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Accumulation and transportation of natural radionuclides in estuary

河口天然放射性核素的富集与迁移

基本信息

批准号：
05680449
负责人：
OSAKI Susumu
金额：
$ 1.22万
依托单位：
KYUSHU UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1993
资助国家：
日本
起止时间：
1993 至 1994
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-05680449/
关键词：
Natural radionuclide Estuary Transportation Distribution coefficient Benthos Conveyer belt feeding

项目摘要

Natural atomospheric radio-nuclides, unsupported ^<210>Pb (^<210>Pb minus ^<214>Bi), and ^7Be in three estuarine sediments from Tatara-Umi estuary were measured. Their profiles of the silty sediments from tidal flat are fitted down to 30 cm on a simplest equation for diffusion (mixing) with the coefficients from 1 to 8 x10^<-7> cm^<2s>ec^<-1>. The monthly profiled of ^7Be in tidal flat sediments show no different mixing on season. This mixing is faster than those expected from microcosmic experiments. The upper 7,8 cm of the silty sediments from reed marsh are well mixed, probably owing to the growth of roots of reeds. Under the well mixed layr, ^<210>Pb and ^7Be are decreased with the depth in a similar manner as tidal flat sediments. In seaside sand sediments their nuclides do not absorbed.The radio-nuclides of ^<22>Na, ^<85>Sr, ^<134>Cs, ^<59>Fe, ^<54>Mn, ^<57>Co and ^<65>Zn had been spiked on untreated or heated estuarine sediments. After 1,2 or 3 months, the profiles of their radio-activities were measured by g-spectrometry simultaneously. In heated samples, Na and Sr are transported down to the bottom of 12cm, Cs down to 3-4 cm, and other elements are hardly transported. In untreated samples, Fe, Mn, Co and Zn are transported down to 4-5 cm and several samples showed peaks, which suggest bioturbation and conveyor-belt deposit feeders. The bioturbation were heterogeneous in time and place in Tatara-Umi estuary. The transfer of these elements can be simulated by an advection-diffusion-reaction model.

测定了Tatara-Umi河口三个河口沉积物中天然大气放射性核素、无载体的^<210>Pb（^<210>Pb减去^<214>Bi）和^7 Be。潮滩粉砂质沉积物的剖面图用最简单的扩散（混合）方程拟合到30 cm，系数为1 - 8 × 10 ^<-7>cm^<2s>ec^<-1>。潮滩沉积物中^7Be的月剖面显示没有季节性的混合差异。这种混合比微观实验所预期的要快。芦苇沼泽上部7.8cm的粉质沉积物混合良好，可能是由于芦苇根的生长。在良好混合层下，^<210>Pb和^7Be随深度的增加而减少，其方式与潮坪沉积物相似。~<22>（13）Na、~（13）<85>Sr、<134>~（13）Cs、~（13）<59>Fe、~<54>（13）Mn、~（13）<57>Co和~<65>（13）Zn等放射性核素在未处理或加热的河口沉积物中被加标。分别于1、2、3个月后用γ谱仪同步测定其放射性分布。在加热样品中，Na和Sr向下迁移到12 cm的底部，Cs向下迁移到3- 4cm，其它元素几乎不迁移。在未处理的样品中，Fe，Mn，Co和Zn被运输到4-5厘米，几个样品显示出峰值，这表明生物扰动和走廊带存款馈线。生物扰动在时间和地点上都是不均匀的。这些元素的迁移可以用对流-扩散-反应模型来模拟。