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The region along the Lower Pra River Basin has been studied for dissolved Hg concentration in the surface water of the river and its tributaries which serve as source of drinking water for communities along the basin. The study area encompassed 6 communities in the Mpohor Wassa East district of the Western Region of Ghana with a population of 122,595. Samples of surface water were collected from locations in the period September 2006 to March 2007 spanning the wet (rainy) seasons and dry seasons chronologically. The seasonal variation in dissolved mercury concentration during the wet and dry seasons in the study area was also investigated. The dissolved Hg concentration in surface water was assessed using cold vapor AAS. The average dissolved Hg concentration in the main river (48.40 ± 26.08 ng/mL) and in the tributaries (27.59 ± 18.23 ng/mL) were above the WHO guideline value of 1.0 ng/mL. The trend in contamination levels along the river Pra suggested incidence of both remote pollution and localized pollution occasioned by artisanal alluvial gold mining activities within this enclave using mobile rigs which constitute rafts with mechanized dredging equipment mounted on them.
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International Journal of Applied Science and Technology Vol. 2 No. 1; January 2012
Assessment of Dissolved Mercury in Surface Water along the Lower Basin of
the River Pra in Ghana
William O. Oduro
Council for Scientific and Industrial Research
Institute of Industrial Research
P. O. Box LG 576 Legon
Accra, Ghana.
Richard Bayitse
Council for Scientific and Industrial Research
Institute of Industrial Research
P. O. Box LG 576 Legon
Accra, Ghana.
Derick Carboo
Department of Chemistry
University of Ghana
P. O. Box LG 56, Legon
Accra, Ghana.
Benony Kortatsi
Council for Scientific and Industrial Research
Water Research Institute, P. O. Box 38
Achimota, Accra, Ghana.
Isaac Hodgson
Council for Scientific and Industrial Research
Water Research Institute, P. O. Box 38
Achimota, Accra, Ghana.
The region along the Lower Pra River Basin has been studied for dissolved Hg concentration in the surface water
of the river and its tributaries which serve as source of drinking water for communities along the basin. The study
area encompassed 6 communities in the Mpohor Wassa East district of the Western Region of Ghana with a
population of 122,595. Samples of surface water were collected from locations in the period September 2006 to
March 2007 spanning the wet (rainy) seasons and dry seasons chronologically. The seasonal variation in
dissolved mercury concentration during the wet and dry seasons in the study area was also investigated. The
dissolved Hg concentration in surface water was assessed using cold vapor AAS. The average dissolved Hg
concentration in the main river (48.40 ± 26.08 ng/mL) and in the tributaries (27.59 ± 18.23 ng/mL) were above
the WHO guideline value of 1.0 ng/mL. The trend in contamination levels along the river Pra suggested incidence
of both remote pollution and localized pollution occasioned by artisanal alluvial gold mining activities within this
enclave using mobile rigs which constitute rafts with mechanized dredging equipment mounted on them.
Keywords: Mercury Pollution, Surface Water, Artisanal Gold Mining.
Mercury (Hg) as a naturally occurring element is predominately found in the earth crust as cinnabar ore (HgS) in
trace amounts in minerals and rocks, and also in fossil fuels such as coal (AMAP/UNEP, 2008; García-Sánchez et
al., 2009). The release of Hg into the environment can be through natural means such as volcano eruption and
weathering as well as a variety of anthropogenic sources such as mining, burning of fossil fuel, and combustion of
municipal and medical waste (Jackson and Jackson, 1995; Li, et al., 2009).
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Mercury in any form is toxic but the acuteness in toxicity mainly lies in how it is absorbed (lipid solubility and
permeability to the blood-brain barrier) and the rate of excretion (Diner and Brenner, 2009). Short alkyl organic
mercury is most toxic, however, when elemental and inorganic mercury is released into the environment, bacterial
action causes them to undergo methylation. The products of methylation, like monomethyl mercury (CH3Hg+), are
soluble in water, readily absorbed by fish and the adipose cells but slow to be eliminated, hence are bio-
accumulated and becomes neurotoxic.
The primary mechanisms for transporting atmospheric Hg to the terrestrial and aquatic systems according to the
Selin model is through wet and dry depositions with the dry deposition more than two fold greater than wet
deposition (AMAP/UNEP, 2008). Elemental Hg can circulate in the air for long period of time before depositing.
This is because of its high dispersion leading to long residence times of between 0.5-2 years in the atmosphere. It
is therefore, normally transported from likely sources of emission to locations remote from the pollution centers
(Schroeder and Munthe, 1998). The effect of Hg pollution may therefore not just be limited to the geographical
location of the discharge point (local pollutant) but several kilometers radius (global pollutant) of the point of
original discharge (Harada et al., 2001; Johansson et al., 2001). Reactive gaseous mercury (RGM) and particulate
mercury tend to fall out of the atmosphere more quickly than elemental Hg and are more likely to deposit closer
to the source from which they are emitted (Schroeder and Munthe, 1998).
Public concern over mercury pollution reached its peak in the 1970s following a number of incidents where the
discharge of elemental mercury into watercourses was linked to fatalities and severe health problems in local
residents (Jackson and Jackson, 1995). The use and discharge of Hg into the environment has since received
stricter control and monitoring. Artisanal small-scale gold mining is the single largest contributor to intentional
discharge of Hg to the environment with a global estimate of 650-1000 tonnes of mercury released per annum
(AMAP/UNEP, 2008). It is also the primary anthropogenic source of environmental Hg in Ghana (Hilson and
Pardie, 2006). Poor amalgamation practices in rudimentary gold mining are responsible for the emission and
abusive discharge of mercury into the ecosystem (Swain et al., 2007; Meech et al., 1998; Pfeiffer and Larceda,
The Pra river system, the longest in south western Ghana, takes its source from the Kwahu plateau and flows 240
km into the Gulf of Guinea through its estuary at Shama (Ayibotele and Nerquaye-Tetteh 1989). The north part of
the Pra River basin (especially its main tributaries) is still worked extensively for artisan gold with amalgamation
the main technique in the isolation of the gold from the gangue (Spiegel, 2009, Hilson and Pardie, 2006).
However, the lower watershed is widely acclaimed to have no direct mercury input source since these areas are
not known for artisanal gold mining (Donkor et al., 2006b). The communities along this watershed depend on the
river Pra as source of their drinking water either directly or through a water works situated in the area (Ghana
Population and Housing Census, 2000). The acute health risk associated with the exposure to Hg pollution
through drinking water supply thus necessitates the continuous monitoring of the lower Pra River basin around
areas perceived as non gold mining areas. The literature available on Hg pollution in Ghana considered survey
data in some of the rivers draining the south-western gold belt with known direct mercury input sources
(Bannerman et al., 2003; Bonzongo et al., 2003; Golow and Adzei, 2002; Golow and Mingle, 2003; Donkor et
al., 2006a; Babut et al., 2003; Adimado and Baah, 2002). However, Donkor et al., (2006b) assessed the mercury
contamination levels along the entire Pra River basin with consideration also given to locations at the lower basin
perceived as non gold mining areas with no known direct mercury input sources.
Periodic assessment of the dissolved mercury levels in surface water at the lower reaches of the Pra River and its
tributaries will provide adequate information on the surface water quality in communities located in areas with no
known source of Hg input and hence the health implications on these communities. It will also provide
information to enable the mapping out of communities remotely or locally affected by the activities of artisanal
gold mining in order to regulate their activities and also effectively protect environment that has not already been
contaminated with Hg.
2. Materials and Methods
2.1 Study area
The study area, as shown in Figure 1, is in six communities namely; Enyinabrim, Abetemasu, Sekyere Nsuta,
Krobo, Daboase and Beposo (arranged in the order of north most to south most) on the lower Pra Basin at Mpohor
Wassa East District in the Western Region of Ghana with a population of 122,595.
International Journal of Applied Science and Technology Vol. 2 No. 1; January 2012
These communities are reported to have no known direct Hg input sources (Donkor, et al., 2006b). Only Daboase
which constitute about 11.3% of the population in the district have access to pipe-borne water, 30.4% depend on
borehole water whilst the remaining 58.3% depend on the river Pra and its tributaries for their source of water
(Ghana Population and Housing Census, 2000).
Figure 1 Map of the Pra River Basin showing the study area, with the letter codes showing the specific
sample location. Inset is a map of Ghana with the study area indicated by arrow.
2.2 Sampling and Method of Analysis
3. Sampling
Surface water samples were taken from the river Pra and its adjoining tributaries (where available) in all the six
(6) communities. The sampling locations were selected to reflect the wider geographical sampling area. At
Beposo and Krobo, samples were taken from the Pra River only, because there are no tributaries located within
the sampling area in these two communities. Samples from tributaries were taken close to the point where the
stream flows into the river Pra at Enyinabrim, Abetemasu, Sekyere-Nsuta and Daboase.
The upstream sampling was taken from Enyinabrim-Pra River (EP), Enyinabrim-Nana Toi stream (ENT),
Abetemasu-Pra River (ABP) and Abetemasu-Abetemasu stream (AB). At the midstream, samples were taken
from Sekyere Nsuta-Pra River (SNP), Sekyere Nsuta Buabasa stream (SNB) and Krobo-Pra River (KP).
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The downstream sampling sites were at Daboase-Pra River (DP), Daboase Subri (DS) and Beposo-Pra River. The
stretch of the Pra River from EP to BP is about 88 km.
Duplicate 1.5 L surface water samples were taken from each sampling location per month from September 2006
to March 2007 giving a total of 140 samples to reflect the seasonal variations with its associated hydrodynamics
and sediment dynamics. Generally, in the tropical climate, the wet season is characterized with considerably
higher river outflow velocities and sediment transport is dominated by advection process (van Maren and
Hoekstra, 2004). The wet season therefore, will more likely reflect pollution of areas with no known direct Hg
input sources as a result of the transport of particulate Hg associated with sediments from artisanal gold mining
activities remote from the sampling areas. On the other hand, in the dry season, tidal currents dominate flow
patterns of rivers in the tropical climate and sediment is mainly resuspended locally (van Maren and Hoekstra,
2004). Thus, the dry season studies can depict accurately cases of local pollution as the dissolved Hg
concentration can be more associated with leaching from sediments in the local environment.
4. Sample Preparation
Surface water samples for mercury analysis were sampled into acid pre-washed 1.5 L polyethylene terephthalate
(PET) plastic bottles, and acidified with concentrated HNO3 acid to the pH of 2 (measured with a HANNA
portable digital pH meter) and clearly labeled. The acidified labeled samples were stored in an ice chest with
melting ice cubes to maintain a temperature of 4 oC or below before transporting to the laboratory for analysis
during each of the monthly sampling periods (Bonzongo et al., 2003).
4.1 Method of Analysis
The pH of the acidified surface water sample was further reduced to a pH of below 2 with HNO3 acid to keep the
Hg ions in solution and filtered through 0.45µm membrane filter to remove particulate matter. The dissolved
mercury concentration (DHg) was analyzed using Pye Unicam 969 Atomic Absorption Spectrophotometer,
equipped with a cold mercury vaporization unit, at a wavelength of 253.7 nm and the concentrations estimated
from a calibration curve (APHA, AWWA, WPCF, 1985).
5. Results and Discussions
5.1 Mean Concentration of Mercury in the aqueous phase
Results from the continuous monitoring of the concentration of total Hg (DHg) in water bodies within the
sampling location over the 7 months period as shown in Figure 2a clearly shows that Hg contamination in the
main Pra River (48.40±26.08 ng/mL) far exceeds that in the tributaries (27.59±18.23 ng/mL). However, the levels
of Hg in the tributaries are still higher than the WHO 1996 recommended guideline value of Hg in water bodies
(1.0 ng/mL). Studies conducted by Donkor et al., (2006b) in the 2002 wet season and 2003 dry season along the
Pra River at the lower river basin at similar sampling locations, where no known direct Hg input sources is
believed to occur, reported an average DHg of 0.26 ng/mL. However, 4 years after that study the DHg
contamination levels have increased several folds to an average value of 48.40 ng/mL. The DHg is highest
downstream (60.69±27.72 ng/mL) at Daboase and Beposo and lowest midstream at Sekyere Nsuta and Krobo
(38.77±16.42 ng/mL). The highest average (67.78±26.59 ng/mL) was recorded on the Pra River around the
Daboase Community.
The distribution in DHg in the surface water samples along the Pra River of the study area (Figure 2b) clearly
shows remote pollution and contamination along sampling locations downstream from EP to KP (a distance of
about 42 km) as a result of the river current carrying species of Hg originally used in the amalgamation process by
artisanal gold mining activities in the more prevalent communities on the upper part of the Pra River Basin
downstream. However, the trend in the DHg contamination levels between KP and BP suggests incidence of
typical cases of illegal gold mining (between KP and DP, a distance of about 38 km) leading to localized
discharge of Hg which adversely affects communities downstream. This contributed to high DHg levels at DP
(67.78±28.72 ng/mL) and BP (53.60±29.07 ng/mL). The high DHg at EP (60.35±24.44 ng/mL) may also be
occasioned by the presence of cataracts on the river Pra at this community causing high turbulence that promotes
the leaching of Hg species in sediments in the riverbed into the surface water.
The concentrations of Hg in sediments have been shown from previous studies in Hg contaminated water bodies
to be relatively high compared to that in the surface water (Li et al., 2009).
International Journal of Applied Science and Technology Vol. 2 No. 1; January 2012
The lowest Hg concentration along the main Pra River is at Krobo (30.87±21.42 ng/mL). The Hg pollution in the
tributaries, ENT (23.61±13.4 ng/mL), AB (30.40±10.99 ng/mL), SNB (32.18±25.09 ng/mL) and DS
(24.17±18.53 ng/mL) could be akin to pollution as a result of reactive gaseous mercury (RGM) from combustion
of the gold amalgam by artisanal miners depositing on soils leading to the formation of Hg-organic complexes
which are eventually leached into water bodies through flood waters in the wet season.
Figure 2 Mean concentrations ± Standard deviation of THg (ppb) over the study period of September to
March spanning both the wet and dry seasons with a) sampling sites of both the river Pra and
tributaries arranged in the order of upstream to downstream and b) showing Concentration of
THg at sampling sites along the river Pra alone.
The importance of soil erosion as a mode of transport of Hg from anthropogenic sources associated with
particulate matter into the aquatic systems has been highlighted by Roulet et al (1998) in his study in the Amazon.
Similar results were found by Couture and Lambert (2003) studying areas in Guyana affected by artisanal and
small scale mining. They concluded that erosion of land sediments caused by storms or hydraulic monitors (used
by gold miners on land) transports high amounts of Hg-bearing organic matter associated with fine particulates
into river bodies.
5.2 Seasonal variation in the concentration of Hg in surface water
Averagely, the wet season (September to November) generally had a lower DHg (29.49±16.66 ng/mL) compared
to the dry season (47.97±9.76 ng/mL) which span the period December to March (Figure 3). It is only in BP the
south most sampling site that the DHg in the wet season was higher than the dry season (Figure 3b).
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Figure 3 The seasonal distribution of mercury in wet and dry seasons a) shows the mean THg ± Standard
deviation (ppb) over the different months b) shows mean THg during the wet (dash line) and dry (solid
line) seasons at the study area and c) shows the monthly variation of Hg concentration along the Pra River.
There are a number of reasons that could be adduced to the seasonal variation in mercury contamination in the
lower basin of the river and its tributaries. Firstly, the swifter current in the water bodies in the wet season could
lead to reduced equilibration time for the partitioning of the different species of Hg between the sediments and the
surface water, hence the lower DHg in the aqueous phase. Secondly, the dilution effect of the increased volume of
water in the water bodies during the sampling period could account for the smaller concentrations during the wet
season. Also AGM activities commonly take place during the dry seasons because the process involves the
extraction of gold from alluvial concentrations in streambeds or riverbeds. Therefore, a slower current aids their
operations better than a swifter current in the wet season by enabling a more efficient dredging of the riverbeds
and streambeds. However, AGM is not exclusively done in the dry season especially with the advent of more
sophistication in the equipment for the trade. The DHg in the entire lower reaches of the Pra River increases from
a low of 5.92±2.46 ng/mL in September to a high of 59.15±15.39 ng/mL in March at the peak of the dry season
when the volume of water in the water bodies is at its lowest (Figure 3a). The high Hg contamination at BP during
the wet season (Figure 3b) indicates the possible effect of the transport of contaminated sediments and flood
waters from remote sources of Hg input to the furthermost downstream sampling location.
Studying the trend in DHg contamination levels along the river Pra for the months of October and November
(which are months which reflect the average DHg over the 7 month period) as shown in Figure 3c gives some
indication of the type of pollution which is predominant in the study area. The mean DHg along the river Pra in
EP is 78.16 ng/mL for October and 76.8 ng/mL for November. The DHg level drops significantly to 46.57 ng/mL
in October and 38.68 ng/mL in November at ABP a nearby location still upstream the river Pra, a distance of
about 8 km south of EP. Moving a further 35 km of south of ABP, the sampling locations midstream generally
had relatively lower contamination levels, SNP (24.27 ng/mL and 30.15 ng/mL) and KP (21.74 ng/mL and 28.06
ng/mL), for the months of October and November respectively. Then the DHg rises sharply at DP (89.84 ng/mL
and 80.24 ng/mL) and BP (96.95 ng/mL and 76.62 ng/mL) sampling locations further downstream about 38 km
south of KP. The sharp variation gives strong indication that mercury contamination is predominantly from
localized activity compared to transportation of the pollutant from a source further upstream. The trend in
distribution of Hg along the study area suggests isolated cases of illegal small scale mining (Galamsey) activities
at places between Krobo and Daboase, the evidence of which is pictorially captured in Plate 1b.
International Journal of Applied Science and Technology Vol. 2 No. 1; January 2012
The Hg concentration in the surface water at KP was low in spite of the mobile alluvial gold mining rig that was
sighted in the area (Plate 1a). This is because the mobile rig was located a few kilometers downstream of the
sampling location suggesting that the pollution activity could more adversely affect sampling locations south of
KP like DP (38 km south of KP) and BP (a further 9 km south of DP) hence the high DHg levels in these
sampling locations. This source of direct Hg discharge as complemented by the deposition and transportation
from the more notorious mining areas north of the study area is proposed as the mechanism for
pollution/contamination of downstream sample locations along the river Pra. The incidence of illegal miners
straying into communities traditionally not noted for artisanal alluvial mining could lead to significant localized
Hg pollution. However, their activities could escape notice due to their mobile nature as shown in Plate 1. The
wide variation in results during the wet season especially in October and November could be due to a more recent
history of artisanal mining activity prior to sampling.
Plate 1 Illegal alluvial gold mining using mobile rigs in the lower Pra Basin a) Krobo during the dry season
and b) Daboase during the wet season.
Elemental Hg is now known to spread very effectively from diverse sources to both terrestrial and aquatic
systems. Sediments function as sinks and potential sources of Hg which once contaminated, pose a risk to aquatic
life for many years. Depending on the environmental conditions present Hg compounds in aquatic systems could
be transformed and liberated from sediments to water phase, ingested by aquatic biota, or be conveyed with
sediment particulate matter to new previously uncontaminated locations (Ullrich et al., 2001).
The investigation of incidence of mercury contamination in surface water describes its presence, variation and
location of sources of Hg input in the lower Pra River system within the study area that covers a stretch 88 km
from the upper most sampling location to the south most sampling location along the river course in an area
previously assessed as not having a known direct Hg input source. The average Hg contamination level along the
main river is 48.40 ng/mL whilst the tributaries have a concentration of 27.59 ng/mL of Hg. The source of
mercury in the system could clearly be traced to incidence of remote pollution up to the midstream locations with
the source of Hg from upper part of the river system. Pollution at the lower watershed of the study area is
occasioned predominantly by direct Hg input source through activities of artisanal gold miners operating from
mobile rigs and to a lesser extent to remote pollution sources through transportation by the river current from
active artisanal gold mining enclaves as a result of weathering of contaminated soil from flood waters as well as
wet and dry depositions. Environmental contamination by mercury is clearly a growing problem even today in the
communities a bit remote from the active artisanal alluvial gold mining areas in the Pra Basin hence
countermeasures need to be adopted before it is too late. In order to prevent damage in the earliest possible
stages, the state of contamination must be constantly monitored and prevention measures like policing the water
bodies, educating artisanal miners of the dangers in mercury use and the deployment of a more efficient and
environmentally friendly gold separation process must be taken.
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... Most biochars introduced to date have been derived from pyrolysis of agricultural and forestry waste, poultry manure, sawdust, and algae (Ullah et al., 2020), which makes it cost-effective for its application to large-scale treatment operations (Uttran et al., 2018;Guilhen et al., 2019) . Several functionalization methods including sulfur have been performed on biochars to modify their surface properties to increase the sorption efficiencies for Hg in solution (Azargohar and Dalai, 2008;Oduro et al., 2012;Singh et al., 2017) Tan et al. (2016). reported an increase in Hg sorption capacity in 500 µg L − 1 HgCl 2 solution by sulfurization of corn straw biochar (by ~77%) Park et al. (2019). ...
... A 1.0 mg L − 1 Hg(II) solution was prepared with deionized water (DIW) using the Hg(II) stock solution for the sorption experiments. This concentration was chosen based on the Hg concentrations in the galamsey contaminated water bodies reported by Oduro et al., 2012. To evaluate the performance of the biochars under several conditions, we tested the effect of biochar mass, reaction time, pH, and initial Hg concentration as described in supplementary information (SI) Table S1. ...
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Elevated mercury (Hg) concentrations in water bodies caused by illegal artisanal gold mining in Ghana is a serious health concern given the toxicity of Hg. As an ecofriendly cost-effective solution for removing Hg from these water bodies, we synthesized biochars using palm kernel (PB) and coconut shells (CB), which are dominant biomass wastes in Ghana. The biochars were sulfurized (SPB, SCB) and fabricated into polysulfone-based beads for Hg(II) sorption. The Hg(II) concentration, contact time, sorbent mass, and solution pH were investigated and were found to be influential on the sorption of Hg(II) from aqueous solution. The sulfurized biochars showed a faster Hg(II) removal (within 1h) compared to the pristine biochars. Sorption tests conducted using natural riverine water samples confirmed the potential use of the biochars, with SPB and SCB showing higher efficiencies than pristine PB and CB. The fabricated beads exhibited 70 -90% efficiency in Hg(II) removal from 1.0 mg L⁻¹ Hg solution and the sorption capacity was below 0.1 mg g⁻¹, which we attribute to the mass of biochar used for the beads. The Hg(II) sorption mechanisms of PB and CB from spectroscopic analyses suggest that the biochars synthesized in this study can be used to treat Hg polluted waters and suitable for large-scale applications in natural water bodies.
... Others (e.g. Oduro et al., 2012, Kusimi and Kusimi, 2012, Kessey and Arko, 2013, Mudyazhezha and Kanhukam, 2014, Macdonald et al., 2015, Appiah-Sefah et al, 2016) concentrated on the impact of mining on water bodies whilst some (e.g. Yeboah, 2008, Addai andBaiden, 2014) emphasized on its impact on air quality. ...
... According to Mensah et al. (2015), the environmental impacts of artisanal and small scale mining on water bodies are numerous and cut across all aspects of the river system. Also, an empirical study by Oduro et al. (2012) scale gold mining activity on the river greatly reduced taxa richness, total count of individual species and the diversity of bethic macro-invertebrate community in the river. ...
... High Hg values reaching to about 0.100 mg L -1 are from samples taken from Site 2 with significant elevated amounts dispersed further downstream. Similarly high values of dissolved Hg were observed in river systems draining small-scale Au mining areas in Ghana (Mantey et al., 2020;Oduro et al., 2012;Rajaee et al., 2015). These elevated values exceed the allowable limit of Class C waters which is about 0.005 mg L -1 DENR DAO, 2016-08 (2016). ...
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Artisanal and small-scale mining activities are most evident among communities surrounding the Acupan River in Itogon Benguet. The mining activities include manual extraction of gold ores, use of improvised ball/rod mills and sluice boxes, and metallurgical processing such as cyanidation, carbon-in-pulp (CIP) and amalgamation. This study evaluates the influence of small-scale mining and the geology/mineralization of the Acupan Au-Ag-Te deposit to the water quality of the Acupan River and to the possible human exposures to Hg within the small-scale mining community. Different water quality parameters were monitored along selected sites along the Acupan River for a year and the results showed that the low average values of dissolve oxygen (DO) (2.54–4.53 mg L⁻¹) and the relatively high average values of pH (8.84–10.10), sulfate (300.00–1133.33 mg L⁻¹), nitrate (11.33–134.67 mg L⁻¹), arsenic (As) (0.227–0.574 mg L⁻¹) and mercury (Hg) (0.004–0.054 mg L⁻¹) have exceeded the acceptable criteria limit of the Department of Environment and Natural Resources for Class C waters. The exceeded values are noted to occur in areas where extensive small-scale mining activities are being done and have affected as well the downstream areas. To test possible human contamination in the use of Hg, hair samples from 56 volunteers were analyzed for total Hg (T-Hg) following standard protocols. The T-Hg concentrations in hair samples are mostly inorganic and are determined in various parameters such as sex, geographic location, occupation, age, fish consumption and localization in hair. Though not significantly different, higher Hg values are noted in males (1.280 ± 0.446 ng mg⁻¹) than among females (0.651 ± 0.163 ng mg⁻¹) as well as those with ages 41–50 years (3.130 ± 2.330 ng mg⁻¹) as compared to other age groups. The higher amounts of inorganic Hg in human hairs could be attributed to the discrete yet prevalent use of amalgamation. The findings of this study emphasize the need for better regulations of the small-scale mining activities and for stricter implementation of the total ban on the use of Hg in ore processing to ensure better water quality of Acupan River as well as the health and safety of the communities surrounding the river.
... Although, it has been a source of employment for some sect of the youth (Amponsah-Tawiah and Dartey-Baah, 2011), and also contributes to the overall gold production annually, its environmental consequences are myriad and very critical. (Appiah and Buaben, 2012;Oduro et al., 2012;Amankwah, 2013;Fatawu and Allan, 2014). Destructions of river banks and river course diversion have led to serious inundations with the slightest downpour (Fatawu and Allan, 2014). ...
Illegal mining (galamsey) is known to cause significant environmental pollution; the chemical used and the waste heaps are a source of long term contamination of soil and water bodies. The thrust of this study was to assess the impact of illegal mining operations on the soil and water bodies at four (4) selected communities (Esaase-Manhyia, Aboabo, Mpatuam and Tetrem) in Bontefufuo in the Amansie West District of Ghana. Three 100m × 100m plots were demarcated at each galamsey site in each community. The extent of environmental damage was assessed in respect of numbers of pits and heaped laterite per plot, area of pits and heaped laterite identified on plots and amount of ore washed. Level of pollution of streams in the study area were also analysed. Large pits were dug and had all their streams polluted to a certain degree. There was a statistical significant difference (p = 0.000) between the mean radii of pits dug in the different communities. Furthermore, many heaps of stockpiles were found at Tetrem as compared to the other mining sites. The radii of the heaped laterite differed statistically (p = 0.021) between the communities. Large quantities of ore were washed daily in the communities and were statistically different (p = 0.001). Turbidity was extremely high above the EPA-Ghana recommended limit of 5NTU with corresponding low level of Dissolved Oxygen in the range of 1.43mg/L, and 2.40mg/L, recorded in all the water bodies at the sites. Notwithstanding, the pH, conductivity and Total Dissolve Solids (TDS) were all within the range of EPA Ghana standards. Mercury was identified as the main chemical used for the gold extraction in all the sites which is polluting the soil and water bodies in the area.
... The relative lower percentage pollution in the wet season might be as a result of rainfall infiltration and percolation resulting in dilution of the aquifers. Studies by Oduro et al. 2012 on surface water including river Pra show mercury levels between 27.59 and 96.95 µg/l. These high values resulting from the indiscriminate use of mercury may be reasons for finding mercury within the basin. ...
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The effects of small-scale gold mining activities on heavy metal levels in groundwater were determined for the Lower Pra Basin of Ghana. Sixty five boreholes in 45 communities were analysed between January 2012 and April 2012 for the dry season and June and October 2012 for the wet season. The test for significance and the use of cluster analysis, a multivariate approach, clearly delineate Cu, Zn, Cd and Hg as possible anthropogenic contributors, whilst As, Se and Pb could be both anthropogenic and natural geochemical process contributors of metal level concentrations in the groundwater. The analysis shows generally low pH values in the basin with more than 95% of dry season and almost all wet season values being acidic or slightly acidic. Approximately 35% of boreholes in the wet season recorded values for cadmium above WHO guideline value of 3.0 µg/l with almost all dry season values falling below 3.0 µg/l except for two boreholes. Generally, high values were recorded for iron, manganese, lead, Al and Hg. In general, lead, copper, cadmium and manganese showed higher wet season values than dry season suggesting anthropogenic influence.
... The burning of the amalgam leads to vaporization and spreading of Hg into a toxic plume (Pfeiffer and Lacerda, 1988). Mercury also reaches the streams of water, where it poses a great threat for the environment and human health (Oduro et al., 2012). A brief review on health effects due to exposures to Hg can be seen at the US-EPA website ( ...
This study aimed at assessing trace element concentrations in two representative estuaries of Ghana (Pra and Ankobra) affected by gold-mining, relative to the levels of the unaffected Volta estuary. Surficial sediments (n = 16–17) were sampled at each estuary and analysed by ICP-MS for 25 elements after pseudo-total digestion. The enrichment and geoaccumulation indexes revealed a moderate to significant contamination of As, Ag and Cu in the Pra and Ankobra estuaries. Spatial maps of concentrations revealed non-localized sources. High As concentrations were attributable to runoff transport and sedimentation of gold mining-tailing particles, as suggested by results from granulometric distributions, correlation and PCA analysis. The probabilities of surpassing the probable effects level (PEL) were 77% for As, 50% for Cr and 27% for Ni in Ankobra; these values were of 13%, 23% and 10% for the Pra. Results reveal potential future implications on ecosystems and human health in these both estuaries as result of the gold-mining activity.
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Contamination of water and soil with toxic heavy metals is a major threat to human health. Although extensive work has been performed on reporting heavy metal pollutions globally, there are limited review articles on addressing this pernicious phenomenon. This paper reviews inorganic nanoparticles and provides a framework for their qualities required as good nanoadsorbents for efficient removal of heavy metals from water. Different inorganic nanoparticles including metals, metal oxides and metal sulfides nanoparticles have been applied as nanoadsorbents to successfully treat water with high contaminations of heavy metals at concentrations greater than 100 mg l −1 , achieving high adsorption capacities up to 3449 mg g −1. It has been identified that the synthesis method, selectivity, stability, regeneration and reusability, and adsorbent separation from solution are critical parameters in deciding on the quality of inorganic nanoadsorbents. Surface functionalized nanoadsorbents were found to possess high selectivity and capacity for heavy metals removal from water even at a very low adsorbent dosage of less than 2 g l −1 , which makes them better than conventional adsorbents in environmental remediation.
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Mining activities over the years have formed an integral part of the economic development of Ghana. Many economists believe the mining industry in many ways has greatly contributed to the socioeconomic growth and development of such countries with mining activities, especially Ghana. These contributions are seen in the area of employment and social infrastructural development, nonetheless, mining activities have for a long time been considered as environmental polluters and a great cause of water pollution. In this paper, we examined some factors influencing participation in illegal mining in Ghana. We sampled 300 respondents from five areas known for illegal mining in Ghana. The data collected was analysed using regression analysis with the aid of statistical package for social science (SPSS). We found poverty, illiteracy rate, unemployment, high dependency rate, and mining mismanagement significantly and positively related to illegal mining. However, unemployment and illiteracy have the strongest influence on illegal mining in Ghana. We concluded that, an educational system of good operating practices for gold and technical assistance should be mounted so the adverse effects of mining on the environment and on themselves will be decreased.
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Background. Mercury (Hg) is a heavy metal that can cause several adverse health effects based on its form (organic, inorganic or elemental), duration and pathway of exposure. Measurement of mercury present in human biological media is often used to assess human exposure to mercury at mining sites. Objectives. The aim of the present study was to measure the concentrations of total mercury in urine, hair, and fingernails of miners and inhabitants of Amansie West District, Ghana. Methods. Concentrations of total mercury were measured in sixty–eight miners and twelve non–miners in the study area using cold vapor atomic absorption spectrophotometry with an automatic mercury analyzer (HG 5000). Results. Total mercury in nails and hair of smelter miners was 3.32 ± 0.36 and 6.59 ± 0.01 μg/g, respectively. Total mercury concentrations in hair samples obtained from smelter miners were above the 1 μg/g guideline set by the United States Environmental Protection Agency (USEPA). Moreover, the total mercury concentration in urine samples was 6.97 ± 0.06 μg/L, far below the >25 μg/L level considered to be a high level of mercury contamination. The total mercury accrued by the individuals was not dependent on age, but was positively associated with duration of stay. Conclusions. Based on the total mercury (THg) levels analyzed in the biological media, artisanal gold mining activities in Amansie West District are on the increase with a potential risk of developing chronic effects. However, the majority of the population, particularly those engaged in artisanal small–scale gold mining, are unmindful of the hazards posed by the use of mercury in mining operations. The results showed that THg in urine, hair, and fingernails more efficiently distinguished mercury exposure in people close to mining and Hg pollution sources than in people living far from the mining sites. Further education on cleaner artisanal gold mining processes could help to minimize the impact of mercury use and exposure on human health and the environment. Participant Consent. Obtained Ethics Approval. This study was approved by the Ghana Environmental Protection Agency and the Ministry of Local Government and Rural Development in Manso Nkwanta. Competing Interests. The authors declare no competing financial interests.
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The paper examines the environmental impact of artisanal mining of gold with mercury (Hg) in Ghana. In spite of its positive socio- economic contributions, it is well known that artisanal mining of gold contributes in no small measure to land degradation, loss of biodiversity and natural resources, deforestation, water pollution, etc. In Ghana, these environmental problems remain poorly studied. In the case of Hg pollution, caused by gold extraction using the amalgamation process, total Hg levels in different environmental compartments of the gold-mining-impacted Pra River basin in southwestern Ghana were determined using the latest sampling and analytical techniques. Artisanal gold mining activities in the Pra River basin are on the increase and even though Hg levels determined in water, soil, and sediments were below WHO safe guideline values, the current state of affairs poses a serious environmental threat. However, the majority of the populace, particularly those engaged in gold mining, are unaware of the dangers posed by the use of Hg in mining operations. This paper seeks to draw the attention of Ghanaians (as well as their foreign counterparts) to the need to take up the mantle in changing the general patterns of environmental damage caused by the artisanal gold miners. The need to regularize artisanal gold mining is long overdue. A legal regime for mines of every size, leading to a transformation of the artisanal mining sector into a legal, regulated industry, will help minimize the impact on the environment.
Mercury (Hg) emissions from informal gold mining operations represent a serious environmental problem in developing countries. In Amazonia, from 70 to 170 tonnes (t) of Hg are discharged annually. The extent of biota contamination is also widespread. Mercury must be rendered soluble and then converted into methylmercury in order to accumulate in the food-chain. Generally, it is regarded that Hg must be oxidized to produce significant dissolution. In this work, we examine the stability of mercury as the unoxidized aqueous elemental Hg°(aq.) in aquatic environments. In contact with organic acids, evidence of Hg-organic complex formation has been found from both thermodynamic analysis and electrochemical experiments. Although methylation of these soluble species is not fully understood, formation of such complexes in darkwater rivers must contribute to increased bioavailability.
In this study, we investigated the extent of contamination of Hg in selected mine-impacted Ghanaian watersheds. Our results are suggestive of a major environmental problem with Hg in Ghana, with total-Hg concentrations ranging from 17 to 2000ng L^{-1} in surface water samples, and in hundreds of ppm for both soils and sediments.
Mercury inputs into the Brazilian Amazon ecosystem due to goldmining activities are quantified based on data from various Brazilian Mineral and Environmental Agencies as well as field works. Total losses of Hg were estimated to be 1.32 kg Hg/kg Au from which 45% are released into rivers and 55% into the atmosphere. Total Hg input to the Amazon may contribute with up to 6% of the global anthropogenic Hg emissions to the atmosphere and the releases into the rivers are at the same order of magnitude as the inputs into the North Sea.
Mercury is one of the most hazardous contaminants that may be present in the aquatic environment, but its ecological and toxicological effects are strongly dependent on the chemical species present. Species distribution and transformation processes in natural aquatic systems are controlled by various physical, chemical, and biological factors. Depending on the prevailing environmental conditions, inorganic mercury species may be converted to many times more toxic methylated forms such as methylmercury, a potent neurotoxin that is readily accumulated by aquatic biota. Despite a considerable amount of literature on the subject, the behavior of mercury and many of the transformation and distribution mechanisms operating in the natural aquatic environment are still poorly understood. This review examines the current state of knowledge on the physicochemical behavior of mercury in the aquatic environment, and in particular the environmental factors influencing its transformation into highly toxic methylated forms.
In an oxisol-spodosol system developed on the terrestrial surface of the lower Tapajos Valley, the determination of total mercury ŽHg., organic carbon ŽC., iron and aluminum oxy-hydroxide ŽFecdb and Alcdb. concentrations in the surface soil horizons are used to characterize the geochemical processes controlling the accumulation of Hg in soils under natural vegetation cover and in deforested and cultivated sites. Oxisols from the plateau have homogeneous and relatively high background Hg contents and burdens constituting an important natural reservoir of Hg for the region Ž90􏰕210 ng􏰛g dry wt. and 19􏰕33 mg􏰛m2 for the first 20 cm.. The Fecdb and Alcdb contents associated with the fine fraction Ž􏰘63 􏰖m. of the soil suggest that oxy-hydroxides and, particularly Al-substituted Fe oxy-hydroxides, control the Hg concentrations observed in all of the soils of the study region. Consequently, the geochemistry of these minerals along the slopes governs the accumulation or the release of the Hg according to the natural evolution of the soil cover and􏰛or following the degradation of soils by erosion after deforestation and cultivation. These observations have important implications for the interpretation of Hg contamination patterns observed in Amazonian aquatic systems that could be linked to different drainage sources of Hg from the terrestrial surface. The sandification and podzolisation that is characteristic of the evolution of numerous pedological systems in the equatorial Amazon could be responsible for exportation of the naturally accumulated Hg, as for other metals, by...
Emissions of Hg, Pb, and Cd to air aretransported over wide areas in Europe and deposited far awayfrom their sources. About 80% of the atmospheric depositionof these metals in south Sweden originate from emissions inother countries. As a result of the increased anthropogenicdeposition the concentrations of Hg, Pb, and Cd in the morlayer of forest soils have increased considerably, mainlyduring the 20th century. Although the atmosphericdeposition of these elements has declined during the mostrecent decades, the reduction of the input of Hg and Pb isnot sufficient to prevent a further accumulation. Theconcentrations of Hg and Pb are still increasing by ca. 0.5and ca. 0.2% annually in the surface layer of forest soils.In contrast, the Cd concentration is currentlydecreasing in a large part of Sweden as a result of bothdeposition decreases and enhanced leaching induced by soilacidification. The accumulation factors of Hg and Pb,especially in the forest topsoils of south Sweden, arealready above those at which adverse effects on soilbiological processes and organisms have been demonstrated instudies of gradients from local emission sources andlaboratory assessment. There are also indications of sucheffects at the current regional concentrations of Hg and Pbin mor layers from south Sweden, judging from observationsin field and laboratory studies. There is an apparent riskof Pb induced reduction in microbial activity over parts ofsouth Sweden. This might cause increased accumulation oforganic matter and a reduced availability of soil nutrients.At current concentrations of Hg in Swedish forest soils,effects similar to those of Pb are likely. Increasedconcentrations of these elements in organs of mammals andbirds have also been measured, though decreases have beendemonstrated in recent years, related to changes inatmospheric deposition rates. As a result of current andpast deposition in south Sweden, concentrations of Hg infish have increased about fivefold during the 20thcentury. This implies risks for human health, when fish frominland waters are used for food. Although the concentrationof Hg in fish has decreased ca. 20% during the last decade,probably as a result of the reduced deposition, the levelstill exceeds the general limit (0.5 mg kg-1) in about half(ca. 40 000) of the Swedish lakes. In order to reduceconcentrations in fish to the level recommended, and avoidfurther accumulation of Hg in soils, the atmosphericdeposition has to be reduced to ca. 20% of the current deposition rate. This can only be achieved by international co-operation.
In April 2000, a UNIDO study was carried out in Dumasi, Ghana, the purpose of which was to determine the environmental impacts of mercury prior to the introduction of (mercury) retorts. The sampling program was intended to identify mercury transfers to rivers, soil systems and groundwater. Results show a diffuse contamination of all environmental media in the village. Although there is no evidence of groundwater contamination, sediments are significantly contaminated, and most fish fillets have mercury contents exceeding the United States Food and Drug Agency (US-FDA) action level, and are therefore unfit for human consumption. Mercury losses mainly occur during amalgamation, and have resulted in widespread pollution of soils and sediments throughout the village. Transparent retorts have been introduced and environmental training is ongoing but these efforts have only partially addressed the mercury problem in Dumasi.
This paper presents a broad overview and synthesis of current knowledge and understanding pertaining to all major aspects of mercury in the atmosphere. The significant physical, chemical, and toxicological properties of this element and its environmentally relebant species encountered in the atmosphere are examined. Atmospheric pathways and processes considered herein include anthropogenic as well as natural sources of Hg emissions to the atmosphere, aerial transport and dispersion (including spatial and temporal variability), atmospheric transformations (both physical and chemical types), wet and dry removal/deposition processes to Earth's surface. In addition, inter-compartmental (air-water/soil/vegetation) transfer and biogeochemical cycling of mercury are considered and discussed. The section on numerical modelling deals with atmospheric transport models as well as process-oriented models. Important gaps in our current knowledge of mercury in the atmospheric environment are identified, and suggestions for future areas of research are offered.