O. Atteia - Academia.edu (original) (raw)

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Institute for Geological and Geochemical Research, Research Centre for Astronomy and Earth Sciences, Hungarian Academy of Sciences

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Papers by O. Atteia

Journal of Hydrology, 2005

In deep aquifers the complex flow pattern originating from the geological structure often leads t... more In deep aquifers the complex flow pattern originating from the geological structure often leads to difficult predictions of water origin, determination of the main flow paths, potential mixing of waters. All these uncertainties prevent an efficient management of the resource. In the context of the Aquitaine basin an original modelling approach suggests that geochemical data can be used to identify flow directions where geological and hydrogeological data are too scarce to provide sufficient information.

Journal of Contaminant Hydrology, 2010

In this comment, we revisit equations concerning the analytical solutions presented by Gutierrez-... more In this comment, we revisit equations concerning the analytical solutions presented by Gutierrez-Neri and co-workers for reactive transport for a pollutant undergoing core and fringe degradations. We state that a correction needs to be made in Eq. (9) of the work of Gutierrez-Neri et al. in order that the equation follows closely previous work published by J. Bear (in 1-D) and P.A. Domenico (in 3-D). Furthermore we derive alternative solutions for Eqs. (13)-(16) which separate more clearly the first-order reaction and the instantaneous reaction. It is shown that the corrected solution agrees better with the results from the numerical model than the previous solution. An improvement is also made by giving a solution which avoids negative concentrations. Furthermore, the corresponding solution for the electron acceptor reacting with the pollutant is given.

Environmental Geology, 1998

Colloids are known to transport contaminants over long distances in natural media. Despite this p... more Colloids are known to transport contaminants over long distances in natural media. Despite this potentially harmful effect, very few studies have been undertaken in subsurface aquifers. This paper presents the first results of a study of natural colloids and particles in a karstic aquifer. The site was chosen for its coverage by clay layers and peat which deliver various and numerous particle types in water. The methodological part describes three methods used for size determination and sample fractionation of surface water and spring water. These methods have been adapted for the treatment of multiple samples due to the rapid discharge variation typical of karstic aquifers. The analysis of many particle size distributions (PSD) shows that they can be described by a Pareto law. The variation of the slope of the PSD at the spring is mainly dependent on discharge. This behavior is interpreted as a washing of the karstic drains during the first phase of high flow events. Fractionation of the samples allowed application of various characterization techniques to particle size classes. X-ray diffraction (XRD) patterns showed that most of the mineral particles originated from Quaternary deposits and limestones. However the use of scanning electron micrsocopy with energy-dispersive spectrometer (SEM-EDS) detailed the composition of individual particles and revealed particles not found by XRD. These techniques also showed the high complexity of the natural particles and the important place of coprecipitation in their formation. Consequences on the fluxes of particulate matter and its potential role as a carrier of contaminants are discussed.

Advances in Water Resources, 2012

ABSTRACT Various numerical reactive transport models were developed in the last decade to simulat... more ABSTRACT Various numerical reactive transport models were developed in the last decade to simulate plumes of pollutants in heterogeneous aquifers. However, these models remain difficult to use for the non-specialist, and the computation times are often long. Users who need to fit several model parameters to match predictions with field data in heterogeneous aquifers may be discouraged by the time needed to run the simulations. The objective of this paper is to provide a set of approximations that allow performing almost instantaneous calculations for transport of redox-reactive pollutants, the most common examples being benzene, toluene, ethylbenzene and xylenes (BTEX). The approach relies on two major tools: (i) the use of flux tubes (FT), a variant of stream tubes that include dispersion, and (ii) sequential superposition of the reactions (Mixed Instantaneous and Kinetics Superposition Sequence (MIKSS)). The calculation of transport is uncoupled from the calculation of reactions. The superposition principle has been used previously for the analytical solution of a bimolecular reaction of an electron donor with an acceptor and is here extended to more than one dissolved electron acceptor reacting with more than one donor. The approach is furthermore improved by including limitations of the kinetic reactions according to the availability of the reactants and by combining kinetic and instantaneous reactions. The results computed with this approach are compared to three well known numerical models (RT3D, PHT3D, PHAST) for various test cases including uniform, slightly diverted or highly irregular flow fields and several reaction schemes for BTEX. The FT-MIKSS solution gives nearly the same results as the other models and proved to be very flexible. The major advantage of the FT-MIKSS solution is fast computation times that are generally 100 to 1000 times faster than other numerical models. This approach might be a useful tool during the long fitting procedure of field data, which may be followed by one single run of a classical numerical model using the best-fit parameters.