@article{oai:repo.qst.go.jp:00043756,
 author = {Zheng, Jian and Yamada, Masatoshi and 鄭 建 and 山田 正俊},
 issue = {8},
 journal = {Journal of Environmental Monitoring},
 month = {Aug},
 note = {The objectives of the present work were to study isotope ratios and inventory of Pu and uranium isotope compositions in sediments from Lake Obuchi, which is in the vicinity of several nuclear fuel facilities in Rokkasho, Japan. Pu and its isotopes were determined using a sector-field ICP-MS and U and its isotopes were determined with ICP-QMS after separation and purification with a combination of ion-exchange and extraction chromatography. The observed 240Pu/239Pu atom ratio (0.186+/-0.016) was similar to that of global fallout, indicating that the possible early tropospheric fallout Pu did not deliver Pu from the Pacific Proving Ground to areas above 40oN. The previously reported higher Pu inventory in the deep water area of Lake Obuchi could be attributed to the lateral transportation of Pu deposited in the shallow area which resulted from the migration of deposited global fallout Pu from the land into the lake by river runoff and from the Pacific Ocean by tide movement and seawater scavenging as well as from direct soil input by winds. The 235U/238U atom ratios ranged from 0.00723 to 0.00732, indicating the natural origin of U in the sediments. The average 234U/238U activity ratio of 1.11 in a sediment core indicated a significant seawater U contribution. No evidence was found for the release of U containing wastes from the nearby nuclear facilities. These results will serve as a reference baseline on the levels of Pu and U in the studied site so that any further contamination from the spent nuclear fuel reprocessing plants, the radioactive waste disposal and storage facilities and the uranium enrichment plant can be identified, and the impact of future release, can be rapidly assessed.},
 pages = {792--797},
 title = {Investigating Pu and U isotopic compositions in sediments: a case study in Lake Obuchi, Rokkasho Village, Japan using sector-field ICP-MS and ICP-QMS},
 volume = {7},
 year = {2005}
}