Eigenvalues Extracted by Principal Factor Analysis

Eigenvalue % Total variance Cumulative eigenvalue Cumulative %

1 2.619194 29.10216 2.619194 29.10216

2 2.321811 25.79790 4.941005 54.90006

3 1.125874 12.50971 6.066879 67.40977

only the combination of the nine parameters (pH; total hardness (TH); HCO3; F; Ca; Mg; Na; Al; and Fe) yielded satisfactory results. The three eigenvalues extracted account for 67% of the total variance (Table 7.2).

The first three principal factors extracted from the dataset and the raw loadings of the parameters on these factors are presented in Table 7.3. Only factor loadings exceeding absolute value of 0.6 are considered. As seen from the table, pH, HCO3, F, and Na are significantly loaded on the first factor, and TH, Ca, and Mg are loaded significantly on the second factor. The third factor is apparently insignificant, so the system can be visualized as being controlled by two factors. The first factor indicates strong mutual influences of F, HCO3, Na, and pH.

As explained earlier on the basis of the equilibrium governing calcite, fluorite, bicarbonate, and fluoride ions, at a constant pH, an increase in the bicarbonate concentration would increase the fluoride concentration in the water. Figure 7.4(a-c) shows the plots of fluoride concentration

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