Comparison of nitrate attenuation characterization methods at the Uranium mill tailing site in Monument Valley, Arizona

Several methods for characterizing the occurrence and rate of nitrate attenuation were tested at a field site near Monument Valley, Arizona. Spatial and temporal nitrate concentration data collected from a transect of monitoring wells located along the plume centerline were analyzed to evaluate the overall rates of natural attenuation. The occurrence and rate of denitrification was evaluated through microcosm experiments, nitrogen isotopic fractionation analysis, and solute-transport modeling. First-order denitrification-rate coefficients calculated with each method were comparable. In addition, the composite natural attenuation rate coefficient was similar to the denitrification-rate coefficients, which suggests that microbially induced decay primarily controls nitrate attenuation at the site. This research highlights the benefits associated with a multiple-method approach for the characterization of natural attenuation.     

Settlement and sustainability in the Polish Sudetes

The paper summarises the history of human settlement in the Sudetes from the Bronze Age. A more intensive stage was reached in the Middle Ages when settlers from the west established new villages deep in the mountain valleys. By the beginning of the 20th century the Sudetes were already overpopulated but after a near-complete ethnic replacement from a German to a Polish population in 1945–8, population continued to grow until the 1980s. However, the economic system was hardly sustainable by this time. There were many polluting industries in the region and massive transboundary pollution from adjacent areas of Czechoslovakia and Germany had a devastating effect on the forests. Moreover, subsidised state agriculture placed heavy pressure on vulnerable mountain grazings. Since 1989 there has been a process of deindustrialisation in the Sudetes and surrounding areas and, with the disappearance of the state farms and the reduction in subsidies, agriculture is now better adjusted to the natural potential and is complemented by a promising start with agrotourism. The population of the region is growing relatively slowly (0.8% per annum 1956–1999), with the rural areas now in decline. A sustainable future for the region is now a possibility, but while there is a consensus for continued environmental reconstruction, supported by alternative economies, this will have to be carefully managed in the years ahead when EU accession may bring heavier development pressures than those evident at the moment. This revised version was published online in July 2006 with corrections to the Cover Date.     

CO2 exchange at air-sea interface in the Huanghai Sea

INTRODUCTIONTheroleoftheoceaniscrucialintheoverallcycleofCOZ,withitsspecialpumpingmechanismssuchassolubilitypumpingattheair-seainterfacewithcarbonatechemistry,biologicalpumpinginsurfacewatersandalsointhewatercolumn,anddynamicpumpingassociatedwithoceancirculation(BroeckerandPeng,1982).Inordertounderstandthesevariouspumpingprocessesintheocean,muchresearchhasbeencarriedoutonaglobalscaleasapartofeffortstounderstandtheglobalgeochemicalcycleofCOZ.TheHuanghaiSea,atypicalmid-latitudeepicontine…     

Last glacial sea-level changes and paleogeography of the Korea (Tsushima) Strait

The Korea (Tsushima) Strait is an important seaway through which the warm Tsushima Current flows into the East Sea (Japan Sea). A paleogeographic map constrained by a regional sea-level curve developed on the basis of a number of recent ¹⁴C radiocarbon dates suggests that the Korea Strait was not closed during the last glacial period. Rather, it was open as a channel-like seaway linking the western North Pacific and the East Sea. Some fraction of the paleo-Tsushima Current inflow presumably continued at that time through the Korea Strait. The activity of the paleo-Tsushima Current is evidenced by the distribution pattern of river-derived lowstand deposits, consisting of a beach/shoreface complex and lowstand deltaic wedges. Received: 16 April 1999 / Revision accepted: 25 February 2000     

Experiments on the ocean sequestration of fossil fuel CO2: pH measurements and hydrate formation

We have carried out a series of in situ experiments to investigate the formation of a CO₂ hydrate (CO₂:5.75 H₂O) for the purpose of evaluating scenarios for ocean fossil fuel CO₂ disposal with a solid hydrate as the sequestered form. The experiments were carried out with a remotely operated vehicle in Monterey Bay at a depth of 619 m. pH measurements made in close proximity to the hydrate–seawater interface showed a wide range of values, depending upon the method of injection and the surface area of the hydrate formed. Rapid injection of liquid CO₂ into an inverted beaker to form a flocculant mass of hydrate resulted in pH initially as low as 4.5 within a few centimeters of the interface, decaying slowly over 1–2 h towards normal seawater values as dense CO₂ rich brine drained from the hydrate mass. In a second experiment, slower injection of the liquid CO₂ to produce a simple two-layer system with a near planar interface of liquid CO₂ with a thin hydrate film yielded pH values indistinguishable from the in situ ocean background level of 7.6. Both field and laboratory results now show that the dissolution rate of a mass of CO₂ hydrate in seawater is slow but finite.     

Tidal Vorticity around a Coastal Promontory

The vorticity generation around a coastal promontory is examined using a transport vorticity equation. The complete vorticity balance analysis is made for the transient and residual vorticity generations around an idealized, symmetric promontory. The topographic vorticity tendency is found to be the dominant forcing term in the production of transient tidal vorticities. This result is different from the previous works which emphasized the effects of lateral and bottom frictions. The residual vorticity balance is between advection and topographic vorticity tendency. The model results are consistent with the observations off Gay Head, Massachusetts. Also, the stability of a promontory as well as the offshore sand bank formation are studied by examining the sand transport pattern around the promontory. Strong deposition occurs off the tip of the promontory while erosion occurs along the upstream slope of the promontory suggesting that an originally symmetric promontory tends to incline cyclonically from the axis normal to the tidal stream. Such tendency is indeed found among coastal promontories.     

Evolution of the eastern margin of Korea: Constraints on the opening of the East Sea (Japan Sea)

We interpreted marine seismic profiles in conjunction with swath bathymetric and magnetic data to investigate rifting to breakup processes at the eastern Korean margin that led to the separation of the southwestern Japan Arc. The eastern Korean margin is rimmed by fundamental elements of rift architecture comprising a seaward succession of a rift basin and an uplifted rift flank passing into the slope, typical of a passive continental margin. In the northern part, rifting occurred in the Korea Plateau that is a continental fragment extended and partially segmented from the Korean Peninsula. Two distinguished rift basins (Onnuri and Bandal Basins) in the Korea Plateau are bounded by major synthetic and smaller antithetic faults, creating wide and considerably symmetric profiles. The large-offset border fault zones of these basins have convex dip slopes and demonstrate a zig-zag arrangement along strike. In contrast, the southern margin is engraved along its length with a single narrow rift basin (Hupo Basin) that is an elongated asymmetric half-graben. Analysis of rift fault patterns suggests that rifting at the Korean margin was primarily controlled by normal faulting resulting from extension rather than strike-slip deformation. Two extension directions for rifting are recognized: the Onnuri and Hupo Basins were rifted in the east-west direction; the Bandal Basin in the east–west and northwest–southeast directions, suggesting two rift stages. We interpret that the east–west direction represents initial rifting at the inner margin; while the Japan Basin widened, rifting propagated southeastward repeatedly from the Japan Basin toward the Korean margin but could not penetrate the strong continental lithosphere of the Korean Shield and changed the direction to the south, resulting in east–west extension to create the rift basins at the Korean margin. The northwest–southeast direction probably represents the direction of rifting orthogonal to the inferred line of breakup along the base of the slope of the Korea Plateau; after breakup the southwestern Japan Arc separated in the southeast direction, indicating a response to tensional tectonics associated with the subduction of the Pacific Plate in the northwest direction. No significant volcanism was involved in initial rifting. In contrast, the inception of sea floor spreading documents a pronounced volcanic phase which appears to reflect asthenospheric upwelling as well as rift-induced convection particularly in the narrow southern margin. We suggest that structural and igneous evolution of the Korean margin, although it is in a back-arc setting, can be explained by the processes occurring at the passive continental margin with magmatism influenced by asthenospheric upwelling.     

含硫化物镁铁质-超镁铁质侵入体中橄榄石Mg、Ni含量的制约:原理、模式及Voisey's Bay侵入体样品研究

镁铁质-超镁铁质岩浆结晶分离早期形成镁铁矿物,镁铁矿物中的Ni和Mg是相容元素。随着结晶分离作用的进行,Ni、Mg在硅酸盐岩浆及后形成的硅酸盐物质中的丰度下降。橄榄石中Ni含量及硅酸盐物质MgO/FeO比值都与母岩浆的相关值相关,据此可推断母岩浆的信息,它们之间可由实验测得的系数相联系。当岩浆饱和硫化物时,在结晶分离过程中硫化物珠滴会与镁铁硅酸盐物质一道析出,同时,与硫化物非饱和岩浆相比,过多的Ni会随之析出。这也反映在Ni、Mg含量比无硫化物分离时有更迅速的降低上。Ni、Mg含量变化值可以在VoiseysBay侵入体的模式曲线上反映出,加拿大Labrador的这一侵入体赋存了一个世界级的Ni-Cu-Co硫化物矿床。过去的作法是将侵入体中橄榄石的Ni、Mg含量与Simkin和Smith得出的各种火成岩中橄榄石的Ni、Mg含量相比较以确定Ni亏损,进而假定橄榄石来自硫化物饱和、有经济价值的岩浆。现在的研究显示这种简单的对比会导致错误。将样品数据与模式曲线对比并反映出侵入体矿物结晶堆积特征是重要的方法。使用这一方法,样品数据能很好地被模式曲线拟合。以在VoiseysBay的研究为例,当硫化物液相与硅酸盐矿物被去除后,硫化物非饱和的分离作用期就会显现出来,随后是硅酸盐结晶作用期。     

Hydrometallurgical processing and recovery of molybdenum trioxide from spent catalyst

Hydrometallurgical processing of spent hydrodesulphurisation (HDS) catalyst for the recovery of molybdenum using sodium carbonate and hydrogen peroxide mixtures was investigated. The results indicated that the recovery of molybdenum was largely dependent on the concentrations of Na₂CO₃ and H₂O₂ in the reaction medium, which controls the acidity of the leach liquor and carry over of impurities such as Al, Ni, P, Si and V. Leaching process was exothermic and leaching efficiency of molybdenum decreased with increasing solid to liquid ratio. Large scale leaching of spent catalyst, under optimum conditions: 20% pulp density, 85 g/L Na₂CO₃, 10 vol.% H₂O₂ and 1 h reaction, resulted a leaching efficiency of 84% Mo. The obtained leach liquor contained (g/L): Mo — 22.0, Ni — 0.015 and Al — 0.82, P — 1.1, Si — 0.094 and minor quantities of V — 8 mg/L, As and Co — < 1 mg/L. Recovery of Mo from leach solution as MoO₃ of 97.30% purity was achieved by ammonium molybdate precipitation method.     

Microstructures of deformed grains in the augen gneisses of southern Menderes Massif (western Turkey) and their tectonic significance

A detailed fabric and microstructural analysis of the granitic mylonites was carried out on the southern side of Bes,parmak Mountain north of Selimiye (Milas). The mylonitic augen gneisses have?a blastomylonitic texture characterized by large retort-shape porphyroclasts or augen of feldspars, around which a more ductile, medium to fine-grained matrix of muscovite, biotite, quartz and feldspar is deflected. Feldspars behave in both plastic and brittle fashion, because size reduction occurs through grain boundary migration and/or subgrain rotation, and also through fracturing. Typical “core-and-mantle” structure, characterized by a large feldspar core surrounded by a mantle of fine recrystallized grains, is very characteristic. The majority of plagioclase twins obey the albite-twin law; however, the association with pericline-law twinning suggests that many of the twins are mechanical. Evidence of strain, such as deformation twins, bent or curved twins, undulatory extinction, deformation bands and kink bands occur characteristically in plagioclase. Myrmekite is ubiquitous at K-feldspar grain boundaries, most notably on the long sides of inequant grains parallel to the S-foliation direction, which invariably face the maximum finite shortening direction. Deformation of quartz in mylonitic augen gneisses commonly results in the development of core-and-mantle structure and “type-4” quartz ribbons of elongated, preferably oriented, newly recrystallized quartz aggregates suggesting a primary dynamic recrystallization. Undulatory extinction, deformation bands and lamellae are the strain-related features associated with quartz porphyroclasts. Micas, especially biotite, undergo internal deformation by bend gliding and kinking. Most of the micas are completely attenuated and aligned such that their (001) planes are subparallel or parallel to the margins of quartz ribbons and define the foliation in the rock. These microstructures of feldspars, quartz and mica in the mylonitic augen gneisses in this part of the southern Menderes Massif are broadly consistent with fabric development under upper-greenschist- to lower-amphibolite-facies conditions, rather than almandine–amphibolite facies, as was previously believed. This supports the previous contention of the authors that the protoliths of augen gneisses are younger granitoids and do not represent an exposed Precambrian Pan-African basement in the Menderes Massif.