An empirical model for salinity intrusion in alluvial estuaries

The main parameters that affect the salinity intrusion in estuaries are their geometric, hydrologic and hydrodynamic characteristics. The recognition of effective parameters and understanding their roles in the salinity intrusion are required for estuarine water management. In this study, the governing equations of the salinity intrusion processes were scaled to derive the effective dimensionless parameters. Then, a previously verified model, CE-QUAL-W2, was utilized as a virtual laboratory to investigate the effects of different governing parameters on the salinity intrusion. Analysis of the results showed that logarithmic functions can be used to describe the effect of dimensionless parameters obtained by scaling of governing equations. Finally, a formula was suggested to predict the salinity intrusion length based on geometrical and hydrodynamic characteristics of alluvial estuaries.     

Post‐stack diffraction imaging in vertical transverse isotropy media using non‐hyperbolic moveout approximations

Diffractions carry valuable information about local discontinuities and small‐scale objects in the subsurface. They are still not commonly used in the process of geological interpretation. Many diffraction imaging techniques have been developed and applied for isotropic media, whereas relatively few techniques have been developed for anisotropic media. Ignoring anisotropy can result in low‐resolution images with wrongly positioned or spurious diffractors. In this article, we suggest taking anisotropy into account in two‐dimensional post‐stack domain by considering P‐wave non‐hyperbolic diffraction traveltime approximations for vertical transverse isotropy media, previously developed for reflection seismology. The accuracy of the final images is directly connected to the accuracy of the diffraction traveltime approximations. We quantified the accuracy of six different approximations, including hyperbolic moveout approximation, by the application of a post‐stack diffraction imaging technique on two‐dimensional synthetic data examples.     

Statistical modeling the effect of sediment physicochemical properties on the concentration of heavy metal (case study: Musa Creek,SW Iran)

Heavy metal accumulation in sediments is important even at low levels due to their irresolvable character and harmful effects. Therefore, contamination of creeks, especially their sediments, is highly important for scientific communities. This study investigates the relationship between heavy metal accumulation and some physicochemical parameters of sediments (pH, EC, calcium carbonate, texture, specific gravity, density, porosity and percentage of organic matter) in a stretch of Musa Creek beaches. The results showed that the studied sediments are extremely salty and have slight variations in terms of pH. Although there are mostly clay-sized sediments in the studied area, their mineralogical composition contains calcite with smaller amounts of dolomite, aragonite and halite minerals. The correlation between each of the parameters and heavy metal concentration was modeled using OLS regression. Cr, Ni, Zn and Pb concentrations are positively correlated with each other and inversely correlated with Cd. The accumulation of heavy metals is directly related to parameters such as EC, organic matter, clay and silt, specific gravity and porosity; it is negatively related to calcium carbonate, sand and density parameters. Owing to slight variations, the pH parameter lacks any significant correlation with heavy metal concentrations.     

A discrete element model to link the microseismic energies recorded in caprock to geomechanics

A discrete element model is presented to study slip-induced microseismic events along weak planes and crack-induced microseismic events within the intact rock for a representative elementary volume, REV, in the caprock of Weyburn reservoir. Also, the effect of varying factors such as orientation, coefficient of friction and elasticity of the weak plane on release of microseismic energies is studied. According to the results, for the conditions studied in this paper, the magnitudes of slip-induced events range from ~?1 to ?6, while crack-induced events range from ~?7 to ?11. Considering the capability of geophones, this suggests that events “recorded” in the caprock are more likely to have slip origins along weak planes than having crack origins within the intact rock. In order to show the applicability of the model in practice, the events recorded in the caprock of Weyburn from September to November of 2010 are analyzed. Also, a simple model is presented that correlates the amount of consumed energy per volume of the REV with the seismic energy released due to stick–slips along a weak plane. The results show that weak planes can be emissive even long before the failure of their surrounding is reached, and therefore, there can be a level of tolerance for the observed microseismic events in the caprock.     

Hexavalent chromium removal from aqueous solutions by using low-cost biological wastes: equilibrium and kinetic studies

The batch removal of hexavalent chromium from aqueous solutions using almond shell, activated sawdust, and activated carbon, which are low-cost biological wastes under different experimental conditions, was investigated in this study. The influences of initial concentration, adsorbent dose, adsorbent particle size, agitation speed, temperature, contact time, and pH of solution were investigated. The adsorption was solution pH dependent and the maximum adsorption was observed at a solution pH of 2.0. The capacity of chromium adsorption under equilibrium conditions increased with the decrease in particle sizes. The equilibrium was achieved for chromium ion after 30?min. Experimental results showed that low-cost biosorbents are effective for the removal of pollutants from aqueous solution. The pseudo-second-order kinetic model gave a better fit of the experimental data as compared to the pseudo-first-order kinetic model. Experimental data showed a good fit with the Freundlich isotherm model. Changes in the thermodynamic parameters, including Gibbs free energy (??G_o), enthalpy (??H_o), and entropy (??S_o), indicated that the biosorption of hexavalent chromium onto almond shell, activated sawdust, and activated carbon was feasible, spontaneous, and endothermic in the temperature range 28?C50?°C.