Assessment of contamination by polychlorinated biphenyls and aliphatic and aromatic hydrocarbons in sediments of the Santos and São Vicente Estuary System, São Paulo, Brazil   总被引：1，自引：0，他引：1  

Bícego MC  Taniguchi S  Yogui GT  Montone RC  Moreira da Silva DA  Lourenço RA  de Castro Martins C  Sasaki ST  Pellizari VH  Weber RR 《Marine pollution bulletin》2006,52(12):1804-1816

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Fractionation,distribution and transport of mercury in rivers and tributaries around Wanshan Hg mining district,Guizhou Province,Southwestern China: Part 2 – Methylmercury     

Hua Zhang  Xinbin Feng  Thorjørn Larssen  Lihai Shang  Rolf D. Vogt  Yan Lin  Ping Li  Hui Zhang 《Applied Geochemistry》2010

Water samples were collected during normal flow (2007) and during a drought period (2008) from five rivers and tributaries draining the Wanshan Hg mining district, Guizhou, China. Unfiltered methylmercury (MeHg) as well as particulate and dissolved fractions of MeHg (P-MeHg, D-MeHg) were measured to assess the spatial and temporal variation of MeHg contamination in the local river system. Most locations (about 80%) displayed higher MeHg concentrations during drought period than during normal discharge conditions. Concentrations of MeHg during the drought period ranged from <0.035 to 11 ng L⁻¹ (geometric mean: 0.43), while during normal flow the concentrations ranged from <0.035 to only 3.4 ng L⁻¹ (geometric mean: 0.21). Concentrations of MeHg were positively correlated with total Hg (THg) concentrations (R² = 0.20–0.58, P < 0.001) and inversely related to distance from the calcines, during both sampling periods (R² = 0.34 and 0.23, P < 0.001, for low and normal flow, respectively) indicating that calcines may be important sources of MeHg to the downstream environment. Approximately 39% of MeHg was bound to particulates and the rest was transported in the dissolved phase along stretches of the entire river, which was different from THg, as this was mainly transported bound to particulates (commonly more than 80%).  相似文献   

The effect of chrysotile nanotubes on the serpentine-fluid Li-isotopic fractionation   总被引：1，自引：0，他引：1  

Bernd Wunder  Fabien Deschamps  Anke Watenphul  Stéphane Guillot  Anette Meixner  Rolf L. Romer  Richard Wirth 《Contributions to Mineralogy and Petrology》2010,159(6):781-790

We determined the lithium isotope fractionation between synthetic Li-bearing serpentine phases lizardite, chrysotile, antigorite, and aqueous fluid in the P,T range 0.2–4.0 GPa, 200–500°C. For experiments in the systems lizardite-fluid and antigorite-fluid, ⁷Li preferentially partitioned into the fluid and Δ⁷Li values followed the T-dependent fractionation of Li-bearing mica-fluid (Wunder et al. 2007). By contrast, for chrysotile-fluid experiments, ⁷Li weakly partitioned into chrysotile. This contrasting behavior might be due to different Li environments in the three serpentine varieties: in lizardite and antigorite lithium is sixfold coordinated, whereas in chrysotile lithium is incorporated in two ways, octahedrally and as Li-bearing water cluster filling the nanotube cores. Low-temperature IR spectroscopic measurements of chrysotile showed significant amounts of water, whose freezing point was suppressed due to the Li contents and the confined geometry of the fluid within the tubes. The small inverse Li-isotopic fractionation for chrysotile-fluid results from intra-crystalline Li isotope fractionation of octahedral Li^[6] with preference to ⁶Li and lithium within the channels (Li^[Ch]) of chrysotile, favoring ⁷Li. The nanotubes of chrysotile possibly serve as important carrier of Li and perhaps also of other fluid-mobile elements in serpentinized oceanic crust. This might explain higher Li abundances for low-T chrysotile-bearing serpentinites relative to high-T serpentinites. Isotopically heavy Li-bearing fluids of chrysotile nanotubes could be released at relatively shallow depths during subduction, prior to complete chrysotile reactions to form antigorite. During further subduction, fluids produced during breakdown of serpentine phases will be depleted in ⁷Li. This behavior might explain some of the Li-isotopic heterogeneities observed for serpentinized peridotites.  相似文献   

Using 87Sr/86Sr, δ18O and δ2H isotopes along with major chemical composition to assess groundwater salinization in lower Shire valley,Malawi     

Maurice Monjerezi  Rolf D. Vogt  Per Aagaard  Asfaw Gebretsadik Gebru  John D.K. Saka 《Applied Geochemistry》2011,26(12):2201-2214

Groundwater resources in some parts of the lower section of Shire River valley, Malawi, are not useable for rural domestic water supply due to high salinity. In this study, a combined assessment of isotopic (⁸⁷Sr/⁸⁶Sr, δ¹⁸O and δ²H) and major ion composition was conducted in order to identify the hydro-geochemical evolution of the groundwater and thereby the causes of salinity. Three major end-members (representing fresh- and saline groundwater, and evaporated recharge) were identified based on major ion and isotopic composition. The saline groundwater is inferred to result from dissolution of evaporitic salts (halite) and the fresh groundwater shows influence of silicate weathering. Conservative mixing models show that brackish groundwater samples result from a three component mixture comprising the identified end-members. Hence their salinity is interpreted to result from mixing of fresh groundwater with evaporated recharge and saline groundwater. On the other hand, the groundwater with low TDS, found at some distance from areas of high salinity, is influenced by mixing of evaporated recharge and fresh groundwater only. Close to the Shire marshes, where there is shallow groundwater, composition of stable isotopes of water indicates that evaporation may also be an important factor.  相似文献   

Early Wisconsinan (MIS 4) Arctic ground squirrel middens and a squirrel-eye-view of the mammoth-steppe     

Grant D. Zazula  Duane G. Froese  Scott A. Elias  Svetlana Kuzmina  Rolf W. Mathewes 《Quaternary Science Reviews》2011,30(17-18):2220-2237

Fossil arctic ground squirrel (Spermophilus parryii) middens were recovered from ice-rich loess sediments in association with Sheep Creek-Klondike and Dominion Creek tephras (ca 80 ka) exposed in west-central Yukon. These middens provide plant and insect macrofossil evidence for a steppe-tundra ecosystem during the Early Wisconsinan (MIS 4) glacial interval. Midden plant and insect macrofossil data are compared with those previously published for Late Wisconsinan middens dating to ～25–29¹⁴C ka BP (MIS 3/2) from the region. Although multivariate statistical comparisons suggest differences between the relative abundances of plant macrofossils, the co-occurrence of steppe-tundra plants and insects (e.g., Elymus trachycaulus, Kobresia myosuroides, Artemisia frigida, Phlox hoodii, Connatichela artemisiae) provides evidence for successive reestablishment of the zonal steppe-tundra habitats during cold stages of the Late Pleistocene. Arctic ground squirrels were well adapted to the cold, arid climates, steppe-tundra vegetation and well-drained loessal soils that characterize cold stages of Late Pleistocene Beringia. These glacial conditions enabled arctic ground squirrel populations to expand their range to the interior regions of Alaska and Yukon, including the Klondike, where they are absent today. Arctic ground squirrels have endured numerous Quaternary climate oscillations by retracting populations to disjunct “interglacial refugia” during warm interglacial periods (e.g., south-facing steppe slopes, well-drained arctic and alpine tundra areas) and expanding their distribution across the mammoth-steppe biome during cold, arid glacial intervals.  相似文献   

The Sarikavak Tephra, Galatea, north central Turkey: a case study of a Miocene complex plinian eruption deposit     

Rolf Schumacher  Ulrike Mues-Schumacher  Vedat Toprak 《Journal of Volcanology and Geothermal Research》2001,112(1-4)

The Sarikavak Tephra from the central Galatean Volcanic Province (Turkey) represents the deposit of a complex multiple phase plinian eruption of Miocene age. The eruptive sequence is subdivided into the Lower-, Middle-, and Upper Sarikavak Tephra (LSKT, MSKT, USKT) which differ in type of deposits, lithology and eruptive mechanisms.The Lower Sarikavak Tephra is characterised by pumice fall deposits with minor interbedded fine-grained ash beds in the lower LSKT-A. Deposits are well stratified and enriched in lithic fragments up to >50 wt% in some layers. The upper LSKT-B is mainly reversely graded pumice fall with minor amounts of lithics. It represents the main plinian phase of the eruption. The LSKT-A and B units are separated from each other by a fine-grained ash fall deposit. The Middle Sarikavak Tephra is predominantly composed of cross-bedded ash-and-pumice surge deposits with minor pumice fall deposits in the lower MSKT-A and major pyroclastic flow deposits in the upper MSKT-B unit. The Upper Sarikavak Tephra shows subaerial laminated surge deposits in USKT-A and subaqueous tephra beds in USKT-B.Isopach maps of the LSKT pumice fall deposits as well as the fine ash at the LSKT-A/B boundary indicate NNE–SSW extending depositional fans with the source area in the western part of the Ovaçik caldera. The MSKT pyroclastic flow and surge deposits form a SW-extending main lobe related to paleotopography where the deposits are thickest.Internal bedding and lithic distribution of the LSKT-A result from intermittent activity due to significant vent wall instabilities. Reductions in eruption power from (partial) plugging of the vent produced fine ash deposits in near-vent locations and subsequent explosive expulsion of wall rock debris was responsible for the high lithic contents of the lapilli fall deposits. A period of vent closure promoted fine ash fall deposition at the end of LSKT-A. The subsequent main plinian phase of the LSKT-B evolved from stable vent conditions after some initial gravitational column collapses during the early ascent of the re-established eruption plume. The ash-and-pumice surges of the MSKT-A are interpreted as deposits from phreatomagmatic activity prior to the main pyroclastic flow formation of the MSKT-B.  相似文献   

Modelling of the nighttime nitrogen and sulfur chemistry in size resolved droplets of an orographic cloud     

Rolf Sander  Jos Lelieveld  Paul J. Crutzen 《Journal of Atmospheric Chemistry》1995,20(1):89-116

A chemistry module has been incorporated into a Lagrangian type model that computes the dynamics and microphysics of an orographical cloud formed in moist air flowing over the summit of Great Dun Fell (GDF) in England. The cloud droplets grow on a maritime aerosol which is assumed to be an external mixture of sea-salt particles and ammonium-sulfate particles. The dry particle radii are in the range 10 nm<r<1 µm. The gas-phase chemical reaction scheme considers reactions of nitrogen compounds that are important at night. The treatment of scavenging of gases into the aqueous phase in the model takes into account the different solubilities and accommodation coefficients. The chemistry in the aqueous phase focusses on the oxidation of S(IV) via different pathways.Sensitivity analyses have been performed to investigate deviations from gas-liquid equilibria according to Henry's law and also to study the influence of iron and of nitrogen compounds on the aqueous-phase oxidation of dissolved SO₂. When addressing these questions, special attention has been given to the dependence on the droplet size distribution and on the chemical composition of the cloud condensation nuclei on which the droplets have formed. It was found that the oxidation of S(IV) via a chain reaction of sulfur radicals can be important under conditions where H₂O₂ is low. However, major uncertainties remain with respect to the interaction of iron with the radical chain. It was shown that mixing of individual cloud droplets, which are not in equilibrium according to Henry's law, can result in a bulk sample in equilibrium with the ambient air. The dependence of the aqueous-phase concentrations on the size of the cloud droplets is discussed for iron, chloride and NO₃.  相似文献   

Modeling Atmospheric Chemistry: Interactions between Gas-Phase Species and Liquid Cloud/Aerosol Particles     

Rolf Sander 《Surveys in Geophysics》1999,20(1):1-31

For detailed modeling of atmospheric chemistry it is necessary to consider aqueous-phase reactions in cloud droplets and deliquesced aerosol particles. Often, the gas-phase concentration is in equilibrium with the aqueous phase. Then Henrys law can be used to describe the distribution between the phases provided that the Henrys law coefficient is known. In some cases, thermodynamic equilibrium will not be reached and it is necessary to use kinetic expressions of the rates involved. These rates depend on diffusion constants, accommodation coefficients, Henrys law coefficients, particle size distributions, and several other parameters. This review describes how these processes can be treated in computer modeling and how the necessary data can be obtained. Even though it is written primarily for use in modeling atmospheric chemistry, some parts will also be useful for waste water and pesticide control and in other areas where the distribution of chemicals between the aqueous and the gas phase is important.  相似文献   

Baugeologische Probleme bei der Gründung des Biggekraftwerkes auf verkarsteten Devonischen Riffkalken im Sauerland und ihre Lösung     

Rolf Klopp 《Rock Mechanics and Rock Engineering》1969,1(2-3):145-156

ZusammenfassungBaugeologische Probleme bei der Gründung des Biggekraftwerkes auf verkarsteten Devonischen Riffkalken im Sauerland und ihre Lösung Im nördlichen Gründungsbereich des Kraftwerkes der Biggetalsperre im Sauerland tauchten steilstehende, kalkige Schichten auf, in die Riffkalkklötze von unterschiedlicher Verteilung eingelagert waren. Während die Kalkmergelschiefer nur starke Entkalkungserscheinungen aufwiesen, zeigten sich in den Riffkalkzonen echte Karsthohlräume.Die Ecke eines wesentlichen Bauwerksteiles des Kraftwerkes lag über einer kolkartig eingebrochenen und mit Geröllen gefüllten Karsthöhle. Diese Kraftwerksbereiche wurden daher auskragend konstruiert. Die Lasten mußte das südlich anschließende nichtverkarstete Gebirge aufnehmen. Das völlig regellose Auftauchen verkarsteter Riffbereiche ließ aber die Gefahr vermuten, daß auch der standfeste Gebirgsteil durch Karsteinbrüche unterschnitten werden könnte. Dies umso mehr, als die Schichtung in Richtung des Karstkolkes einfiel und Schichtpakete des an sich standfesten Gebirges abgleiten könnten. Um dies zu verhindern, wurden den besonderen Verkarstungsbedingungen angepaßte systematische Injektionen in 3 Phasen ausgeführt. Eingepreßt wurde ein Gemisch aus ca. 70% Zement, 25% Sand und 5% Bentonit.Als wesentlichste Folgerung für den Felsbau werden die Unterschiede der Verkarstung zwischen homogenen Kalksteinen und Riffkalksteinen herausgestellt.Zur sicheren Gründung von Bauwerken wird eine ausreichende baugeologische Untersuchung, enge Zusammenarbeit zwischen Geologen und Ingenieur während der Planung und beim Bau sowie Anpassung der Bauausführung an die Besonderheiten des Karstes empfohlen.

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SummaryEngineering Geological Problems During the Foundation of the Biggetal Power Plant on Karstified Devonian Reef Limestones in the Sauerland, and Their Solution In the northern foundation of the powerstation of the Biggetalsperre in Sauerland inclined marly slate with intercalated parts of reef knolls of different distribution is existing. These marly slate shows partly heavy decalcification. But the reef knolls exclusively were cavernous.The corner of an essential part of the powerstation was situated above a collapsed underground karstbridge, now filled with gravel. Therefore this part was constructed with cantilever and the weight had to be borne by the noncavernous rock neighboured in the south.The appearance of karstificated reef knolls without any preferred orientation seemed to be a danger for the stability of the rock in the south, that had to bear the total weight of the construction. This danger existed also in undercutting the solid rock. Beyond it the strata fell in the direction of the karst holes and therefore some sedimentary complexes of this rock incline to sliding. To prevent this a systematic injection program was started, the injection material consisting of 70% cement, 25% sand and 5% bentonite.The most important conclusions for construction in rock are that it is necessary to distinguish between the karstification of homogeneous limestone and rock with reefknollfacies. To obtain a solid foundation in such rock sufficient geological investigations are necessary. A tight teamwork between geologists and engineers during the planning period and the time of construction is as neccessary as to accomodate the construction on the speciality of karst.

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RésuméProblèmes géologiques posés par la fondation de la centrale du barrage du Bigge sur les calcaires coralliens karstiques du Devonien dans le Sauerland et ses solutions Cet article traite la fondation de la centrale du barrage du Bigge (Biggetalsperre) construite sur des couches calcaires du Devonien moyen supérieur dans le Sauerland (Allemagne occidentale).Dans la zone nord des fondations on est en présence de stratifications calcaires fortement inclinées parmi lesquelles se trouvent des blocs coralliens intercalés avec une répartition variable. Alors que les schistes marneux accusent une décalcification prononcée, de véritables vides karstiques apparaissent dans les zones coralliennes.La pointe d'une partie importante de l'ouvrage se trouvait justement sur une cavité karstique creusée depuis longtemps et à présent remplie d'éboulis (cailloux). Cette partie de la centrale fut construite en porte à faux. Les charges résultant de cette construction sont transmises à la partie sud non karstique du massif.L'émergement tout à fait irrégulier des récifs karstiques faisait apparaître le risque de voir la partie saine du massif se fragmenter sous l'influence de phénomènes karstiques. Ceci d'autant plus que la stratification avait un pendage vers le calcaire corallien et que l'ensemble des couches d'un rocher sain en lui-même pouvait glisser. Pour écarter ce risque un programme systématique d'injection fut entrepris en suivant un mode opératoire particulier s'accommodant aux phénomènes karstiques. Le coulis d'injection utilisé était un mélange d'environ 70% de ciment, 25% de sable et 5% de bentonite.L'apport essentiel pour la mécanique des roches est constitué par la différence qui a été faite concernant les phénomènes karstiques entre les calcaires homogènes et les calcaires coralliens. Pour effectuer une fondation sure d'ouvrages il est conseillé de faire des études géologiques suffisantes, d'avoir une coopération étroite entre le géologue et l'ingénieur pendant le projet et lors de la construction et enfin d'adopter les procédés de construction aux phénomènes karstiques.

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Mit 4 Abbildungen  相似文献   

Stable and Unstable Eigensolutions of Laplace’s Tidal Equations for Zonal Wavenumber Zero   总被引：1，自引：0，他引：1  

Rolf Müller 《大气科学进展》1993,10(1):21-40

Laplace's tidal equations are of great importance in various fields of geophysics. Here, the special case of zonal symmetry (zonal wavenumber m = 0) is investigated, where degenerate sets of eigensolutions appear. New results are presented for the inclusion of dissipative processes and the case of unstable conditions. In both instances the (nonzero) eigenfrequencies are complex. In the latter case, additional stable (i.e. real) eigenfrequencies appear in the numerical results for the absolute value of the Lambparameter ε being larger than a critical value εc. Further, it is shown that any degeneracies are removed through the inclusion of dissipation. Moreover, asymptotic relations are derived employing the relation of Laplace's tidal equations for m = 0 to the spheroidal differential equation. The implications of these findings to numerical techniques are demonstrated and results of computations are presented.  相似文献