THE TEMPORAL AND SPATIAL VARIATION OF CS-137 CONCENTRATION IN THE WESTERN NORTH PACIFIC AND ITS MARGINAL SEAS DURING THE PERIOD FROM 1979 TO 1988

被引:57
作者
AOYAMA, M
HIROSE, K
机构
[1] Ocean Research Department, Japan Marine Science and Technology Center, Yokosuka, 237
[2] Geochemical Research Division, Meteorological Research Institute, Tsukuba, 305
关键词
D O I
10.1016/0265-931X(94)00050-7
中图分类号
X [环境科学、安全科学];
学科分类号
08 ; 0830 ;
摘要
Observations to determine the time-dependent geographical distributions of caesium isotopes in the surface water were carried out in the western North Pacific during the period from 1979 to 1988. After the Chernobyl accident, the enhanced observation was carried out to study the geographical distribution of the Chernobyl radioactivity. Large volume samples (40-2000 liter) were collected and filtered, then both dissolved and particulate caesium isotopes were determined by gamma-ray spectrometry. The Cs-137 concentrations in the surface wafer along the (137)degrees E transect during the period from 1979 to 1988 were 5.0-10.6 mBql(-1) between 30 degrees N and 24 degrees N, 3.4-7.8 mBql(-1) between 24 degrees N and 7 degrees N, and 2.1-6.9 mBql(-1) between 7 degrees N and the Equator. The Cs-137 concentrations at stations between 30 degrees N and 7 degrees N did not show clear temporal variation, while those at stations South of 7 degrees N increased from 1986 to 1988. The Cs-137 concentration south of 7 degrees N becomes the same magnitude in two latitude bands north of 7 degrees N in 1987 and 1988. The Chernobyl derived Cs-134 was detected in the surface water at the marginal seas around Japan north of about latitude 30 degrees N, which reflects the meridional distribution of the Chernobyl derived Cs-134 in the surface air over the western North Pacific. The particulate caesium isotope concentration ranged from 0.1 to 1.0% of the total caesium isotope concentration in 1986 and 1987.
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页码:57 / 74
页数:18
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