海水对近岸沉积物中放射性同位素~(90)Sr(~(85)Sr)、~(137)Cs、~(60)Co及~(106)Ru的解吸性能研究

本文应用同位素示踪和γ能谱测定方法,就海水对近岸沉积物中放射性同位素~(90)Sr(~(85)Sr)、~(137)Cs、~(60)Co及~(106)Ru的解吸性能进行了初步研究。海水对沉积物中四种同位素解吸性能的变化顺序为~(90)Sr(~(85)Sr)>~(106)Ru>~(60)Co>~(137)Cs,沉积物吸附的~(90)Sr(~(85)Sr)易被海水解吸,而~(137)Cs和~(60)Co则易被沉积物吸附固定。     

海水中137Cs/90Sr的比值

在海洋环境中,放射性核素~(90)Sr和~(137)Cs的测定占有重要的位置。 研究~(137)Cs/~(90)Sr比值,有助于了解这两个核素的地球化学过程、分馏现象以及在海洋中的归宿。同时,还可以根据其比值和其中一个核素的含量,推算出另一个核素的浓度。 一、核爆炸后的~(137)Cs/~(90)Sr比值 1965年,Harley等人根据百万吨级的核     

近岸沉积物对~(90)Sr(~(85)Sr),~(137)CS,~(60)CO及~(106)Ru的吸附性能

本文应用同位素示踪和γ能谱分析方法,就近岸沉积物对放射性同位素~(90)Sr((~85)Sr),~(137)Cs,~60Co及~(106)Ru的吸附性能进行了研究。对同种类型的沉积物,吸附分配系数Kd值的变化顺序大致为~(137)Cs>~(60)Co>~(106)Ru>~(90)Sr;对同种放射性同位素,吸附分配系数Kd值与沉积物的粒度系数(Mdφ)存在正相关关系;在低活度示踪条件下,Kd值不变。实验结果与相应海区的实际调查结果相符,沿岸核企业在设计排污方案时,亦应考虑沉积物对放射性同位素的吸附及其污染影响。     

辽河口海岸带沉积物中137Cs的分布特征及来源

选取辽河口海岸带沉积物作为研究对象,通过测定沉积物中~(137)Cs比活度,来分析沉积物中~(137)Cs比活度、蓄积总量的分布特征及影响因素,并基于~(137)Cs的测年原理估算该区域的沉积速率。结果表明:辽河口海岸带表层沉积物中~(137)Cs比活度的变化范围为(1.03±1.01)～(15.68±1.13)Bq/kg,平均值为5.09±0.34Bq/kg(n=17),变化幅度较大;在空间上呈现出由陆地向潮滩、由西向东逐渐降低的趋势。该区域沉积物柱样中~(137)Cs比活度的垂直分布主要呈现出单峰型、双峰型和不规则曲线的分布态势。采用~(137)Cs起始层位法与最大峰值法计算辽河口海岸带沉积物的沉积速率,均发现辽河口海岸带沉积物的沉积速率呈现出从北到南(从陆地到海洋)逐渐增大的趋势。沉积物中~(137)Cs蓄积总量范围为(980±46)～(6094±92)Bq/m2,平均值为2278±42Bq/m2,高于研究区~(137)Cs的全球大气沉降通量值1310Bq/m2(衰变校正到2015年);全球大气沉降的~(137)Cs约占该区域~(137)Cs蓄积总量约57.5%,表明该区域沉积物中~(137)Cs的主要来源是全球大气直接沉降。     

渤海湾沉积物中钚的测定

1958年,Thomas等人首次测定了海洋生物中的鈈(Pu),从而开始了海洋环境中超铀元素的研究。七十年代,超铀元素的研究已成了海洋同位素化学的重要內容之一,甚至超过了对~(90)Sr,~(187)Cs等核素的研究。因为超铀元     

用Ge（Li）γ谱仪测定海底沉积物中137Cs、40K、U、Ra、Th的方法研究

对~(137)Cs、~(40)U、Ra、Th等放射性元素,过去一般采用放化分析方法。要对每种核素进行单个的分离、测定,操作比较麻烦、费时。对于海底沉积物来说,还有个浸取是否完全的问题,困难更大些。     

渤海海洋环境中90Sr分布规律的研究

本文根据1980—1981年间渤海放射性调查获得的资料,探讨了渤海环境中~(90)Sr的含量分布及其变化规律。认为大陆径流以及~(90)Sr、~(137)Cs两核素被土壤吸附和从土壤中解吸的能力差异,是影响渤海环境中~(90)Sr分布及造成~(137)Cs/~(90)Sr比值严重反常的主要因素。     

广东近岸海域表层水中^90Sr和^137Cs的分布

本文提供了1989～1991年广东近岸表层水中~(90)Sr和~(137)Cs含量的分析结果。在调查海区,~(90)Sr含量为2.31～3.75mBq/L,平均值为3.21±0.45mBq/L。~(137)Cs含量为2.10～4.49mBq/L,平均值为3.47±0.89mBq/L。~(137)Cs/~(90)Sr放射性的比值为0.63～1.69,平均值为1.11±0.35。调查结果表明,近三年来未发现广东近岸海域有明显的人工放射性污染。目前广东近岸海水中的~(90)Sr和~(137)Cs主要仍是以往核试验所产生的放射性落下灰残余。     

冲绳海槽沉积物中人工放射性137Cs的分布规律

过去几十年中,各国多偏重于海水中~(137)Cs的研究,而对沉积物中~(137)Cs的研究较少。1981年,我们乘“科学一号”船在冲绳海槽区取得了部分沉积物。本文试就~(137)Cs在沉积物中的分布及相关因素作简单探讨。     

某滨海核电厂低放射性废水的海洋环境影响预评价

以某滨海核电厂为例,分析确定58 Co、60Co、90Sr、134 Cs、137 Cs和110m Ag等放射性核素为该核电厂低放射性废水中的主要海洋环境影响评价因子.根据国际原子能机构推荐的评估模式预测了上述放射性核素排海后对电厂排放口海域环境(海水水质和沉积物质量)的影响,预测结果表明该核电厂低放射性废水正常排放后,排放口附近海域海水中的58 Co、60Co、134Cs、1 10m Ag比活度低于放射性核素比活度背景值检测限2～3个数量级;90Sr低于背景值4个数量级;137Cs略高于背景值,对周围海水环境未造成放射性污染.但58 Co、60Co、134Cs、137Cs、110m Ag在排放口近岸海域沉积物中的沉积量分别比背景值检测限高2～5个数量级,其中60Co和110m Ag沉积量最大;90Sr沉积量低于放射性背景值2个数量级.最后提出可以从生物辐射评价和核素的迁移转化规律、联合效应(综合考虑温排水、低放射性废水和余氯)和选取合适的指示生物3个方面进行跟进研究的建议,以便更完善和全面地评价核电厂低放射性废水对排放口附近海域环境的影响.     

大亚湾近岸沉积物对人工放射性核素的吸附

用大亚湾近岸沉积物进行人工放射性核素的吸附研究。测得各放射性核素的吸附分配系数分别为：＾８５Ｓｒ，１６０；＾１３４Ｃｓ，３３０；＾６０Ｃｏ，６４００；＾１４１Ｃｅ，９５００；＾５９Ｆｅ，９４００；＾５４Ｍｎ，１５０００。并测得核素吸附分配系数随悬浮物浓度和示踪剂活度变化的规律。当悬浮物浓度增加时，＾８５Ｓｒ，＾５９Ｆｅ的Ｋｄ值显著降低，＾１４１Ｃｅ，＾５４Ｍｎ，＾６０Ｃｏ的Ｋｄ值稍有降低，而＾１３     

Forty years of anthropogenic radionuclides in surface seawater. Italian and Japanese data

The concentrations of man made radionuclides in surface seawater since early ′60s are here reported as measured in Italy and Japan. Most of the data refers to⁹⁰Sr and¹³⁷Cs, but occasionally the concentrations of⁸⁹Sr and¹³⁴Cs in some Italian samples are also given. The main sources of man made radionuclides were the global fallout produced by the nuclear weapon tests and the Chernobyl accident. The respective contributions to the contamination of surface seawater around both countries are discussed.     

A field study of physico-chemical states of artificial radionuclides in seawater

The physico-chemical states of artificial radionuclides,⁹⁰Sr,¹³⁷Cs and¹⁴⁴Ce in seawater were investigated by radiochemical analysis of filtered and unfiltered seawater. The difference of radionuclide concentrations between unfiltered and filtered seawaters was defined as the particulate form radioisotope and its particle ratio was discussed.Practically no particulate⁹⁰Sr, greater than 0.22 in size, was observed in both coastal and open seawaters, but some of¹³⁷Cs seemed to be insoluble in some circumstances, especially in coastal waters. A considerable amount of¹⁴⁴Ce was found to be particulate.An estimation of the radionuclides in particulate form was made for Kashima-nada seawaters collected in 1970 to 1972, and it was shown that the possible occurrence of particulate radionuclides, greater than 0.22 in size, were 1% or less for⁹⁰Sr and 6% for¹³⁷Cs. In the coastal water, 80 % of¹⁴⁴Ce were seemed to be in particulate form, but in the open seawater only a few%. The influences of suspended materials to¹³⁷Cs and¹⁴⁴Ce concentration levels in seawater were not negligible and further investigations are desirable.     

厦门邻近海域海洋环境放射性水平及评价

良好的环境质量是厦门成为一个宜居和滨海旅游城市的重要基石。自日本福岛核事故发生和福建省核电站陆续运行之后,厦门邻近海域潜在的核污染风险受到公众和管理部门的关注。本研究测定了2015年2月和8月厦门邻近海域海水和海洋沉积物中主要放射性核素的含量水平,并据此评价了该海域的环境放射性质量状况。结果表明海水中总铀、90Sr、226Ra、137Cs处于我国海洋放射性水平变化范围以内,无明显季节差异,其他放射性核素58Co、60Co、134Cs、110mAg、59Fe、54Mn、65Zn均未检出,海水中90Sr和137Cs的活度最大值远低于国家海水水质标准限值,海洋沉积物中放射性核素活度水平亦在我国海洋放射性水平变化范围以内。利用我国现有的海洋放射性环境质量评价方法对厦门邻近海域放射性质量状况进行分级评价得出其海水放射性质量为2级,海洋沉积物放射性环境质量为1级,均属于安全级别。研究结果表明2015年在厦门附近海域未观测到放射性污染现象。     

Artificial radionuclides in the western Northwest Pacific (I)90Sr and137Cs in the deep waters

⁹⁰Sr and¹³⁷Cs concentrations and their vertical distributions were determined in deep waters in the western Northwest Pacific, including the adjacent seas of Japan, from 1976 to 1979.The profiles of the radionuclides show distribution patterns with two parts with an exponential variation of radioisotope content with depth in both parts.Generally speaking, the inventories of⁹⁰Sr and¹³⁷Cs in the open waters of the northwestern Pacific correspond fairly well to the fallout inputs, but in some circumstances there seems to be considerable removal of radionuclides from the water column or they are diluted with water of lower radioactivity from other regions.The possibility of radioisotope remobilization from the bottom sediment or particulate matter is also discussed.     

Dispersion and accumulation of radionuclides in sediment of Urazoko Bay (I)

Contents of⁹⁰Sr,¹³⁷Cs and⁶⁰Co in surface sediments were investigated in and around Urazoko Bay, Fukui Prefecture, where a nuclear power plant has been operating since 1969 and the waste effluent has been released into the sea. The main source of⁹⁰Sr and¹³⁷Cs was recognized to be radioactive fallout, whereas⁶⁰Co was considered to originate from the nuclear power plant. Using the¹³⁷Cs concentration as an indicator of sorption capacity of the sediment, the behaviour of⁶⁰Co was investigated. No seasonal variation was observed in the distribution pattern of⁶⁰Co/¹³⁷Cs ratio and the retention of the heavy initial discharge in 1969 was considered to dominate the radionuclide level in the sediment. Correlation of⁶⁰Co/¹³⁷Cs ratio in the sediment and the distance from the discharge outlet was expressed by a simple exponential function of the distance. It was suggested that the contamination is spreading out gradually to the outer region of Urazoko Bay.     

THE MIGRATION PROCESS OF RADIONUCLIDES IN ARTIFICIAL MICROHABITAT

According to the principle of photosythesis with sunlight and CO2 by phytoplankton supplying food for marine organisms, while the nitrogenous compounds excreted by marine animals are transferred by bacteria into the nitrate for the use of phytoplankton, an artificial microhabitat is built to investigate comprehensively distributive relationship of 127Cs, 134Cs, 65Zn, 60Co, 50Fe, 54Mn In the parts of the microhabitat. The results show that 78% of the 134Cs and 137Cs in ion state are present in sea water, with 28 % of them nearly homogenous envolved in the exchanging processes of the suspensates and organisms, and that 80% of 59Fe, 54Mn, 65Zn, 60Co were concentrated by solid substance, whose motion was mainly controlled by biological processes. The factors affecting the distribution of nuclides in each composition are discussed. As another type of research on the controlled ecological system which is a subject currently studied in the world, the present paper is of reference value for studying quantitativ     

EFFECTS OF PHOTOPERIOD AND SALINITY ON GROWTH AND UPTAKE OF 60Co AND 137Cs FOR CHLORELLA SP.

The effects of three photoperiods (24 hr illumination, 12 hr illumination + 12 hr darkness and 24 hr darkness) and three salinities (20‰, 30‰ and 35‰) on the uptake of 60Co and 137Cs for Chlorella sp. and on the growth of its algae are studied. The uptake of 60Co for the algae is two orders of magnitude higher than that of 137Cs. Of factorial effects, the effect of photoperiod is most significant either on the uptake of the radionuclides or on the growth of the algae; the effect of salinity comes next in order and that of their interaction remains with the last. The uptake of the two radionuclides increases with extended photoperiod while the uptake of 137Cs declines with increasing of salinity. The growth of the algae appears to be the best under the conditions of 24 hr illumination and 30‰ salinity.     

The process of self-purification of the Baltic Sea waters from artificial radionuclides

An analysis of the variations in the concentrations of ¹³⁷Cs and ⁹⁰Sr radionuclides in the Baltic Sea surface waters after the accident at the Chernobyl nuclear power plant was performed. An instability of the ¹³⁷Cs concentration values during the short-term observations was found, when these values were differed 2-to 3-fold. The concentrations of ⁹⁰Sr appeared to be more stable; meanwhile, their deviations sometimes exceeded the ranges of the experimental errors. By the variations in the monthly average values of the radionuclide concentrations in the surface waters of the Baltic Sea in 1989–1995, no trend of the water self-purification was observed. The theoretical results obtained confirmed the potential of the formation and propagation of patches with increased concentrations of ¹³⁷Cs in the southeastern part of the Baltic Sea. The most reliable factor that controlled the process of self-purification of the Baltic Sea water appeared to be the mean annual value of the concentration of radionuclides. Pronounced divergences were obtained between the measured and calculated mean annual concentrations of ¹³⁷Cs and ⁹⁰Sr radionuclides in the surface waters of the Baltic Sea in 1989–2001. These divergences are explained by the potential influence of the waters from the Gulf of Bothnia and by other additional supplies of radionuclides to the marine environment, which were not included into the mathematical models.     

The transfer of reprocessing wastes from north-west Europe to the Arctic

The discharge of radioactive waste, from nuclear fuel reprocessing facilities, into the coastal waters of north-west Europe has resulted in a significant increase in the inventories of a number of artificial radionuclides in the North Atlantic. Radiocaesium, ⁹⁰Sr and ⁹⁹Tc, which behave conservatively in seawater, have been used widely as tracers of water movement through the North Sea, Norwegian Coastal Current, Barents Sea, Greenland Sea, Fram Strait, Eurasian Basin, East Greenland Current and Denmark Strait overflow. These studies are summarised in the present paper. It has been estimated that 22% of the ¹³⁷Cs Sellafield discharge has passed into the Barents Sea, en route to the Nansen Basin, via the Bjomoya-Fugloya Section, with another 13% passing through the Fram Strait. This amounts to 14 PBq ¹³⁷Cs. Quantifying the influx of other radionuclides has been more problematic. The inflowing Atlantic water now appears to be diluting waters in the Arctic Basin, which were contaminated in the late 1970s and early 1980s as a result of the substantial decrease in the discharge of reprocessing wastes. Sellafield (U.K.) has dominated the supply of ¹³⁴Cs, ¹³⁷Cs, ⁹⁰Sr, ⁹⁹Tc and Pu, whereas La Hague (France) has contributed a larger proportion of ¹²⁹I and ¹²⁵Sb.