美国五大湖工业区产业结构演变的城市化响应机理辨析

城市化对产业结构升级的响应已成为新时期城市化推进的主要目标和产业结构优化的重要途径。美国五大湖工业区的成功转型所体现出来的工业型区域产业结构演变城市化响应的发展规律将为东北老工业基地的改造提供有益的借鉴与启示。文章分析了美国五大湖工业区产业结构演变城市化响应的过程,并根据其影响机制,得出了东北老工业基地可以从中获得的启示和可借鉴的经验,为东北老工业基地的改造提出较为符合实际的发展对策。     

那棱格勒河流域及尾闾盐湖水文循环动力学模型的选择

流域水文模型的研制是水文科学中最重要的分支之一。其中包括集总式和分布式流域水文模型,分布式流域水文模型的种类很多,在我国的研究和应用比较普遍。那棱格勒河是柴达木盆地最大的一条河流,正确评价该河流的水文情况,对开发柴达木盆地盐湖资源具有十分重要的意义。应用分布式流域水文模型理论,对适用于那棱格勒河流域的水文循环动力学模型的类型进行选择,通过分析对比,选择出最适合本地区特殊条件的TOPKAPI模型,以便于探讨该地区水文循环的特点与规律,从而阐明盐湖区各类水体间的相互补给关系。     

Application of the QUILF thermobarometer to the peralkaline trachytes and pantellerites of the Eburru volcanic complex, East African Rift, Kenya

The Quaternary Eburru volcanic complex in the south-central Kenya Rift consists of pantelleritic trachytes and pantellerites. The phenocryst assemblage in the trachytes is sanidine + fayalite + ferrohedenbergite + aenigmatite ± quartz ± ilmenite ± magnetite ± pyrrhotite ± pyrite. In the pantellerites, the assemblage is sanidine + quartz + ferrohedenbergite + fayalite + aenigmatite + ferrorichterite + pyrrhotite ± apatite, although fayalite, ferrohedenbergite and ilmenite are absent from more evolved rocks (e.g. with SiO₂ > 71%). QUILF temperature calculations for the trachytes range from 709 to 793 °C and for the pantellerites 668–708 °C, the latter temperatures being among the lowest recorded for peralkaline silicic magmas. The QUILF thermobarometer demonstrates that the Eburru magmas crystallized at relatively low oxidation states (ΔFMQ + 0.5 to − 1.6) for both trachytes and pantellerites. The trachytes and pantellerites evolved along separate liquid lines of descent, the trachytes possibly deriving from a more mafic parent by fractional crystallization and the pantellerites from extreme fractionation of comenditic magmas.     

Study of geothermal water intrusion due to groundwater exploitation in the Puebla Valley aquifer system, Mexico

Significant intrusion of geothermal water into fresh groundwater takes place in the Puebla Valley aquifer system, Mexico. The decline in the potentiometric surface due to the overexploitation of the groundwater induces this intrusion. This hydrological system comprises three aquifers located in Plio-Quaternary volcanic sediments and Mesozoic calcareous rocks. The hydraulic balance of the aquifer shows that the annual output exceeds the natural inputs by 12 million m³. Between 1973 and 2002, a drop in the potentiometric surface, with an 80 m cone of depression, was identified in a 5-km-wide area located southwest of the city of Puebla. Chemical analyses performed on water samples since 1990 have shown an increase in total dissolved solids (TDS) of more than 500 mg/L, coinciding with the region showing a cone of depression in the potentiometric surface. A three-dimensional flow and transport model, based on the hydrogeological and geophysical studies, was computed by using the MODFLOW and MT3D software. This model reproduces the evolution of the aquifer system during the last 30 years and predicts for 2010 an additional drawdown in the potentiometric surface of 15 m, and an increase in the geothermal water intrusion.     

Soil quality changes in land degradation as indicated by soil chemical, biochemical and microbiological properties in a karst area of southwest Guizhou, China

Not only the nutritional status and biological activity but also the soil ecological functioning or soil health has been impacted profoundly by land degradation in the karst area of southwest China where the karst ecosystems are generally considered as extremely vulnerable to land degradation under intensified land-use changes. The objectives of this study are to elucidate the changes in overall soil quality by a holistic approach of soil nutritional, biological activity, and soil health indicators in the karst area as impacted by intense cultivation and vegetation degradation. Topsoil samples were collected on selected eco-tesserae in a sequence of land degradation in a karst area of southwest Guizhou in 2004. The soil nutrient pools of organic carbon (C_org), extractable extracellular carbon (C_ext), total soil nitrogen (N_t), alkali-hydrolyzable nitrogen (N_ah), total phosphorus (P_t), available phosphorus (P_a) were analyzed by wet soil chemistry. The soil biological properties were studied by means of measurements of microbial biomass carbon (both by fumigation–extraction, FE-C_mic, and by calculation from substrate-incubation respiration, SIR-C_mic) of respiration [respiration without addition of substrates, basal respiration (BR), and potential respiration (PR) with substrate-incubation] and of soil enzyme activities (invertase, urease, and alkaline phosphatase). Soil health status was assessed by simple indices of C_mic/C_org and BR/C_mic in conjunction with bacterial community structures determined by polymerase chain reaction and denaturing gradient gel electrophoresis. While the nutritional pool parameters, such as C_org and C_ext, described basically the changes in soil life-supporting capacity with cultivation interference and vegetation declined, those parameters of biological activity such as FE-C_mic, SIR, and SIR-C_mic as well as bacterial community structures measured by molecular method evidenced well the changes in soil functioning for ecosystem health with the land degradation.     

Optimization of SAGD Well Elevation

The application of steam-assisted gravity drainage (SAGD) to recover heavy oil sands is becoming increasingly important in the northern Alberta McMurray Formation because of the vast resources/reserves accessible with this mechanism. Selecting the stratigraphic elevations of SAGD well pairs is a vital decision for reservoir evaluation and planning. The inherent uncertainty in the distribution of geological variables significantly influences this decision. Geostatistical simulation is used to capture geological uncertainty, which is used can be transformed into a distribution of the best possible well pair elevations. A simple exhaustive calculation scheme is used to determine the optimum stratigraphic location of a SAGD well pair where the recovery R is maximized. There are three basic steps to the methodology: (1) model the uncertainty in the top continuous bitumen (TCB) and bottom continuous bitumen (BCB) surfaces, (2) calculate the recovery at all possible elevation increments within the TCB and BCB interval, and (3) identify the elevation that maximizes R. This is repeated for multiple TCB/BCB pairs of surfaces to assess uncertainty. The methodology is described and implemented on a subset of data from the Athabasca Oilsands in Fort McMurray, Alberta.     

3D numerical modelling of fluid flow in the Val-d’Or orogenic gold district: major crustal shear zones drain fluids from overpressured vein fields

Fluid flow patterns have been determined using oxygen isotope isopleths in the Val-d’Or orogenic gold district. 3D numerical modelling of fluid flow and oxygen isotope exchange in the vein field shows that the fluid flow patterns can be reproduced if the lower boundary of the model is permeable, which represents middle or lower crustal rocks that are infiltrated by a metamorphic fluid generated at deeper levels. This boundary condition implies that the major crustal faults so conspicuous in vein fields do not act as the only major channel for upward fluid flow. The upper model boundary is impermeable except along the trace of major crustal faults where fluids are allowed to drain out of the vein field. This upper impermeable boundary condition represents a low-permeability layer in the crust that separates the overpressured fluid from the overlying hydrostatic fluid pressure regime. We propose that the role of major crustal faults in overpressured vein fields, independent of tectonic setting, is to drain hydrothermal fluids out of the vein field along a breach across an impermeable layer higher in the crust and above the vein field. This breach is crucial to allow flow out of the vein field and accumulation of metals in the fractures, and this breach has major implications for exploration for mineral resources. We propose that tectonic events that cause episodic metamorphic dehydration create a short-lived pulse of metamorphic fluid to rise along zones of transient permeability. This results in a fluid wave that propagates upward carrying metals to the mineralized area. Earthquakes along crustal shear zones cause dilation near jogs that draw fluids and deposit metals in an interconnected network of subsidiary shear zones. Fluid flow is arrested by an impermeable barrier separating the hydrostatic and lithostatic fluid pressure regimes. Fluids flow through the evolving and interconnected network of shear zones and by advection through the rock matrix. Episodic breaches in the impermeable barrier along the crustal shear zones allow fluid flow out of the vein field.     

秦皇岛市矿产开发引发的地质环境问题及对策

秦皇岛市矿产资源丰富,矿业已成为秦皇岛市特别是地方经济的支柱之一。伴随着矿业的发展,在矿产开发过程中引发的地质环境问题日益突出,如采空区地表变形(地面塌陷、地裂缝等)、岩溶塌陷、露天采矿边坡失稳、尾矿引发的泥石流、水土流失以及地貌景观的破坏等。这些地质环境问题主要分布在北部的山区和丘陵台地区。形成的原因复杂,主要有法制不健全、缺乏强制恢复机制、布局不合理、监管不到位、开采技术落后、不合理开采、资金缺乏以及从业者环保意识淡薄等方面的原因。对于矿山地质环境的保护,应采取加强立法、建立保证金制度、统一规划、加强监管、加大宣传力度以及建立责任追究制度等措施。     

基于遥感技术的中国北方沙漠及沙质荒漠化土地区划研究

根据影响沙漠、沙质荒漠化土地的地质地貌、植被、气候和人类活动等特征,通过确定地域分异、发生学、多级序列等区划原则,建立了以地质地貌类型组合、气候为沙漠、沙质荒漠化土地区(Ⅰ级区)划分和以沙质荒漠化土地类型空间分布特征为沙漠、沙质荒漠化土地亚区(Ⅱ级区)划分的指标体系。采用遥感方法,将中国北方沙漠、沙质荒漠化土地划分为贺兰山以西干旱沙漠、沙质荒漠化区;贺兰山-大兴安岭干旱、半干旱沙漠、沙质荒漠化区和大兴安岭以东半干旱、半湿润沙质荒漠化区等3个区和17个亚区。并对沙漠、沙质荒漠化土地区进行了现状分析。     

酶法催化餐饮废油制备生物柴油的研究

以废物资源转化为宗旨,利用固定化脂肪酶催化餐饮废油与乙醇反应制备生物柴油,通过实验获得最佳酯化反应条件:反应温度47℃、有机溶剂为正己烷、醇油比3∶1,5次投加乙醇,酶用量为0.3g,反应时间32h时,生物柴油产率可达81%。