应力腐蚀开裂的一种概率竞争机制

１９９８年１月,采用极化曲线,慢应变速率及扫描电镜等试验技术,研究了奥氏体不锈钢的应力腐蚀开裂。结果表明,奥氏体不锈钢在酸性氯离子溶液中处于活性阳极溶解状态,但去发生应力腐蚀开裂,其断口形貌具有解理特征。这种ＳＣＣ无法用钝化膜破裂一再钝化理论和氢脆理论解释。本文以阳极溶解和表变的相互作用,激光散斑干涉术对裂纹尖端应变行为的测量,断口形貌观察等实验结果为基础,结合韧性和脆性断裂概率竞争的观点,提出了     

Mass transport modelling for assessement of groundwater contamination around Mathura oil refinery, Mathura, Uttar Pradesh, India

Mathura oil refinery was commissioned during 1977 and effluent storage ponds were constructed at the same time. These storage ponds receive wastewater from the refinery at a rate of 10000 m³/day. After treatment, waste water is discharged through a 3-km pipeline to a stream leading to the Yamuna river. The groundwater-monitoring as well as water-quality monitoring was carried at 24 observation wells in the refinery site during 1997. The water quality measurements indicated total dissolved chloride and sulphate concentration of native groundwater as 400 mg/l, whereas elevated levels up to 600 mg/l were found at the wells close to polishing ponds. Thus combined transport of chloride and sulphate was simulated in the mass transport model. A three-dimensional flow, pathlines and mass transport model of the aquifer system were constructed to analyze the impact of seepage from polishing ponds contaminating the groundwater regime. The permeability of aquifer varies between 1.5–2.5 m/day. The porosity of formation was assumed as 0.2. The constant head and constant concentration boundaries were assigned to the nodes representing effluent storage ponds. Longitudinal dispersivity of 100 m, horizontal transverse dispersivity of 10 m and vertical transverse dispersivity of 0.01 m were assumed. The mass transport model was calibrated for 20 years by comparing total dissolved chloride and sulphate concentrations from 1997. The model predictions indicate further migration of contaminants on the east of effluent ponds in future. Received: 4 January 1999 · Accepted: 12 July 1999     

Coupled study of water-stable isotopes and anions in porewater for characterizing aqueous transport through the Mesozoic sedimentary series in the eastern Paris Basin

This study presents data on chloride and bromide concentrations in porewater, water and anion diffusion coefficients, and their accessible porosities based on radial diffusion experiments on rock samples collected from a 2000 m-deep borehole (EST433) drilled by Andra in the eastern Paris Basin. The distributions of water stable isotope and chloride concentrations in porewater along this column reveal transient flows of water and solutes between the aquitard layers and the surrounding aquifers. These distributions confirm the occurrence of two separate aquitard/aquifer systems: “Oxfordian/Callovo–Oxfordian/Dogger” and “Dogger/Liassic/Rhaetian”. This separation is confirmed by Cl⁻/Br⁻ ratios, which are low in Liassic and Dogger porewater, suggesting the influence of primary brines, and which are close to the marine ratio in the Dogger groundwater. Based on these results, transport simulations in the two systems were carried out according to different scenarios. The simulation results confirm that transport properties obtained in the laboratory at sample scale may be extrapolated to the formation scale. It is highly probable that diffusion is the main transport process in the Callovo–Oxfordian formation. This may also be the case in the Dogger/Liassic layer, although a limited contribution from advection cannot be totally excluded. By testing different scenarios of boundary conditions in diffusive models, it is proposed that the Dogger aquifer was first activated in the Early Miocene.     

Inhibitory effects of chloride ions on concrete sulfate attack in the marine adsorption environment

To study the inhibitory effects of chloride ions on concrete sulfate attack in the marine adsorption environment, a series of cubic concrete specimens was fabricated. These specimens were totally submerged or partially submerged in 10% Na₂SO₄ solutions with 0, 0.5, 2, and 5% NaCl concentration. Three specific aspects, namely, superficial phenomenon, compressive strength degradation, and X-ray fluorescence spectrometry analysis, were studied during 450 days of long-term exposure. Results showed that Na₂SO₄ solution had a strong corrosive effect on concrete in both the adsorption and submersion zones, especially in the adsorption zone. Chloride ions exerted inhibitory effects on concrete sulfate attack in both the submersion and adsorption zones, and higher concentration of chloride ions will produce stronger inhibitory effects. However, given the different inhibitory effects of chloride ions on concrete sulfate attack with different corrosion mechanisms, the inhibitory effect of the same chloride concentration on concrete sulfate attack was a little lower in the adsorption zone than in the submersion zone.     

Precipitation induced stream flow: An event based chemical and isotopic study of a small stream in the Great Plains region of the USA

A small stream in the Great Plains of USA was sampled to understand the streamflow components following intense precipitation and the influence of water storage structures in the drainage basin. Precipitation, stream, ponds, ground-water and soil moisture were sampled for determination of isotopic (D, ¹⁸O) and chemical (Cl, SO₄) composition before and after two intense rain events. Following the first storm event, flow at the downstream locations was generated primarily through shallow subsurface flow and runoff whereas in the headwaters region – where a pond is located in the stream channel – shallow ground-water and pond outflow contributed to the flow. The distinct isotopic signatures of precipitation and the evaporated pond water allowed separation of the event water from the other sources that contributed to the flow. Similarly, variations in the Cl and SO₄ concentrations helped identify the relative contributions of ground-water and soil moisture to the streamflow. The relationship between deuterium excess and Cl or SO₄ content reveals that the early contributions from a rain event to streamflow depend upon the antecedent climatic conditions and the position along the stream channel within the watershed. The design of this study, in which data from several locations within a watershed were collected, shows that in small streams changes in relative contributions from ground water and soil moisture complicate hydrograph separation, with surface-water bodies providing additional complexity. It also demonstrates the usefulness of combined chemical and isotopic methods in hydrologic investigations, especially the utility of the deuterium excess parameter in quantifying the relative contributions of various source components to the stream flow.     

Altitude et géochimie des eaux de source,Nord-Ouest du Massif central,France

In the northwestern Massif Central (France), groundwater chloride concentrations are inversely correlated with elevation, when nitrate-poor. This can be explained by an evolution of the ratio evapotranspiration/rainfall, or of the rainwater composition. Such a relationship may be used for the detection of denitrification phenomena in groundwaters, or nitrate assimilation in surface waters, or for the computation of evapotranspiration, using the chloride mass balance method. However, the main objective will be the selection of groundwaters free of any chloride-bearing contamination, in order to define the natural groundwater quality background. To cite this article: J. Barbier, C. R. Geoscience 337 (2005).     

罗布泊卤水的相图分析研究

通过对罗布泊北部卤水依据不同温度下的Na~+、K~+、Mg~(2+)||Cl~-、SO_4~(2-)—H_2O体系相图分析,分别给出氯化钠、氯化钾、硫酸钾、一水硫酸镁综合开发利用罗布泊卤水的原则性工艺流程,并提出了在不同的生产阶段科学的工艺路线。这一具有较高的回收率和产品质量,为开发利用罗布泊北部卤水提供了理论依据。     

Using remote sensing to regionalize local precipitation recharge rates obtained from the Chloride Method

Water supply in semiarid Botswana is, to a large extent, based on groundwater. In the planning of a groundwater abstraction scheme, criteria for the sustainability of the abstraction with respect to both quantity and quality have to be satisfied. The most important parameter in the context of quantitative sustainability is the long-term average groundwater recharge together with its spatial distribution. A method is developed to calculate a recharge map that can be used in a groundwater model. The relative distribution of recharge is obtained from remotely sensed data and then calibrated with local values of recharge derived from the Chloride Method. The method was tested for two sites in Botswana, the Chobe Region and Ngamiland.     

Genetic link between saline and carbonatitic mantle fluids: The system NaCl-CaCO3-MgCO3 ± H2O ± Fe0 at 6 GPa

Melt inclusions in kimberlitic minerals and diamonds indicate that chlorides are important constituents of mantle carbonatite melts. Besides, alkaline chlorides are important constituents of saline high-density fluids (HDFs) found in diamonds from kimberlites and placers around the world. Continuous compositional variations suggest that saline and carbonatitic HDFs could be genetically linked. However, the essence of this link remains unclear owing to the lack of data on phase relations in the chloride-carbonate systems under pressure. Here we studied subsolidus and melting phase relations in the system NaCl–CaCO₃–MgCO₃ at 6 GPa and 1000–1600 °C using a Kawai-type multianvil press. We found that at 1000 °C, subsolidus assemblage consists of halite, magnesite, and aragonite. At higher temperatures, the stabilization of dolomite splits the subsolidus area into two partial ternary fields: halite + magnesite + dolomite and halite + dolomite + aragonite. The minimum on the liquidus surface corresponds to the halite-dolomite-aragonite ternary eutectic, situated at 1100 °C. The eutectic melt has Ca# 89 and contains 30 wt.% NaCl (26 mol% 2NaCl). The system has two ternary peritectics: halite + dolomite = magnesite + liquid located near the ternary eutectic and magnesite + dolomite = Mg-dolomite + liquid situated between 1300 and 1400 °C. Although under dry conditions incipient melting yields carbonate-dominated melt, the addition of water facilitates the fusion of NaCl and expands the liquid field to NaCl-rich compositions with up to 70 wt.% NaCl. The obtained results favor the idea that hydrous saline melts/fluids (brines) found as inclusions in diamonds could be a lower temperature derivative of mantle carbonatite melts and disagree with the hypothesis on chloride melt generation owing to the chloride-carbonate liquid immiscibility since no such immiscibility was established. We also studied the interaction of the NaCl–CaCO₃–MgCO₃ system with iron metal and found that carbonate reduction produces C-bearing species (Fe⁰, Fe-C melt, Fe₃C, Fe₇C₃, C⁰) and wüstite containing Na₂O, CaO, and MgO. Besides, a carbonate chloride compound, Ca₂Cl₂CO₃, was established among the reaction products. The interaction between NaCl-bearing carbonate melt shifts its composition toward Mg-poor and NaCl-rich. Given the above, an alternative hypothesis can be proposed, according to which the interaction of alkaline chloride-bearing carbonate melts formed in the subduction zones with the reduced mantle should be accompanied by diamond crystallization and shift the composition of the melt from carbonatitic to alkali-rich saline.     

Use of Pitzer Equations to Examine the Formation of Mercury(II) Hydroxide and Chloride Complexes in NaClO<Subscript>4</Subscript> Media

The thermodynamic stability constants for the hydrolysis and formation of mercury (Hg²⁺) chloride complexes