SIMS测定玻璃固化样品中铀分布的分析方法研究

玻璃固化是一种常用的高放废液固化方法,其优点在于具有较高的抗化学介质侵蚀的能力和很好的辐照稳定性、热稳定性和机械稳定性,其不足之处在于抗水浸出等性能有所下降而使其安全性需要进一步通过抗浸出实验来进行衡量和确认。使用二次离子质谱(SIMS)分析玻璃固化体中的放射性成分(如铀元素)的分布及浸出行为等各项指标,是一种评估玻璃固化体抗浸出性能的分析手段。本文应用SIMS测试模拟玻璃固化体,以碳作为镀膜材料通过真空蒸发镀碳的方法优化样品制备条件,有效地解决了样品导电性差的问题,~(235)U/~(238)U同位素测定结果约为7.9‰±0.395‰,基本符合制作模拟样品时所使用的天然铀的同位素特征(~(235)U/~(238)U参考值约7.3‰)。研究表明,建立的方法实现了铀元素同位素丰度的测量,能直接显示铀的分布情况,该方法可为研究玻璃固化体中放射性元素的浸出行为提供一定的技术支持。     

Combination of single and sequential chemical extractions to study the mobility and host phases of potentially toxic elements in airborne particulate matter

Risk assessment of metals associated to airborne particulate matter (PM) has usually been based on the analysis of their total concentrations, which is a poor indicator of metal mobility. Chemical fractionation processes may provide an additional level of information, however, chemical complexity and small sample sizes do not allow to combine several extraction methods. Additionally, analysing the metal concentrations during the extractions exceptionally provides restricted information about metals’ speciation. To overcome these limitations we collected total suspended particulate matter (TSP) samples from the air filters placed in the air supply channel of methane-heated turbines of thermal power stations which allows collecting large amounts of TSP materials. Additionally, we combined single and sequential chemical extractions in which not only the concentrations of potentially toxic elements (PTE) (Cd, Cr, Cu, Ni, Pb, Zn) but also that of the major chemical components (Al, Ca, Fe, K, Mg, Mn, Na, P, S, Ti) were analysed. Our aims were to study these metals’ mobility and speciation through the study of their association to major chemical components.Accumulation of the studied PTEs in the TSP material suggests moderate contamination for Ni, Cd and Cr whereas a heavy one for Cu, Zn and Pb. Three groups of these PTEs could be distinguished based on their mobility. The highly mobile Zn and Cd (large ratios of water and weak acid soluble fractions) can be considered as especially harmful elements to environment. The moderately mobile Pb and Cu (large ratios of reducible and oxidizable fractions, respectively) may potentially have a negative effect on the environment, whereas the immobile Cr and Ni cannot be expected to pose a serious risk. Based on the statistical evaluation of extraction data, the potential phases for Zn and Cu are presented by metal-sulphates, -nitrates, -chlorides, -carbonates and -hydroxides, as well as sorbed forms. Lead primarily hosted by metal-carbonates and sorbed forms, as well as by -hydroxides, whereas Cu by organic matter. Finally, Cr and Ni are mostly incorporated into very resistant phases, most probably by magnetite or other resistant metal-oxides.Combination of single and sequential extractions, as well as that of the analysis of not only the target elements but also the major chemical components were found to be a very effective tool to study the host phases of PTEs in the TSP material. The necessity for relatively large sample amounts for such analyses could be fulfilled using special sampling methodology; however, obvious disadvantages of this kind of sampling must be taken into account when resulted data are evaluated.     

Exploration on compound water circulation system to solve water resources problems of North China Plain

In order to solve water resources problems in the North China Plain, this paper explored human-nature compound water circulation system from three aspects including urban flood control, surface drainage and saline water in the central and eastern of the North China Plain. Results show that: (1) The technical methods have achieved zero increase in rainwater runoff in urban areas, (2) surface drainage depletion problems can be solved through abandoned water and river water separation method, (3) and technical method through promoting rainwater infiltration would be used to solve problem of saline water in the central and eastern parts. This research provides a new perspective to the ultimate solutions to water resources problems in the North China Plain, and a fresh research direction for the development of hydro-geological science.     

2014年春末黄海中华哲水蚤(Calanus sinicus)的呼吸率与油脂积累

春末是黄海冷水团中华哲水蚤(Calanus sinicus)度夏种群形成的关键时期。在此期间,中华哲水蚤C5期桡足类幼体(简称C5期)的油脂积累程度关系到种群能否顺利度夏。本文从呼吸率、油囊体积以及种群组成等角度,对春末黄海冷水团内外以及冷水团区表、底层的中华哲水蚤进行比较研究。结果表明,2014年5月底黄海冷水团初步形成,此时冷水团区中华哲水蚤C4和C5期幼体丰度占总体的62%—93%,种群处于度夏前的准备阶段。冷水团区C5期的平均呼吸率是近岸C5期的68%,同时冷水团底层C5期的油囊体积百分数是近岸种群的2.4倍。由此推测,冷水团区次表层较厚的温跃层(19—25m,0.3—0.5°C/m)以及冷水团的低温环境有利于C5期幼体降低呼吸消耗,进而增加油脂的积累。此外,冷水团区表、底层C5期的呼吸率相近,但底层C5期油囊体积百分数为表层的1.9—4.2倍,积累大量油脂的C5期偏向在冷水团底部活动。     

Institutional change and the political economy of water megaprojects: China’s south-north water transfer

This paper analyses the relationship between megaproject construction and change in water management institutions. Due to the wide geographical distribution of their costs and benefits, which often spans national and provincial borders, water supply megaprojects frequently prompt intentional or evolutionary institutional change. China’s South-North Water Transfer Project (Middle Route), the world’s largest interbasin transfer project, was completed in December 2014 and is now in operation. Based on extensive fieldwork and analysis of Chinese documents, this paper introduces the government actors involved in, and impacted by, the planning and construction of the project. By detailing the interests of these actors, and the way those interests have been affected by the political, economic and environmental changes wrought by the megaproject, it shows that the Middle Route project has already contributed to change in one major financial institution – water pricing – and is exerting pressure on at least two others—infrastructure financing and compensation. Despite the regulatory efforts of the Chinese central government, incomplete institutional change processes threaten the long-term viability of the megaproject. Megaprojects demand institutional change and this must be factored into policymaking processes; business as usual will not suffice if the real benefits of the South-North Water Transfer are to be fairly distributed and its negative social, economic and environmental effects mitigated and appropriately compensated.     

Water security and rainwater harvesting: A conceptual framework and candidate indicators

Rainwater-harvesting tanks (reservoirs) in Tamil Nadu, India support agricultural livelihoods, mitigate water insecurity, and enable ecosystem services. However, many tanks have fallen into disrepair, as private wells have supplanted collectively managed tanks as the dominant irrigation source. Meanwhile, encroachment by peri-urban development, landless farmers, and Prosopis juliflora has reduced inflow and tank capacity. This exploratory study presents a conceptual framework and proposed indicator set for measuring water security in the context of rainwater harvesting tanks. The primary benefits of tanks and threats to their functionality are profiled as a precursor to construction of a causal network of water security. The causal network identifies the key components, causal linkages, and outcomes of water security processes, and is used to derive a suite of indicators that reflect the multiple economic and socio-ecological uses of tanks. Recommendations are provided for future research and data collection to operationalize the indicators to support planning and assessing the effectiveness of tank rehabilitation.     

Adapting water management to climate change: Institutional involvement,inter-institutional networks and barriers in India

The capacity of a nation to address the hydrological impacts of climate change depends on the institutions through which water is governed. Inter-institutional networks that enable institutions to adapt and the factors that hinder smooth coordination are poorly understood. Using water governance in India as an example of a complex top-down bureaucratic system that requires effective networks between all key institutions, this research unravels the barriers to adaptation by combining quantitative internet data mining and qualitative analysis of interviews with representatives from twenty-six key institutions operating at the national level.Institutions' online presence shows a disconnect in the institutional discourse between climate change and water with institutions such as the Ministries of Water Resources, Earth Sciences and Agriculture, indicating a lesser involvement compared to institutions such as the Ministries of Finance, External Affairs, Planning Commission. The online documents also indicate a more centralised inter-institutional network, emanating from or pointing to a few key institutions including the Planning Commission and Ministry of Environment and Forests. However, the interviews suggest more complex relational dynamics between institutions and also demonstrate a gap between the aspirational ideals of the National Water Mission under the National Action Plan on Climate Change and the realities of climate change adaptation. This arises from institutional barriers, including lengthy bureaucratic processes and systemic failures, that hinder effective inter-institutional networks to facilitate adaptation. The study provides new understanding of the involvement and barriers of complex multi-layered institutions in climate change adaptation.     

Lessons learned from the 2013 Calgary flood: Assessing risk of drinking water well contamination

A devastating flood occurred in southern Alberta on June 19, 2013, from greater than normal snowfalls in the Rocky Mountains and excess precipitation during the early spring that left soils saturated and unable to absorb any additional precipitation. This flood was Canada's most costly natural disaster, with five to six billion Canadian dollars in damages. The first objective of this study was to determine if the flood caused an increase in private drinking water well contamination in the Calgary Health Zone by comparing contamination rates to previous years. The second objective was to determine which environmental factors were associated with contamination during this flood event. Test results of total coliforms (TC) and Escherichia coli (EC) of private water wells were used to determine contamination. A geographically weighted Poisson regression analysis suggested that TC contamination was not associated with this flood. The EC contamination is positively associated with floodways, flood fringe, farms, and negatively associated with intermittent water (sloughs). These results suggest that for the 2013 flood, individual well characteristics are more important than surrounding geographic features. Thus, it is recommended that homeowners who live in a high-risk area ensure their wells are properly maintained to reduce risk of water well contamination.     

Application of desingularized approach to water wave propagation over three-dimensional topography

A numerical approach based on desingularized boundary element method and mixed Eulerian–Lagrangian formulation [Zhang et al., 2006. Wave propagation in a fully nonlinear numerical wave tank: a desingularized method. Ocean Engineering 33, 2310–2331] is extended to solve the water wave propagation over arbitrary topography in a three-dimensional wave tank. A robust damping layer applicable for regular and irregular incident waves is employed to minimize the outgoing wave reflection back into the wave tank. Numerical results on the propagation of regular and irregular incident waves over the flat bottom and linear incident waves over an elliptical shoal show good concurrence with the corresponding analytical solutions and experimental data.     

Computation of wet deck bow slam loads for catamaran arched cross sections

A computational model for catamaran wet deck slamming is developed on the basis of the variation of added mass as the hulls enter the water. In the case of a wave-piercing catamaran the bow cross section has a double arch cross section and slamming occurs when the arches fill. Residual air is entrained at the top of the arch due to bubble formation by turbulent mixing and this modifies the effect of the water added mass on the hull. The computational model therefore introduces a soft connection between the water added mass associated with the slam and the hull. The method has been evaluated by comparison with two-dimensional model drop tests in terms of the maximum forces and acceleration imposed on the hull, the variation of velocity during the slam event and the depth of penetration into the water. It is concluded that the added mass computation is adequate for slam modelling in global motions and loads calculations since it gives a good representation of the maximum total forces on the section and their duration.