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31.
This paper presents an example of application of the double solid reactant method (DSRM) of Accornero and Marini (Environmental
Geology, 2007a), an effective way for modeling the fate of several dissolved trace elements during water–rock interaction. The EQ3/6 software
package was used for simulating the irreversible water–rock mass transfer accompanying the generation of the groundwaters
of the Porto Plain shallow aquifer, starting from a degassed diluted crateric steam condensate. Reaction path modeling was
performed in reaction progress mode and under closed-system conditions. The simulations assumed: (1) bulk dissolution (i.e.,
without any constraint on the kinetics of dissolution/precipitation reactions) of a single solid phase, a leucite-latitic
glass, and (2) precipitation of amorphous silica, barite, alunite, jarosite, anhydrite, kaolinite, a solid mixture of smectites,
fluorite, a solid mixture of hydroxides, illite-K, a solid mixture of saponites, a solid mixture of trigonal carbonates and
a solid mixture of orthorhombic carbonates. Analytical concentrations of major chemical elements and several trace elements
(Cr, Mn, Fe, Ni, Cu, Zn, As, Sr and Ba) in groundwaters were satisfactorily reproduced. In addition to these simulations,
similar runs for a rhyolite, a latite and a trachyte permitted to calculate major oxide contents for the authigenic paragenesis
which are comparable, to a first approximation, with the corresponding data measured for local altered rocks belonging to
the silicic, advanced argillic and intermediate argillic alteration facies. The important role played by both the solid mixture
of trigonal carbonates as sequestrator of Mn, Zn, Cu and Ni and the solid mixture of orthorhombic carbonates as scavenger
of Sr and Ba is emphasized.
相似文献
Luigi Marini (Corresponding author)Email: |
32.
Shear strength characterization of municipal solid waste at the Suzhou landfill, China 总被引:5,自引:0,他引:5
The current practice of slope stability analysis for a municipal solid waste (MSW) landfill usually overlooks the dependence of waste properties on the fill age or embedment depth. Changes in shear strength of MSW as a function of fill age were investigated by performing field and laboratory studies on the Suzhou landfill in China. The field study included sampling from five boreholes advanced to the bottom of the landfill, cone penetration tests and monitoring of pore fluid pressures. Twenty-six borehole samples representative of different fill ages (0 to 13 years) were used to perform drained triaxial compression tests. The field and laboratory study showed that the waste body in the landfill can be sub-divided into several strata corresponding to different ranges of fill age. Each of the waste strata has individual composition and shear strength characteristics. The triaxial test results showed that the MSW samples exhibited a strain-hardening and contractive behavior. As the fill age of the waste increased from 1.7 years to 11 years, the cohesion mobilized at a strain level of 10% was found to decrease from 23.3 kPa to 0 kPa, and the mobilized friction angle at the same strain level increasing from 9.9° to 26°. For a confinement stress level greater than 50 kPa, the shear strength of the recently-placed MSW seemed to be lower than that of the older MSW. This behavior was consistent with the cone penetration test results. The field measurement of pore pressures revealed a perched leachate mound above an intermediate cover of soils and a substantial leachate mound near the bottom of the landfill. The measurements of shear strength properties and pore pressures were utilized to assess the slope stability of the Suzhou landfill. 相似文献
33.
Complexity theory has received considerable attention over the past decade from a wide variety of disciplines. Some who write on this topic suggest that complexity theory will lead to a unifying understanding of complex phenomena; others dismiss it as a passing and disruptive fad. We suggest that for the analysis of coupled natural/human systems, the truth emerges from the middle ground. As an approach focused as much on the connections among system elements as the elements themselves, we argue that complexity theory provides a useful conceptual framework for the study of coupled natural/human systems. It is, if nothing else, a framework that leads us to ask interesting questions about, for example, sustainability, resilience, threshold events, and predictability.In this paper we attempt to demystify the ongoing discussions on complexity theory by linking its evocative and overloaded terminology to real-world processes. We illustrate how a shift in focus from system elements to connections among elements can lead to meaningful insight into human-environment interactions that might otherwise be overlooked. We ground our discussion in ongoing interdisciplinary research surrounding Yellowstone National Park’s northern elk winter range; a tightly coupled natural/human system that has been the center of debate, conflict, and compromise for more than 135 years. 相似文献
34.
Klauea historical summit lavas have a wide range in matrix 18OVSMOWvalues (4·9–5·6) with lower values in rockserupted following a major summit collapse or eruptive hiatus.In contrast, 18O values for olivines in most of these lavasare nearly constant (5·1 ± 0·1). The disequilibriumbetween matrix and olivine 18O values in many samples indicatesthat the lower matrix values were acquired by the magma afterolivine growth, probably just before or during eruption. BothMauna Loa and Klauea basement rocks are the likely sources ofthe contamination, based on O, Pb and Sr isotope data. However,the extent of crustal contamination of Klauea historical magmasis probably minor (< 12%, depending on the assumed contaminant)and it is superimposed on a longer-term, cyclic geochemicalvariation that reflects source heterogeneity. Klauea's heterogeneoussource, which is well represented by the historical summit lavas,probably has magma 18O values within the normal mid-ocean ridgebasalt mantle range (5·4–5·8) based on thenew olivine 18O values. KEY WORDS: Hawaii; Klauea; basalt; oxygen isotopes; crustal contamination 相似文献
35.
This article describes a unique flood hazard, produced by the dramatic expansion of wetlands in Nelson County, located within
the North American Prairie Pothole Region of North Dakota, USA. There has been an unprecedented increase in the number, average
size, and permanence of prairie wetlands, and a significant increase in the size of a closed lake (Stump Lake) due to a decade-long
wet spell that began in 1993 following a prolonged drying trend. Base-line land cover information from the 1992 USGS National
Land Cover Characterization dataset, and a Landsat TM scene acquired 9 July 2001 are used to assess the growth of the closed
lake and wetland pond surface areas, and to analyze the type and area of various land cover classes inundated between 1992
and 2001. The open water profile in Nelson County changed from one marked by relatively comparable coverage of closed lake
and wetland pond areas in 1992, to one in which wetland open water accounted for the vast majority of total open water in
2001. The bulk of the wetland pond area expansion occurred by displacing existing wetland vegetation and agricultural cropland.
Producers responded to the flood hazard by filing Federal Crop Insurance Corporation (FCIC) claims and enrolling cropland
in the Conservation Reserve Program (CRP), a federal land retirement program. Land taken out of agricultural production has
had an enormous impact upon the agricultural sector that forms the economic base of the rural economy. In 2001 the land taken
out of production due to CRP enrollment and preventive planting claims represented nearly 42% of Nelson County’s 205.2 K ha
base agricultural land. The patterns obtained from this detailed study of Nelson County are likely to be the representative
of the more publicized flood disaster occurring within the Devils Lake Basin of North Dakota. 相似文献
36.
The Cambrian-Vendian groundwater body plays an important role in drinking water supply of capital Tallinn and other settlements
in northern Estonia. Water quality in this deep-seated confined groundwater body is influenced by the intrusion of present-day
seawater and pumping-induced upward migration of deeper saline groundwater. The aim of this study is to evaluate the threshold
values applying the methodology worked out within the EU 6th FP project “Background criteria for the identification of groundwater
thresholds (BRIDGE)” and to compare the results with the values proposed by local authorities. A database containing 250 monitoring
points was completed and used for the calculation of natural background levels (as the 90 and 97.7 percentile) in groundwater.
The calculation of threshold values is based on natural background levels and reference values. In case of Cambrian-Vendian
groundwater body the receptor is drinking water, thus limit values set by Estonian drinking water standard were used as reference
values. The threshold values proposed by local authorities are more or less the same as calculated by BRIDGE methodology.
Exceptionally different values are derived in case of chloride and ammonium. 相似文献
37.
松南海坨子—大布苏地区泉四段— 姚家组层序地层研究 总被引:2,自引:1,他引:1
根据工区内现有的钻井、测井和地震资料,应用以多级次基准面旋回为参照面的高分辨层序地层学理论与研究方法,对松辽盆地南部海坨子—大布苏地区的泉四段—姚家组地层进行了详细的层序地层研究,共识别出5个长期基准面旋回(相当于三级层序),9个中期基准面旋回(相当于四级层序),建立了研究区的层序划分方案,在连井剖面的层序地层对比基础上,建立了该区的地层格架,并对层序构成特征进行了分析,研究了储集层在层序格架内的分布规律,揭示出浊积砂体和三角洲前缘相的分流河道形成于基准面上升期,三角洲前缘相的河口坝、远砂坝和席状砂沉积形成于基准面下降期,指出浊积砂体和三角洲前缘相的远砂坝、席状砂沉积是研究区形成岩性油气藏的有利储集体。 相似文献
38.
39.
橄榄岩—熔体相互作用过程中Re-Os体系的变化趋势: 对华北新生代地幔橄榄岩Re-Os年龄含义的启示 总被引:1,自引:0,他引:1
橄榄岩的Re-Os同位素体系作为探讨岩石圈地幔形成年龄的重要手段已受到人们越来越多的重视。然而,Re-Os体系是否会受到橄榄岩的低温蚀变如蛇纹石化和地幔交代作用或橄榄岩—熔体相互作用的影响并不十分清楚。本文在总结国际上典型造山带橄榄岩剖面研究和地幔橄榄岩捕虏体研究的基础上,发现橄榄岩的Re-Os同位素体系基本不受蛇纹石化等低温蚀变作用的影响; 但橄榄岩—熔体相互作用会造成橄榄岩的Re-Os体系的变化即Re或Os的带入。当熔体/岩石比例较小时(≤1),橄榄岩—熔体相互作用会造成橄榄岩的Re含量显著增加,而放射成因的Os同位素即187Os增量有限。但当熔体/岩石比例很大时(≥1),会造成187Os同位素显著增加。同时,橄榄岩的Re含量与中等程度不相容主、微量元素如Al、Ti、Yb的正相关关系可以通过橄榄岩的两阶段演化模式来解释,即早期的部分熔融残留和后期的橄榄岩—熔体相互作用共同影响的结果。橄榄岩的Re含量与Cr含量的正相关关系进一步说明了这一问题。上述结果对华北东部岩石圈地幔的演化过程有重要的启示作用。因为华北东部古生代时期的确存在太古宙岩石圈地幔,然而新生代时期地幔橄榄岩捕虏体普遍具有元古宙而非太古宙的事实证明橄榄岩—熔体的相互作用的确广泛存在,从而造成岩石圈地幔橄榄岩变年轻。因此,新生代地幔捕虏体的Re-Os同位素年龄并不是岩石圈地幔的形成年龄,而是混合作用的结果。汉诺坝地幔橄榄岩的Re含量和Sr、Nd同位素组成符合橄榄岩—多元熔体相互作用的混合趋势,其橄榄岩的全岩Al2O3含量和橄榄石Fo的反相关性能够通过橄榄岩—熔体相互作用来解释。 相似文献
40.
对川东华蓥山二叠系/三叠系界线附近粘土层中的粘土矿物进行野外采样和室内X射线衍射分析,结果表明,这些粘土矿物主要由规则混层伊利石-蒙脱石组成,其中1个样品可能舍有少量不规则混层绿泥石-蒙脱石等粘土矿物。总地看来.该界线粘土层中的规则混层伊利石-蒙脱石中伊利石层的含量自下而上呈现减少的趋势,平均含量约83%,所经历的最大古地温在125-150℃之间。这些粘土矿物的构成和特征与前人在华南其他地区相同层位取得的成果总体上具有较好的一致性.显示了该粘土层成因的相同性及所具有的等时意义。不同地区粘土矿物构成的差异性(如高岭石的存在与含量)可能与二叠系/三叠系界线不整合的存在与否或间断时间有关,规则混层伊利石-蒙脱石的混层比则与埋藏历史和沉积-沉积期后的流体介质有关。 相似文献