*3.2.4 The spatial distribution both of water type and F- concentration according to pH*

The distribution type of groundwater according to pH showed that, from Mg-So4 type through a Na-HCO3, Na-So4 and Na-Cl type groundwater to Mg-Cl and *GIS and Statistical Evaluation of Fluoride Content in Southern Part of Upper Rasyan Aquifer… DOI: http://dx.doi.org/10.5772/intechopen.91329*

**Figure 21.**

*Distribution of water type according to pH.*


#### **Table 6.**

*Logistic regression univariate and multivariate model for fluoride variation.*

ultimately Ca-Cl when the pH range between 7.3 and 8 was more lower than pH 6¼ [7.3–8] (**Figure 21**) and the comparison of the groups "pH [7.3–8]" and "pH ¼6 [7.3–8]" showed a significant difference in fluoride concentration (p < 0.05).

Results of the multivariate analysis are shown in **Table 6**. In the two logistic regression model, after adjusting for pH, water type and sub-basin (ORa = 0.366; CI: 1.76–0.76), the water type (ORa = 1.71; CI: 1.261–2.32) remained dependently associated with abnormal fluoride concentration (**Table 6**).
