Natural hazards in British Columbia: an interdisciplinary and inter-institutional challenge

 Although British Columbia experiences many natural hazards, there is as yet no unified policy to promote natural hazard management in the province. The problem is not in the quantity and quality of geoscience assessment of natural hazards, but instead, it is suggested, in the isolation of that work from broader risk perspectives and in the lack of clarity of division of responsibilities between various levels of government. The example of recent changes in perception of the terrain stability problem illustrates how natural hazard problems are driven by social and political priorities rather than by geoscience priorities. Received: 22 November 1998 / Accepted: 22 November 1998     

Polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans in sediments from Hong Kong

Concentrations of 2,3,7,8-substituted polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) were determined in 14 sediment samples collected from four sites in the Mai Po Marshes Nature Reserve (within a RAMSAR Site) and from another six sites in Victoria Harbour and along the Hong Kong coastline. Elevated levels of PCDDs, and particularly OCDD, were detectable in all samples collected from the Mai Po Marshes and five of the six sites. In contrast to PCDDs, PCDFs were mainly found in sediment samples collected from industrial areas (Kwun Tong and To Kwa Wan) in Victoria Harbour. PCDD/F levels and congener profiles in the samples from the Mai Po Marshes Nature Reserve in particular show strong similarities to those reported in studies which have attributed similar elevated PCDD concentrations to nonanthropogenic PCDD sources.     

Natural Gas Hazard (CO2, 222 Rn) within a Quiescent Volcanic Region and Its Relations with Tectonics: The Case of the Ciampino-Marino Area, Alban Hills Volcano, Italy

Groundwater surveys were performed by detailed(around 300 sites) grid-analysis of water temperature, pH, redox potential, electrical conductivity, ²²²Rn, alkalinity and by calculating the pCO₂, throughout the Ciampino and Marino towns in the Alban Hills quiescent volcano (Central Italy). Following several episodes of dangerous CO₂ exhalation from soils during the last 20 years and earlier ashistorically recorded, the work aimed at assessing the Natural Gas Hazard (NGH) including the indoor-Rn hazard. The NGH was defined as the probability of an area to become a site of poisonous peri-volcanic gas exhalations from soils to the lower atmosphere (comprising buildings). CO₂ was found to be a ``carrier' for the other poisonous minor and in trace components (H<sub>s</sub>S, CH<sub>4</sub>, <sup>222</sup>Rn, etc.). This assessment was performed by extrapolating in the aquifer CO<sub>2</sub> and <sup>222</sup>Rn conditions, and discriminating sectors where future CO<sub>2</sub> flux in soils as well as indoor-Rn measurements have to be noted. A preliminary indoor-Rn survey was performed at about 200 sites. The highest values were found in the highest pCO<sub>2</sub> and high <sup>222</sup>Rn values in groundwater. This indicates convection and enhanced permeability in certain sectors of the main aquifer, i.e., along the bordering faults and inside the gas-trap of the Ciampino Horst., where ``continuous gas-phase micro-macro seepage mechanism' is invoked to explain the high peri-volcanic gases flux.     

周、秦、汉、唐时期关中地区自然灾害与粮食安全问题研究

周、秦、汉、唐时期,关中农业较为发达,为多个王朝建都之地。京师之地的粮食问题十分重要,汉代以后屡屡出现粮食紧张局面,其原因除移民、战乱等因素外,自然灾害的影响不容忽视。研究发现,周、秦、汉、唐时期,关中的粮食在秦以前基本自给,两汉、魏晋以后依赖关东趋于明显,隋唐时期关中粮食所需则自产自给和漕运并重。这一演变过程,与关中自然灾害的发生状况有着紧密联系。随着西汉以后生态环境的破坏和人类垦殖活动的日益加剧,关中地区水旱灾害发生频繁,对粮食安全产生了严重影响。期间的中央政府不断采取扩大农业垦殖、提高农业生产技术和漕运等手段,以解决京师用粮。     

酸碱滴定法测定天然石膏中的碳酸盐(无水碳酸)

建立了用溴百里酚蓝—酚红作指示剂,酸碱滴定法测定天然石膏中碳酸盐的方法。在确定了试验条件的基础上,对石膏国家一级标准物质GBW03109a和GBE03110分析,相对标准偏差分别为0.08%、1.05%;分析3个天然石膏样品,相对标准偏差分别为1.47%、1.67%和0.25%;对试样进行加标回收,回收率在95.53%～97.02%之间;方法检出限为0.15%。表明用该方法测试,结果准确可靠。     

New method for in situ characterization of loose material for landslide mapping purpose

The assessment of grain size distribution and plasticity of loose geological material, during in situ geological investigations, is not obvious. Visual appreciation allows an approximative quantification of the coarse granulometric fractions, but not of the fine ones. Field soils determination methods suggested until now, are visual and tactile tests leading to a very rough estimate, which is only qualitative and not very reproducible. The new proposed field test (GEOLEP method) allows a quick quantification of the fine fraction of loose material. It allows the determination of the sand fraction (fine and medium grained sands) as well as the methylene blue value of the samples. The necessary equipment to perform this test is light and compact and the time needed to analyze one sample is approximately 15 min. Thus it is also possible to carry out numerous measurements in one day. The calibrations were carried out on a selection of 13 natural samples, chosen for their representativeness of the typical alpine quaternary deposits. The results obtained with GEOLEP method are relevant compared with standardized laboratory tests; the obtained correlation indexes are of 73% for the comparison with laboratory stain test results and of 89% with a laboratory method using a similar procedure than the field test. The correlation we performed with Atterberg's limits tests shows that a rough approximation of plasticity index can also be obtained (R² = 75%). This method thus brings a new tool which should allow taking into account the lithological factor (by some quantitative and representative variables) in a reliable way for the evaluation of landslide hazards.     

自然灾害复杂性研究

从自然灾害系统的观点出发,阐述了自然灾害系统的特点,提出了自然灾害复杂性的概念。基于前人研究的一些成果,讨论了分形,混沌,人工神经网络等非线性理论以及定性与定量综合集成技术在自然灾复杂性研究中的应用。     

中国传统民居建筑文化的自然地理背景

讨论了气候、地貌与水文、地质与植被等自然地理要素对中国传统民居建筑的格局、型式、风格、特色等方面的影响。在此基础上分析了以功利观、审美观和生态观为内涵的中国传统民居建筑文化的自然观。     

自然类比法对张北──尚义6.2级地震序列类型和震后趋势早期判断实例

用自然类比法对1998年1月10日张北─尚义6．2级地震序列类型和震后趋势进行了早期判断,找出了与之最相似的四个序列是1976年9月23日巴音木仁6．2级地震（S17）、1996年5月3日包头6．4级地震（558）、1985年4月18日禄劝6．3级地震（S34）和1984年5月21日南黄海6．0级地震（S33）。由此判断张北地震序列为主震余震型,推算最大余震震级应在4．3～4．7之间,一个月内4级以上余震数可能在11～22次之间。实测结果张北地震最大余震震级4．6,一个月内4级以上余震数18次,均在预测范围内。     

Monitoring,causality, and uncertainty in a stratospheric context

Our increasingly complex understanding of stratospheric chemistry and transport processes leaves us with various theoretical possibilities of appreciable and perhaps serious environmental impact due to human activities. These possibilities raise policy questions in which the economic and other costs of regulating human activities must be weighed against the possible consequences of no such regulation. The natural variability of the atmosphere, the physical and other limitations on our global sampling and monitoring abilities, and the difficulties in establishing causal connections leave us in a state of uncertainty as to the reality and magnitude of at least some of these theoretical environmental impacts. Policy-makers must make decisions in the face of these uncertainties.The proper role of scientists as such in narrowing and quantifying the uncertainties is discussed, with particular regard to the evidence that cultural and other biases often affect individual scientists' conclusions. Conscious efforts are needed to minimize bias, quantify uncertainties, and speed up the process of scientific consensus-building. A careful distinction should be drawn between scientifically determined probabilities, and cost-benefit analyses which necessarily involve value judgments.