European Journal of Scientific Research - EuroJournals

873 Faten Semadi, Vincent Valles and Jose Luis Gonzalez Barrios
Materials and methods
ACP
The analysis of principal components (ACP) is a multivariable method for statistical analysis. It could
be useful for quantify and order with hierarchical basis the mechanisms responsible of water quality. In
this work, it is calculated starting from a matrix of correlation. The variables are then centred and
reduced, making possible the solution of unit changes restrictions. Thus, a parameter such as the
electric conductivity expressed in dS m -1 will be treated like a concentration value expressed in M L -1 .
The ACP makes possible to find the factorial axes with linear combinations of parameters,
because all of them are not playing the same roll. In hydrochemistry, the experience shows that a
factorial axis usually represents a process or a source of variability.
It is important to say that the factorial axes are orthogonal, it means independent; they represent
mechanisms between them. For the ACP, the processes do not interfere between them. It makes
possible to group different chemical parameters by their behaviour, it means that it makes a behaviour
typology for the chemical parameters observed. The ACP let also group the water samples with similar
characteristics within all observed parameters.
Monte Carlo Method
It is a simulation method based on the distribution laws of all the parameters. This operation is repeated
hundreds or thousands of times, making possible the calculation of an average value and its standard
deviation.
Calculations of speciation: modeling thermodynamic of chemical balances
When water contacts soil minerals, a great number of chemical reactions take place into the aqueous
phase and within solution and minerals. According to the case, the ions content in the solution
increases or decrease like a "source" or a "sink" in a forecasting model of the solution transfers.
Geochemical models were developed in this work with the purpose of present briefly:
Modelling thermodynamic balances
It consists of studying three tools of current use in geochemistry: the interactions of water - rocks by
thermodynamic balances. The majority of natural solutions contain a great number of chemical species
distributed in different phases (liquid, solid and gaseous) ready to interact between them. That is why
the study of balances between solutions and minerals leads to the estimation of activities of dissolved
chemical species from the solute concentrations. Knowing the activities, it is possible to calculate the
saturation state of the solutions related to minerals present in the environment by its solubility product
(generally reported on thermodynamic data bases).
Analyze of concentration diagrams
The second approach is the study of solute concentration evolution in aqueous solutions while
solutions are concentrated (Al-Droubi, 1976; Gac, 1980; Fritz, 1981, Vallès, 1987, Ribolzi and Al,
1993). This method is based on the examination of concentration diagrams and is adapted to
groundwater concentration by evaporation (Mediterranean and, arid climates). The development of
these diagrams requires data of measurement (Al-Droubi, 1976; Gac, 1980; Vallès, 1987; Barbiéro,
1994) or the calculation of the concentration factor in solutions by a reference tracer (Gac, 1980;
Gonzalez-Barrios, 1992; Ribolzi et al, 1993; Barbiéro, 1994).