadpoles [Rana (Pelophylax) porosa porosa] in rice paddies with and without decontamination practice at Fukushima. Radiocesium was accumulated in surface part of soils both in the control and decontaminated paddies one year after decontamination. Mean
134 Cs and137 Cs concentrations in tadpoles in the control and decontaminated paddies were 3000 and 4500, and 600 and 890 Bq/kg dry weight, respectively. Radiocesium concentrations in surface soil (0–5 cm depth) and tadpoles in the decontaminated paddy were five times smaller than in the control paddy. These results suggest that decontamination practice can reduce radiocesium concentrations in both soil and tadpoles. However, at the decontaminated paddy, radiocesium concentrations in surface soils became 3.8 times greater one year after decontamination, which indicates that monitoring the subsequent movement of radiocesium in rice paddies and surrounding areas is essential for examining contamination propagation. [Copyright &y& Elsevier]- Published
- 2014
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16. A Nitrogen‐Saturated Plantation of Cryptomeria japonicaand Chamaecyparis obtusain Japan Is a Large Nonpoint Nitrogen Source
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Chiwa, Masaaki, Saito, Takami, Haga, Hirokazu, Kato, Hiroaki, Otsuki, Kyoichi, and Onda, Yuichi
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Japanese cedar (Cryptomeria japonica) and Japanese cypress (Chamaecyparis obtusa) plantations account for approximately 30% of the total forested area in Japan. Both are arbuscular mycorrhizal trees that leach more NO3−in response to nitrogen (N) deposition than do forests of ectomycorrhizal trees. However, little information is available about the size of N exports from these plantations. The aim of this study was to evaluate nonpoint source N exports from a N‐saturated plantation. We collected stream water samples in base‐flow (25 samples) and storm‐flow conditions (20 events) in a watershed (2.98 ha) where Japanese cypress and Japanese cedar were planted in 1969 (41 yr old). The annual NO3−export was calculated from load–discharge relationships. Atmospheric N deposition was also determined. The stream water contained high NO3−concentrations (160 and 165 μmol L−1during base flow and storm flow, respectively), indicating N saturation in the watershed. High bulk atmospheric N deposition (16.5 kg N ha−1yr−1) could explain the N saturation. There were only small variations in NO3−concentrations in stream water in response to discharge volume, because of the N saturation of the forest ecosystem. Consequently, there were only small errors in estimating annual NO3−exports from the studied watershed. The annual NO3−export was high (36.1 kg N ha−1yr−1), comparable to values reported for agricultural and urbanized areas. These results suggest that N‐saturated forest plantations can become important nonpoint N sources. Our results also suggest that N exports from forest plantations across Japan should be quantified to evaluate nonpoint source N accurately.
- Published
- 2015
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17. Incident rainfall partitioning and canopy interception modeling for an abandoned Japanese cypress stand
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Sun, Xinchao, Onda, Yuichi, and Kato, Hiroaki
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AbstractInterception loss (Ei) in forests has been studied widely. However, Eiparameters and modeling as well as spatial patterns of throughfall (TF) in abandoned Japanese cypress (Chamaecyparisobtusa) plantations remain poorly documented. In this study, gross precipitation (PG), stemflow (SF), and TFwere monitored in an unmanaged 32-year-old Japanese cypress stand throughout the 2011 rainy season. Results indicate that PGpartitioning into TF, SF, and Eiwere, respectively, 64.2 ± 3.6, 10.6 ± 0.6, and 25.2 ± 1.1 % of the 880.8 mm cumulative PGfrom 29 rainfall events. Direct throughfall proportion (p) and drainage from the canopy contributed about 14 ± 7 and 50 ± 21 % of the total TFfor the events, respectively. The mean canopy storage capacity (S) was 2.4 ± 0.7 mm. The coefficient of variability (CV) of TFrate decreased asymptotically with increasing PGamount, ranging from 16 to 56 % with median 26 %. The CV of TFrate was not significantly correlated with canopy cover (r= 0.152, P= 0.521, n= 20) and distance from the nearest trunk (r= 0.196, P= 0.408, n= 20). Based on the revised Gash analytical model, the total simulated Eiwas close to the observed, with a general underestimation magnitude of 5.7 %. The Eicomponents were quantified, and most of the interception loss (62.9 %) evaporated during rainfall, while 26.8 % evaporated after rainfall ceased. Climatic and forest structural parameters required by the model were identified and analyzed by sensitivity analysis, implying that the revised Gash analytical model is robust and reliable enough for abandoned Japanese cypress plantations in a maritime climate.
- Published
- 2014
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18. Incident rainfall partitioning and canopy interception modeling for an abandoned Japanese cypress stand
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Sun, Xinchao, Onda, Yuichi, and Kato, Hiroaki
- Abstract
Interception loss (Ei) in forests has been studied widely. However, Eiparameters and modeling as well as spatial patterns of throughfall (TF) in abandoned Japanese cypress (Chamaecyparisobtusa) plantations remain poorly documented. In this study, gross precipitation (PG), stemflow (SF), and TFwere monitored in an unmanaged 32-year-old Japanese cypress stand throughout the 2011 rainy season. Results indicate that PGpartitioning into TF, SF, and Eiwere, respectively, 64.2 ± 3.6, 10.6 ± 0.6, and 25.2 ± 1.1 % of the 880.8 mm cumulative PGfrom 29 rainfall events. Direct throughfall proportion (p) and drainage from the canopy contributed about 14 ± 7 and 50 ± 21 % of the total TFfor the events, respectively. The mean canopy storage capacity (S) was 2.4 ± 0.7 mm. The coefficient of variability (CV) of TFrate decreased asymptotically with increasing PGamount, ranging from 16 to 56 % with median 26 %. The CV of TFrate was not significantly correlated with canopy cover (r= 0.152, P= 0.521, n= 20) and distance from the nearest trunk (r= 0.196, P= 0.408, n= 20). Based on the revised Gash analytical model, the total simulated Eiwas close to the observed, with a general underestimation magnitude of 5.7 %. The Eicomponents were quantified, and most of the interception loss (62.9 %) evaporated during rainfall, while 26.8 % evaporated after rainfall ceased. Climatic and forest structural parameters required by the model were identified and analyzed by sensitivity analysis, implying that the revised Gash analytical model is robust and reliable enough for abandoned Japanese cypress plantations in a maritime climate.
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- 2014
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19. Factors Controlling the Dissolved 137Cs Seasonal Fluctuations in the Abukuma River Under the Influence of the Fukushima Nuclear Power Plant Accident
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Igarashi, Yasunori, Nanba, Kenji, Wada, Toshihiro, Wakiyama, Yoshifumi, Onda, Yuichi, Moritaka, Shota, and Konoplev, Alexei
- Abstract
The 2011 Fukushima Daiichi Nuclear Power Plant (FDNPP) accident released large amounts of radioactive materials into the environment. River systems play an important role in the terrestrial redistribution of FDNPP‐derived 137Cs in association with water and sediment movement. We examined the seasonal fluctuations in dissolved and particulate 137Cs activity concentrations and clarified the biological and physicochemical factors controlling 137Cs seasonality in the Abukuma River's middle course in the region affected by the FDNPP accident. The results showed seasonal fluctuations in the dissolved 137Cs activity concentration, with an increase in summer and a decrease in winter, although there was no clear seasonal change in the particulate 137Cs activity concentration. Water temperature and K+concentration dominated the seasonality of the dissolved 137Cs activity concentration. The volumetric activity concentration of the organically bound 137Cs was found to be several orders of magnitude lower than that of the dissolved 137Cs. Therefore, we concluded that the 137Cs in organic matter is not a source of dissolved 137Cs in river water. The study also revealed the temperature dependence of Kdin riverine environments from a Van't Hoff equation. The standard reaction enthalpy of 137Cs in the Abukuma River was calculated to be approximately −19.3 kJ/mol. This was the first study to clearly reveal the mechanisms by which the dissolved 137Cs activity concentration and Kdare influenced by chemical and thermodynamic processes in the middle course of a large river, and it is expected to lead to an improved model of 137Cs dynamics in rivers. The 2011 Fukushima Daiichi Nuclear Power Plant (FDNPP) accident released large amounts of radioactive materials into the environment. River systems play an important role in the terrestrial redistribution of FDNPP‐derived 137Cs in association with water and sediment movement. The dissolved 137Cs activity concentration in the Abukuma River showed clear seasonal fluctuations, with an increase in summer and a decrease in winter, although there was no clear seasonal change in the particulate 137Cs activity concentration. Water temperature and K+concentration dominated the seasonality of the dissolved 137Cs activity concentration. Previously, decomposition of 137Cs‐contaminated organic matter was thought to be the reason for the seasonality of the dissolved 137Cs activity concentration in rivers. However, in the middle course of the river, the organically bound 137Cs activity concentration is much lower than that of the dissolved 137Cs activity concentration, indicating that the decomposition of organic matter does not directly affect the dissolved 137Cs in the middle course. This study revealed that seasonal fluctuations in river temperature determine the seasonality of the dissolved 137Cs activity concentration in the middle course in the region affected by the FDNPP accident. Dissolved 137Cs in the Abukuma River displays significant seasonal fluctuationsThe main factors determining the seasonality of dissolved 137Cs activity concentrations are water temperature and K+The standard enthalpy of 137Cs desorption from sediments was determined to be approximately −19.3 kJ/mol Dissolved 137Cs in the Abukuma River displays significant seasonal fluctuations The main factors determining the seasonality of dissolved 137Cs activity concentrations are water temperature and K+ The standard enthalpy of 137Cs desorption from sediments was determined to be approximately −19.3 kJ/mol
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- 2022
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20. Factors affecting the infiltration capacity in bamboo groves
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Hiraoka, Marino and Onda, Yuichi
- Abstract
Abstract: To determine the effects of the characteristics of litter and surface soil on the infiltration capacity in bamboo groves, infiltration rates were measured on a plot-scale using an oscillating-nozzle rainfall simulator at seven Moso bamboo (Phyllostachys pubescens) sites and one Madake (P. bambusoides) site in Japan. The maximum final infiltration rate (FIR
max ), which was defined in this study as the infiltration capacity, was calculated, and the correlation between FIRmax and earth surface properties was analyzed. The FIRmax ranged from 9 to 308 mm h−1 , showing little correlation with litter as surface cover, and a weak correlation with bulk density (0.3–0.9 g cm−3 ) and organic matter content (10.4–45.9%). These results suggest that the bulk density and organic matter content of surface soil, rather than surface cover, can be the controlling factors of infiltration capacity in bamboo groves. The bulk density of surface soil correlated significantly with the soil organic matter content, represented by bamboo rhizomes, suggesting that the infiltration capacity can increase with the amount of root networks present, related to macropore formation. The stand density showed a weak positive correlation, although not significant, with the soil organic matter content and a positive correlation with FIRmax . Thus, the infiltration capacity of bamboo groves can increase as the stand density of culms and bamboo rhizomes increase.- Published
- 2012
- Full Text
- View/download PDF
21. Factors affecting the infiltration capacity in bamboo groves
- Author
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Hiraoka, Marino and Onda, Yuichi
- Abstract
AbstractTo determine the effects of the characteristics of litter and surface soil on the infiltration capacity in bamboo groves, infiltration rates were measured on a plot-scale using an oscillating-nozzle rainfall simulator at seven Moso bamboo (Phyllostachys pubescens) sites and one Madake (P. bambusoides) site in Japan. The maximum final infiltration rate (FIRmax), which was defined in this study as the infiltration capacity, was calculated, and the correlation between FIRmaxand earth surface properties was analyzed. The FIRmaxranged from 9 to 308 mm h−1, showing little correlation with litter as surface cover, and a weak correlation with bulk density (0.3–0.9 g cm−3) and organic matter content (10.4–45.9%). These results suggest that the bulk density and organic matter content of surface soil, rather than surface cover, can be the controlling factors of infiltration capacity in bamboo groves. The bulk density of surface soil correlated significantly with the soil organic matter content, represented by bamboo rhizomes, suggesting that the infiltration capacity can increase with the amount of root networks present, related to macropore formation. The stand density showed a weak positive correlation, although not significant, with the soil organic matter content and a positive correlation with FIRmax. Thus, the infiltration capacity of bamboo groves can increase as the stand density of culms and bamboo rhizomes increase.
- Published
- 2012
- Full Text
- View/download PDF
22. Simple monitoring method for precaution of landslides watching tilting and water contents on slopes surface
- Author
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Uchimura, Taro, Towhata, Ikuo, Lan Anh, Trinh, Fukuda, Jou, Bautista, Carlos, Wang, Lin, Seko, Ichiro, Uchida, Taro, Matsuoka, Akira, Ito, Yosuke, Onda, Yuichi, Iwagami, Sho, Kim, Min-Seok, and Sakai, Naoki
- Abstract
Abstract: A low-cost and simple monitoring method for early warning of landslides is proposed. To detect abnormal deformation of a slope, this method employs a tilt sensor in place of an extensometer on the slope surface. In order to examine the relevance of measuring rotation angle on a slope surface by tilt sensor, model tests were conducted, and rotation on the slope surface was observed together with slide displacement along the surface. The rotation data responded 30 min before failure in a model test, which could be useful as a signal for early warning. However, the behavior of rotation before failure varies from case to case, and thus, criteria to issue warning should be defined more carefully. For a model slope made of uniform loose sand, measurement of slide displacement along the slope surface is sensitive to failure at the toe, while the measurement of rotation on the slope surface is useful to detect the development of progressive failure upward along the slope. Wireless sensor units with microelectromechanical systems (MEMS) tilt sensor and volumetric water content sensor were also examined on a real slope in Kobe City, and a long-term monitoring was attempted. A simple but possible way to define the criteria of judgment to issue warning can be proposed based on combination of data obtained by the tilt sensors and volumetric water content sensors.
- Published
- 2010
- Full Text
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23. Long-term changes in lake sediments and their infl uences on lake water quality in Japanese shallow lakes
- Author
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Fukushima, Takehiko, Kamiya, Koichi, Onda, Yuichi, Imai, Akio, and Matsushige, Kazuo
- Abstract
In order to elucidate the nutrient dynamics in lakes with special reference to sediments, the changes in vertical distributions of sediment nutrients over 20 years were analyzed with the aid of sediment dating at the centers of two shallow, eutrophic lakes in Japan, i.e.Lakes Kasumigaura and Suwa. Peaks of137 Cs and apparent density gave estimated sedimentation rates of around 1 and 2 kg m-2 y-1 in Lakes Kasumigaura and Suwa, respectively. Slight decreases of TP and TN contents (0.07 and 0.63 mg g-1 for TP and TN, respectively, in Lake Kasumigaura and 0.90 mg g-1 for TN in Lake Suwa) were observed by comparison between the cores obtained around 1980 and those of recent years except for a considerable decrease in TP in Lake Suwa (1.0 mg g-1). This decrease probably came from the higher percentage of easily releasable phosphorus in the past sediments of Lake Suwa. Using the TP and TN increases in lake waters during summer, the averaged nutrient release rates were estimated to be within the ranges of those observed by laboratory core experiments and by measuring the vertical profi les of interstitial concentrations except for a smaller estimation of TN in Lake Kasumigaura. On the other hand, the nutrient release rates were also determined using the long-term changes in sediment nutrient contents. The estimated rates were a little lower than the rates determined by the method using the increase in lake nutrient concentrations other than the higher ones for TP in Lake Suwa, which were originally based on the higher percentage of easily releasable phosphorus as mentioned above. Net sedimentation rates for 24 years in Lake Kasumigaura and those for 26 years in Lake Suwa calculated as the sum of new sedimentation and changes in old sediments during these periods were compared with the net input loads based on the per capita/exporting method. In the case of TP, we observed a fairly good agreement because of its conservation, whereas the residuals were larger for TN due to denitrifi cation in the overlying waters of sediments. The rates estimated from the imbalances in TN were in the ranges of the measured denitrifi cation rates in laboratory tests with the sediments. Thus, the information on the long-term changes in sediment nutrients could provide the average rates of these fundamental processes in lake environments.
- Published
- 2010
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24. Changes in sedimentation rates and phosphorus accumulation in shallow Japanese lakes during 30 years
- Author
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Kamiya, Koichi, Fukushima, Takehiko, Onda, Yuichi, Matsushige, Kazuo, and Mizugaki, Shigeru
- Published
- 2009
- Full Text
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25. Correction to Transport and Redistribution of Radiocesium in Fukushima Fallout through Rivers
- Author
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Taniguchi, Keisuke, Onda, Yuichi, Smith, Hugh G., Blake, William, Yoshimura, Kazuya, Yamashiki, Yosuke, Kuramoto, Takayuki, and Saito, Kimiaki
- Published
- 2021
- Full Text
- View/download PDF
26. Impact of wildfire on 137Cs and 90Sr wash-off in heavily contaminated forests in the Chernobyl exclusion zone.
- Author
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Igarashi, Yasunori, Onda, Yuichi, Wakiyama, Yoshifumi, Konoplev, Alexei, Zheleznyak, Mark, Lisovyi, Hlib, Laptev, Gennady, Damiyanovich, Volodyill, Samoilov, Dmitry, Nanba, Kenji, and Kirieiev, Serhii
- Subjects
WILDFIRES ,POST-fire forests ,SOIL erosion ,RADIOISOTOPES ,RUNOFF - Abstract
Wildfires may play a role in redistributing radionuclides in the environment in combination with hydrological processes such as surface runoff and soil erosion. We investigated plot-scale radionuclide wash-off at forest sites affected by wildfires in the Chernobyl Exclusion Zone (CEZ). We also compared speciation of the washed-off radionuclides with those in previous studies conducted just after the accident in 1986. We observed the surface runoff and the radionuclide wash-off with a soil erosion plot at forest and post-fire sites during May–September 2018. In the post-fire site, 2.81 mm of surface runoff was observed in at least three flow events resulting from 285.8 mm total rainfall. The fluxes of dissolved and particulate
137 Cs were estimated as 4.9 and 161 Bq m−2 , respectively. The dissolved phase90 Sr flux was estimated as 214 Bq m−2 . At the forest site, a single surface runoff (0.67 mm) event was generated by rainfall of 182.2 mm. The fluxes of dissolved and particulate137 Cs wash-off values were 6.2 and 8.6 Bq m−2 , respectively. The flux of dissolved90 Sr wash-off from the forest was estimated as 45.1 Bq m−2 . The distribution coefficient, which indicates the dissolved-particulate form of radionuclides, in the post-fire site was 30 times higher than that in the forest site, indicating the importance of particulate137 Cs wash-off after fire in the CEZ. The entrainment coefficients for dissolved and particulate137 Cs concentrations were around 50 times lower than those obtained in the corresponding position within the CEZ immediately after the accident in 1987. The effect of downward migration of137 Cs over 30 years led to decreased entrainment coefficients for dissolved and particulate137 Cs. The effect of downward migration of radionuclides was considered sufficient to indicate changes in normalized liquid and solid radionuclides wash-off entrainment coefficient and the distribution coefficient in this study. Image 1 • Radionuclide wash-off was observed from a post-fire site in the CEZ. • K d in the post-fire site was 30 times higher than that in the undisturbed forest site. • Particulate137 Cs wash-off is important after fire. • The downward migration effect decreased N l (137 Cs) and N s (137 Cs) during the 30-years. [ABSTRACT FROM AUTHOR]- Published
- 2020
- Full Text
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27. An experimental study on the burrowing activity of river crabs on subsurface water movement and piping erosion
- Author
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Onda, Yuichi and Itakura, Naoko
- Abstract
The effects of the burrowing activity of river crabs on subsurface water movement and piping erosion were studied through a flume experiment. Cohesive field soil was used and constant fluvial head was applied. During the experiments with river crabs, burrows were excavated downwards under the groundwater level. At the outlet of each burrow, the crabs excavated pellets of soil and stacked them in piles, in the form of cone mounds. These mounds acted as effective dams for subsurface outflow, but they sometimes collapsed. The roofs of the burrows also caved in occasionally, whereby the crabs would excavate new burrows. The burrowing activity of the crabs led to marked erosion. In contrast, no marked erosion was observed in experiments without crabs, indicating that piping erosion occurs through the assistance of burrowing activity. It was observed that burrowing activity and piping erosion was pronounced when the hydraulic head was not significantly high (0.21–0.25). Analysis of the potential distribution of the soil mass indicated that the head loss close to the burrow was small in the case of experiments with crabs. This suggests that the burrow enhances rapid discharge of subsurface water. Consequently, burrowing activity was found to play an important role in piping erosion and rapid discharge of subsurface water.
- Published
- 1997
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28. Influence of water storage capacity in the regolith zone on hydrological characteristics, slope processes, and slope form
- Author
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Onda, Yuichi
- Abstract
Zwischen den Verwitterungsraten, den hydrologischen Prozessen, Hangrutschen, der Tiefe des Verwitterungsmantels und der Hangform wurde eine Rückkopplung gefunden in vier Einzugsgebieten der Obara-Region, Zentral-Japan. Die Hänge im Granodiorit haben eine geringe Anzahl von flachen Rutschen, konvexe Profile und einen dicken Verwitterungsmantel mit hoher Wasserspeicher-Kapazität. Im Gegensatz dazu haben die Hänge im Granit eine hohe Zahl von Rutschen, ein konkaves Profil und einen dünnen Verwitterungsmantel mit geringer Wasserhaltefähigkeit. Weil der Verwitterungsmantel als ein Niederschlagsreservoir wirkt, kontrolliert er den Abfluß, seine eigene Aufnahmefähigkeit bis zur Sättigung und das Auftreten von Hangrutschen, während seine Mächtigkeit von der Abtragung durch Hangrutsche kontrolliert wird. Hangrutsche sind verantwortlich für eine konkave Hangform, während die kontinuierliche Abtragung durch Sickerung die konvexe Hangform bedingt, wo Rutschprozesse nicht dominieren.
- Published
- 1992
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29. Specific Inhibitor of Placental Alkaline Phosphatase Isolated from a DNA-Encoded Chemical Library Targets Tumor of the Female Reproductive Tract
- Author
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Bassi, Gabriele, Favalli, Nicholas, Pellegrino, Christian, Onda, Yuichi, Scheuermann, Jörg, Cazzamalli, Samuele, Manz, Markus G., and Neri, Dario
- Abstract
Placental alkaline phosphatase (PLAP) is an abundant surface antigen in the malignancies of the female reproductive tract. Nevertheless, the discovery of PLAP-specific small organic ligands for targeting applications has been hindered by ligand cross-reactivity with the ubiquitous tissue non-specific alkaline phosphatase (TNAP). In this study, we used DNA-encoded chemical libraries to discover a potent (IC50= 32 nM) and selective PLAP inhibitor, with no detectable inhibition of TNAP activity. Subsequently, the PLAP ligand was conjugated to fluorescein; it specifically bound to PLAP-positive tumors in vitroand targeted cervical cancer in vivoin a mouse model of the disease. Ultimately, the fluorescent derivative of the PLAP inhibitor functioned as a bispecific engager redirecting the killing of chimeric antigen receptor-T cells specific to fluorescein on PLAP-positive tumor cells.
- Published
- 2021
- Full Text
- View/download PDF
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