海水入侵模拟方法VFT3D及应用

海水入侵是困扰沿海地区经济社会发展的重大资源、环境问题,严重影响沿海地区地下水资源。定量模拟、预测和可视化管理是对海水入侵进行有效监测和机理分析的重要手段。基于前期海水入侵模拟的理论研究及方法,提出了海水入侵模拟及预测模型VFT3D,该模型综合考虑地表水-地下水对海水入侵的协同控制作用,能够模拟变密度地下水流及复杂反应性迁移,实现模拟海水入侵的完整水文循环过程。文章介绍了VFT3D模型,利用VFT3D模型模拟了一个海水入侵案例,并与SEAWAT模型模拟结果进行了对比分析。结果表明VFT3D 模型模拟水头与SEAWAT模型模拟结果相差不大,但SEAWAT模型无法模拟海水入侵中复杂的化学反应过程。VFT3D 模型模拟发现,水文地球化学过程（阳离子吸附交换作用）对阳离子（Na+、K+、Mg2+和Ca2+）运移产生明显影响,同时引起过渡带中离子组分浓度发生变化,对海水入侵过程产生较大影响。因此,考虑变密度和复杂反应过程,才能更加准确地描述海水入侵,从而有利于地下咸水治理工程的科学实施。     

Panel 5: Chemical processes at the ocean bottom

Novel techniques and existing knowledge from chemical research that could be applied to understanding processes at the ocean bottom are by and large analytical, but not entirely. Microelectrodes developed for both the study of electron transfer at interfaces and for application in medical research could be readily modified to investigate gradients at the sediment-water interface. The body of knowledge assembled for, and derived from, election transfer research should be a valuable resource of understanding the mechanisms of redox reactions that occur in the ocean. Chemiluminescent methods for measuring metals in seawater would become much more generally applicable if additional luminescing compounds that chelate metals with great specificity could be identified or synthesized. Collaboration with analytical chemists might enable the development of this method to a wide variety of marine analytical problems. Recent advances in optical detector technology should catalize the adaptation of chemiluminescent methods to in situ analysis.A variety of separation techniques developed for chemical research could be applied to the problems of separating both dissolved and particulate organic matter from their natural matrices. If this can be accomplished it will remove a major barrier in the characterization of organic matter in the ocean. A potential approach for determining the biochemical character of this material after separation is degradation using bacterial enzymes, and then identification of subunits of the polymers by techniques such as ¹³C-NMR.Relatively recent application of GC-MS and high pressure liquid chromatography to marine organic analysis has already produced more data than is interpretable by marine organic chemists. Chemometric and statistical methods developed by chemists to maximize data interpretation could be used to interpret large data sets plan future experimental approaches.High analytical precision and extremely low detection limits are prerequisites for solving many of the problems associated with hydrothermal circulation and paleoceanography. Some examples of emerging analytical methodology for improving these are echelle spectrography coupled with highly sensitive charge transfer device detectors to enable determination of elemental ratios at high precision, and ICP-mass spectrometry which achieves very low detection limits for some elements.     

Strontium isotope geochemistry of Icelandic geothermal systems and implications for sea water chemistry

Chemical and Sr isotopic analyses have been made of waters from 16 geothermal sites in Iceland with particular reference to the systems at Reykjanes and Svartsengi for which compositions of geothermal sea water and fresh and hydrothermally-altered rocks have been compared. The alkalies display mixing relationships indicating a hydrothermal input of Rb and K to local meteoric and sea waters as do results for Sr and Ca involving high-temperature fluids. ${}^{87}\text{Sr}{}^{86}\text{Sr}$ ratios of the geothermal waters of meteoric origin parallel those of associated rocks but are higher. Ratios for geothermal sea waters are 0.7042 (Reykjanes) and 0.7040 (Svartsengi), lower than for normal sea water (0.7092) because of leaching of Sr from rocks followed by partial removal into alteration minerals, of which epidote and chlorite may be most important. Consequently, associated hydrothermally-altered rocks have been subject to significant Sr isotopic contamination by sea water Sr raising ${}^{87}\text{Sr}{}^{86}\text{Sr}$ ratios from 0.7032 for fresh rock to 0.7038–0.7042 (Reykjanes) and to 0.7039–0.7041 (Svartsengi). Altered basalt is only ~50% equilibrated isotopically with geothermal sea water, at a water/rock ratio of ~2, but is internally equilibrated whereas palagonitized rocks (water/rock ratio of 3 to 4) are close to Sr isotopic equilibrium with associated sea water but show significant internal Sr disequilibrium. Hydrothermal input is unlikely to be important in the oceanic mass balance of Sr but is likely to be highly significant in controlling the strontium isotopic composition of sea water.     

Chemical reactions of sea water with rocks and freshwater: Experimental and field observations on brackish waters in Israel

Four major processes are observed to take place in the coastal aquifer of Israel, detectable even in the short times of water contact with the carbonate-containing host rocks. Three are chemical reactions, Ca²⁺-Mg²⁺ exchange, Na⁺-Ca²⁺ or Na⁺-Mg²⁺ base exchange, SO^2?₄ reduction and the fourth is dilution by freshwater. These reactions and their effects on the chemical composition of the waters were demonstrated experimentally. The range of chemical changes observed in the laboratory experiments overlap the range of the studied natural waters. This indicates that simulation of geologically long-term rock-water interaction could be achieved in laboratory experiments even at low temperatures.     

Chemical models of vitrinite reflectance evolution

A global kinetic model of vitrinite reflectance evolution is developed to illustrate a new approach to vitrinite reflectance modelling. The method utilizes quantitative pyrolysisgas Chromatographic data from isolated vitrinite kerogens to derive the concentrations of structurally specific moieties (alkylphenol precursors) in vitrinite kerogens as a function of rank. This data set is used to calibrate a gaussian distributed activation energy model for phenol-precursor loss from vitrinites using published burial histories. Phenol yield is then correlated with vitrinite reflectance. The predictive vitrinite reflectance model based on this phenol system is tested against a well from the US Gulf Coast area, the results being compared with a Lopatin model of the same well. This type of vitrinite reflectance model is numerically compatible with current generation kinetic models of hydrocarbon production from source rock kerogens, and has a better heating rate independence than Lopatin's method.

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Zusammenfassung Um eine neue Annäherung an das Modellieren der Vitrinit-Reflexion zu demonstrieren, wurde ein global-kinetisches Modell der Entwicklung der Vitrinit-Reflexion erstellt. Die Methode verwendet Daten von quantitativer Pyrolyse-Gas Chromatographie isolierten Vitrinitkerogens, um die Konzentration von strukturspezifischen Moieten (Alkylophenol-Vorläufer) in Vitrinitkerogen als Funktion der Reihenfolge zu erhalten. Verwendet werden diese Daten, um ein nach Gauss verteiltes Aktivierungsenergiemodell zu kalibrieren, das mit Hilfe von veröffentlichten Ablagerungsgeschichten den Phenol-Vorläuferverlust von Vitriniten beschreibt. Die Phenol-Ausbeute wird dann mit der Vitrinit-Reflexion korreliert. Das auf dem Phenolsystem basierende Vitrinit-Reflexionsmodell wird in einem Test einem Bohrloch an der amerikanischen Golfküste gegenübergestellt. Die Ergebnisse werden mit dem Lopatinmodell des selben Bohrlochs verglichen. Diese Art eines Vitrinit-Reflexionsmodells ist numerisch wettbewerbsfähig mit der heutigen Generation kinetischer Modelle der Kohlenwasserstofferzeugung aus Trägergesteinskerogenen. Außerdem ist seine Unabhängigkeit von der Erhitzungsrate größer als mit der Lopatin-Methode.

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Résumé L'auteur présente un modèle cinétique global de l'évaluation du pouvoir réflecteur de la vitrinite, afin d'illuster une approche nouvelle dans la modélisation de ce pourvoir réflecteur. Cette méthode utilise des données quantitatives fournies par la pyrolyse combinée à la Chromatographie en phase gazeuse et relatives à des kérogènes de vitrinite. A partir de ces données, on exprime les concentrations des fractions à structure spécifique dans les kérogènes vitrinitiques en fonction du degré d'évolution. A partir de cet ensemble de données, on établit un modèle de l'énergie d'activation selon une distribution gaussienne, applicable à la perte de phénol-précurseur dans les vitrinites, en se référant à cet effet aux déroulements historiques de l'enfouissement fournis par la littérature. La production de phénol est alors mise en relation avec le pourvoir réflecteur de la vitrinite. Le modèle du pouvoir réflecteur prévisible, basé sur ce système des phénols a été contrôlé dans un forage de la côte du golfe du Mexique (USA), et les résultats comparés à ceux du modèle de Lopatin appliqué au même forage. Le modèle présenté est numériquement compatible avec les modèles cinétiques habituels qui rendent compte de la production d'hydrocarbure à partir des kérogènes des roches-mères; il présente une meilleure indépendance que la méthode de Lopatin par rapport au taux d'échauffement.

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The equilibration of clay minerals with sea water: exchange reactions

Studies of seawater-sediment and seawater-clay mineral exchange equilibria demonstrate that rinsing procedures employed in many previous studies have grossly shifted the exchange equilibria away from the true seawater conditions. Exchange complements have been determined here by measurement of compositional changes in seawater that result from reaction with clays, thereby avoiding rinsing. These data show that exchangeable Na⁺ is normally greater than or equal to exchangeable Mg²⁺ on clays and sediments in exchange equilibrium with seawater.On introduction to seawater, fluvial clays are shown to give up their exchangeable Ca²⁺ for Na⁺, a process of importance in the geochemical budget of Na⁺.     

Chemical geothermometry in geothermal systems

The application of chemical and isotopic geothermometry to geothermal systems is reviewed, pointing out the uses and limitations of specific reactions in estimating deep temperatures from well, hot-spring and fumarole discharges.At present the most reliable indicators are: the silica-water equilibria; the Na/K ratio; the isotopic distributions Δ²H(H₂“H₂O), Δ²H(H₂“CH₄), Δ¹⁸O(H₂O“HSO^?₄); and the gas reactions CO₂ + 4H₂ ? CH₄ + 2H₂O, and 2NH₃ ? N₂ + 3H₂. Many other qualitative chemical indicators exist.     

The extension of chemical models for sea water to include trace components at 25°C and 1 atm pressure

Chemical models for sea water based on the Brønsted-Guggenheim hypothesis of specific ionic interaction and on the ionic interaction equations of Pitzer are extended to encompass a range of trace constituents. Conventional single-ion activity coefficients of 23 trace components in sea water are listed over a range of ionic strengths (0.2–3 M) together with the ionic interactions that have been accounted for in their calculation. It is suggested that these data might provide the basis of a coherent (hybrid) model for sea water incorporating many of the advantages of the ion-association and specific interaction models.     

Thermodynamic models in cosmochemical systems

Generalized computer methods are developed for inferring details of the formation of cosmochemical systems. Compositions of ideal gas mixtures existing in equilibrium with multicomponent solid and liquid phases are calculated. A comparison of computed results with experimental data is made for the ternary system MgO-FeO-SiO₂. While the ideal-solution approximation is shown to be inaccurate in dealing with the silicate melts, in a system where there are only solids and gas, the stable phases and compositions can be accurately calculated. A model system containing the elements H, O, Si, Mg, S, C, Cl and F is investigated over a range of compositions involving the gas and ten solid phases, to show the power of the technique in dealing with complex gas-solid equilibria. Systems close to cosmic composition are next considered, both with and without iron. When present, most of the iron is computed to be in the metallic state with little going into pyroxene or olivine solid solutions. At low hydrogen concentration and low temperature, troilite becomes the stable iron-bearing phase. The calculated equilibrium concentrations are very sensitive to the assumed ratio of magnesium to silicon. The computational method described is easily applied to complex systems of solids and gases and represents an important tool with which to investigate cosmochemical systems.     

Solubility of cyclooctasulfur in pure water and sea water at different temperatures

The solubility of cyclooctasulfur in water and sea water at various temperatures in the range between 4 and 80 °C was determined. Cyclooctasulfur in equilibrium with rhombic sulfur reacted with hot acidic aqueous potassium cyanide to form thiocyanate anion which was measured by anion chromatography. Sulfur solubility in pure water was found to increase with temperature by more than 78 times: from 6.1 nM S₈ at 4 °C to 478 nM S₈ at 80 °C. The following thermodynamic values for solubilisation of S₈ in water were calculated from the experimental data: K° = 3.01 ± 1.04 × 10⁻⁸, ΔG_r° = 42.93 ± 0.73 kJ mol⁻¹, ΔH_r° = 47.4 ± 3.6 kJmol⁻¹, ΔS_r° = 15.0 ± 11.7 J mol⁻¹ K⁻¹). Solubility of cyclooctasulfur in sea water was found to be 61 ± 13% of the solubility in pure water regardless of the temperature.     

Metals of Kupferschiefer supplied by normal sea water

In the Kupferschiefer sea by constant winds a sluggish circulation of an estuarine-like type developed, that means an outflow of surface water followed by an inflow of deeper water, overturning in the inner parts of the sea. This circulation led to trapping of the trace elements concentrated by the living plankton, and to high production in the innermost parts. The oxygen content of the inflowing water decreased in the direction of flow by decomposition of dead plankton sinking to depth, and this led to anoxic conditions in bottom waters, the oxygen demand surpassing circulatory replenishment of oxygen.

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Zusammenfassung Unter dem Einfluß von konstanten Winden entwickelte sich im Kupferschiefermeer eine langsame Zirkulation dem Estuarientyp ähnlich, d. h. ein Ausstrom von Oberflächenwasser, und als Ersatz dafür eine entgegengesetzt laufende Unterströmung, im hinteren Teil des Binnenmeeres zur Oberfläche hinaufbiegend. Diese Zirkulation verursachte eine große Planktonproduktion im Beckeninnern, und ein Akkumulieren derjenigen Elemente, die vom Plankton konzentriert werden. Die Oxydation der absinkenden, abgestorbenen Organismen führte zu einem starken Sauerstoffverbrauch im Unterstrom; der Gehalt verringerte sich zum Beckeninnern hin, und dies führte zu Sauerstofflosigkeit im Bodenwasser, weil der Bedarf an Sauerstoff die Zufuhr durch Zirkulation übertraf. Bei den ersten Spuren von Schwefelwasserstoff wurden Sulfide von Silber und Kupfer gefällt, denen mit absinkenden Eh-Werten Sulfide von andren Metallen folgten.

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Résumé Dans la mer du « Kupferschiefer » des vents de direction constante ont dû produire une circulation lente ressemblant au type estuarien; cela veut dire qu'un courant superficiel se dirigeait vers l'entrée du bassin, tandis qu'un courant plus profond gagnait le centre, où l'eau montait vers la surface. Cette circulation a provoqué un enrichissement en éléments en traces concentrées par le plancton. L'enrichissement a dû être le plus fort dans la zone interne du bassin. La teneur en oxygène dans le courant profond a dû décroître vers le centre à cause de la décomposition du plancton mort descendant au fond; cela créait en effet des conditions anoxygènes, puisque le besoin d'oxygène dépassait l'apport par la circulation. Avec l'apparition de l'hydrogène sulfuré commençait la précipitation de sulfures d'argent et de cuivre, suivie, avec Eh décroissant, par celle d'autres métaux.

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A preliminary paper on the present problem was read at the Jahrestagung der Geologischen Vereinigung, March 1965. Remarks made by Prof. K. H.Wedepohl during the discussion led to further considerations, and these in their turn to the present exposition.     

The recovery of sodium chloride from sea water

The recovery of sodium chloride from the sea has been practised since ancient times. Modern knowledge of phase rules enables us to recover fairly clean sodium chloride from sea water, which consists of a complex mixture of salts and other minerals. According to quality requirements, two procedures can be applied; solar pre-concentration of the sea water with subsequent vacuum distillation, or solar pre-concentration with subsequent over-saturation and precipitation of the salt. The individual product requirements and cost factors have to be diligently studied in order to decide which procedure is the more feasible.     

Geo-environmental parametric 3D models of SARS-CoV-2 virus circulation in hospital ventilation systems

The novel coronavirus, SARS-CoV-2, has the potential to cause natural ventilation systems in hospital environments to be rendered inadequate, not only for workers but also for people who transit through these environments even for a limited duration. Studies in of the fields of geosciences and engineering, when combined with appropriate technologies, allow for the possibility of reducing the impacts of the SARS-CoV-2 virus in the environment, including those of hospitals which are critical centers for healthcare. In this work, we build parametric 3D models to assess the possible circulation of the SARS-CoV-2 virus in the natural ventilation system of a hospital built to care infected patients during the COVID-19 pandemic. Building Information Modeling (BIM) was performed, generating 3D models of hospital environments utilizing Revit software for Autodesk CFD 2021. The evaluation considered dimensional analyses of 0°, 45°, 90° and 180°. The analysis of natural ventilation patterns on both internal and external surfaces and the distribution of windows in relation to the displacement dynamics of the SARS-CoV-2 virus through the air were considered. The results showed that in the external area of the hospital, the wind speed reached velocities up to 2.1 m/s when entering the building through open windows. In contact with the furniture, this value decreased to 0.78 m/s. In some internal isolation wards that house patients with COVID-19, areas that should be equipped with negative room pressure, air velocity was null. Our study provides insights into the possibility of SARS-CoV-2 contamination in internal hospital environments as well as external areas surrounding hospitals, both of which encounter high pedestrian traffic in cities worldwide.     

电感耦合等离子体发射光谱法测定海水中微量钡

研究了用ICP-AES测定海水中微量钡的方法,选取了最佳工作条件,检出限为0.003mg·L-1,RSD为0.64%～0.84%,回收率在98.2%～104%之间。该法简便、快速、准确,结果令人满意。     

Development of reaction models for ground-water systems

Methods are described for developing geochemical reaction models from the observed chemical compositions of ground water along a hydrologic flow path. The roles of thermodynamic speciation programs, mass balance calculations, and reaction-path simulations in developing and testing reaction models are contrasted. Electron transfer is included in the mass balance equations to properly account for redox reactions in ground water. The mass balance calculations determine net mass transfer models which must be checked against the thermodynamic calculations of speciation and reaction-path programs. Although reaction-path simulations of ground-water chemistry are thermodynamically valid, they must be checked against the net mass transfer defined by the mass balance calculations. An example is given testing multiple reaction hypotheses along a flow path in the Floridan aquifer where several reaction models are eliminated. Use of carbon and sulfur isotopic data with mass balance calculations indicates a net reaction of incongruent dissolution of dolomite (dolomite dissolution with calcite precipitation) driven irreversibly by gypsum dissolution, accompanied by minor sulfate reduction, ferric hydroxide dissolution, and pyrite precipitation in central Florida. Along the flow path, the aquifer appears to be open to CO₂ initially, and open to organic carbon at more distant points down gradient.     

Evaluation of sea water ingress into an Indian atoll

Groundwater is the prime source of fresh water in most part of world. The groundwater floats in the form of thin lens which is vulnerable to various stresses such as tide, cyclone, draught, abstraction, etc. The problem of getting this meager resource of fresh groundwater sustained for longer time, becomes more difficult task on tiny atoll with large population depending on it. In order to develop sustainable management scheme and identify vulnerable part of aquifer, systematic assessment of groundwater quality on such island have become imperative. Detailed hydrochemical study has been carried out to identify potential fresh groundwater resources on Andrott Island, UT of Lakshadweep, India. The analysis has given an early signal of deterioration in groundwater quality in some parts of the island during non-monsoon period, whereas the quality becomes slightly better during monsoon period. The study suggests immediate measures for arresting the deterioration in groundwater quality as well as augmentation for restoration of aquifer in some parts of the island.     

中国南海海水蒸发实验过程中地球化学行径

本文所介绍的是中国南海海水室内等温蒸发过程中析序列、常量及微量元素含量分布规律，着重研究了海水蒸发过程中液相和固相矿物中结晶水氢氧同位素组成变化规律，并与四川盆地深层海源同生卤水进行了对比，从而，对卤水形成机理、资源远景评价综合利用途径等提供了科学依据。     

Changes in the water regime of the caspian sea

The article deals with issues of structure and dynamics of the Caspian Sea water balance. On the base of historical, paleogeomorphological and other data the evolution history of the Caspian Sea and its basin has been observed for different time intervals down to 400 thous. years ago. Presented are computerized data on water balance components in the current centenary obtained from instrumental observations, revealed are causes of the sea-level fluctuations within that time interval and anthropogenic factor contribution to this process. Based on the analysis of this material, an attempt has been undertaken to present a scenarion of a possible sea-level position of the Caspian Sea with the expected versions of climatic changes at the end of the XX and beginning of the XXI centuries.     

Geochemical models of metasomatism in ultramafic systems: serpentinization, rodingitization, and sea floor carbonate chimney precipitation

In a series of water-rock reaction simulations, we assess the processes of serpentinization of harzburgite and related calcium metasomatism resulting in rodingite-type alteration, and seafloor carbonate chimney precipitation. At temperatures from 25 to 300°C (P = 10 to 100 bar), using either fresh water or seawater, serpentinization simulations produce an assemblage commonly observed in natural systems, dominated by serpentine, magnetite, and brucite. The reacted waters in the simulations show similar trends in composition with decreasing water-rock ratios, becoming hyper-alkaline and strongly reducing, with increased dissolved calcium. At 25°C and w/r less than ∼32, conditions are sufficiently reducing to yield H₂ gas, nickel-iron alloy and native copper. Hyperalkalinity results from OH⁻ production by olivine and pyroxene dissolution in the absence of counterbalancing OH⁻ consumption by alteration mineral precipitation except at very high pH; at moderate pH there are no stable calcium minerals and only a small amount of chlorite forms, limited by aluminum, thus allowing Mg²⁺ and Ca²⁺ to accumulate in the aqueous phase in exchange for H⁺. The reducing conditions result from oxidation of ferrous iron in olivine and pyroxene to ferric iron in magnetite. Trace metals are computed to be nearly insoluble below 300°C, except for mercury, for which high pH stabilizes aqueous and gaseous Hg°. In serpentinization by seawater at 300°C, Ag, Au, Pd, and Pt may approach ore-forming concentrations in sulfide complexes. Simulated mixing of the fluid derived from serpentinization with cold seawater produces a mineral assemblage dominated by calcite, similar to recently discovered submarine, ultramafic rock-hosted, carbonate mineral deposits precipitating at hydrothermal vents. Simulated reaction of gabbroic or basaltic rocks with the hyperalkaline calcium- and aluminum-rich fluid produced during serpentinization at 300°C yields rodingite-type mineral assemblages, including grossular, clinozoisite, vesuvianite, prehnite, chlorite, and diopside.