自然灾害社会脆弱性评估研究——以上海市为例

基于投影寻踪聚类模型(PPC),结合基于实数编码的加速遗传算法(RAGA),对上海市进行了自然灾害社会脆弱性评估的尝试。结果表明:①灾害社会脆弱性最高的为崇明县,其次为宝山区和金山区;②灾害社会脆弱性最低的是黄埔区,其次是徐汇区和静安区;③总体而言,灾害脆弱性较低的地区集中于上海城市中心区,而城市边缘区的社会脆弱性一般较高。     

一种基于最短路径的地震救援力量部署模型

针对地震救援这一非常态社会活动,在灾情信息上报及时且全面的前提下,对现有救援力量尤其是善于应对困难情况的各支专业救援队进行部署,以达到救援力量的有效利用,尤其是在讲究效率的黄金72 h中显得格外重要。在各救援点优先等级研究的基础上,建立合理的数学模型,利用图论的路径分析功能在地图上实现救援力量的合理部署。     

混凝土大坝震害评估模型的研究及对黄河上游大坝的分析

利用前人所编的历代(共四代)地震烈度(地震动)区划图,组合叠加后得到一个综合烈度(地震动)。这种叠加是一个集成的专家系统综合认识结果,以此作为坝体可能遭受地震破坏危险的因素。初步研究建立了混凝土大坝震害评估模型,此模型是考虑了坝体的结构类型、建设年代、使用现状、场地条件、抗震设防水平等因素,用逐步线性拟合方法进行回归分析得到的。用此模型对汶川地震破坏的坝体进行了实例分析,分析结果比较符合实际。最后,用这个模型对黄河上游10座重点混凝土大坝做了震害评估分析。     

软土等向固结与K_0固结条件下的三轴试验研究

对某软土重塑样分别进行等向固结和K0固结条件下的三轴试验,研究了不同固结条件、不同围压下软土的强度和应力应变特性,并对试验结果进行了分析和对比。结果表明:低围压下,等向固结三轴压缩试验和K0固结三轴压缩试验土样破坏时的主应力差差别不大,随着围压增大,K0固结条件下试验土体的主应力差要明显大于等向固结条件下的试验土体;与等向固结相比,K0固结条件下的土体粘聚力c值减小,而内摩擦角增大;土体呈现剪缩特性。运用等向固结三轴压缩试验确定的邓肯模型参数模拟K0固结条件下土体的试验曲线,吻合较好,初步验证了邓肯模型参数对K0固结土体的适用性。     

Plutonium isotopes concentration in seawater and bottom sediment off the Pacific coast of Aomori sea area during 1991-2005

A radioactivity survey was launched in 1991 to determine the background levels of ^239+240Pu in the marine environment off a commercial spent nuclear fuel reprocessing plant before full operation of the facility. Particular attention was focused on the ²⁴⁰Pu/²³⁹Pu atom ratio in seawater and bottom sediment to identify the origins of Pu isotopes. The concentration of ^239+240Pu was almost uniform in surface water, decreasing slowly over time. Conversely, the ^239+240Pu concentration varied markedly in the bottom water and was dependent upon the sampling point, with higher concentrations of ^239+240Pu observed in the bottom water sample at sampling points having greater depth. The ²⁴⁰Pu/²³⁹Pu atom ratio in the seawater and sediment samples was higher than that of global fallout Pu, and comparable with the data in the other sea area around Japan which has likely been affected by close-in fallout Pu originating from the Pacific Proving Grounds. The ²⁴⁰Pu/²³⁹Pu atom ratio in bottom sediment samples decreased with sea depth. The land-originated Pu is not considered as the reason of the increasing ^239+240Pu concentration and also decreasing the ²⁴⁰Pu/²³⁹Pu atom ratio with sea depth, and further study is required to clarify it.     

Cs, Pu concentrations and the Pu/Pu atom ratio in a sediment core from the sub-aqueous delta of Yangtze River estuary

A sediment core collected from the sub-aqueous delta of the Yangtze River estuary was subjected to analyses of ¹³⁷Cs and plutonium (Pu) isotopes. The ¹³⁷Cs was measured using γ-spectrometry at the laboratories at the Nanjing University and Pu isotopes were determined with Accelerator Mass Spectrometry (AMS), measurements made at the Australian National University. The results show considerable structure in the depth concentration profiles of the ¹³⁷Cs and ^239+240Pu. The shape of the vertical ¹³⁷Cs distribution in the sediment core was similar to that of the Pu. The maximum ¹³⁷Cs and ^239+240Pu concentrations were 16.21 ± 0.95 mBq/g and 0.716 ± 0.030 mBq/g, respectively, and appear at same depth. The average ²⁴⁰Pu/²³⁹Pu atom ratio was 0.238 ± 0.007 in the sediment core, slightly higher than the average global fallout value. The changes in the ²⁴⁰Pu/²³⁹Pu atom ratios in the sediment core indicate the presence of at least two different Pu sources, i.e., global fallout and another source, most likely close-in fallout from the Pacific Proving Grounds (PPG) in the Marshall Islands, and suggest the possibility that Pu isotopes are useful as a geochronological tool for coastal sediment studies. The ¹³⁷Cs and ^239+240Pu inventories were estimated to be 7100 ± 1200 Bq/m² and 407 ± 27 Bq/m², respectively. Approximately 40% of the ^239+240Pu inventory originated from the PPG close-in fallout and about 50% has derived from land-origin global fallout transported to the estuary by the river. This study confirms that AMS is a useful tool to measure ²⁴⁰Pu/²³⁹Pu atom ratio and can provide valuable information on sedimentary processes in the coastal environment.     

Detection of tritium sorption on four soil materials

In order to measure groundwater age and design nuclear waste disposal sites, it is important to understand the sorption behavior of tritium on soils. In this study, batch tests were carried out using four soils from China: silty clays from An County and Jiangyou County in Sichuan Province, both of which could be considered candidate sites for Very Low Level Waste disposal; silty sand from Beijing; and loess from Yuci County in Shanxi Province, a typical Chinese loess region. The experimental results indicated that in these soil media, the distribution coefficient of tritium is slightly influenced by adsorption time, water/solid ratio, initial tritium specific activity, pH, and the content of humic and fulvic acids. The average distribution coefficient from all of these influencing factors was about 0.1-0.2 mL/g for the four types of soil samples. This relatively modest sorption of tritium in soils needs to be considered in fate and transport studies of tritium in the environment.     

Depth profile of ²³⁶U/²³⁸U in soil samples in La Palma, Canary Islands

The vertical distribution of the ²³⁶U/²³⁸U isotopic ratio was investigated in soil samples from three different locations on La Palma (one of the seven Canary Islands, Spain). Additionally the ²⁴⁰Pu/²³⁹Pu atomic ratio, as it is a well establish tool for the source identification, was determined. The radiochemical procedure consisted of a U separation step by extraction chromatography using UTEVA^® Resin (Eichrom Technologies, Inc.). Afterwards Pu was separated from Th and Np by anion exchange using Dowex 1x2 (Dow Chemical Co.). Furthermore a new chemical procedure with tandem columns to separate Pu and U from the matrix was tested. For the determination of the uranium and plutonium isotopes by alpha spectrometry thin sources were prepared by microprecipitation techniques. Additionally these fractions separated from the soil samples were measured by Accelerator Mass Spectrometry (AMS) to get information on the isotopic ratios ²³⁶U/²³⁸U, ²⁴⁰Pu/²³⁹Pu and ²³⁶U/²³⁹Pu, respectively. The ²³⁶U concentrations [atoms/g] in each surface layer (∼2 cm) were surprisingly high compared to deeper layers where values around two orders of magnitude smaller were found. Since the isotopic ratio ²⁴⁰Pu/²³⁹Pu indicated a global fallout signature we assume the same origin as the probable source for ²³⁶U. Our measured ²³⁶U/²³⁹Pu value of around 0.2 is within the expected range for this contamination source.     

基于底泥再悬浮试验的太湖水质模拟

为探索浅水湖泊水动力扰动作用对底泥再悬浮影响的规律,在室内矩形水槽内模拟了各种水动力条件下太湖底泥的起动规律,得到了太湖底泥在3种不同起动标准下的起动流速,通过考察上覆水中悬浮物浓度的变化,建立了底泥沉积物再悬浮通量与水体流速的定量化关系。结果表明:太湖底泥在个别动、少量动、普遍动3种标准下的起动流速分别为15、30和40 cm/s,且底泥沉积物再悬浮通量与流速呈现线性正相关关系,再悬浮通量随流速增大而增大,且相关性较好。将该试验结果应用于太湖的水量水质数学模型中,并和太湖实测资料进行了对比,取得了比较满意的效果。该模拟装置能够在室内可控条件下较好地反映太湖沉积物再悬浮特征,对太湖的富营养化治理具有重要意义。     

An occupational exposure assessment of polychlorinated dibenzo-p-dioxin and dibenzofurans in firefighters

Polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) are unintentional byproducts of combustion and industrial processes. Firefighters face the risk of occupational exposure to PCDD/Fs. Congener-specific analyses of 17 PCDD/Fs were performed on 20 serum samples collected from firefighters and fire scene investigators, and four soot samples that had deposited on the surfaces of the fire helmets and were collected after the firefighters had fought fires. The PCDD/F concentrations on the helmets that were contaminated by being worn at the fire scenes were 63-285 times higher than those on a clean helmet. The median serum PCDD/F concentration of the 16 firefighters (12 pg WHO₂₀₀₅-TEQ g⁻¹ lipid) was not different from those of the males from the general Taiwanese population (9.4 pg WHO₂₀₀₅-TEQ g⁻¹ lipid). However, the median PCDD/F level in the four fire scene investigators (15 pg WHO₂₀₀₅-TEQ g⁻¹ lipid) was higher than those in the male from the general Taiwanese population (Mann-Whitney U test, p < 0.01). Furthermore, the serum samples from the firefighters and fire scene investigators, and the soot samples from the fire scenes presented similarly distinctive PCDD/F profiles that had elevated proportions for 10 PCDF congeners. Limited data indicated that the fire scene investigators were occupationally exposed to PCDD/Fs at the fire scenes. We suggested that the firefighters were not occupationally exposed to PCDD/Fs at the fire scenes due to appropriate protection. However, the fire scene investigators may have had more occupational exposure to PCDD/Fs due to poor protection, and further research must be performed to confirm this.