Origin of the water at the bottom of the mine
Principal component analysis (PCA) was used to explain the origin at the bottom of the mine. The PCA is a multi-variegated analysis method allowing the simultaneous study of a large number of variables whose total information cannot be visualized because of a space with more than three dimensions (Mouissi and Alyat, 2016). This method would make it possible to clarify the relationships between the variables and the phenomena at the origin of these relationships. The objective is to have information concentrated on a minimum of axis (Ayadi et al., 2008). This method is widely used to interpret hydrochemical data (WHO, 2000).
The statistical analysis of the physico-chemical data was carried out on a data matrix consisting of ten (10) variables and ten (10) samples distributed around the Kherzet Youcef deposit. The statistical software Statistica version 10 was used for data processing.
The correlation matrix gives a first idea of the existing associations between the different variables such as bicarbonate, chlorine, sulphates and pH. These parameters are relatively well correlated with each other (Table 2).
Table 2: Correlation matrix between variables on all stations studied
|
Ca++
|
Mg++
|
Na++K+
|
HCO3-
|
Cl-
|
SO4--
|
pH
|
Depth
|
Ca++
|
1,00000
|
|
|
|
Mg++
|
0,044073
|
1,000000
|
|
|
Na++K+
|
-0,404123
|
0,462396
|
1,000000
|
HCO3-
|
-0,143872
|
0,428250
|
0,619449
|
1,000000
|
|
Cl-
|
-0,231317
|
-0,101159
|
0,646032
|
0,015681
|
1,000000
|
SO4--
|
-0,181831
|
0,731061
|
0,927202
|
0,574229
|
0,508859
|
1,000000
|
|
PH
|
-0,057180
|
0,814775
|
0,475717
|
0,320496
|
0,174403
|
0,678729
|
1,000000
|
Depth
|
0,300030
|
-0,070292
|
-0,235833
|
-0,667114
|
0,120997
|
-0,108149
|
0,109819
|
1,000000
|
The eigenvalues of the correlation matrix make it possible to measure the percentage of the variance explained by each factorial (Fig. 4). The eigenvalue graph shows that the first factorial plane, consisting of the axes F1 and F2, represents 66.42% of the total inertia. It proves to be sufficient to reflect the essence of this inertia. Because if we observe the distribution of the eigenvalues, we find that the main offset occurs just after the first two values, which means that the first two axes are sufficient to represent the information in its entirety.
The graphs resulting from factor analysis, highlight groupings, oppositions and directional trends. The F1 axis expresses 46.37% of the variance and represents most of the variables in the same direction in a negative way, these are bicarbonate, alkaline earth, sulphates and pH (Fig. 5). Which expresses the same origin of these variables. For two variables, depth and calcium are related and evolve in the same direction and differ on the F2 axis which expresses 20.05% of the variance.
Principal component analysis (Fig. 6) makes it possible to determine the waters according to their origin, the waters belonging to the surface table and the waters coming from the Barremian table, these waters are of bicarbonated character. For water from the bottom of the mine (Pit II) are individualized and do not belong to any group. This can be explained by the change in the chemical quality of the waters after the rock is crushed and the time it takes to store the water at the bottom of the mine before discharging it to the outside.
Kherzet Youcef mine water suitability for irrigation
In the vicinity of the Kherzet Youcef deposit lies a vast expanse. This area is agricultural land used for potato and cereal crop production.
A decision has been made to use the drainage water of the Kherzet Youcef deposit for irrigation of a perimeter on an area of about 350 ha.
To characterize the irrigability of exhaust water, we use the values of electrical conductivity at 25°C and those of the sodium adsorption ratio (SAR).

The SAR is less than 5 (Fig. 7) and waters do not cause the risk of alkalinization of soils (WHO, 2000) (Subramani et al., 2005). The transfer of the samples placed on the irrigation water classification diagram shows that the waters are between the good class (S1) and the middle class (S2) where the danger of alkalinization of the soil is appreciable in soils with fine texture and high exchange capacity.
The exchangeable Na+ ions can replace the alkaline earth ions (Ca2+ and Mg2+) of the clays, thus causing the blocking of the soil pores and thus its waterproofing.
Suitability of neogene groundwater for drinking water supply
The results of analysis of the trace metal elements are shown in Figs. 8, 9 and 10. These values are compared to the limit values set by the Algerian regulations (Decree 11-219 of 12 June 2011) and the limit values set by WHO (WHO 2006). Note that the WHO has no indication regarding the maximum allowable value of iron (WHO 2006).
For Zn (Fig. 8), the analysis values on all waters sampled do not exceed 1 mg/l. this result remains admissible by the WHO standard set at 3 mg/l and the Algerian standard, less demanding, set at 5 mg/l.
For Muac (Fig. 9), the majority of assay values are not permissible under the WHO standard (0.01 mg/l). For the Algerian standard, always remains less demanding, 0.05 mg/l.
Only one sample, on borehole 3 dated July 2016, we note that this value is higher than the Algerian standard.
As regards the Fe element, the majority of the values of the results obtained are higher than the maximum value fixed by the Algerian regulations.