*3.2.6 The comparison of the abnormal and normal fluoride concentration according to TDS*

The comparison of the abnormal and normal fluoride concentration according to TDS (total dissolved solids) in the three sub-basins showed a significant differences between the three sub-basins (p < 0.0001) and positive relationship between the fluoride concentration and TDS (r = 0.5; p < 0.0001). A multiple comparison of median concentration among these sub-basins in fluoride shows that Al-Hawban and Al-Burayhi and Hedran sub-basins reach higher fluoride content which is more

4.87 mg/L, No. 26 with 1.58 mg/L and well No. 10 with 3.33 mg/L) and Al-Burayhi and Hedran (source No. 81 with 2.66 mg/L); and with water type both of Ca-SO4 (wells No. 38 and 8 in Al-Hawban sub-basin), Ca-Cl (wells No. 71, 73 and 91 in the Al-Burayhi and Hedran sub-basin and well No. 31 in Al-Hawban sub-basin) and Mg-SO4 (well No. 7 in Al-Hawban sub-basin). **Figure 20** illustrated that there are no significant different in the fluoride concentration between the sources of

**Water type Normal concentration N (%) Abnormal concentration N (%) P-value** Mg-HCO3 5 (100%) NIL 1 Ca-HCO3 5 (62.5%) 3 (37.5%) 0.3 Mg-SO4 Nil 1 (100%) 0.10 Na-HCO3 7 (26.9%) 19 (73.1%) 0.01 Na-SO4 2 (22.22%) 7 (77.78%) 0.02 Na-Cl 8 (23.53%) 26 (76.47%) 0.01 Ca-SO4 Nil 2 (100.0%) 0.05 Mg-Cl Nil 4 (100%) 0.02 Ca-Cl Nil 4 (100%) 0.02

*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

groundwater samples according to the water type.

*The difference of means for F- mg/L with 95% Cl.*

*Water type, normal and abnormal of F- mg/L and number of wells.*

**Table 5.**

*Resources of Water*

**Figure 20.**

**138**

than 1.5 mg/L and similar but significantly higher than the Al-Dhabab sub-basin; Al-Hawban-Al-Burayhi and Hedran: (p > 0.072); Al-Hawban-Al-Dhabab: (p < 0.003); Al-Dhabab-Al-Burayhi and Hedran: (p < 0.0001). Moreover, this increase in TDS has been found only at two sub-basins when the fluoride is abnormal content (**Figure 22**). The results of the study samples of electrical conductivity

*GIS and Statistical Evaluation of Fluoride Content in Southern Part of Upper Rasyan Aquifer…*

In order to enable sustainable development of groundwater resources, it is necessary to delineate the safe and unsafe zones with reference of fluoride content (1.5 mg/L); hence spatial distribution of fluoride's concentration was mapped in

Based on the Kruskal-Wallis test for the various sub-basins, the level of significance was (p < 0.05). This result illustrated that there were a significant differences between three sun-basins with regard to the concentration of fluoride in groundwater. The differences of means for fluoride concentration in groundwater for the three sub-basins show the mean's fluoride in Al-Burayhi and Hedran (F-) > Al-Hawban (F-) > Al-Dhabab (F-). A multiple comparison of mean concentration of fluoride among these sub-basins shows that there is no a significant difference between the Al-Hawban and Al-Burayhi and Hedran sub-basins P-value 0.277, there is a significant difference between the Al-Hawban and Al-Dhabab sub-basins P-value 0.017 and there is a significant difference between the Al-Burayhi and

Fluoride concentration variation is widely in the study area from 0.1 mg/L (in well No.93 in Al-Burayhi and Hedran sub-basin) to 6 mg/L [in Well No. 83, of the same sub-basin (Al-Burayhi and Hedran sub-basin)]. We observed that the concentration of fluoride in the Al-Dhabab sub-basin is the optimal concentration

It is clearly observed that the Al-Burayhi and Hedran and Al-Hawban sub-basins have the highest concentration of fluoride ion in the chemistry of water. Highest

according to the WHO drinking water guidelines value of 1.5 mg/L.

Waters with high fluoride concentrations occur in large and extensive geographical belts associated with (a) sediments of marine origin in mountainous areas, (b) volcanic rocks and (c) granitic and gneissic rocks [21], and the high concentration of fluoride widely accepted that most of the F are derived mainly from acidic volcanic rocks such as pumice, obsidians, pyroclastic deposits, ignimbrites and rhyolite, and the main minerals for F are fluorite, fluorapatite, micas and hornblende [22]. Because the geology of study mainly constituent from the acid and basic volcanic and grants rocks, the level of fluoride concentration in the Al-Dhabab sub-basin can be explained by the nature on aquiver in this study area (Cretaceous Tawilah Sandstone), while the groundwater in the other sub-basin is produced either from Tertiary fractured volcanic (that have F- bearing mineral and the groundwater in this aquiver have long-time contact with aquiver, which adjudge the important factors leading to the high fluoride concentration result of interaction between the groundwater and the aquiver) or from the Quaternary alluvium aquiver, where the Wadi sediments deposited are derived from the alteration of volcanic ash and tufa mainly of (Tr1); this quiver depends on their recharge mainly on the wastewater of the urban and industrial activates; this aquiver exposed to over exploration of their groundwater and finally the dry and semi-dry condition plays an important role in the degradation of groundwater in this aquiver.

and TDS according to study sub-basins are given in **Figure 23**.

the three sub-basins of the study area (**Figure 24**).

Hedran and Al-Dhabab sub-basins P-value 0.001.

**4. Discussion**

**141**

*3.2.7 Spatial distribution of fluoride*

*DOI: http://dx.doi.org/10.5772/intechopen.91329*

#### **Figure 22.**

*Box plot for the maxi, min and average of the fluoride content in groundwater according to TDS of three sub-basins.*

#### **Figure 23.**

*Box plot for the max, min and average of electrical conductivity and total dissolved solids according to study sub-basins.*

**Figure 24.** *Spatial distribution of fluoride concentration in the study area.*

### *GIS and Statistical Evaluation of Fluoride Content in Southern Part of Upper Rasyan Aquifer… DOI: http://dx.doi.org/10.5772/intechopen.91329*

than 1.5 mg/L and similar but significantly higher than the Al-Dhabab sub-basin; Al-Hawban-Al-Burayhi and Hedran: (p > 0.072); Al-Hawban-Al-Dhabab: (p < 0.003); Al-Dhabab-Al-Burayhi and Hedran: (p < 0.0001). Moreover, this increase in TDS has been found only at two sub-basins when the fluoride is abnormal content (**Figure 22**). The results of the study samples of electrical conductivity and TDS according to study sub-basins are given in **Figure 23**.
