Heliyon 8 (2022) e12323Contents lists available at ScienceDirect
Heliyon
journal homepage: www.cell.com/heliyonResearch articleImpact of artisanal small-scale (gold and diamond) mining activities on the
Offin, Oda and Pra rivers in Southern Ghana, West Africa: A scientific
response to public concern
Samuel Nunoo *, Johnson Manu, Francis K.B. Owusu-Akyaw, Frank K. Nyame
Department of Earth Sciences, School of Physical and Mathematical Sciences, University of Ghana, Legon, P. O. Box LG 58, Accra, GhanaG R A P H I C A L A B S T R A C TA R T I C L E I N F O
Keywords:
Illegal mining
River pollution
Birimian
Tarkwaian* Corresponding author.
E-mail address: snunoo@ug.edu.gh (S. Nunoo).
https://doi.org/10.1016/j.heliyon.2022.e12323
Received 11 August 2022; Received in revised form
2405-8440/© 2022 The Author(s). Published by Els
nc-nd/4.0/).A B S T R A C T
The surface water systems of Ghana serve as a major source of drinking water, besides other multi-purpose benefit
of hydro-electrical power generation and transportation. Thus, the dependence and benefits from such resources
are of national interest. For instance, the Pra river of the South-Western surface water system of Ghana was a
major consideration for a projected 5 billion m3 water demand in the year 2020 and “African Water Vision 2025”.
In recent times, the colour state of the Pra river and similar surface water bodies of the Offin and Oda rivers has
attracted intense public discussion. The prime issue relates to incessant illegal artisanal gold/diamond mining on
or along these rivers. In order to assess the state of these rivers, water samples were taken, and analysed at the
Council of Scientific and Industrial Research Laboratory (CSIR, Accra-Ghana) to investigate their physico-
chemical quality. The research objective was to assess the extent of their water pollution by measuring
physico-chemical parameters of turbidity, colour, pH and content of selected metals. A total of 18 preserved
bottled samples [(5 from Offin river and 2 boreholes), 5 from Oda river and 5 from Pra river and 1 borehole)]
were analysed, and results compared with portable water standards as defined by the WHO and CSIR (GS-175-1)
of Ghana.
Results on turbidity, colour, mercury and iron from the river and water samples generally exceed WHO or GS-
175-1 limit. The Pra river recorded the most alarming result; range for turbidity (2,010 to 2,745 NTU), colour
(3,000 to 4,500 Hz), total suspended solutes (2,240 to 2,570 mg/L) and total dissolved solutes (97.80–99.60 mg/
L, excluding 319.00 to 25,440 mg/L). The Oda river shows lowest parameter values among the three rivers, as the
areas have been dormant from illegal gold mining for 5 years. Current data suggests polluted river bodies and
boreholes, and that none of these water resources meets the portable water consumption criteria unless treated
prior to usage. As the current state of the water bodies may incur higher cost of water treatment or purification, an15 September 2022; Accepted 6 December 2022
evier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-
S. Nunoo et al. Heliyon 8 (2022) e12323Figure 1. Ghana leads in gintegrated water governance under Ghana's Ministry of Water Resource, Work and Housing, and the Minerals
Commission and Environmental Protection Agency are recommended for the management of these valuable water
resources.1. Introduction
Ghana is known globally for gold (and diamond) mining, and this ac-
tivity contributes more than one-third of Ghana's export revenues. During
the global COVID-19 pandemic, the mining sector was one major area that
was largely considered as an essential sector, especially in Ghana (GCM,
2020), possibly due to its impact on the economy. Such consideration is a
testament of a country whose economic growth is significantly influenced
by the mining sector. For example, in 2013 and 2014, a respective gold
production of 2.63 Moz and 3.48 Moz represent 95% of the country's
revenue from mining (GCM-ICMM, 2015; Smith et al., 2016). Although,
gold production declined from 2019 to 2020 at 4.577 Moz and 4.023 Moz
respectively (GCM, 2020), such values made Ghana the largest gold pro-
ducer in Africa; having taken over South Africa (Figure 1). The mining
sector continues to expand, marked by an increased in exploration activ-
ities within the southern and northern segments of the nation (e.g. Griffis
et al., 2002; Amponsah et al., 2015). Ghana is a prominent gold producer
in West Africa (Pigois et al., 2003), and her stance comes as an output of
large and small scale mining companies, and the artisanal miners (known
locally in Ghana as "Galamsey").
Although, substantive revenues come from gold mining in Ghana, its
operational effects on the environment or the ecosystem cannot be
overlooked. According to Mengistu et al. (2012), mining is among the
ventures of income worldwide with over a century of practice, and leaves
huge volumes of mined tailings and abandoned mine sites. Andrea and
John (2010) emphasized that mining operations often contaminate water
bodies (both surface and groundwater), and causes life threatening dis-
eases upon ingestion; ends up in the human body through eating or
drinking, or by inhalation of associated dust particles. Likewise, Fungaro
et al. (2012) have indicated that several mine wastes are radioactive,
toxic and carcinogens, which affect primary health when consumed in
water or indirectly by certain edible plants.old production in Africa after a t
2
Over the past years, there have been serious concerns raised both in
the Ghanaian media and public discussions regarding detrimental effects
of artisanal scale gold mining activities in many parts of the country,
especially on land degradation, destruction of arable lands and the
quality of water in streams and rivers. In southern Ghana, streams and
rivers including the Offin, Oda and Pra that drain mineralized gold and
diamond-bearing areas have reportedly been drastically affected in
various ways by artisanal gold and diamond mining. For example, Ellahi
et al. (2021) reported that particulate matter, visible organisms,
turbidity, and colour can be observed by users and may generate worries
about the worth and suitability of drinking water supplies. Although the
perceived pollution including change in colour and increased turbidity of
the streams and rivers in manymining areas have often been attributed to
artisanal scale mining activities, not much scientific data have been ac-
quired and/or published to support many of the assertions made. This
study primarily acquired (field) data from water samples taken in the
Offin, Oda and Pra Rivers which were subsequently analysed and in-
terpretations made as a contribution to the currently active discourse on
the impacts of artisanal scale gold mining activities on the quality of
water in southern Ghana. The obtained data or observation has been
equally linked to existing National Water Policy of Ghana (MWRWH,
2007), and an integrated solution proposed.
2. Study area and geology
The study area is the domains drained by the Offin, Oda and the Pra
rivers. The Oda and Offin sampled localities were in the Ashanti Region
whiles the Pra samples are from the Western Region. Details on sampled
localities have been provided in Table 1, and specific sampled points
shown on Figure 2a and 2b. The Ashanti Region belongs to the wet semi-
equatorial climatic region, with the mean annual rainfall between 125
and 200 cm. The heaviest rainfall occurs in June and a second rainfallakeover from South Africa (World Gold Council, 2021).
S. Nunoo et al. Heliyon 8 (2022) e12323
Table 1. Sample identification and location.
Sample ID Water source GPS Coordinates Nearest location/Town
Northern Western
OF1 Offin* 6
3802700 2
0002200 NE of Nyinahin
OF2 Offin* 6
3703000 2
0101400 NE of Nyinahin
OF2BH Borehole 6
3703000 2
0101400
OF3 Offin* 6
3601100 2
0202600 Adiembra
OF4 Offin* 6
3201100 2
0205100 Ntobroso
OF4BH Borehole 6
3201100 2
0205100 Ntobroso
OF5 Offin* 6
2803800 2
0202900 Achiase
ODA1 Oda* 6
2700900 1
3800800
ODA2 Oda* 6
2704700 1
3704700
ODA3 Oda* 6
4202100 1
2703700 Odaho
ODA4 Oda* 6
4202100 1
2703700 Ejisu
ODA5 Oda* 6
4603300 1
2605400 Ejisu
PR1 Pra* 5
0100900 1
3704400 Shama
PR2 Pra* 5
0702500 1
3700000 Beposo
PR3 Pra* 5
1403600 1
3505100 Sekyere-Krobo
PR4 Pra* 5
1700000 1
3503400 Didiso
PR4BH Borehole 5
1700000 1
3503400 Didiso
PR5 Pra* 5
0500300 1
3700500 Atweaboanda
* Major river.from September to October. The Western Region is part of the south-
western equatorial climatic region and is the wettest area in Ghana, with
a mean annual rainfall above 190 cm (Dickson and Benneh, 2004).
The sampled areas are part of the Birimian geological terrane of
southern Ghana, which constitute deformed and metamorphosed
volcano-sedimentary rocks intruded by granitoids (Oberthür et al., 1998;
Feybesse et al., 2006). The metavolcanic rocks include basalts and an-
desites with minor volcaniclastic rocks (Dampare et al., 2008). The
metasedimentary rocks comprise greywacke, phyllitic siltstone and
shale, locally rich in graphite, interbedded with volcaniclastic rocks (e.g.,
Adadey et al., 2009; Nunoo et al., 2016). The intruded granitoids include
granite, tonalite, trondhjemite and granodiorite (TTGs) pulses, and are
coeval with the 2.2–2.0 Ga Eburnean orogeny (Leube et al., 1990; Taylor
et al., 1992; Feybesse et al., 2006).
3. Materials and methods
A total of 18 preserved bottled samples (7 from the Offin catchment
(of which 5 were along the river and 2 from boreholes), 5 from the Oda
river and 6 from the Pra catchment (of which 5 were along the river and 1
borehole) were collected and analysed at the Council for Scientific and
Industrial Research Laboratory (CSIR, Accra‒Ghana). The data was excel-
treated and results compared to World Health Organization (WHO) and
CSIR (GS-175-1) standards on potable water for human consumption.
Descriptive statistical method was as well deployed to define the mini-
mum, maximum, range and standard deviations of obtained results. The
original meta data obtained on samples has been included as appendix 1
for reference purposes. Sampling protocols were dully observed to avoid
any form of contamination. For instance, all the 500 mL polyethylene
bottles for sample storage were pre-conditioned prior to sampling. Rivers
were sampled at where there was a steady continuous flow and reason-
able distance (e.g. mid-way) from the river bank. Sampling was done in
May, 2021, and mostly in the morning. For selected boreholes samples,
each borehole was pumped for a minimum duration of 5 min before
sampling. In other to avoid bare hand interaction with bottle and water,
disposable gloves were used. Samples were stored in ice-coolers and
transported to the laboratory within 12 h. CSIR standard methods used in
analysing for each parameter have been provided in Table 2. In all, ten
standard methods were deployed in the analysis of the twenty-nine3
physico-chemical parameters. The inclusion to test for the presence of
mercury, zinc and lead for only Pra samples, was later suggestion due to
restricted project budget.
4. Results
4.1. Offin river
Results from seventeen measured parameters (Table 3) have been
compared to WHO and CSIR standards. Descriptive statistical summary
of the measured parameters from river and borehole water samples has
been presented respectively in Tables 4 and 5. The values of parameter
recorded from each river sample follow a decreasing order of turbidity
(126.00–469.00 NTU), colour (75.00–400.00 Hz), TDS (157.00–166.00
mg/L), total hardness as CaCO3 (73.60–78.60 mg/L), Na (21.00–25.00
mg/L), Ca (21.00–23.10 mg/L), Cl (18.70–23.80 mg/L), total Fe
(3.66–12.30 mg/L), SO4 (7.00–10.00 mg/L), pH (7.04–7.20), K
(5.00–5.80 mg/L), Mg (5.03–5.47 mg/L), NH4–N (<0.001–0.89 mg/L),
NO3–N (0.23–0.86 mg/L), NO2–N (0.02–0.16 mg/L), Mn (<0.005–0.04
mg/L) and F (<0.005 mg/L). Borehole samples (OF2BH and OF4BH,
Table 3) have lower values relative to river samples and standards, except
few variations for Mn, F, Cl, total Fe content and total hardness as CaCO3
(Table 3). For example, sample OF2BH has Mn content of 0.53 mg/L,
which is highest in all samples and the standards. Also Cl content of this
sample measures 30.00 mg/L that is lower than standards but higher
relative to all analysed samples.
Visual observation of the river shows an obvious change in colour of
water from possibly clean to muddy (Figure 3a) due to increase of sedi-
ment input. Stacked bar graph plot (Figure 3b) of selected parameters,
show higher value or content of colour, turbidity and total Fe of most
samples, except TDS when compared to the adopted standards. The mean
and minimum values of colour, turbidity and total iron (Table 4) still
show higher relative to the standards. For boreholes, all parameters are
lower, except total iron content for borehole water sample OF4BH, which
is higher relative to standards (Figure 3b). However, the minimum and
mean values (Table 5) from the borehole samples are generally lower
relative to standards and river samples.4.2. Oda river
Table 6 presents seventeen measured parameters compared to WHO
and CSIR standards. A summary descriptive statistic of parameter, that
covers minimum, maximum, range and deviations has also been tabu-
lated (Table 7). Decreasing order of value measured for various param-
eters follow a sequence of TDS (93.60–412.00 mg/L), turbidity
(12.70–245.00 NTU), colour (20.00–125.00 Hz), total hardness as CaCO3
(50.60–112.00 mg/L), Na (10.00–75.00 mg/L), Cl (12.00–55.00 mg/L),
Ca (9.14–33.80 mg/L), SO4 (4.00–30.00 mg/L), K (3.00–10.20 mg/L),
NH4–N (0.55–7.99mg/L), pH (6.39–7.40), Mg (4.75–6.76mg/L), NO3–N
(0.06–6.40 mg/L), total Fe (0.53–3.15 mg/L), NO2–N (0.03–1.66 mg/L),
Mn (0.004–0.14), and F (<0.005–0.09 mg/L). Turbidity and colour
values either individually (Table 6) or respective mean 73.92 mg/L and
55.00 Hz show higher values compared to the standards. Sample OD2
show higher nitrite of 1.66 mg/L relate to all samples and standards, but
the average value of 0.58 (Table 7) is 42% less compared with WHO and
GS 175-1 standards. This same sample shows the lowest total iron con-
tent compared to all samples.
The physical observation of the Oda River around Odaho (Figure 4a)
showing a muddy brown colouration. The stack bar graph of selected
parameters (Figure 4b) shows all samples have lower TDS relative to the
used standards. However, the parameters of colour, turbidity and total
iron recorded higher values compared to the standards, except sample
ODA2 with lowest total Fe content (Figure 4b). From the samples, ODA1
and ODA2 show higher values in most measured parameters, but the
former surpasses the later.
S. Nunoo et al. Heliyon 8 (2022) e123234.3. Pra river
Nineteen physico-chemical parameters were measured, and quanti-
tative values are presented in Table 8, and their summary descriptive
statistic also in Table 9. The values as measured are presented here in a
decreasing order; TDS (97.80–25,440 mg/L), Cl (18.50–12,499 mg/L),Figure 2. Map showing sample points along the rivers or
4
Na (8.80–7,000 mg/L), total hardness as CaCO3 (58.00–5,420 mg/L),
colour (30.00–4,500 Hz), turbidity (15.00–2,750 NTU), Mg (6.21–1,078
mg/L), SO4 (5.00–445.00 mg/L), Ca (8.26–393.00 mg/L), K
(4.00–300.00 mg/L), pH (7.00–7.42), total Fe (0.83–3.37 mg/L), F
(<0.005–1.64 mg/L), NO3–N (0.32–1.65 mg/L), Mn (0.004–0.54),
NH4–N (0.07–0.29 mg/L), NO2–N (0.03–0.17 mg/L), Zn (0.01–0.24 mg/tributaries of the (a) Pra and (b) Offin and Oda rivers.
S. Nunoo et al. Heliyon 8 (2022) e12323
Table 2. CSIR instruments/methods used in analysing the parameters.
Parameter Unit Standard Method
Turbidity NTU Nephelometric
Colour (apparent) Hz Visual comparison
pH pH Units pH meter
Conductivity μS/cm Electrometric
Total Suspended Solids (TSS) mg/L Gravimetric
Total Dissolved Solids (TDS) mg/L Gravimetric
Sodium mg/L Flame photometric
Potassium mg/L Flame photometric
Calcium mg/L Titrimetric
Magnesium mg/L EDTA Titrimetric
Total Iron mg/L Spectrophotometric
Ammonia (NH4–N) mg/L Spectrophotometric
Chloride mg/L Argentometric
Sulphate (SO4) mg/L Spectrophotometric Table 4. Descriptive statistical summary of measured parameters of water sam-
Phosphate (PO4–P) mg/L Spectrophotometric ples from the Offin river.
Manganese mg/L Spectrophotometric Parameter N Range Minimum Maximum Mean Std.
Nitrite (NO2–N) mg/L Spectrophotometric Deviation
Nitrate (NO3–N) mg/L Spectrophotometric Turbidity 5 343.00 126.00 469.00 275.00 169.46
Total Hardness (as CaCO3) mg/L Spectrophotometric Colour 5 325.00 75.00 400.00 205.00 120.42
Total Alkalinity (as CaCO3) mg/L Titrimetric with acid pH 5 0.08 7.04 7.12 7.07 0.04
Calcium Hardness (as CaCO3) mg/L EDTA Titrimetric TDS 5 9.00 157.00 166.00 162.00 3.81
Mag. Hardness as CaCO3) mg/L EDTA Titrimetric Sodium (Na) 5 4.00 21.00 25.00 22.80 1.48
Fluoride mg/L Spectrophotometric Potassium (K) 5 0.80 5.00 5.80 5.52 0.30
Bicarbonate (as CaCO3) mg/L EDTA Titrimetric Calcium (Ca) 5 2.10 21.00 23.10 22.12 0.97
Carbonate (as CaCO3) mg/L EDTA Titrimetric Magnesium (Mg) 5 0.44 5.03 5.47 5.19 0.16
Mercury mg/L Mercury Analyser Total Iron (Fe) 5 8.64 3.66 12.30 7.38 4.05
Lead mg/L Spectrophotometric Ammonia 5 0.89 0.00 0.89 0.53 0.32
Zinc mg/L Spectrophotometric (NH4–N)
Copper mg/L Spectrophotometric Chloride (Cl) 5 5.10 18.70 23.80 20.96 1.98
Sulphate (SO4) 5 3.00 7.00 10.00 8.00 1.22
Manganese (Mn) 5 0.04 0.00 0.04 0.02 0.02
Nitrite (NO2–N) 5 0.19 0.02 0.21 0.10 0.08
Nitrate (NO3–N) 5 0.63 0.23 0.86 0.55 0.23
Total Hardness 5 5.00 73.60 78.60 76.68 2.10
(as CaCO3)
Fluoride (F) 5 0.00 0.004 0.004 0.004 0.00L) and Hg (0.003–0.004 mg/L). The astronomical values in TDS, Cl, Na,
Mg and total hardness as CaCO3 content for sample PR1 is due to prox-
imity to the sea, where the river enters the sea. But values of such pa-
rameters decrease upstream (Table 8 and Figure 2a). From the
descriptive statistic result, such parameters respectively have higherTable 3. Measured parameter of water samples from along the Offin River and nearb
mg/L, except turbidity, colour and pH as NTU, Hz and pH units, respectively.
Parameter OF1 OF2 OF3 OF4
Turbidity 126.00 155.00 175.00 450.00
Colour 75.00 150.00 200.00 400.00
pH 7.04 7.10 7.12 7.04
TDS 164.00 164.00 166.00 159.00
Na 21.00 23.00 25.00 22.00
K 5.60 5.60 5.60 5.00
Ca 21.20 22.90 22.40 23.10
Mg 5.47 5.17 5.17 5.03
Fe-total 4.44 3.66 5.32 12.30
NH4–N 0.89 0.61 0.58 0.58
Cl 18.70 19.60 21.80 20.90
SO4 8.00 8.00 10.00 7.00
Mn 0.03 <0.005 <0.005 0.01
NO2–N 0.21 0.02 0.05 0.06
NO3–N 0.23 0.86 0.53 0.66
Total Hardness (as CaCO3) 75.60 78.60 77.20 78.40
F <0.005 <0.005 <0.005 <0.005
*river samples (OF1, OF2, OF3, OF4 and OF5), borehole samples (OF2BH and OF4BH
5
standard deviations to the calculated mean (i.e. Std. Deviation in
Table 9). In Table 9, mercury (Hg) values show zero, and not as recorded
of 0.003–0.004 mg/L (Table 8). These zeros in Table 9 relates to decimal
places defect, and the mean for Hg is 0.0032 mg/L, three-times of WHO
and GS 175-1 standard value (Table 8).
Aerial view (Figure 5a) and on-site (Figure 5b) observation of the
river show muddy brown colouration. The stack bar graph (Figure 5c) of
selected parameters shows similar trend for turbidity, colour and total
iron, as higher values in river relative to WHO and GS 175-1 standards.
Mercury content shows higher values in river and borehole samples
compared to standards (Figure 5c). TDS content varies in samples, for
example PR1 and PR2 show higher values in all samples (including
borehole sample), and when compared to standards (Figure 5c). Total Fe
is only lower in PR4BH compared to all samples and standards
(Figure 5c).y boreholes compared with adopted standards. All parameters were measured in
OF5 OF2BH OF4BH GS 175-1 WHO Guideline
469.00 1.15 3.66 5.00 5.00
200.00 2.50 10.00 5.00 15.00
7.06 6.08 5.05 6.50–8.50 6.50–8.50
157.00 205.00 63.00 1000.00 1000.00
23.00 24.00 6.50 200.00 200.00
5.80 6.20 2.00 30.00 30.00
21.00 24.80 1.52 200.00 200.00
5.13 13.90 7.63 150.00 150.00
11.20 0.05 3.14 0.30 0.30
<0.001 0.05 0.06 0.00–1.50 0.00–1.50
23.80 30.00 19.30 250.00 250.00
7.00 8.30 2.00 250.00 250.00
0.04 0.52 0.21 0.40 0.40
0.16 0.02 0.02 1.00 1.00
0.46 0.42 0.62 10.00 10.00
73.60 119.00 35.20 500.00 500.00
<0.005 0.69 <0.005 1.50 1.50
), GS 175-1 ¼ standard from Council for Scientific and Industrial Research Lab.
S. Nunoo et al. Heliyon 8 (2022) e12323
Table 5. Descriptive statistical summary of measured parameters of water sam-
ples from boreholes closer to the Offin river.
N Range Minimum Maximum Mean Std.
Deviation
Turbidity 2 2.51 1.15 3.66 2.41 1.77
Colour (apparent) 2 7.50 2.50 10.00 6.25 5.30
pH 2 1.03 5.05 6.08 5.57 0.73
TDS 2 142.00 63.00 205.00 134.00 100.41
Sodium (Na) 2 17.50 6.50 24.00 15.25 12.37
Potassium (K) 2 4.20 2.00 6.20 4.10 2.97
Calcium (Ca) 2 23.28 1.52 24.80 13.16 16.46
Magnesium (Mg) 2 6.27 7.63 13.90 10.77 4.43
Total Iron (Fe) 2 3.09 0.05 3.14 1.59 2.19
Ammonia 2 0.01 0.05 0.06 0.05 0.01
(NH4–N)
Chloride (Cl) 2 10.70 19.30 30.00 24.65 7.57
Sulphate (SO4) 2 6.30 2.00 8.30 5.15 4.45
Manganese (Mn) 2 0.32 0.21 0.52 0.36 0.22
Nitrite (NO2–N) 2 0.00 0.02 0.02 0.02 0.00
Nitrate (NO3–N) 2 0.20 0.42 0.62 0.52 0.14
Total Hardness 2 83.80 35.20 119.00 77.10 59.26
(as CaCO3)
Fluoride (F) 2 0.69 0.00 0.69 0.35 0.49
Figure 3. The state of the Offin River at Achiase and selected parameters compared
bank of the river. (b)Except TDS (Total Dissolved Solids), other parameters of colo
standards values. For boreholes, all parameters are lower, except total iron content
6
5. Discussion
Data collected from the three major rivers and a number of boreholes
identified closer to the river course is considered here as a scientific basis
to ascertain if such water bodies and associated borehole water are
polluted. Activities that may have contributed to higher levels of the
measured physico-chemical parameters are discussed as well as the
possible health implications likely to arise from the intake of such water,
as these water bodies or boreholes serve as sources of drinking water or
for domestic usage.5.1. The extent of river pollution and likely sources
A common trend observable in all rivers sampled is the variable de-
grees of muddy brown colouration (e.g. Figures 3a, 4a and 5a and 5b).
According to Lehmann et al. (2018), colour is based on the sensual
perception of the human eye and is an intuitive and a broadly applicable
water measurement. For instance, such an approach has often been used
by people to discern water's suitability for consumption, recreation and
aesthetic value (Smith and Davies-Colley, 1992; West et al., 2016; Ellahi
et al., 2021). From the aerial view of the Pra river (i.e. Figure 5a) and
on-site observation, the muddy brown colouration could be seen by the
eye. Colour is one of the oldest measurement of water quality, hence, the
current colour of the Oda, Offin and Pra rivers possibly indicate saturated
presence of sediments and other dissolved materials. Colour judgement
mostly does not require knowledge of inherent optical properties ofwith WHO. (a) Muddy river show brown colouration and dredge miners at the
ur, turbidity and total iron values of river samples exceed WHO and GS 175-1
for borehole water sample OF4BH, which is higher relative to standards.
S. Nunoo et al. Heliyon 8 (2022) e12323
Table 6. Measured parameters of water samples from along the Oda River compared with adopted standards. All parameters were measured in mg/L, except turbidity,
colour and pH as NTU, Hz and pH units, respectively.
Parameter ODA1 ODA2 ODA3 ODA4 ODA5 GS 175-1 WHO Guideline
Turbidity 245.00 75.40 12.70 12.70 23.80 5.00 5.00
Colour 125.00 75.00 25.00 20.00 30.00 5.00 15.00
pH 7.40 7.36 7.08 6.61 6.39 6.50–8.50 6.50–8.50
TDS 394.00 412.00 113.00 146.00 93.60 1000.00 1000.00
Sodium 90.00 95.00 10.00 28.00 7.50 200.00 200.00
Potassium 10.20 10.00 3.80 6.40 3.00 30.00 30.00
Calcium 33.70 33.80 13.00 12.90 9.14 200.00 200.00
Magnesium 6.76 6.71 5.43 4.75 6.74 150.00 150.00
Total Iron 0.53 0.18 2.70 1.89 3.15 0.30 0.30
Ammonia (NH4–N) 7.93 7.99 0.60 0.55 0.72 0.00–1.50 0.00–1.50
Chloride 52.50 55.00 13.00 23.60 12.00 250.00 250.00
Sulphate (SO4) 25.00 30.00 5.00 15.00 4.00 250.00 250.00
Manganese 0.11 0.004 0.03 0.02 0.14 0.40 0.40
Nitrite (NO2–N) 0.78 1.66 0.03 0.21 0.21 1.00 1.00
Nitrate (NO3–N) 0.06 6.40 0.54 0.80 0.85 10.00 10.00
Total Hardness (as CaCO3) 112.00 112.00 54.80 51.80 50.60 500.00 500.00
Fluoride <0.005 <0.005 <0.005 <0.005 0.09 1.50 1.50
*river samples (ODA1, ODA2, ODA3, ODA4 and ODA5), GS 175-1 ¼ standard from Council for Scientific and Industrial Research Lab.
Table 7. Descriptive statistical summary of measured parameters of water sam-
ples from the Oda river.
Parameter N Range Minimum Maximum Mean Std.
Deviation
Turbidity 5 232.30 12.70 245.00 73.92 99.09
Colour 5 105.00 20.00 125.00 55.00 44.86
pH 5 1.01 6.39 7.40 6.97 0.45
TDS 5 318.40 93.60 412.00 231.72 157.60
Sodium 5 87.50 7.50 95.00 46.10 43.13
Potassium 5 7.20 3.00 10.20 6.68 3.37
Calcium 5 24.66 9.14 33.80 20.51 12.19
Magnesium 5 2.01 4.75 6.76 6.08 0.93
Total Iron 5 2.97 0.18 3.15 1.69 1.31
Ammonia 5 7.44 0.55 7.99 3.56 4.02
(NH4–N)
Chloride 5 43.00 12.00 55.00 31.22 21.08
Sulphate (SO4) 5 26.00 4.00 30.00 15.80 11.65
Manganese 5 0.13 0.00 0.14 0.06 0.06
Nitrite (NO2–N) 5 1.63 0.03 1.66 0.58 0.67
Nitrate (NO3–N) 5 6.34 0.06 6.40 1.73 2.63
Total Hardness 5 61.40 50.60 112.00 76.24 32.68
(as CaCO3)
Fluoride 5 0.09 0.00 0.09 0.02 0.04water, but directly measurable by any optical imager with bands within
the visible spectrum (e.g. Giardino et al., 2001; Van der Woerd and
Wernand, 2018). The measured laboratory data of colour from the
samples compared with WHO (15 Hz) and CSIR (5 Hz) standards in-
dicates several folds of intense colour obliteration. Comparatively,
average values for river colour increase from the Oda river (average
55.00  20.00 Hz) through Offin river (average 205.00  54.00 Hz) to
Pra river (2,286  928.00 Hz).
In addition to the above higher values of colour, river samples (Oda,
Offin and Pra) are marked by respective excessive average turbidity
values of 74.00  44.00, 275.00  76.00 and 1,428  565.00 NTU, and
total Fe contents of 1.69 0.58, 7.38 1.81 and 2.11 0.52 mg/L. Such
values are suggestive of huge amount of suspended materials (e.g., sed-
iments and charged iron). Elsewhere (e.g., Health Canada, 2012), a
combination of colour and turbidity has been a way in measuring water7
quality, which gets influenced by factors such as sediments traps, soil
run-off and algae incubators (e.g. Vo€ro€smarty et al., 2003; Gardner et al.,
2021). Parameters of colour and turbidity are often observable by
humans, and may induce worries about the suitability of the water for
consumption or other usage (e.g. Ellahi et al., 2021).
Current data as exemplified by the measured physico-chemical pa-
rameters (e.g. colour, turbidity, pH, total iron and TDS among others)
may be largely through the activities of illegal artisanal mining (locally
called "Galamsey"), as such practices are common in the upstream and
along the banks of river bodies. Illegal miners adopt unprofessional
rudimentary style of mining, for example, dredging on rivers (Figure 3a)
using pressure-regulated tubes to mine the gold-bearing river-beds. The
geology (Figure 6) and the tropical climatic condition that characterized
the area make availability of the alluvial forms of Birimian-Tarkwaian
gold from a highly weathered metamorphosed ferruginous-shales or
Fe-rich sedimentary rocks (e.g., Manu et al., 2013; Asiedu et al., 2019). In
addition, the elevated contents of mercury in Pra samples, ~ three to four
times higher compared to standards (Fig, 5c), likely relates to excessive
usage of Hg in gold processing by artisanal miners, a known practise
among illegal miners. The higher levels of ammonia and nitrite (relative to
standards) in some Oda samples (Table 7) and sulphate in two Pra sam-
ples (Table 8) are likely related to run-off of excess usage of fertilizers
from cocoa farmlands or sources yet to be known. Run-off of excess
fertilizers from farmland is possible through heavy-down pours, which is
climate dependant. According to Murphy and Sprague (2019) and Stets
et al. (2020), changes in hydroclimate is an effective driver for river
colour change, as all manner of materials (e.g. sediments and chemicals)
could be washed into water bodies. Alternatively, farmlands closer to
river bodies may have been mined directly by illegal miners, and thereby
getting such substances into the river. The Pra river among the three
sampled rivers shows the highest amount of pollutant. Such pollutants
arise from vigorous and continues illegal mining operations, and or likely
sampling from the downstream part of Pra; acting as a sink that receives
pollutant from upstream.
For theboreholes, the higher content of certain chemical parameters, for
example, Hg in the Pra samples (i.e. PR4BH, Table 8), and total iron and
colour in the Offin borehole sample (i.e. OF4BH, Table 3) suggest certain
degree of interconnectivity between the river bodies and groundwater
closer to the catchment areas. The seepage of source water or polluted
materials into groundwater is a higher possibility within the Birimian
terrane, as rocks are characterized by fractures, foliations and folds
S. Nunoo et al. Heliyon 8 (2022) e12323
Figure 4. The state of the Oda River and plotted parameters compared with WHO. (a) River shows light brown colouration. (b) Stack bar graph of selected parameters
shows samples recorded lowest TDS relate to standards, but turbidity and colour values of samples exceed WHO. Total Fe content of samples exceed WHO, except
sample ODA2.structures, which serves as weak zones or conduits suitable for fluid infil-
tration (e.g., Perrouty et al., 2012;Nunooet al., 2016).Comparatively to the
river samples, the borehole samples are less polluted, andmay be due to the
adsorption of pollutants into soils as water percolates into aquifers.
5.2. Portability of the water and possible health implications
Selected physico-chemical parameters of turbidity, colour and iron
content from all rivers samples, pH of all boreholes and variable levels of
fluoride, mercury, zinc, ammonia, sulphate and nitrite in all samples
suggest contamination, which makes neither river nor borehole ideal for8
human consumption or domestic usage. These parameters compared
with both the WHO and CSIR (GS-175-1) standards are often higher,
although few lower values do occur that indicate deficiency relative to
the standards. In all the areas where existing boreholes are being used,
perhaps the colour of the water is based on eye judgement as a measure to
know whether the water is clean without any form of contamination.
However, the laboratory results indicate that none of the samples from
the river and borehole make them suitable for human consumption, and
could induce possible health issues when consumed in their current state.
For instance, water samples from boreholes recorded pH from 4.72 to
6.08 (Tables 3 and 8) but these values are lower than the WHO
S. Nunoo et al. Heliyon 8 (2022) e12323
Table 8.Measured parameters of water samples from along the Pra River and nearby borehole compared with adopted standards. All parameters were measured in mg/
L, except turbidity, colour and pH as NTU, Hz and pH units respectively.
Parameter PR1 PR2 PR3 PR4 PR5 PR4BH GS 175-1 WHO Guideline
Turbidity 15.00 2235.00 2010.00 2745.00 138.00 <1.00 5.00 5.00
Colour 30.00 3750.00 3000.00 4500.00 150.00 <2.50 5.00 15.00
pH 7.42 7.15 7.00 7.03 7.36 4.72 6.50–8.50 6.50–8.50
TDS 25440.00 98.40 99.60 97.80 3444.00 319.00 1000.00 1000.00
Sodium (Na) 7000.00 9.00 8.80 9.00 850.00 60.00 200.00 200.00
Potassium (K) 300.00 4.50 4.00 4.00 26.00 9.00 30.00 30.00
Calcium (Ca) 393.00 13.10 12.80 8.26 33.30 23.40 200.00 200.00
Magnesium (Mg) 1078.00 6.21 8.30 9.08 115.00 17.90 150.00 150.00
Total Iron (Fe) 1.06 2.19 3.12 3.37 0.83 0.01 0.30 0.30
Ammonia (NH4–N) 0.25 0.12 0.20 0.07 0.40 0.29 0.00–1.50 0.00–1.50
Chloride (Cl) 12499.00 18.50 20.80 18.90 1310.00 180.00 250.00 250.00
Sulphate (SO4) 445.00 5.00 5.00 5.00 285.00 6.35 250.00 250.00
Manganese (Mn) 0.54 0.13 0.16 0.17 0.004 0.01 0.40 0.40
Nitrite (NO2–N) 0.03 0.08 0.05 0.17 0.05 0.01 1.00 1.00
Nitrate (NO3–N) 0.46 1.52 1.65 1.33 0.32 1.36 10.00 10.00
Total Hardness (as CaCO3) 5420.00 58.40 66.20 58.00 612.00 132.00 500.00 500.00
Fluoride (F) 1.64 <0.005 <0.005 <0.005 <0.005 <0.005 1.50 1.50
Mercury (Hg) 0.003 0.003 0.004 0.003 0.003 0.003 0.001 0.001
Zinc (Zn) 0.02 0.24 0.02 0.01 0.03 0.13 - -
*river samples (PR1, PR2, PR3, PR4 and PR5), borehole (PR4BH), GS 175-1 ¼ standard from Council for Scientific and Industrial Research Lab.
Table 9. Descriptive statistical summary of measured parameters of water samples from the Pra river.
N Range Minimum Maximum Mean Std. Deviation
Turbidity 5 2730.00 15.00 2745.00 1428.60 1263.44
Colour (apparent) 5 4470.00 30.00 4500.00 2286.00 2074.06
pH 5 0.42 7.00 7.42 7.19 0.19
TDS 5 25342.20 97.80 25440.00 5835.96 11054.32
Sodium (Na) 5 6991.20 8.80 7000.00 1575.36 3054.26
Potassium (K) 5 296.00 4.00 300.00 67.70 130.20
Calcium (Ca) 5 384.74 8.26 393.00 92.09 168.49
Magnesium (Mg) 5 1071.79 6.21 1078.00 243.32 468.90
Total Iron (Fe) 5 2.54 0.83 3.37 2.11 1.16
Ammonia (NH4–N) 5 0.33 0.07 0.40 0.21 0.13
Chloride (Cl) 5 12480.50 18.50 12499.00 2773.44 5465.40
Sulphate (SO4) 5 440.00 5.00 445.00 149.00 205.13
Manganese (Mn) 5 0.54 0.00 0.54 0.20 0.20
Nitrite (NO2–N) 5 0.14 0.03 0.17 0.08 0.05
Nitrate (NO3–N) 5 1.33 0.32 1.65 1.05 0.62
Total Hardness (as CaCO3) 5 5362.00 58.00 5420.00 1242.92 2347.22
Fluoride (F) 5 1.64 0.00 1.64 0.33 0.73
Mercury (Hg) 5 0.00 0.00 0.00 0.00 0.00
Zinc (Zn) 5 0.23 0.01 0.24 0.06 0.10recommended range of 6.50–8.50, which indicate an acidic nature of the
water from the boreholes. The presence of calcium carbonate acts as
natural buffer to make pH close to alkalinity (e.g. McNally and Mehta,
2004), yet the borehole sample shows higher acidity. Limited neutrality
may be due to lower content of the CaCO3 content in the borehole water
samples (35.20, 119.00 and 132.00 mg/L) relative to the WHO standard
of 500.00 mg/L. The CaCO3 content of samples is significantly small, and
may contribute less to increasing pH close to neutrality, especially for
sample PR4BH (pH 4.72). In addition, others (e.g. Griffiths et al., 2006)
have emphasized the occurrence of volcanic ash and sulphate that lowers
pH.
According to WHO (1996, 2003), waters with pH values not within
their range, when consumed, can lead to skin disorders, redness of the
eye and damage to epithelium. Although, the number of samples may be9
relatively small for an in-depth health-related deduction, higher levels of
iron and mercury particularly in the Pra river samples relative to the
WHO and CSIR standards cannot be overlooked. For example, WHO
compilation of mercury data emphasized its potent to cause severe
disruption of any tissue (concentration dependant), however, the main
effects of mercury poisoning are neurological and renal disturbances. It
has long been reported (e.g. Stockinger, 1981) that the ingestion of
mercury could result in swelling of the salivary glands, stomatitis, loos-
ening of the teeth, nephritis, anuria and hepatitis. From the results of this
research, Hg levels range from 0.003 to 0.004 mg/L as against WHO and
CSIR recommended value of 0.001 mg/L; such increment close to
quadruple could be detrimental. For example, Skerfving and Vostal
(1972) indicated that hours of exposure to 1–3 mg/m3 of Hg may give
rise to pulmonary irritation and destruction of lung tissue and
S. Nunoo et al. Heliyon 8 (2022) e12323
Figure 5. The muddy state of the Pra River and selected parameters compared with WHO. (a & b) Muddy river show brown colouration from an aerial view and at the
bank of the river. (c) Respective turbidity, colour and total iron values of samples exceed WHO, except for borehole PR4BH. The TDS of PR1 and PR2 measures higher
relative to samples and standards. Mercury content of both river and borehole sample exceed WHO.occasionally to central nervous system disorders. The health discussion of
this current work requires comprehensive data and an approach of some
medical data which is an aspect for future research. However, the current
state of the water bodies and borehole water when consumed could pose
health issues.
5.3. Current data in relation to Ghana water policy
The water policy of Ghana is driven by the United Nation (UN) Mil-
lenniumDevelopment Goals (MDGs) and the New Partnership for African
Development (NEPAD), both explore strategic ways to harness growth
and reduce poverty (MWRWH, 2007). For instance, a core feature
recognized in both strategies is the improvement in the provision of
water supply and sanitation services. Specifically, regarding the MDGs,
the Government of Ghana has endorsed a number of principles for water
(MWRWH, 2007), which include (i) improving access to safe water
supply and sanitation to reduce the proportion of population without
access to basic water supply and sanitation by 50% by 2015 and 75% by
2025, (ii) promoting efficient and sustainable use of water to address
food security and income generation, and (iii) using integrated water
resource management (IWRM) to promote cooperation in national and
shared water basins for the mutual benefit of all water users and their
communities, (iv) acting to prevent, mitigate and manage water related
disasters by developing a prevention based culture, strengthening ca-
pacity to monitor and mitigate the effects of climate variability and to
manage disasters.
The current illegal mining along river courses as mentioned earlier,
and supplemented by the obtained data defeat the outlined principles
by the Ministry of Water Resources Work and Housing (MWRWH,102007) of Ghana. According to MWRWH (2007), the Pra river forms a
major river body under the South-Western surface river systems under
surface water of Ghana, and was considered a major source of water
for projected 5 billion m3 water demand in the year 2020. Thus, Pra
and the other surficial water sources (e.g., Offin and Oda) are valuable
water resources that should be protected from all manner of pollution.
The current states of the investigated rivers also challenge the NEPAD
vision of an “African Water Vision 2025” that focuses on more equi-
table and sustainable use of water resources for poverty alleviation,
socio-economic development, regional cooperation and the environ-
ment ((MWRWH, 2007). In addition, the data as well questions Gha-
na's Water Vision for 2025 aimed to “promote an efficient and
effective management system and environmentally sound develop-
ment of all water resources in Ghana” (Section 1.2 of MWRWH, 2007).
The current state of the examined river bodies is likely to register
ripple effects such as a higher purification and maintenance cost,
health-related crises from consumption and non-suitable as a source
water for irrigation. For instance, it has been demonstrated elsewhere
that the quality of irrigation water has effect on crop yield, internal
and external qualities of the product (Rusan et al., 2007; Zavadil,
2009; Mzini and Winter, 2015).
In recent times, the Ghana Water Policy of 2007 has been review by
Frimpong et al. (2021). The team (Frimpong et al., 2021) drew attention
to ineffective expectation of the policy as supposed to turn fortunes of the
country around in the context of water resource management. High-
lighted setbacks since implementation include inadequate institutional
capacity and ineffective enforcement of existing regulations among
others (Frimpong et al., 2021). The recent observation (this study) of the
surface water, especially in the south-western sector of the nation attest
S. Nunoo et al. Heliyon 8 (2022) e12323
Figure 6. Geological map of Southern Ghana (GSD, 2009) showing the sampling points in relation to the underlying rocks incised by the Offin, Oda and Pra Rivers.to a major problem of ineffectiveness governance of the investigated
surface water resources. For effective governance, an integrated effort
and measures are required from major relevant policy making bodies
such as the Water-related institutions under MWRWH, the Inspectorate
Division of the Minerals Commission and the Environmental Protection
Agency of Ghana.
6. Conclusion and recommendations
6.1. Conclusion
Major rivers of the Offin, Oda and Pra basins and few nearby
boreholes were sampled and analyzed to ascertain if polluted, as colour
of the rivers observed posed worries to the public. The data obtained
from 15 river samples and 3 borehole samples offer three main
deductions:
 The current state of the three rivers and nearby borehole waters in-
dicates contamination as values of colour, turbidity, total Fe, mer-
cury, ammonia and sulphates exceed potable water limits by theWHO
and Ghana CSIR standards.
 Potential activity believed to have largely necessitated the observed
trends in the apparent colour, suspended sediments level and other
chemical constituents can be related to practices of illegal alluvial
gold mining. In some samples, especially in the Pra and Oda rivers,
high values of ammonia, nitrite and sulphate could come from excess
run-off from farmland fertilizers or other sources yet to be
established.
 Among the three rivers, the data indicate an increase of pollution
from the Oda through Offin to the Pra Rivers. The current state of
these rivers are not desirable for human consumption without any
treatment, particularly, that of the Pra River and the associated
boreholes which are much acidic with extreme high levels of chlorine
and mercury likely to pose health issues.116.2. Recommendations
 The need to monitor all the rivers and associated borehole water
should be of a national concern and for this reason regular or periodic
sampling is needed to check levels of contamination and give advice
on the suitability of using the water especially for drinking.
 Future research should be focused on other major rivers, such as the
Birim, Ankobra and the Tano within the country, which drain areas
with some mining activities.
 Future work should consider soil analysis, especially, the likelihood of
pollutants adsorbedby soil during the percolationofwater into aquifers.
Declarations
Author contribution statement
Samuel Nunoo; Francis K.B Owusu-Akyaw: Conceived and designed the
experiments;Performedtheexperiments;Analyzedand interpreted thedata;
Contributed reagents, materials, analysis tools or data; Wrote the paper.
Frank K. Nyame; Johnson Manu: Analyzed and interpreted the data;
Wrote the paper.
Funding statement
This work was supported by Francis K.B Owusu-Akyaw and the
Council for Scientific and Industrial Research Laboratory.
Data availability statement
Data will be made available on request.
Declaration of interest’s statement
The authors declare no competing interests.
S. Nunoo et al. Heliyon 8 (2022) e12323Additional information
No additional information is available for this paper.
Acknowledgements
Special thanks to Mr. Frimpong of Ashanti Region for his immense
support during the data collection. We also acknowledge reviewers for
contribution and suggestion.
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