Function Of Chemical Parameters Research Articles

Hydrogeochemical and Stable Isotope Data of the Groundwater of a Multi-Aquifer System in the Maknessy Basin (Mediterranean Area, Central Tunisia)

The Maknessy plain in central Tunisia is one of the most important agricultural basins in Tunisia. Given the semi-arid climate conditions, the irrigation of cultivated crops relies principally on the abstraction from groundwater resources. The assessment of the quality of the used water for agricultural purposes is crucial for safe production. Thus, the objective of this work is to assess the physicochemical quality of the irrigation water resources in this catchment area using a combined chemical, isotopic, and statistical approach. The waters analyzed are represented by two types of groundwater, mainly calcium hyper chloride and calcium sulfate. A multivariate statistical analysis (PCA and HCA) and a geochemical approach have been applied to study water quality as a function of chemical parameters, showing that the EC and TDS are the parameters influencing water quality. The stable isotopic compositions of the sampled waters range from −7.53 to −4.90% vs. VSMOW and from −53.6 to −32.2% vs. VSMOW for δ18O and δ2H; they show the exchange between groundwater and rock and the evaporation effect. The isotopic data form three groups such as recent water, paleowater, and mixing water indicate the evaporation effect and interaction of the groundwater, and confirm that this aquifer has been recharged by current rainwater. So, these aquifers were recharged by precipitation derived from a mixture of cloud masses from the Atlantic Ocean and the Mediterranean Sea. The findings of this research are of important relevance for effective water resources management in this agro-based region. Indeed, the increased exploitation of these resources will induce a continuous reduction in the available resources and progressive degradation of the used water quality that may adversely impact the safe agricultural production and the economic resilience of the local population.

Implementing the Variability of Crystal Surface Reactivity in Reactive Transport Modeling

Current reactive transport model (RTM) uses transport control as the sole arbiter of differences in reactivity. For the simulation of crystal dissolution, a constant reaction rate is assumed for the entire crystal surface as a function of chemical parameters. However, multiple dissolution experiments confirmed the existence of an intrinsic variability of reaction rates, spanning two to three orders of magnitude. Modeling this variance in the dissolution process is vital for predicting the dissolution of minerals in multiple systems. Novel approaches to solve this problem are currently under discussion. Critical applications include reactions in reservoir rocks, corrosion of materials, or contaminated soils. The goal of this study is to provide an algorithm for multi-rate dissolution of single crystals, to discuss its software implementation, and to present case studies illustrating the difference between the single rate and multi-rate dissolution models. This improved model approach is applied to a set of test cases in order to illustrate the difference between the new model and the standard approach. First, a Kossel crystal is utilized to illustrate the existence of critical rate modes of crystal faces, edges, and corners. A second system exemplifies the effect of multiple rate modes in a reservoir rock system during calcite cement dissolution in a sandstone. The results suggest that reported variations in average dissolution rates can be explained by the multi-rate model, depending on the geometric configurations of the crystal surfaces.

Studies of IGA intergranular attack/stress corrosion cracking related parameters and remedies

The parameters influencing the appearance of intergranular corrosion of steam generator tubes are examined: the sludge zone located above the tube sheet, the secondary system materials (copper alloys), the age of the unit and the design of the tube support plates, which plays an important role in the hide out and in the hide out return of chemical species. The occurrence of intergranular attack/stress corrosion cracking (IGA/SCC) as a function of chemical parameters is also examined. These parameters include the following: sodium hydroxide, partly brought by the cooling water condenser inlets or by makeup water pollution, calculations of pH at high temperature in zones of restructed flow show a generally alkaline tendency; lead, often found on cracked tubes at particularly high concentrations, and well known as an aggravating element; copper, found in abnormal quantities on tubes pulled from Fessenheim unit 1, thus the relation between the materials of the secondary system, the copper concentrations on pulled tubes and the presence of IGA is carefully studied too; phosphate pollution, generally brought by the intermediate cooling system. Finally, the remedies implemented by EDF to limit the degradations with time are described.

A new strong brass alloy containing silicon

The parameters influencing the appearance of intergranular corrosion of steam generator tubes are examined: the sludge zone located above the tube sheet, the secondary system materials (copper alloys), the age of the unit and the design of the tube support plates, which plays an important role in the hide out and in the hide out return of chemical species. The occurrence of intergranular attack/stress corrosion cracking (IGA/SCC) as a function of chemical parameters is also examined. These parameters include the following: sodium hydroxide, partly brought by the cooling water condenser inlets or by makeup water pollution, calculations of pH at high temperature in zones of restructed flow show a generally alkaline tendency; lead, often found on cracked tubes at particularly high concentrations, and well known as an aggravating element; copper, found in abnormal quantities on tubes pulled from Fessenheim unit 1, thus the relation between the materials of the secondary system, the copper concentrations on pulled tubes and the presence of IGA is carefully studied too; phosphate pollution, generally brought by the intermediate cooling system. Finally, the remedies implemented by EDF to limit the degradations with time are described.