Basically the main study area was conducted in the Adenta Municipality in the Accra Metropolis of Greater Accra Region, in Ghana as shown in Figure 4. Adenta has two main rainfall patterns and it is found within the wet-semi equatorial climate region. The primary rainfall pattern begins in May to June and the secondary rainfall part hen starts from September to October. Most at times, the recorded temperature is 26˚C.

Among the sixteen districts in the Greater Accra Region, Adenta is specially one of the sixteen districts in Greater Accra Region and it is found on Latitude 5'43'' north and longitude 0'09'' west and located 10 kilometres to the North-east of Accra as shown in Figure 4, Figure 5(a) and Figure 5(b) respectively.

There are several rivers in Adenta, prominent among are the Ogbojo stream and Nugete River. Water scarcity is common in the municipality. The inhabitant normally relies on water vendors, built tanks and pollutants to store water. The boreholes water samples are then transported into the Alpha spectrometry Laboratory of Ghana Atomic Energy Commission for storage, preparation and analysis.

1000 ml of the borehole water samples were filled in a clean Marilina Beakers and tightly sealed for a period of one month to in order to permit daughter radionuclides to attain equilibrium with parent radionuclide. Daughter nuclides are the remaining nuclide left over from radioactive decay. Each borehole water sample was weighed and the masses were also recorded. Later each sample was analysed using a gamma spectrometry system with a counting assembly.

The electronic analyser that was used for the measurement was a Gamma-Spec- trometry system, which is attached to a computer-based multichannel analyser. The Gamma Spectrometry system is also made up of n-type HPGE detector.

The energy resolution of the detector is 1.8 KeV at gamma ray of 1332 KeV of Co and a relative efficiency of 25%. A quality control measure is conducted on the detector to determine the background distribution of the detector and is performed by filling eight (8) Marilina beakers with distilled water and counted for 36,000 s in the same geometry as the samples.

A software known as Genie ? 2000 is used to determine the qualitative analysis of radionuclides and identifying individual’s radionuclides as shown in Figure 6 respectively. This was done by using their gamma ray energies. A background spectra was used to determine the minimum detectable activities of ⁴⁰K (0.19 Bq/L) ²²⁶Ra (0.11 Bq/L) and ²³²Th (0.13 Bq/L) respectively [8] [9] . The net peaks areas of the peaks areas of the gamma rays were collected using the background spectra.

A multi nuclide reference standard solution was used to calibrate the reference standard in solid water as shown in Figure 7. This standard solution was obtained from the International Atomic Energy Commission (IAEA) and it was used to determine the energy and efficiency calibration. This is conducted before commencing the analysis on the samples to ensure quantification and identification of the radionuclides as shown in Figure 7 respectively.

The multi nuclides reference standard solution is made of the following radionuclides with corresponding energies:

²⁰³Hg (279.20 Ke), ²⁴¹Am (59.54 KeV), ⁸⁸y (898.04 KeV and 1836.1 KeV), ¹³⁹Ce (165.86 KeV), ⁸⁵Sr (514.01 KeV), ⁶⁰Co (1173.2 KeV and 1332.5 KeV), ¹¹³Sn (391.69 KeV), ¹⁰⁹Cd (88.03 KeV) and ⁵⁷Co (122.06 KeV).

Four radionuclides were used to determine the radionuclides, these consist of: ⁶⁰Co, ²⁴¹Am, ¹³⁷Cs and ⁵⁷Co respectively. To acquire the spectra data, the standard was poured into a one litre Marilina beaker for measurement and counted for 36,000 Seconds.

The principal gamma rays energies in the Spectrum were calibrated both manually and the use of a computer system. A standard reference material was used to calibrate the spectrum in the channel number of the spectrometer.

The equation is express as:

Eɤ = a_o + a₁ + CN

where:

Eɤ = the energy in KeV.

a_o + a₁ = calibration constant.

CN = channel number.

To determine the known activities efficiency calibration as shown in Figure 8 respectively, a standard radionuclide with define energies ranged from 60 - 2000 KeV was used.

A net count rate was used to determine the photo peaks for all the energies:

The equation is expressed used is given as:

E (Eɤ) = N/(A * P* t)

where:

Eɤ = the energy in KeV (Gamma emission).

N = the full energy peaks net count.

A = the activities of the source.

P = gamma emission probability.

T = the counting time.

Furthermore, another equation was used to calculate the activity concentrations in Bq/L as shown in Figure 9 respectively. The borehole water sample this equation is given as:

Asp = Specific activity concentration.

Nsam = background of samples.

PE = is the gamma yield.

E = the total counting efficiency.

Tc = sample counting time.

M = mass of sample (Kg).

Each radionuclide was used to determine the committed effective dose, this was done by estimation it from the activity concentrations and using the WHO yearly water consumption rates for adults which was done by estimation it from the activity concentration and using the WHO yearly water consumption rates for adults which was given as 730 L/year using the expression:

Annual Effective dose, Et = e (Aw * DCFw) * Iw

where:

Et = Annual effective dose.

Aw = the activity concentration.

DCF = the dose conversion factor in mSv/Bq.

World Health Organization recommend that for every adult, the annual consumption rate of water per year should be 730 L/year, which gives an estimation of 2 L of water per year for an adult. This implies that for every radionuclide ingested per year, in water consumption the concentration of that radionuclide in the water is multiplied by 730 L respectively. Normally water supply contains more than two radionuclides.

This is calculated using the following equation:

Annual dose (mSv/year) = Dose per unit intake (mSv/Bq) × Annual water consumption (Litre/year) × Radionuclide concentration (Bq/L).

A Microsoft Excel as used to record the data collected. The data was expressed as mean ± standard deviation differences and the mean average activity concentration of the borehole water samples. Correction test was also used to determine the activity concentration of the radionuclides and the physical parameters measured (between the pH, the total dissolved solids, conductivity and temperature). The Ghana Standard Authority and World Health Organization recommended limits were analysed using one-sample―t-test.

The physical parameters were measured such as pH, conductivity, total dissolve solids and temperature as shown in Table 2 respectively. From the results obtained, the results recorded that the temperature of the borehole samples ranged from 22˚C to 29˚C with BW₂ the highest temperature and BW₁₃ recording the lowest temperature (22˚C). The average temperature of the borehole was 25˚C.

The study was carried out to determine the activity concentration of fifth teen (15) different borehole water samples in different areas at the Adenta Municipality. Table 3 demonstrates the sample IDs and the coordinates of the boreholes from which the water sample was collected.

The temperature range from 22˚C to 29˚C respectively, as shown in Figure 10 respectively. BW₁₈ recorded the lowest temperature and BW₈ recorded the highest temperature. The average temperature was 25˚C.

The pH ranged from 4 - 7 as shown in Figure 11 respectively, with an average of 5.89. BW₂₀ recorded the lowest pH and BW₁₄ recorded the highest. There was no significant relationship between temperature and pH.

The total dissolved solids ranged from 349 - 1320 ppm, BW₁₇ recorded the highest value of 1320 ppm and BW₁ recorded the lowest (349 ppm) as shown in Figure 12 respectively. The mean average total dissolved solids was 756.6 ppm. BW₃, BW₆ and BW₉ however recorded values higher that the GSA recommended limit of 1000 mg/L.

BW₇ which recorded the highest TDS also recorded the highest conductivity (2720 µs/cm) and BW₈ which also recorded the lowest TDS, as shown in Figure 13 respectively, again recorded the lowest conductivity of 720 µs/cm. The average conductivity was 1152 µs/cm. There was a very strong positive correlation between TDS and conductivity value.

The WHO recommended limit for committed annual effective dose is 100 µSv/yr. However, BW_2, BW_7, recorded doses higher than the recommended limit. The committed annual effective dose ranged from 5.45 to 138.41 µSv/year with an average value of 33.86 µSv/yr. BW₂ recorded the highest annual effective dose while BW₆ gave the lowest effective dose. This shows that water from the borehole with identification BW₂ gave the highest internal exposure to its consumers. ⁴⁰K contributed the largest dose to the annual effective dose. The activity concentrations of ⁴⁰K, ²²⁶Ra and ²³²Th was used to calculate the committed annual effective as a result of direct consumption of the borehole water.

The activity concentrations of ²²⁶Ra, ²³²Th and ⁴⁰K in borehole water samples were measured accurately in the Adenta municipality. The mean concentration was 0.77 ± 0.42, 0.93 ± 0.62 and 9.77 ± 4.55 Bq/L for ²²⁶Ra, ²³²Th and ⁴⁰K respectively. The activity concentrations of ²²⁶Ra, ²³²Th and ⁴⁰K ranged from 0.13 ± 0.08 to 1.83 ± 0.55 Bq/L, 0.10 ± 0.06 to 4.29 ± 0.27 Bq/L and 1.24 ± 0.16 to 31.73 ± 4.73 Bq/L respectively. BW₆ had the lowest activity concentration of ²²⁶Ra while BW₁₇ had the highest concentration. The highest and lowest activity concentration values of ²³²Th were found in samples with identifications BW₂ and BW₇ respectively while the highest activity concentration of ⁴⁰K was found in sample with BW₁₉ and the lowest in BW₁₅.

For ²²⁶Ra, BW₂, and ²³²Th BW₇ exceeded the WHO recommended limit of 1000 Bq/L.