黑潮及邻近海域铯-137的分布

1986年5-6月,在黑潮及其邻近海域(28°28′—36°31′N,126°29′—145°00′E)调查了~(137)Cs的活度分布。从采集34个站区表层水样的分析结果表明,~(137)Cs的活度范围为(0.55—7.6)×10~(-2)Bq/L,平均值为2.43×10~(-2)Bq/L,~(137)Cs的分布趋势是本州东南部海区~(137)Cs放射性水平略高于日本南部海区和东海东北部海区,海水中~(137)Cs的活度与盐度之间没有明显的相关关系。     

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。     

青岛近海悬浮物含量及吸附性能研究

海洋中的大量微细悬浮物,由于其表面积很大,所以有很强的吸附效应,它们对于微量元素(包括放射性核素)在海洋中的转移过程起着非常重要的作用。悬浮物中的无机组份对海水中各种微量元素的吸附,国内外曾进行了一些研究,但对放射性核素的吸附性能研究得比较少。为了进一步探讨青岛近海的自净能力,我们对该海区的悬浮物含量、组成及吸附性能进行了调查、研究。本次着重调查研究了长寿命裂变产物~(90)Sr,~(137)Cs,~(106)Ru及感生同位素~(60)Co在海水和天然悬浮物之间的分配情况,并用~(137)Cs,~(60)Co两种示踪剂对悬浮物的吸附性能进行了研究。     

渤、黄、东、南海沉积物中~(226)Ra的含量比较

我们测定了渤海、黄海、东海和南海沉积物中~(226)Ra的含量,从所测结果表明:四大海区的所有近岸河口区,~(226)Ra的含量都小于0.017Bq/g,而南海中部的深海区,~(226)Ra的含量基本上都大于0.017Bq/g。另一方面,在近岸河口区,~(226)Ra的含量也有差别,其中珠江口最低,为0.006Bq/g;九龙江口最高,为0.014Bq/g;长江口、黄海和渤海三个海区,~(226)Ra的含量基本相等,即在0.012～0.013Bq/g之间。这些现象说明,在近岸河口区~(226)Ra主要来源于陆源物质;在深海区~(226)Ra主要来源于海底沉积物中~(230)Th的衰变产物,这种规律和世界其他海区基本一致。     

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     

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。     

环渤海石油污染对海区环境和海洋生物的影响研究

通过调查环渤海湾多个海域表层海水、沉积物及海洋生物体中石油烃总量及苯并(a)芘的含量,研究了石油污染对海区环境和生物的影响。并通过分子荧光法和液相色谱法分别研究不同海洋环境中、同一海区不同生物品种中、不同海区相同生物品种中以及同一海区的环境和生物体中石油烃及苯并(a)芘含量的关系,分析不同海区石油烃污染状况,对比不同生物品种对石油烃的富集能力。结果表明,所监测海域生物体中石油烃和苯并(a)芘含量趋势均为:棘皮类贝类甲壳类鱼类;调查海域海水中石油烃含量范围为(0.013~0.285mg/L),属轻度石油烃污染,;海洋生物中石油烃和苯并(a)芘含量范围分别为(0~57.2mg/kg)和(0~2.29μg/kg),样品中苯并(a)芘含量均低于限量值,石油烃超标率为6.7%,基本达到水产品食用安全标准。     

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。     

长江口及其邻近陆架沉积物中226Ra和210Pb的分布特征

本文利用放射化学分析法测定了长江口及其邻近陆架沉积物中~(226)Ra和~(210)Pb的含量。结果表明,在该海区的沉积物中,~(226)Ra含量的水平分布随经度增加而直线下降,而~(210)Pb含量的水平分布则随经度增加而直线上升,二者形成明显的同步反向分布。     

亚铁氰化铜-硅胶现场浓集γ能谱法测定海水中137Cs

本文介绍用无机离子吸附剂CuFC-SiO_2从海水中浓集~(137)Cs,然后用r能谱仪测定海水中~(137)Cs活度的简易分析测定方法。研究了过柱海水速度和海水中~(137)Cs活度变化时吸附剂对海水中~(137)Cs吸附效率的影响,探讨最佳过柱速度和吸附效率。本方法与磷钼酸铵-碘铋酸铯-β计数法有良好可比性。方法准确,简便,安全且易于掌握。     

Horizontal and vertical distributions of <Superscript>137</Superscript>Cs in seabed sediments around the river mouth near Fukushima Daiichi Nuclear Power Plant

Investigations including a bathymetric survey, sonic prospecting, and vibrocoring were performed to understand the horizontal and vertical distribution of ¹³⁷Cs in seabed sediments in shallow seas with depths less than 30 m near the Fukushima Daiichi Nuclear Power Plant. Especially, features of ¹³⁷Cs distributions in deeper sections of the seabed sediments were studied to evaluate the vertical heterogeneity of ¹³⁷Cs distribution in the seabed sediments in shallow seas. The distribution area of the seabed sediments was less than half of the investigation area, and the locations of the seabed sediments were divided into flat and terrace-like seafloors based on their topographical features. The thicknesses of the seabed sediment layers were mostly <2 m. The ¹³⁷Cs inventories in the seabed sediments varied from 13 ± 1 to 3,510 ± 26 kBq m^?2, and continuous distributions of ¹³⁷Cs at depths greater than 81 cm were observed. The ¹³⁷Cs distributions were not uniform; however, the ¹³⁷Cs inventories tended to be larger near the base of the steeper ascending slopes than in the terrace-like seafloors themselves. Based on the relationship between the ¹³⁷Cs inventories and mean shear stress, features of the seafloor topography were inferred to be significant control factors governing the horizontal and vertical distribution of ¹³⁷Cs in the seabed sediments. Rapid changes and multiple peaks in the vertical profile of the ¹³⁷Cs distributions suggest that they are related to pulse input caused by heavy-rain events. Change in the ¹³⁷Cs inventories with depth in this study are larger than those reported in previous studies, indicating earlier results of ¹³⁷Cs inventories per unit in seabed sediments in shallow seas, especially near the river mouth, which drains a radiologically highly-contaminated basin, were underestimated.     

Activity Concentrations and Fluxes of Radiocesium in the Southern Baltic Sea

The activity concentrations of dissolved¹³⁷Cs have been determined in the water column and¹³⁷Cs and¹³⁴Cs in the sediments and the sediment porewaters of the southern Baltic Sea. The mean activity concentration of dissolved¹³⁷Cs in the Gdansk Deep declined from 109 Bq m⁻³in June 1986 to 61 Bq m⁻³in 1999. In sediments, the activity concentrations of¹³⁷Cs (33-231 Bq kg⁻¹) were highest in muds and the activity concentrations of¹³⁴Cs were about 6% of the total Cs activity. The Chernobyl contribution to¹³⁷Cs activity was between 43% and 77%. The porewater activity concentrations of¹³⁷Cs in muddy sediments were in the range 71 to 3900 Bq m⁻³and were higher than those in the overlying seawater. The diffusive flux of dissolved¹³⁷Cs from the muddy sediments was estimated in the range 5 to 480 Bq m⁻²year⁻¹. The flux of¹³⁷Cs from sediment porewaters of the southern Baltic Sea was about 45% of the total, including fluxes of¹³⁷Cs from wet and dry atmospheric deposition and the fluvial inputs. The results were used to elucidate the rate of recovery of the sediments and the waters of the southern Baltic from Chernobyl-derived¹³⁷Cs.     

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。     

Plutonium and cesium radionuclides in sediments of the Savannah River estuary

A study was made of the ²³⁹Pu, ²⁴⁰Pu, ²³⁸Pu and ¹³⁷Cs concentrations in tidal marsh sediments of the Savannah River estuary. Tidal marshes are identified as special locations for plutonium deposition because of the high biological productivity and relative stability of sediments as compared to channel sediments. The ^239,240Pu deposition averaged 3·2 mCi km⁻², which is higher than land-based fallout values of about 2 mCi km⁻². The ^239,240Pu to ¹³⁷Cs ratio was about three times higher than fallout deposition estimates, indicating a more rapid desorption of ¹³⁷Cs from sediment in the saline waters of the area.     

Processes affecting long-term changes in <Superscript>137</Superscript>Cs concentration in surface sediments off Fukushima

Temporal changes in cesium-137 (¹³⁷Cs) concentrations in the surface (0–10 cm) layer of seabed sediment were quantified from continuous observation data at 71 stations within a 150-km radius of the Fukushima Daiichi Nuclear Power Plant, and the primary processes affecting temporal changes were identified. From March 2011 to the end of 2015, about 80% of the initially deposited ¹³⁷Cs in the surface sediment in the coastal region (bottom depth ≤100 m) region has dissipated (radioactive decay is not included). Such a remarkable change in the ¹³⁷Cs concentration was not observed in the offshore (>100 m) region. This paper focuses on the following three processes that affected the decrease in the ¹³⁷Cs concentrations, and assesses their relative importance; (1) resuspension and transport of ¹³⁷Cs-bound sediment, (2) desorption of ¹³⁷Cs from the sediment, and (3) dilution of ¹³⁷Cs by vertical mixing of sediment. Consequently, it was estimated that the first two processes together have potentially contributed to reduce the ¹³⁷Cs inventory in the top 10 cm of the coastal region by at most 35%. Furthermore, by applying a pulse input sediment mixing model to the observed vertical distribution of sedimentary ¹³⁷Cs, it was also estimated that more than 43% of the ¹³⁷Cs in the surface sediment was transported to deeper sediment layers by vertical mixing of the sediment. This indicates that the decrease of ¹³⁷Cs concentrations in coastal sediments was mainly affected by mixing of ¹³⁷Cs-bound surface sediment with less contaminated sediment in the deeper layers.     

Decline in radiocesium in seafloor sediments off Fukushima and nearby prefectures

Radioactivity has been monitored in seafloor sediments off Fukushima and nearby prefectures regularly. During the initial monitoring period (May–September 2011), ¹³⁷Cs concentrations in the surface sediments (0–3 cm) generally increased to 8–580 Bq/kg. Subsequently, concentrations decreased at variable rates. In the latest data, from February 2016, concentrations were still higher at 0.8–141 Bq/kg than the pre-accident level. The geometric mean concentration declined steadily from 47 Bq/kg in September 2011 to 13 Bq/kg in February 2016. The ¹³⁷Cs abundance (Bq/m²) in the surface sediment at each station decreased similarly. The rate of decrease of surface abundance varied spatially by almost one order of magnitude, ranging from 1.1 × 10^?4 to 1.7 × 10^?3/day, equivalent to halving times of 16–1.1 years, respectively. The rate of decrease was related to the median sediment grain size at each station. In addition, bottom-water dynamics, through the redistribution of bottom sediments, may have caused spatial variability in the rate of decrease, whereas vertical profiles of ¹³⁷Cs concentrations in the sediment suggest that vertical migration of ¹³⁷Cs was not a major mechanism reducing the surface ¹³⁷Cs concentration. From September 2011 to February 2016, the overall halving time of ¹³⁷Cs in the surface sediment in the monitoring area, excluding the area inside a 30-km radius from the Fukushima Dai-ichi Nuclear Power Plant, was 2.3 years. Thus, 76% of the originally deposited ¹³⁷Cs (46 × 10¹² Bq) in the surface sediment was transported out of the area during that period.     

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.     

Geochemical associations and post-depositional mobility of heavy metals in coastal sediments: Loch Etive,Scotland

Surficial sediments of a Scottish sea loch exhibit enrichment profiles for the minor metals Cu, Pb and Zn. ¹³⁷Cs data indicate enrichment during the last 20–40 years of deposition. Variations in the onset of enrichment between sites within the fjord, which have similar accumulation rates, infer that whilst the metal inputs may originally have been of an anthropogenic nature the present distribution of the metals in the sediments is controlled by organic matter diagenesis. These processes are especially important within the sulphate reducing zone. This suggestion is supported by the similar behaviour of the heavy metals and I/C_org ratios in the sediments. Diagenetic recycling of Pb may also explain discrepanceis that were observed between ²¹⁰Pb and ¹³⁷Cs chronologies. The source and diagenetic remobilisation of these elements is discussed with relation to the fate of anthropogenic metals in coastal sediments.     

黄河下游及河口区表层沉积物中U,Ra,Th,40K和137Cs的测定

本文从地球化学和环境保护的角度,用8180—4Kγ谱仪直接测定方法确定了天然放射性元素U,Ra,Th,~(40)K,及人工核素~(137)Cs的含量,讨论了它们的分布特点及其影响因素,指出了河口区与下游段元素变化的差异及其制约条件。