美国稳定全球气候政策的方案选择

本文介绍了美国稳定全球气候政策方案选择研究项目的概况,分析了快速变化的世界和慢速变化的世界远景。     

Greenhouse Gases as Clues to Permanence of Farmlands

Abstract:  Farmlands are expansive, diverse, and intensively managed ecosystems. These lands, so critical to human welfare, are threatened by growing stresses as demand for food escalates, fresh water wanes, cheap fuels deplete, and other uses jostle for space. With these coming pressures, how can we foster permanence on the lands that sustain us? In this essay I contemplate the hypothesis that the greenhouse gases, because they emanate from the interwoven flows of C, N, and energy in ecosystems, can help steer us toward permanence (sustainability). Alongside other indicators these emissions may detect the ecosystem's pulse, alerting us to inefficiencies and guiding us to better practices. To be effective signals, however, the greenhouse gases will need to be considered in their local settings, monitored longer and in more "listening places," and measured across boundaries of disciplines and biomes. This approach may help reduce greenhouse gas emissions from our farmlands. But we may find that, in the long run, the main beneficiaries of our inquiry have been, not just the atmosphere, but our fragile lands, perhaps in ways we cannot yet foresee.     

Redox potential and uranium sorption onto sediments: kinetic and thermodynamic characteristics

ABSTRACT

The effects of the flooding and initial Eh of sediments on the sorption of uranium onto the sediments were analysed by flooding and static experiments. The changes in uranium species with Eh and kinetic and thermodynamic characteristics of the uranium sorption onto the sediments were investigated. The flooding experiment indicates that the initial Eh of the sediment gradually decreased with the increase in flooding time. Based on the redox potential in the flooding experiment, simulation results obtained using the geochemical simulation software PHREEQC show that the concentration of U (VI) decreased. In contrast, the concentrations of U (III), U (IV), and U (V) gradually increased. The pseudo-second-order kinetic model well fitted the experimental data, which shows that the sorption was mainly chemical sorption. The thermodynamic parameters suggest that the entropy and enthalpy under the used conditions were positive and that ΔG^θ was negative. A thermodynamic analysis shows that the sorption was endothermic and spontaneous. These results are useful for the understanding of the sorption mechanism and migration of uranium onto the sediment under different initial sediment redox potentials and provide a good theoretical foundation for radioactive pollution remediation.     

交通运输网络可靠性研究分析

重点分析连通可靠性、出行时间可靠性、能力可靠性、行为可靠性和潜在可靠性等评价道路网络性能的指标,在回顾和总结交通网络可靠性研究发展的基础上,针对国内外的研究现状,提出了目前研究中存在的问题,描述了该领域有待研究的方向。     

Effects of Riparian Areas,Stream Order,and Land Use Disturbance on Watershed‐Scale Habitat Potential: An Ecohydrologic Approach to Policy1

Abstract: Spatio‐temporal linkages between hydrologic and ecologic dimensions of watersheds play a critical role in conservation policies. Habitat potential is influenced by variation along longitudinal and lateral gradients and land use disturbance. An assessment of these influences provides critical information for protecting watershed ecosystems and in making spatially explicit, conservation decisions. We use an ecohydrologic approach that focuses on interface between hydrological and ecological processes. This study focuses on changes in watershed habitat potentials along lateral (riparian), and longitudinal (stream order) dimensions and disturbance (land use). The habitat potentials were evaluated for amphibians, reptiles, mammals, and birds in the Westfield River Watershed of Massachusetts using geographic information systems and multivariate analysis. We use a polynomial model to study nonlinear effects using robust regression. Various spatial policies were modeled and evaluated for influence on species diversity. All habitat potentials showed a strong influence along spatial dimensions and disturbance. The habitat potential for all vertebrate groups studied decreased as the distance from the riparian zone increased. Headwaters and lower order subwatersheds had higher levels of species diversity compared to higher order subwatersheds. It was observed that locations with the least disturbance also had higher habitat potential. The study identifies three policy criteria that could be used to identify critical areas within a watershed to conserve habitat suitable for various species through management and restoration activities. A spatially variable policy that is based on stream order, riparian distance, and land use can be used to maximize watershed ecological benefits. Wider riparian zones with variable widths, protection of headwaters and lower order subwatersheds, and minimizing disturbance in riparian and headwater areas can be used in watershed policy. These management objectives could be achieved using targeted economic incentives, best management practices, zoning laws, and educational programs using a watershed perspective.     

Alteration of brain electrical activity by electromagnetic field

To better understand the affect of different levels of EMF on one’s brain activity, the Hodgkin–Huxley model has been used to describe the generation of an active potential in the nerve cell membrane. The theoretical calculations have shown that by the simultaneous affect of both passing an electrical potential and external very low frequency AC, one’s excitation pulses may be suppressed beginning with a certain level of external current. The level of this current depends on the frequency. It is postulated that to eliminate this suppression, the brain increases its normal level relatively to the lower limit. It is also postulated that the brain “tunes up” in the presence of external AC, by increasing the amplitude of its own excitation signals so that suppression does not occur. It is possible that this “tuning” process lasts some time after removing the external EMF as the brain adapts. This has been observed experimentally.     

城市级危险废物转移安全监管系统设计研究

通过对我国危险废物运输安全现状的分析,以及危险废物转移运输管理中存在的问题,借鉴国内外先进经验,提出构建低成本城市级危险废物转移监控系统的设想,为城市危险废物管理提供辅助工具。以广州市为例,将自建监控中心与基于商业平台监管危险废物转移的设计方案作对比,发现两者构建技术大致相同,但基于商业平台的监管方案节省系统的建设和运行费用50%以上,其不仅可实现政府部门通过内网进行正常业务管理,还可实现政府和危险废物运输企业通过外网对危险废物运输车辆进行实时安全监控,能有效地提高政企对危险废物运输的两级安全监管效能,为突发污染事件提供查询和应急辅助决策,同时为我国各城市危险废物运输的安全监管提供借鉴意义。     

基于层次分析法的事故隐患模糊综合评价研究

根据某市重特大事故隐患评估的实际情况,结合其不同特点将其分为7大类,4种等级。以泄漏类事故隐患为例,建立了泄漏类事故隐患评估指标体系,对事故隐患的影响因素进行量化,利用层次分析法确定评价指标的权重,采用模糊综合评价方法对其进行评估,计算出隐患等级。评估结果与实际评估结果相一致。该方法已在实际工作中得到了验证,对重大事故隐患的评估有一定的参考作用。     

城市化与北京增温的协整分析

城市增温现象和城市热岛效应对人居环境的影响日益显著，而城市化是否是城市增温现象的一个主要影响因素，为此。利用协整分析等经济计量方法研究城市化对城市增温现象的影响。协整分析是近年来计量经济学发展的最新成果，能够揭示变量之间存在着的长期均衡变动关系。分析发现，城市化因子与城市气候因子之间存在着协整关系。长期看北京市的年平均最低温度与人口密度基本上处于同步增长状态；短期内城市气温的变动受人口和城市化因素的影响较大。为此可知，北京市70年代以来，城市气温的升高基本上与城市化的发展相一致。二者具有长期协同变动的均衡关系。这些发现对我们制定减缓城市热岛效应的城市规划以及合理人口规模的城市发展战略都有很大的帮助。     

GIS-based assessment of the threat to world forests by patterns of non-sustainable civilisation nature interaction

The paper presents a novel transdisciplinary approach to investigate non-sustainable civilisation–nature interactions in the context of global change. The approach rests on the decomposition of intricate dynamics of Global Change into problematic patterns civilisation nature interactions (‘syndromes’) this is done by an iterative process of observations, data and theoretical system analysis and GIS-based modelling attempts. These syndromes of global change characterise endangering and risky developments of civilisation nature interaction and represent a baseline for measuring and indicating ‘non-sustainability’; in order to have a sustainable development it is necessary to have a far-reaching absence of syndromes. They encompass the core problems of global change, e.g. soil degradation, climate change, threats to biodiversity or global deforestation. Patterns are defined as characteristic constellations of global change trends (‘symptoms’). Cause–effect schemes of symptoms and their interrelations are constituted as complex phenomena resulting from interactions over the different spheres of the Earth system (biosphere, atmosphere, hydrosphere, population, pedosphere, economy, psychosocial sphere, social organisation, science and technology). The approach is illustrated by an analysis of civilisation–nature interaction patterns relevant for global deforestation. Global forest ecosystems have been chosen for this investigation because of their important role in the global carbon cycle and their importance for biological diversity. The resulting geographical patchwork of the combined dispositions and intensities of the different syndromes describes current and future regional threats to forests by their underlying global cause–effect patterns of civilisation–nature interaction.