Brackish Aquifer Research Articles

Aspects of numerical and representational methods related to the finite-difference simulation of advective and dispersive transport of freshwater in a thin brackish aquifer

The simulation of the transport of injected freshwater in a thin brackish aquifer, overlain and underlain by confining layers containing more saline water, is shown to be influenced by the choice of the finite-difference approximation method, the algorithm for representing vertical advective and dispersive fluxes, and the values assigned to parametric coefficients that specify the degree of vertical dispersion and molecular diffusion that occurs. Computed potable water recovery efficiencies will differ depending upon the choice of algorithm and approximation method, as will dispersion coefficients estimated based on the calibration of simulations to match measured data. A comparison of centered and backward finite-difference approximation methods shows that substantially different transition zones between injected and native waters are depicted by the different methods, and computed recovery efficiencies vary greatly. Standard and experimental algorithms and a variety of values for molecular diffusivity, transverse dispersivity, and vertical scaling factor were compared in simulations of freshwater storage in a thin brackish aquifer. Computed recovery efficiencies vary considerably, and appreciable differences are observed in the distribution of injected freshwater in the various cases tested. The results demonstrate both a qualitatively different description of transport using the experimental algorithms and the interrelated influences of molecular diffusion and transverse dispersion on simulated recovery efficiency. When simulating natural aquifer flow in cross-section, flushing of the aquifer occurred for all tested coefficient choices using both standard and experimental algorithms.

Relations between chemical species distribution and the fluctuating activity of Vulcano (Italy)

Abstract Five years of systematic observation of the fumaroles of Vulcano have allowed us to detect some compositional trends coincident with a fluctuation in temperature. A gradual decrease of CO2, H2S+SO2, HF is observed with the lowering of temperature, while HCl slightly increases. These physical-chemical characters of the system are not readily explained as simply produced by different stages in magma degassing, and the previous hypothesis of the significant influence of a brackish aquifer on the fumaroles still appears a reliable working model. R-mode factor analysis allowed to distinguish the differentiated role of chemical species for which different genetic processes can be derived. The ratios HF HCl and SO 2 H 2 S are taken as indicators of the changing activity of the system, and also the available data for Usu (Japan) and Mount St. Helens (USA) are considered.