*2.2.1 Water sampling and analysis*

The selections of sampling sites (**Figure 3**) were based on a number of factors such as the ongoing land use activities (farming and illegal artisanal gold mining) and geological settings. Twenty-four (24) well-distributed groundwater point sources (boreholes) functioning hand pumps within the study area according to protocols developed by [17, 18] were sampled in 0.5 litre polythene containers. The containers were conditioned by thoroughly washing with detergent, rinsed several times with acidified water (2%) HNO3 to prevent contamination. Boreholes were purged for over five (5) minutes so as to obtain fresh samples that were filtered through a 0.45-micron membrane. At each well-site, two (2) samples were obtained for the determination of heavy metals and major ions. To analyze for heavy metals in the laboratory, one sample is filtered and acidified with 2% v/v of HNO3 to keep ions in solution while unacidified samples were used for major cation and anion analysis. Electrical conductivity (EC), pH and alkalinity were measured at point sampling in the field, using a calibrated WTW field conductivity meter model LFT 91, WTW

**Figure 3.** *The study area showing water sampling points.*

field pH meter model pH 95 and a HACH digital titrator respectively. A multipurpose electronic DR/890 Colorimeter was used to measure the color, turbidity, total dissolved solids. Sodium and Potassium were analyzed in the laboratory using the flame photometer. Calcium and Magnesium were analyzed using the AA240FS the Fast Sequential Atomic Absorption Spectrometer whilst ICS-90 Ion Chromatograph (DIONEX ICS -90) was used for carrying out chloride (Cl), fluoride (F), nitrate (NO3) and sulphate (SO4) analyses. Phosphate was determined by the ascorbic acid method using the ultraviolet spectrophotometer (UV-1201). Five (5) ml of each acidified water sample was measured and 6 ml of nitric acid, 3 ml of HCl and 5 drops of hydrogen peroxide (H2O2) were added for acid digestion and placed in a milestone microwave lab station ETHOS 900. The digestate was then assayed for the presence of Zinc (Zn), lead (Pb), Copper (Cu), Chromium (Cr) and Cobalt (Co) using VARIAN AAS240FS Atomic Absorption Spectrum in an acetylene-air flame. Arsenic (As) and Mercury (Hg) were determined using argon-air flame.

## *2.2.2 Estimation of water quality index (WQI)*

To evaluate the general suitability of groundwater for drinking purposes, the water quality index (WQI), a rating and index concept, which was originally proposed by [19] as has been found to be a widely acceptable approach. According to [20], WQI is a rating that reflects the composite influence of different water quality parameters on a picture of the quality of groundwater for most domestic uses. The estimation of WQI requires the utilization of significant parameters that may influence the purpose to which the water is required. Major cations and anions as well as heavy metals that may impose health implications to human health selected are pH, Electrical Conductivity (EC), Sodium, and Calcium, Nitrate, Fluoride, Chloride, Sulphate, Zinc, Lead and Cadmium, and were used to calculate the WQI for this study. The highest weight of five (5) was assigned to lead, nitrate, and fluoride due to their health significance to human health. The water quality index (WQI) for each groundwater source (borehole) is estimated using the following series of relations (1, 2, 3 and 4), and the result was compared to the criteria defined by [20];

$$\mathbf{W}\_{\!i} = \frac{\mathbf{w}\_{\!i}}{\sum\_{\!i=1}^{n} \mathbf{w}\_{\!i}} \tag{1}$$

where, Wi is known as the relative weight; wi is the assigned weight to an influential parameter relative to its impact on the overall quality for drinking purpose and also health implications to humans; <sup>n</sup> <sup>i</sup> i 1w ∑ <sup>=</sup> is the summation of assigned weights of all the influential parameters

$$\mathbf{q}\_{\parallel} = \frac{\mathbf{C}\_{\parallel}}{\mathbf{S}\_{\parallel}} \times \mathbf{100} \tag{2}$$

where, *qi* is referred to as the water quality rating; *Ci* and *Si* represent the

measured concentration in sampled groundwater and the respective standard [7] of the ith influential parameter. The water quality sub-index for each of the influential parameter (SIi) is estimated as

$$\mathbf{S}I\_{\mathbf{i}} = \mathbf{q}\_{\mathbf{i}} \times \mathbf{W}\_{\mathbf{i}} \tag{3}$$

*Effects of Illegal Artisanal Gold Mining Operations on Groundwater Quality in Ghana… DOI: http://dx.doi.org/10.5772/intechopen.100242*

where, the symbols have their usual meanings.

$$\mathcal{W}QI = \sum\_{l=1}^{n} \mathcal{SI}\_{l} \tag{4}$$

Thus, the sum of all the water quality sub-indices is resulting in the estimated water quality index for ith influential parameter.
