**3. Results and discussion**

### **3.1 Analysis of physical and chemical parameters**

Even though people may not be affected directly by some of these parameters, elevated levels can cause unfavorable conditions and discomfort. For instance, drinking water with elevated pH will taste bitter [32]. Parameters such as electrical conductivity, pH, turbidity, and temperature as shown in (**Table 1)** were measured in this study**.** Water samples from the mining sites were acidic with pH values of some of the sites recording as low as 3.51. The pH of the pristine samples was, however, within the normal WHO's range of 6.5–8.5. The low pH values for mine samples might be responsible for the high metal levels measured.

The electrical conductivity values measured for the water samples were below the WHO normal range (400–600 μS/cm) [33]. The temperature values for the samples were below the recommended WHO's value of 29°C. Turbidity values for the mine samples were higher than those measured for the pristine samples due to activity of mining in those rivers. Other measured parameters such as salinity and total dissolved solids were relatively low. Low turbidity of the pristine samples indicates the absence of disease-causing organisms such as bacteria, viruses, and parasites that cause symptoms such as nausea, cramps, diarrhea, and associated headaches [34].

#### **3.2 Concentration of heavy metals in water**

The mean concentrations of the heavy metals obtained from ICP/MS instruments were presented in the attached **Table 2.** The mean concentrations were compared with the threshold/permissible values as shown in **Table 3**. The concentrations of Fe and Al especially from the mining sites were higher than the permissible values [35].


**Table 1.**

*Physical and chemical parameters for the water samples from the sites.*


*Effect of Mining on Heavy Metals Toxicity and Health Risk in Selected Rivers of Ghana DOI: http://dx.doi.org/10.5772/intechopen.102093*

> **Table 2.**

*Mean concentrations (mg/L) of heavy metals in the rivers from pristine and mining areas (Hadzi et al., 2018).*


#### **Table 3.**

*Maximum permitted heavy metal concentrations (mg/L) for drinking water quality and protection of freshwater aquatic life.*

Metal concentrations from this study were safe for aquatic life. Hg and Cd were below detection limit. In general, higher concentrations of heavy metals were measured in mine sample with maximum concentrations of 13.847, 20.355, 2.667, 0.088, 0.245, 0.111, 0.226, and 0.026 mg/l for Al, Fe, Mn, Cr, Cu, Zn, As, and Pb, respectively. The concentrations of most metals in the pristine samples were either below their permissible limits or far below levels obtained from the mining sites, which suggests less anthropogenic activity in the pristine sites. Distribution of Al, Fe, and Zn is the same at the pristine and the mining sites. In assessing the heavy metal contaminations of the various sites, the levels were compared with previous studies from the same sampling sites and other natural rivers, and it was realized that the metal concentrations in this study are lower [36, 37]. A study conducted by Hadzi et al., in 2015 on the same rivers indicated a low metal input. However, similar low concentrations of Cd, Hg, As, Mn, Cu, and Zn in river Samre in the Wassa Amenfi West District in the Western region and Nangodi and Tinga drinking water sources in the Northern region of Ghana were reported. In a separate study in 2013, Cobbina et al., found relatively low concentrations of heavy metals in surface water and boreholes at Tinga in the Bole-Bamboi District of Ghana. According to Bowen [38], freshwater contains 0.1, 3.0, 3.0, and 15 mg/l of Cd, Cu, Pb, and Zn, respectively. However, the concentrations of metals reported at the pristine sites of this study are far less than those reported in freshwater bodies. Aladesanmi et al., in a similar study in Nigeria, 2014 [39], reported concentrations of Cd and As below detection limits and levels of Pb, Cr, Co, and Cu ranging from 0.003 to 0.009 mg/L.

#### **3.3 Statistical analysis of data**

Possible correlations and variability checks were conducted on the metal concentrations. The cluster analysis, as shown in **Figure 1 (attached),** indicates two main groups of metals. Cluster 1 comprised V, Co, Cr, Ni, Pb, Cu, Zn, and As with some association with Mn. Cluster 2 comprised Fe and Al with some association with Mn. The measurement of metals such as Pb, Co, Zn, Cu, As, and Cr indicates anthropogenic sources such as mining around the study sites. The PCA analysis identified two components that were significant with eigenvalues greater than 1 and were extracted accounting for total percent variance of 88.6% as shown in **Table 4.** Component 1 accounted for 74.1% of the total variance, and Component **2,** 14.5% of the total variance. This association of the metals into components as shown in **Figure 2** was confirmed by the correlation results in which As and Mn correlated

*Effect of Mining on Heavy Metals Toxicity and Health Risk in Selected Rivers of Ghana DOI: http://dx.doi.org/10.5772/intechopen.102093*

#### **Figure 1.**

*A plot of concentration against sampling sites from ICP/MS results source: [12].*


#### **Table 4.**

*Factor loading for select heavy metals in water from mining and pristine sites.*

weakly with all metals except Mn and Fe (0.76) as shown in **Table 5.** Manganese and As co-precipitate when Mn hydroxide and oxides in clay minerals act as nucleation sites for adsorption of As [40]. There was strong correlation between Pb and Cu, Co, V and Al. Lead was not detected in the pristine samples; therefore, the metal occurrence in the mining samples may be due to anthropogenic activities of mining.

Component 1, which explains majority of the total variance (74.1%), had strong loadings on Fe, Al, Pb, V, Cu, Zn, Co, Ni, and Cr. The presence of metals such as Pb, Cu, Co, Ni, Zn, and Cr suggests that mining might have contributed to metal

**Figure 2.**

*Dendogram showing clustering of metals in rivers from pristine and mining sites.*


#### **Table 5.**

*Correlation matrix of select heavy metals in water samples from pristine and mining sites, n = 44.*

contamination of the rivers [41]. Component 2 had strong loading on As and moderate loading on Mn suggesting that these two metals may be coming from different pollution sources. The ANOVA two-way computed indicates significant difference in metal concentrations since the probability associated with the p-value (0.005) is less than 0.05 (F = 2.89, Fcrit = 1.99). The p value (0.015) for the site study indicates significant


#### **Table 6.**

*Two-way ANOVA showing differences between sites and metals.*

differences in site concentrations (F = 2.37, Fcrit = 1.94) as shown in **Table 6**. These differences were confirmed by PCA, cluster analysis, and the correlation results. The study identifies anthropogenic activities as a major source of metal contamination of the rivers especially from the mining areas.
