黄土高原丘陵沟壑区城市土地持续利用评价研究

从城市用地规模结构合理性、经济可行性、社会可接受度、对区域环境影响4个方面选择了32个因素作为参评因子,利用层次分析法、线性加权函数建立黄土高原丘陵沟壑区城市土地利用评价指标体系数学模型,并对定西市2006年城市土地可持续利用状况进行了综合评价。结果表明,2006年定西市土地利用处于非可持续利用阶段,并针对评价结果,提出可持续利用具体对策,为相关工作提供参考。     

Germination and establishment of the invasive cordgrass Spartina densiflora in acidic and metal polluted sediments of the Tinto River

Heavy metal pollution is common in rivers in the vicinity of mining areas. In these polluted environments, the survival of alien species with a high tolerance to metals may be favored. The Tinto River (Southwest Iberian Peninsula) is an excellent natural laboratory for the study of plants’ responses to acidic and metal polluted sediments. This work analyzes the tolerance of the alien species Spartina densiflora to low pH and high metal loads in the Tinto River. The main aim of this study was to determine if this alien species can invade landward along the banks of the Tinto River. S. densiflora seeds were able to germinate in heavy metal polluted aerobic sediments even at pH 2. However, these conditions decreased S. densiflora final germination, altered germination dynamics, decreased aerial and subterranean growth rates, and prevented its establishment.     

The role of the lowermost boundary conditions in the hydrological response of shallow sloping covers

In many areas of the world, slopes covered by shallow unsaturated non-plastic soil layers experience rainfall-induced landslides causing heavy damage and casualties every year. Landslide occurrence depends on the amount of water infiltrated and stored. Among the contributing factors are the hydraulic conditions at the lowermost boundary, a feature that is often disregarded. The paper focuses on this topic, presenting the results of some laboratory and numerical experiments on ash-pumice interfaces. A strategy is then proposed for selecting the lowermost boundary condition, and some studies are carried out to compare the results obtained with the proposed solution and other more popular ones.     

Long-term variation in the salinity of the Southern Yellow Sea Cold Water Mass, 1976–2006

This paper discusses the long-term variation in the salinity of the Southern Yellow Sea Cold Water Mass (SYSCWM) and examines factors influencing the SYSCWM based on hydrographic datasets of the China National Standard section and the Korea Oceanographic Data Center. The mean salinity at the center of the SYSCWM showed a decreasing long-term trend. In empirical orthogonal function (EOF) analysis, the second EOF mode showed a similar long-term trend. The mean salinity of the center of the SYSCWM was related to the intrusion of saline water from the Yellow Sea Warm Current (YSWC), the salinity of the source area of the YSWC, the evaporation minus precipitation (E–P) flux, and discharge from the Changjiang River. The decreasing salinity trend to the southwest of Cheju Island produced a freshening trend in the YSWC, resulting in a reduction in the salinity of the SYSCWM. The freshening trends of the water from the northwest Pacific and the South China Sea were seen as the reason for the decreasing salinity trend from the intrusion of water into the Yellow Sea (YS). The freshwater flux influenced the surface salinity and was brought to deep layers by strong mixing in winter. The mean E–P flux signal and Changjiang River discharge signal lagged the first principal component of the SYSCWM by approximately 5 months.     

Pseudo-plane strain analysis of wave propagation problems arising from detonations of explosives in cylindrical boreholes

Wave propagation problems, such as blasting for excavation of a new tunnel oriented perpendicular to an existing tunnel, are truly three dimensional in nature. Dynamic finite element analysis with three-dimensional elements is, however, very expensive. The cheaper and simpler alternative would be to model the problem approximately in two dimensions. This paper shows that dynamic finite element analysis of such problems using conventional two-dimensional plane strain elements produces responses which are erroneously excessive. This is accredited to the inability to the inability of the two-dimensional elements to correctly model the rapid attenuation of the amplitudes of the outward propagating waves. To overcome this problem, a pseudo-plane strain concept is introduced and has been found to be a viable alternative. Numerical results are presented to demonstrate the application of the concept.     

Propagation of seismic slip from brittle to ductile crust: Evidence from pseudotachylyte of the Woodroffe thrust, central Australia

The Woodroffe thrust, central Australia, is a > 1.5-km-wide mylonitized shear zone marked by large volumes of mm- to cm-scale pseudotachylyte veins. The pseudotachylytes display typical melt-origin features, including rounded and embayed clasts, spherulitic and dentritic microlites, and flow structures within a fine-grained matrix. Three types of pseudotachylyte are identified on the basis of deformation texture, vein morphology, and host-rock lithology: cataclasite-related (C-Pt), mylonite-related (M-Pt), and ultramylonite-related (Um-Pt). The M-Pt and Um-Pt veins intrude into mylonite and ultramylonite and are themselves overprinted by subsequent mylonitization. These pseudotachylytes contain an internal foliation defined by flattened porphyroclasts and layering of the fine-grained vein matrix, and the foliation is generally oriented parallel to foliation in the surrounding mylonite and ultramylonite. These observations constrain the timing and environment of M-Pt and Um-Pt pseudotachylyte formation to a protracted period of deformation and mylonitization within the ductile regime of the crust. The M-Pt and Um-Pt veins, as well as the host mylonite, are overprinted by cataclasis and multiple generations of late-stage C-Pt veins that were generated in the brittle-dominated regime of the upper crust during uplift and exhumation of the shear zone.The coexistence of multiple generations of voluminous C-Pt, M-Pt, and Um-Pt veins indicates that the pseudotachylyte veins represent a large number of large earthquakes and accompanying seismic slip over an extended period of seismicity on the Woodroffe thrust. The timing and distribution of pseudotachylyte indicate that the earthquakes nucleated at the base of the brittle-dominated seismogenic zone and propagated down through the brittle–ductile transition into the ductile-dominated regime of the crust.     

Metal Complexation with Different types of Soluble and Adsorbed Freshwater Ligands Followed by DPASV

In order to understand metal speciation in a polluted river (Este River, Northern Portugal) filtrate, freeze dried particles and organics desorbed from surfaces were titrated with Cd(II) and Zn(II), followed by differential pulse anodic stripping voltammetry (DPASV). The obtained results are compared with those previously published for Pb(II) and Cu(II). Due to the heterogeneity of the system, a continuous and a discrete ligand model were used to interpret the titration data. Two types of ligands could be detected and quantified by the discrete ligand model: small molecules with high affinities for cations such as Cd(II), Cu(I), and Zn(II) and macromolecules with higher affinities for Pb(II) and Cu(II). Small ligands were strongly adsorbed onto the particles, as inferred from the desorption of Zn(II) during titration with Pb(II) and Cd(II). The total concentrations of the different ligands and the complex formation constants with the different metals are reported.     

Analysis of the mobilization of solid loads and heavy metals in runoff waters from granite quarries

The cutting operations of dimension stone at quarries produce a large amount of fines that, in turn, cause a negative environmental impact over local surface waters. This article presents a detailed analysis of the mobilized contamination associated with runoff waters in a large granite quarry (～200 ha) which is located in Porriño (Galicia, NW Spain), the most important production centre of dimension stone in Spain. There, an intensive monitoring survey was developed in order to characterize the hydrology of the system as well as the release and transport of pollutants. This was accomplished by means of different control sections for the flow and by the collection of 52 random water samples. Automatic samplers were also used to collect 192 water samples associated with runoff generated by significant rain events. For each of the samples collected, a wide battery of analytic determinations was performed, including solid loads, turbidity, organic pollution, nutrient and selected metals. Upon careful examination it has been possible to obtain different parameters related to the contamination control, like the “event mean concentration” (EMC), maximum concentrations and specific sediment loads. Moreover, a comprehensive statistical study including parameter correlation and cumulative probability analyses helped to understand the pollutant mobilization behaviour within the quarry system. It can be concluded that mobilized contamination shows the anomalous presence of some metals, whose concentrations are in excess when compared to the natural rock. This excess metal amount must be attributed to an anthropogenic source associated to mining and cutting operations.     

The Serra Pelada Au-PGE deposit, Serra dos Carajás (Pará State, Brazil): geological and geochemical indications for a composite mineralising process

The Serra Pelada Au-PGE-rich deposit is located in the Serra dos Carajás, a leading mining area in Brazil. This region is characterised by a complex geological and structural framework and is affected by deep lateritisation which has lasted for more than 70 Ma. The Serra Pelada deposit is emplaced in a late-Archean low-grade metasedimentary sequence (Rio Fresco/Águas Claras Formation) which is host to other gold deposits in the region (Igarapé Bahia, Águas Claras). The Rio Fresco/Águas Claras sequence was deposited in tectonic basins developed on Archean basement and Au-bearing greenstone terranes which were intruded by PGE-rich layered mafic complexes (e.g. Luanga). The Serra Pelada mineralisation is located along a regional, complex system of strike-slip faults (Cinzento-Carajás systems) which were active during the late Archean to early Proterozoic. The mineralisation appears to be concentrated along a faulted hinge zone of a fold. Ore zone rock facies are dominated by low-grade ferruginous to carbonaceous metasiltstones and minor sandstones, locally brecciated and cemented by quartz (-sulphide) stockwork. Supergene alteration led to partial to total transformation into friable aggregates of kaolinite, Fe oxide-hydroxides, silica and secondary phosphate-sulphates even at depths exceeding 200 m. Precious metals are exceptionally enriched, with up to more than 1,000 ppm Au+PGE in some peculiar ferruginous-graphitic zones locally called "hidrotermalito". Geochemistry shows complex patterns of major and trace elements, particularly rare-earth elements (REE), in mineralised vs. nonmineralised samples. These patterns are interpreted in terms of variable degree of superposition of hydrothermal and supergene alteration. Precious metals show progressive increase from samples with hydrothermal imprint to samples with supergene imprint. The geological evolution of the Carajás region and the characteristics of mineralisation at Serra Pelada may suggest a composite mineralising process: hydrothermal activity (by fluids likely originated from granitoids) was followed by supergene alteration during long-lasting lateritisation to develop extreme precious metal enrichments in a geological context probably already anomalous for Au and PGE.     

Cold subduction zone in northern Calabria (Italy) revealed by lawsonite–clinopyroxene blueschists

Lawsonite blueschists are important markers of cold subduction zones, subjected to intense fluid circulation. This is because lawsonite preservation in exhumed blueschists and eclogites is typically linked to cold exhumation paths, accompanied by hydration. In the Catena Costiera (Calabria, southern Italy), lawsonite–clinopyroxene blueschists of the Diamante–Terranova Unit, affected by ductile shearing and retrogression, are exposed. Blueschists contain zoned clinopyroxene crystals, showing core–rim compositional variation from diopside to omphacite and hosting primary inclusions of lawsonite and titanite. Thermodynamic modelling of phase equilibria in the NCKFMASHTO system revealed peak metamorphic conditions of 2.0–2.1 GPa and 475–490°C for the Alpine subduction in Calabria. The subsequent post-peak metamorphic evolution mainly proceeded along a decompression and cooling path up to ~1.1 GPa and ~380°C. The final exhumation stages are recorded in the sheared blueschists where a mylonitic to ultramylonitic foliation developed at ~0.7 GPa and 290–315°C. Therefore, the P–T evolution of the Diamante–Terranova blueschists mostly occurred in the stability field of lawsonite, sustained by H₂O-saturated conditions during the exhumation path. The results of this study indicate that the blueschists underwent peak metamorphic conditions higher than previously thought, reaching a maximum depth of ~70 km under a very cold geothermal gradient (~6.6°C/km), during the Eocene subduction of the Ligurian Tethys oceanic crust in Calabria.