开放构造系低温矿床的几个重要特征──以四川大竹拱桥坝锶矿床为例

以四川大竹拱桥坝锶矿床为例，探讨了开放构造系低温矿床可能具有的某些重要特征。指出了低温矿床的矿石矿物组合及围岩蚀变简单；矿床具隐蔽垂向分带；成矿作用发生于浅成环境；浅层大气降水与深层建造水的混合导致了矿质的沉淀。     

Fuel particles in the Chernobyl cooling pond: current state and prediction for remediation options

During the coming years, a management and remediation strategy for the Chernobyl cooling pond (CP) will be implemented. Remediation options include a controlled reduction in surface water level of the cooling pond and stabilisation of exposed sediments. In terrestrial soils, fuel particles deposited during the Chernobyl accident have now almost completely disintegrated. However, in the CP sediments the majority of ⁹⁰Sr activity is still in the form of fuel particles. Due to the low dissolved oxygen concentration and high pH, dissolution of fuel particles in the CP sediments is significantly slower than in soils. After the planned cessation of water pumping from the Pripyat River to the Pond, significant areas of sediments will be drained and exposed to the air. This will significantly enhance the dissolution rate and, correspondingly, the mobility and bioavailability of radionuclides will increase with time. The rate of acidification of exposed bottom sediments was predicted on the basis of acidification of similar soils after liming. Using empirical equations relating the fuel particle dissolution rate to soil and sediment pH allowed prediction of fuel particle dissolution and ⁹⁰Sr mobilisation for different remediation scenarios. It is shown that in exposed sediments, fuel particles will be almost completely dissolved in 15–25 years, while in parts of the cooling pond which remain flooded, fuel particle dissolution will take about a century.     

Sources and pathways of Sr in the North Atlantic–Arctic region: present day and global warming

The spatial and temporal distributions of the anthropogenic radionuclides ¹³⁷Cs and ⁹⁰Sr, originating from nuclear bomb testing, the Sellafield reprocessing plant in the Irish Sea (UK), and from the Ob and Yenisey river discharges to the Arctic Ocean, have been simulated using the global version of the Miami Isopycnic Coordinate Ocean Model (MICOM). The physical model is forced with daily atmospheric re-analysis fields for the period of 1948–1999. Comparison of the temporal evolution of the observed and the simulated concentrations of ⁹⁰Sr has been performed in the Kara Sea. The relative contributions of the different sources on the temporal and spatial distributions of the surface ⁹⁰Sr are quantified over the simulated period. It follows that the Ob river discharge dominated the surface ⁹⁰Sr over most of the Arctic Ocean and along the eastern and western coasts of Greenland before 1960. During the period of 1980–1990, the atmospheric fallout and the Ob river discharge were equally important for the ⁹⁰Sr distribution in the Arctic Ocean. Furthermore, an attempt has been made to explore the possible dispersion of accidental released ⁹⁰Sr from the Ob and Yenisey rivers under a global warming scenario (2 × CO₂). The difference between the present-day and the global warming scenario runs indicates that more of the released ⁹⁰Sr from the Ob and Yenisey rivers is confined to the Arctic Ocean in the global warming run, particularly in the near coastal, non-European part of the Arctic Ocean.     

土壤中^90Sr测量的不确定度评估

为满足新实验室认证准则,准确报告测量结果的不确定度,本文对土壤中^90Sr测量的不确定度进行评估。通过分析测量结果不确定度来源,逐一对其不确定度分量进行量化,从而获得测量结果的合成相对不确定度和相对扩展不确定度。对于环境本底水平土壤样品合成相对不确定度和相对扩展不确定度分别为22％和44％（k=2）。结果表明,对测量结果不确定度的贡献大的因素依次是β放射性测量、仪器探测效率、样品钇化学回收率、样品质量、样品锶化学回收率,其相对不确定度分别是22％、4．4％、1．1％、0．83％、0．69％。     

Determination of C(5)-C(12) perfluoroalkyl carboxylic acids in river water samples in the Czech Republic by GC-MS after SPE preconcentration

A method employing solid phase extraction followed by gas chromatography-mass spectrometry with negative chemical ionization has been developed for determination of ultratrace concentrations of perfluoroalkyl carboxylic acids in river water. The effects of the experimental parameters, such as the pH, additions of NaCl and an ion-pairing agent (tetraethylammonium bromide) and the kind of the elution agent, on the efficiency of the test acid extraction have been studied. The analyte extraction recoveries and the limits of detection and determination have been found. The method developed has been tested on determinations of perfluoroalkyl carboxylic acids in the waters of the two largest Czech rivers, Vltava and Labe (Elbe). The best extraction results have been attained without any alteration of the sample pH, with an addition of tetrabutylammonium bromide (a concentration of 50 μg mL⁻¹ in the sample) and using methanol as the elution agent. Under these conditions, the recoveries of the test acids in the spiked real samples are within ranges from 60% to 104% and 53% to 111% for analyte concentration levels of 1.40 ng mL⁻¹ and 0.14 ng mL⁻¹, respectively, depending on the lengths of the perfluorinated chains of the acids. In general, the recovery decreases with increasing length of this chain. The method developed exhibits very low limits of detection and determination and the results are fully comparable with those obtained when using more expensive HPLC-MS/MS instrumentation. Typical values amount to tenths to tens of pg mL⁻¹ and units to one hundred pg mL⁻¹ for the limits of detection and determination, respectively; the measuring sensitivity increases with increasing length of the analyte chain. The analyzes of real samples from the Vltava and Elbe rivers have demonstrated that the results obtained are similar to the values published for contamination of the Elbe and other rivers in western and central Europe. The concentrations determined are of the order of units to tens of pg mL⁻¹ and the C₈-C₁₀ acids occur most often.     

Human bones obtained from routine joint replacement surgery as a tool for studies of plutonium, americium and ⁹⁰Sr body-burden in general public

The paper presents a new sampling method for studying in-body radioactive contamination by bone-seeking radionuclides such as ⁹⁰Sr, ^239+240Pu, ²³⁸Pu, ²⁴¹Am and selected gamma-emitters, in human bones. The presented results were obtained for samples retrieved from routine surgeries, namely knee or hip joints replacements with implants, performed on individuals from Southern Poland. This allowed to collect representative sets of general public samples. The applied analytical radiochemical procedure for bone matrix is described in details. Due to low concentrations of ²³⁸Pu the ratio of Pu isotopes which might be used for Pu source identification is obtained only as upper limits other then global fallout (for example Chernobyl) origin of Pu. Calculated concentrations of radioisotopes are comparable to the existing data from post-mortem studies on human bones retrieved from autopsy or exhumations. Human bones removed during knee or hip joint surgery provide a simple and ethical way for obtaining samples for plutonium, americium and ⁹⁰Sr in-body contamination studies in general public.     

Integrating Modeling and Field Experiments to Evaluate Impacts of Vegetative Practices on Ponderosa Pine Watersheds1

Abstract: Determining watershed response to vegetation treatment has been the subject of numerous hydrologic studies over the years. However, generalizing the information obtained from traditional paired‐watershed studies to other watersheds in a region is problematic because of the empirical nature of such studies and the context dependence of hydrologic responses. This paper addresses the issue of generalizing hydrologic information through integration of process‐based modeling and field observations from small‐scale watershed experiments. To this end, the results from application of a process‐based model were compared with the results from small‐scale watershed experiments in ponderosa pine forests of Arizona. The model simulated treatment impacts reasonably well when compared to the traditional paired‐watershed approach. However, the model tended to overestimate water yields during periods of low flow, and there was a significant difference between the two approaches in the estimation of treatment impacts during the first four years following treatment. The results indicate that the lumped‐parameter modeling approach used here may be limited in its ability to detect small changes, and tends to overestimate changes that occur immediately following treatment. It is concluded that watershed experiments can be highly informative due to their direct examination of cause‐effect relationships, while process‐based models are useful for their processing power and focus on functional relationships. The integrated use of both watershed experiments and process‐based models provides a way to generalize hydrologic information, illuminate the processes behind landscape treatment effects, and to generate and test hypotheses.     

What Anthropogenic Radionuclides (90Sr and 137Cs in Atmospheric Deposition, Surface Soils and Aeolian Dusts Suggest for Dust Transport over Japan

Currently, atmospheric anthropogenic radionuclides (particulate) are controlled by suspension of the surface dust containing those radionuclides (resuspension). We have found, therefore, that such radionuclides can be used as tracers of the surface dust suspension, transport and its subsequent deposition in distant areas. The ¹³⁷Cs/⁹⁰Sr activity ratios in the atmospheric deposition, without the direct influence of nuclear tests and accidents, at the Meteorological Research Institute (MRI, Tsukuba, Japan) during the 1990s were fairly low (average: 2.1). This value is not in agreement with the ratios in Japanese surface soils (range of averages: 4–7), which had been considered as the primary source of the deposited dust. This suggests that the current atmospheric dust deposition in Japan is a mixture of local and remote components. The remote component could be an aeolian dust that has been transported long distances from arid areas. The major component is most likely to be Asian dust. It was further hypothesized that other remote source may exist beyond the Asian domain, based on accumulated observations and model results. To obtain more information about the dust transport, Sahara dust deposited in Monaco in 2002 and a suspended dust collected in the Taklamakan area in 2001 were analyzed for ⁹⁰Sr and ¹³⁷Cs. The Taklamakan dust exhibited a ¹³⁷Cs/⁹⁰Sr ratio of about 4, which is within the range of atmospheric deposition observed at the MRI, while the Sahara dust exhibited a higher ¹³⁷Cs/⁹⁰Sr ratio (about 13). Although the present Sahara datum was negative for our hypothesis of ‘hyper-range transport’, the seasonal change of the ¹³⁷Cs/⁹⁰Sr ratio in the atmospheric deposition observed at the MRI requires an aeolian dust source having a low ¹³⁷Cs/⁹⁰Sr ratio, other than Asian dust.     

碳酸盐岩Sr同位素比值的选择性溶解及测定技术

传统的碳酸盐岩的Sr同位素比值测定由于采用盐酸溶样 ,虽然具有溶解迅速的优点 ,但同时也使非碳酸盐组分被溶解而往往导致测定值偏高 ,同时也增加了Sr分离与纯化的难度。因此 ,我们考虑用弱酸来溶解碳酸盐岩矿样 ,以改进传统方法的不足。实验中采用醋酸作为溶解介质 ,对比了不同浓度的醋酸的溶解效果 ,对较难溶解的白云岩样品作了弱酸溶解实验 ,同时比较了 2 .5mol/L盐酸和 4mol/L醋酸溶样后的测定结果和测定精度。实验结果表明碳酸盐岩Sr同位素的选择性测定技术可以使溶解对象局限于样品中的目标组分———碳酸盐岩 ,防止样品中的非碳酸盐岩组分的溶解 ,避免过多的杂质进入溶解液 ,使碳酸盐岩中的微量元素———Sr(通常含量在 10 4 — 10 5范围内 )的同位素比值测定趋于准确和可靠 ,同时也减少了杂质元素的干扰 ,便于Sr的分离与纯化。     

晋江河口沉积物重金属污染历史与来源

为研究沉积物重金属元素的主要来源,分别采用电感耦合等离子体质谱法和冷原子吸收法,测定了晋江河口柱状沉积物中15种重金属元素(Pb、Sr、Cr、Cd、Zn、Cu、Fe、Mn、V、Ni、Co、Cs、Sn、Sb和Hg)的质量分数,结合210Pb定年技术,运用Pb、Sr同位素示踪技术及多元统计分析方法(聚类分析法),探讨沉积物中15种重金属元素的垂向分布特征及污染历史. 结果表明:①近300 a来晋江河口受到不同程度的重金属污染. ②柱状沉积物中的Pb主要来自于上游流域的采矿活动(贡献率为47.5%~83.7%)和土壤母质(贡献率为16.3%~52.5%). ③沉积物的87Sr/86Sr为0.716 37~0.719 26,高于人为源(≤0.711 72),说明沉积物中的Sr受人类活动影响较小,主要来源于土壤母质. ④聚类分析结果显示,15种重金属元素可分两大类,Ⅰ类为Sr、Hg、Cr、V、Ni和Cs,以自然源为主;Ⅱ类为Pb、Fe、Mn、Zn、Cd、Sb、Sn、Cu和Co,以人为源为主,主要与上游流域的采矿活动有关.