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S. E. Beaubien G. Ciotoli S. Lombardi 《Journal of Volcanology and Geothermal Research》2003,123(1-2):63
The sudden and catastrophic, or slow and continuous, release at surface of naturally occurring toxic gases like CO2, H2S and Rn poses a serious health risk to people living in geologically active regions. In general this problem receives little attention from local governments, although public concern is raised periodically when anomalous toxic-gas concentrations suddenly kill humans or livestock. For example, elevated CO2 concentrations have been linked to the death of at least 10 people in the central Italian region of Lazio over the last 20 years, while it was the CO2 asphyxiation of 30 cows in a heavily populated area near Rome in 1999 which prompted the present soil-gas study into the distribution of the local health risk. A detailed geochemical survey was carried out in an area of about 4 km2 in the Ciampino and Marino districts, whereby a total of 274 soil-gas samples were collected and analysed for more than 10 major and trace gas species. Data were then processed using both statistical and geostatistical methods, and the resulting maps were examined in order to highlight areas of elevated risk. General trends of elevated CO2 and Rn concentrations imply the presence of preferential pathways (i.e. faults and fractures) along which deep gases are able to migrate towards the surface. The CO2 and Rn anomalous trends often correspond to and are usually elongated parallel to the Apennine mountain range, the controlling structural feature in central Italy. Because of this fundamental anisotropy in the factors controlling the soil-gas distribution, it was found that a geostatistical approach using variogram analysis allowed for a better interpretation of the data. With regard to the health risk to local inhabitants, it was found that although some high risk areas had been zoned as parkland, others had been heavily developed for residential purposes. For example, many new houses were found to have been built on ground which has soil-gas CO2 concentrations of more than 70% and radon values of more than 250 kBq m−3. It is recommended that land-use planners incorporate soil-gas and/or gas flux measurements in environmental assessments in areas of possible risk (i.e. volcanic or structurally active areas). 相似文献
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研究区虎睛石矿床在地质特征、矿物组合、化学成分及琢雕效果等方面与国外虎睛石矿床是完全不同的,属于一种特殊的罕见类型。在分析虎睛石地质特征、开发利用现状的基础上,认为该区的虎睛石资源丰富,琢雕效果好,在国内外市场上具有一定的竞争力和良好的开发利用前景。 相似文献
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探讨活性氧(reactive oxygen species,ROS)在温石棉激活线粒体通路诱导A549凋亡中的作用。采用不同浓度温石棉粉尘染毒人肺上皮细胞(A549)后,MTT法检测细胞存活率,流式细胞术检测ROS抑制剂N-乙酰半胱氨酸(N-acetyl-L-cysteine,NAC)预处理前后的细胞凋亡率、胞内ROS水平及线粒体膜电位,Western Blot法检测各组细胞半胱天冬氨酸蛋白酶3(caspase-3)、p53蛋白表达水平。实验结果显示,温石棉可降低A549细胞存活率,呈现时间-剂量效应关系;NAC可显著减少胞内ROS水平、阻止线粒体膜电位下降,并下调caspase-3、p53蛋白的表达水平,抑制部分细胞凋亡的发生。表明ROS可通过诱导p53蛋白过表达,激活线粒体凋亡通路,诱导A549细胞发生凋亡。 相似文献
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钒是工业国家重点关注和争夺的资源,已被部分国家列为关键金属。本文对矿床类型、地质特征、时空分布以及成矿机制等方面进行了系统总结和分析,以期丰富钒成矿理论研究,为提高钒资源的预测和勘查效率提供支撑,为钒资源储备提供保障。研究发现,钒矿床主要分为岩浆型和沉积型,其中岩浆型钒矿床(主要指钒钛磁铁矿床)成矿与铁镁质–超铁镁质岩及部分斜长岩侵位密切相关,成矿年龄与成岩年龄一致,钒可能来自上地幔并在岩浆演化过程中结晶析出赋存于含钒钛磁铁矿中;沉积型钒矿床多形成于黑色岩系及部分砂岩中,成矿多集中于上寒武世,钒可能来自海水和赋矿围岩,由于氧化还原电位降低,以吸附和类质同象等形式赋存于有机质和硅酸盐矿物中。同时,钒矿床的成因研究存在较多问题,如成矿物质钒的来源、迁移过程、赋存形式及富集条件等。笔者建议在今后研究中通过分析钒化学行为、围岩沉积物理–化学–生物条件及岩浆演化的地质动力背景来解析钒矿床成因机制。 相似文献
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利用1961—2016年新疆塔里木盆地43个气象站逐日平均气温及最低气温,建立其近56 a的寒潮过程序列,并结合NCEP/NCAR高度场的逐日再分析资料,对塔里木盆地区域寒潮过程气候变化特征及环流异常进行分析。结果表明:塔里木盆地单站寒潮频次北部多于南部,山区多于平原的分布特点与地形特征有直接关系,全区寒潮频次有一致变化的特征且在1980年左右经历由多到少的转变,共有13站存在显著减少趋势。塔里木盆地区域性寒潮过程易在4月、2月和10月发生,寒潮频次减少趋势不显著,有14~16、7~9、4 a左右的明显振荡;区域性寒潮过程持续日数一般在2~5 d,寒潮范围在13~42站,其中1月寒潮过程持续时间最长、3月与9月最短,5月寒潮范围最大、2月最小,在塔里木盆地最易发生持续日数为2 d、寒潮范围达半数以上站点的寒潮过程。500 hPa新疆东部高度负异常配合乌拉尔山高度正异常与塔里木盆地寒潮频次有密切联系,乌拉尔山正变高中心接近平均正变高中心或偏南时,利于区域性寒潮爆发,且正变高中心强度与寒潮范围有良好的一致性。 相似文献
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A unified approach to modeling flows of slightly compressible fluids through naturally fractured media is presented. The unified fractional differential model is derived by combining the flow at micro scale for matrix blocks and macro scale for fractures, using the transient interporosity flow behavior at the interface between matrix blocks and fractures. The derived model is able to unify existing transient interporosity flow models formulated for different shapes of matrix blocks in any medium dimensions. The model is formulated in the form of a fractional order partial differential equation that involves Caputo derivative of order 1/2 with respect to time. Explicit solutions for the unified model are derived for different axisymmetrical spatial domains using Hankel or Hankel–Weber finite or infinite transforms. Comparisons between the predictions of the unified model and those obtained from existing transient interporosity flow models for matrix blocks in the form of slabs, spheres and cylinders are presented. It is shown that the unified fractional derivative model leads to solutions that are very close to those of transient interporosity flow models for fracture-dominant and transitional fracture-to-matrix dominant flow regimes. An analysis of the results of the unified model reveals that the pressure varies linearly with the logarithm of time for different flow regimes, with half slope for the transitional fracture-to-matrix dominant flow regime vs. the fracture and matrix dominant flow regimes. In addition, a new re-scaling that involves the characteristic length in the form of matrix block volume to surface area ratio is derived for the transient interporosity flow models for matrix blocks of different shapes. It is shown that the re-scaled transient interporosity flow models are governed by two dimensionless parameters Θ and Λ compared to only one dimensionless parameter Θ for the unified model. It is shown that the solutions of the transient interporosity flow models for different shapes of matrix blocks are almost identical for the re-scaled variables. Furthermore, the driving parameters for solution behavior are identified based on asymptotic approximations for different flow regimes. It is found that the matrix diffusion and the matrix area-to-volume ratio affect the solution behavior only for the transitional fracture-to-matrix dominant flow regime, that the capacitance ratio affects the solution behavior only for transitional and matrix dominant flow regimes and that the fracture diffusion is involved in all three flow regimes. Similar identification of the driving parameters is also presented in the re-scaled case. 相似文献
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基于石棉尾矿中富含氧化镁组分的特点,在矿物学特征研究基础上,采用硫酸铵焙烧法提取氧化镁,利用浸出液硫酸镁制备碱式碳酸镁。采用XRD、SEM、FT-IR和TG-DTA对不同温度条件下所获得的产物的物相、形貌、分子振动光谱和热效应变化等特征进行了分析和表征。结果表明:利用硫酸铵焙烧产物的浸取液,在低于65℃的水溶液中所制备的产物为针状水合碳酸镁;在高于85℃时制备的产物为片状碱式碳酸镁;在75℃温度时形成短柱状或颗粒状水合碳酸镁和片状碱式碳酸镁的混合物。对水合碳酸镁加热,在100℃脱去部分水合水和二氧化碳后转变为片状碱式碳酸镁。研究结果对石棉尾矿的资源化利用和环境保护具有一定的理论和实际意义。 相似文献