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Journal Articles

Estimation of $$^{222}$$Rn flux and its effect on the atmospheric $$^{222}$$Rn concentration at Hachijo-jima island, Japan

Okura, Takehisa; Yamazawa, Hiromi*; Moriizumi, Jun*; Hirao, Shigekazu*; Iida, Takao*

Hoken Butsuri, 45(3), p.270 - 277, 2010/09

Measurements of $$^{222}$$Rn flux from the ground and $$^{226}$$Ra content in soil were made on Hachijo-jima, which is a solitary island in the Pacific about 200 km to the south of the main island of Japan, to evaluate effect of locally exhaled $$^{222}$$Rn to the surface air concentration of $$^{222}$$Rn measured on this island. Averages of $$^{222}$$Rn flux and $$^{226}$$Ra content in dry soil were 0.88 mBq m$$^{-2}$$ s$$^{-1}$$ and 6.8 Bq kg$$^{-1}$$ at Hachijo-jima and 9.7 mBq m$$^{-2}$$ s$$^{-1}$$ and 23.2 Bq kg$$^{-1}$$ at Nagoya, respectively. The low level $$^{226}$$Ra content in soil is one of main causes for the small $$^{222}$$Rn flux at the island. With this $$^{222}$$Rn flux, the contribution of locally exhaled $$^{222}$$Rn from the island was estimated by a simple model to occur at concentration of 0.035 to 0.072 Bq m$$^{-3}$$ (relative contribution is 4 to 12%) under typical nocturnal condition. Under diurnal condition effect is lower than that of nocturnal condition. This local $$^{222}$$Rn component is negligible as compared with concentration of long-range transported $$^{222}$$Rn of 0.5 to 3 Bq m$$^{-3}$$.

Journal Articles

Monitoring network of atmospheric Radon-222 concentration in East Asia and backward trajectory analysis of Radon-222 concentration trend at a small solitary island on Pacific Ocean

Okura, Takehisa; Yamazawa, Hiromi*; Moriizumi, Jun*; Hirao, Shigekazu*; Guo, Q.*; Tojima, Yasunori*; Iida, Takao*

Proceedings of 3rd Asian and Oceanic Congress on Radiation Protection (AOCRP-3) (CD-ROM), 3 Pages, 2010/05

Monitoring network of $$^{222}$$Rn concentration in air which was measured in Beijing, Nagoya, Hegura-jima, Hachijo-jima and Hateruma-jima, as a tracer for long-range transport in East Asia was established. At inland sites, Beijing and Nagoya, high concentrations $$^{222}$$Rn were measured, at marine sites, Hachijo-jima and Hateruma-jima, $$^{222}$$Rn concentrations level was very low. Seasonal variations of the $$^{222}$$Rn concentration show that $$^{222}$$Rn concentration was the lowest in the summer and the highest in the winter. Diurnal variations were measured at inland sites. At marine sites several-day-cycle variations were measured. It was pointed out by this study that the several-day-cycle variations at Hachijo-jima were dependent on synoptic-scale atmospheric disturbance. Backward trajectory analysis of the relationship between atmospheric $$^{222}$$Rn concentrations at Hachijo-jima and transport pathway of air mass indicates that atmospheric $$^{222}$$Rn at Hachijo-jima has much to do with transport pathway of air.

Journal Articles

The Change of the carbon isotopic ratio in the CO$$_{2}$$ derived from soil organic matter decomposition over the incubation time

Moriya, Koichi*; Moriizumi, Jun*; Yamazawa, Hiromi*; Koarashi, Jun; Atarashi-Andoh, Mariko

KURRI-KR-153, p.53 - 59, 2010/03

To understand the decomposition mechanism in the soil, we researched the relationship between compositions of SOM and CO$$_{2}$$ derived from SOM decomposition (SOMD-CO$$_{2}$$) by using $$^{13}$$C and $$^{14}$$C. With the soil incubation, we measured CO$$_{2}$$ production rates of soil and carbon isotopic ratios in SOMD-CO$$_{2}$$. The CO$$_{2}$$ production rates decreased rapidly at the beginning of incubation, and then decreased slowly. On the other hand, $$delta$$$$^{13}$$C$$_{rm SOMD-CO2}$$ before incubation was larger than $$delta$$$$^{13}$$C$$_{rm SOM}$$. After 40-70 days of incubation, $$delta$$$$^{13}$$C$$_{rm SOMD-CO2}$$ became smaller than $$delta$$$$^{13}$$C$$_{rm SOM}$$, and then $$delta$$$$^{13}$$C$$_{rm SOMD-CO2}$$ after 120-170 days approached $$delta$$$$^{13}$$C$$_{rm SOM}$$. We consider these results as follows. SOM is composed of three components, rapidly decomposable SOM that has large $$delta$$$$^{13}$$C, slowly decomposable SOM that has small $$delta$$$$^{13}$$C and passive SOM that has the same value as $$delta$$$$^{13}$$C$$_{rm SOM}$$. With the progress of soil decomposition, the dominant component in SOMD-CO$$_{2}$$ changed. Therefore, $$delta$$$$^{13}$$C$$_{rm SOMD-CO2}$$ changed too.

Journal Articles

Monitoring network of atmospheric Radon-222 concentration in East Asia and backward trajectory analysis of Radon-222 concentration trend at a small solitary island on Pacific Ocean

Okura, Takehisa; Yamazawa, Hiromi*; Moriizumi, Jun*; Hirao, Shigekazu*; Guo, Q.*; Tojima, Yasunori*; Iida, Takao*

Taiki Kankyo Gakkai-Shi, 44(1), p.42 - 51, 2009/01

Monitoring network of $$^{222}$$Rn concentration in air which was measured in Beijing, Nagoya, Hegura-jima, Hachijo-jima and Hateruma-jima, as a tracer for long-range transport in East Asia was established. At inland sites, Beijing and Nagoya, high concentrations $$^{222}$$Rn were measured, at marine sites, Hachijo-jima and Hateruma-jima, $$^{222}$$Rn concentrations level was very low. Seasonal variations of the $$^{222}$$Rn concentration show that $$^{222}$$Rn concentration was the lowest in the summer and the highest in the winter. Diurnal variations were measured at inland sites. At marine sites several-day-cycle variations were measured. It was pointed out by this study that the several-day-cycle variations at Hachijo-jima were dependent on synoptic-scale atmospheric disturbance. Backward trajectory analysis of the relationship between atmospheric $$^{222}$$Rn concentrations at Hachijo-jima and transport pathway of air mass indicates that atmospheric $$^{222}$$Rn at Hachijo-jima has much to do with transport pathway of air.

Journal Articles

Development of three-dimensional numerical model for $$^{222}$$Rn and its decay products coupled with a mesoscale meteorological model, 1; Model description and validation

Nishizawa, Masato; Nagai, Haruyasu; Chino, Masamichi; Moriizumi, Jun*; Yoshioka, Katsuhiro*; Okura, Takehisa; Yamazawa, Hiromi*; Iida, Takao*; Mukai, Hitoshi*; Tojima, Yasunori*; et al.

Journal of Nuclear Science and Technology, 44(11), p.1458 - 1466, 2007/11

 Times Cited Count:4 Percentile:31.57(Nuclear Science & Technology)

A three-dimensional Eulerian numerical model for $$^{222}$$Rn and its decay products coupled with a mesoscale meteorological model has been developed and applied to the reproduction of the daily and monthly variations of $$^{222}$$Rn concentration, the monthly variation of $$^{210}$$Pb deposition in Japan and the temporal variation of $$gamma$$ dose rate after the cold front passage in the coastal area of the Japan Sea for the verification of model capability. The results are as follows: (1) The model reproduced the monthly variation of surface $$^{222}$$Rn concentration in remote islands, but underestimated inland concentration due to coarse vertical resolution near the surface of the model. (2) The model reproduced the seasonal variation of the observed and the long-term yearly averaged $$^{210}$$Pb depositions as long as precipitations are predicted precisely. (3) The model reproduced the rise of $$gamma$$ dose rate in precipitation accompanied with the cold front passage. In particular, $$^{222}$$Rn decay products in melted snow and graupel contributed the rise of $$gamma$$ dose rate.

Journal Articles

Diurnal and seasonal variations in $$^{222}$$Rn concentration profile in soil

Iskandar, D.*; Yamazawa, Hiromi*; Yamasoto, Kotaro; Ota, Masakazu*; Koarashi, Jun; Moriizumi, Jun*; Bunawas*; Iida, Takao*

Hoken Butsuri, 42(1), p.98 - 104, 2007/03

The $$^{222}$$Rn concentrations in soil and $$^{222}$$Rn flux were measured at 6 depths in soil to analyze the seasonal- day-to-day and diurnal variations. The variations of $$^{222}$$Rn concentrations in soil were larger in shallow depths. It seems that the $$^{222}$$Rn concentration in soil during night-time was slightly lower than day-time especially at depth of 15 cm. The precipitation may have affected the concentration insoil differently depending on its amounts. The large decrease in air pressure during one day increased the concentration in soil at shallow soil layers. The effect of soil water content on $$^{222}$$Rn concentration in soil was also observed.

Journal Articles

Evaluation of aerosol sizing characteristic of an impactor using imaging plate technique

Rahman, N. M.*; Iida, Takao*; Saito, Fumihiro; Koarashi, Jun; Yamasaki, Keizo*; Yamazawa, Hiromi*; Moriizumi, Jun*

Radiation Protection Dosimetry, 123(2), p.171 - 181, 2007/02

 Times Cited Count:11 Percentile:61.35(Environmental Sciences)

no abstracts in English

Journal Articles

Evaluation of$$^{14}$$C Abundance in Soil Respiration using Accelerator Mass Spectrometry

Koarashi, Jun; Iida, Takao*; Moriizumi, Jun*; Asano, Tomohiro

Journal of Environmental Radioactivity, 75(2), 117 Pages, 2004/00

 Times Cited Count:5 Percentile:11.43(Environmental Sciences)

None

Journal Articles

Soil Carbon Dynamics Inferred from Carbon Isotope Compositions of Soil Organic Matter and Soil Respiration

Koarashi, Jun; Iida, Takao*; Moriizumi, Jun*; Asano, Tomohiro

Proceedings of International Symposium on Radioecology and Environmental Dosimetry, p.92 - 99, 2003/10

Soil organic matter (SOM) is a significant carbon reservoir in terrestrial ecosystems. Therefore, knowledge of SOM dynamics is essential for better understanding not only the global carbon cycle but also the environmental behabior of additional 14C produced by the nuclear power industry. In this study, carbon isotope compositions were determiend for chemically fractionated SOM and soil respiration in an urban forest, to investigate the formation, storage and decomposition of SOM.

Journal Articles

Estimation of $$^{14}$$CO$$_{2}$$ flux at soil-atmosphere interface and distribution of $$^{14}$$C in forest ecosystem

Koarashi, Jun; Amano, Hikaru; Atarashi-Andoh, Mariko; Iida, Takao*; Moriizumi, Jun*

Journal of Environmental Radioactivity, 60(3), p.249 - 261, 2002/06

 Times Cited Count:15 Percentile:34.34(Environmental Sciences)

no abstracts in English

Oral presentation

Stable carbon isotopic ratios of soil organic matter and CO$$_{2}$$ derived from SOM decomposition

Moriya, Koichi; Moriizumi, Jun*; Yamazawa, Hiromi*; Iida, Takao*; Koarashi, Jun; Atarashi-Andoh, Mariko

no journal, , 

Stable carbon isotopic ratios in soil organic matter (SOM) and CO$$_{2}$$ derived from SOM decomposition were measured for two forests with different vegetation. The results showed the followings in both forests: (1) older SOM in deeper soil layer had higher $$^{13}$$C isotopic ratios ($$delta$$$$^{13}$$C), (2) CO$$_{2}$$ derived from SOM decomposition showed higher $$delta$$$$^{13}$$C than the original SOM. These results probably suggest that the stable carbon isotopic ratios change with its decomposition, due to the isotopic discrimination and the variation of the SOM compositions that have different isotopic ratios.

Oral presentation

Carbon isotopic ratios of soil organic matters and CO$$_{2}$$ produced through SOM decompositions

Moriya, Koichi*; Moriizumi, Jun*; Yamazawa, Hiromi*; Koarashi, Jun; Atarashi-Andoh, Mariko

no journal, , 

no abstracts in English

Oral presentation

Identifying sizes and turnover times of rapidly-cycling soil organic carbon pools by thin-layered soil incubations and $$^{14}$$C measurements

Moriya, Koichi*; Koarashi, Jun; Atarashi-Andoh, Mariko; Moriizumi, Jun*; Yamazawa, Hiromi*; Hirai, Keizo*

no journal, , 

Soil organic carbon (SOC) decomposition is an important component of the global carbon cycle, because SOC is the largest carbon reservoir in terrestrial ecosystems and a small change in the CO$$_{2}$$ flux from SOC may lead to a large change in atmospheric CO$$_{2}$$ concentration. For the accurate estimation of SOC decomposition, it is important to identify sizes and turnover times of SOC pools. We tried to estimate three SOC pools (active, slow and resistant) with different mean residence times (MRTs) by a combination of soil incubation and $$^{14}$$C analysis. The active SOC held $$sim$$1% of the total SOC with MRTs of 1-3 weeks. The slow SOC accounted for 20-50% of the total with MRTs of 1 to 17 years. The active and slow SOC contributed greatly to the total CO$$_{2}$$ production, and the primary source shifted from the active to the slow one. Our result shows the importance of quantifying the dynamics of rapidly-cycling SOC pools to accurately predicting the response of soils to climate change.

Oral presentation

Soil organic matter degradability in four Japanese forest soils

Moriya, Koichi; Koarashi, Jun; Atarashi-Andoh, Mariko; Moriizumi, Jun*; Yamazawa, Hiromi*; Ishizuka, Shigehiro*

no journal, , 

no abstracts in English

Oral presentation

Soil organic matter degradability in four Japanese forest soils

Moriya, Koichi; Koarashi, Jun; Atarashi-Andoh, Mariko; Moriizumi, Jun*; Yamazawa, Hiromi*; Ishizuka, Shigehiro*

no journal, , 

no abstracts in English

Oral presentation

Estimation of the depth profiles of soil organic carbon degradability by using radiocarbon

Moriya, Koichi; Koarashi, Jun; Atarashi-Andoh, Mariko; Moriizumi, Jun*; Yamazawa, Hiromi*; Hirai, Keizo*

no journal, , 

no abstracts in English

Oral presentation

Temperature sensitivity of soil organic carbon decomposition in four Japanese forest soils

Moriya, Koichi; Koarashi, Jun; Atarashi-Andoh, Mariko; Ishizuka, Shigehiro*; Moriizumi, Jun*; Yamazawa, Hiromi*

no journal, , 

no abstracts in English

Oral presentation

Development of a compartment model for tritium transport in the environment and comparison with a detailed model

Ishida, Yamato*; Hirao, Shigekazu*; Moriizumi, Jun*; Yamazawa, Hiromi*; Atarashi-Andoh, Mariko

no journal, , 

no abstracts in English

Oral presentation

Numerical analysis of effects by environmental factors on HT- and HTO-transfer

Yamazawa, Hiromi*; Moriizumi, Jun*; Atarashi-Andoh, Mariko

no journal, , 

no abstracts in English

19 (Records 1-19 displayed on this page)
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