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Total Mercury (Hg) concentrations were determined in soil, river sediments and six (6) species of fish from the River Pra Basin in southwestern Ghana by Cold Vapour Atomic Absorption Spectrometry. Mercury concentration (microg g(-1)) ranged from 0.042 to 0.145 for soil: from 0.390 to 0.707 for sediments and from <0.001 to 0.370 for fish. All the fish samples had Hg concentration below the World Health Organisation (WHO) permissible limit of 0.5 microg g(-1) whereas all the sediment samples had levels higher than the US-EPA value of 0.2 microg g(-1). The results obtained from this study showed that fish from River Pra Basin are unlikely to constitute any significant mercury exposure to the public through consumption. No apparent trend of increasing mercury concentration along the main river as it flows downward toward the sea was observed.
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Total Mercury in Fish, Sediments and Soil from the River Pra
Basin, Southwestern Ghana
S. O. B. Oppong R. B. Voegborlo
S. E. Agorku A. A. Adimado
Received: 4 February 2010 / Accepted: 14 June 2010 / Published online: 29 June 2010
ÓSpringer Science+Business Media, LLC 2010
Abstract Total Mercury (Hg) concentrations were
determined in soil, river sediments and six (6) species of
fish from the River Pra Basin in southwestern Ghana by
Cold Vapour Atomic Absorption Spectrometry. Mercury
concentration (lgg
) ranged from 0.042 to 0.145 for soil:
from 0.390 to 0.707 for sediments and from \0.001 to
0.370 for fish. All the fish samples had Hg concentration
below the World Health Organisation (WHO) permissible
limit of 0.5 lgg
whereas all the sediment samples had
levels higher than the US-EPA value of 0.2 lgg
The results obtained from this study showed that fish from
River Pra Basin are unlikely to constitute any significant
mercury exposure to the public through consumption.
No apparent trend of increasing mercury concentration
along the main river as it flows downward toward the sea
was observed.
Keywords Mercury Fish Soil Sediment
River Pra basin Ghana
Mercury is a highly toxic metal and its contamination of
the environment has become a major issue of global con-
cern. Mercury is a natural component of the earth crust, and
it does not have any role in the human body. Mercury
comes from a range of natural sources such as volcanoes,
soils, mercury rich geological zones and forest fires, as well
as from fresh water, lakes, rivers and the ocean (Renzoni
et al. 1998). Increased use of mercury in gold recovery in
mining operations in many developing countries in recent
years has raised world concern over the release of this toxic
metal into the environment. Previous experiences of human
mercury poisoning in Manamata Bay in Japan (Irukayama
1977) and in Iraq (Bakir et al. 1973) indicate the dangers
associated with mercury contamination. Recent research
activities on the environmental impact of mercury from
gold mining have concentrated mainly on Latin America,
particularly the Brazilian Amazon. As a result, several
research papers and scientific reports have been published
on mercury contamination and health effects in the Ama-
zon (Pfeiffer and Larceda 1988; Larceda and Salomons
1991; Nriagu et al. 1992; Akagi et al. 1995) Some work,
however, has been undertaken to study environmental
mercury contamination in Ghana where an increasing large
number of people are engaged in artisanal gold mining
using mercury amalgamation technique. Studies on
assessment of mercury levels in water, sediments, soil,
food crops, fish and some human tissues have been carried
out in different areas including River Ankobra and Pra
basins. (Amonoo-Neizer et al. 1996; Adimado and Baah
2002; Golow and Adzei 2003; Bannerman et al. 2003;
Bonzongo et al. 2003; Babut et al. 2003; Golow and
Mingle 2002; Donkor et al. 2006). But most of these
studies did not attempt to link levels of mercury in the
different compartments to the artisanal gold mining activ-
ities and therefore did not suggest that gold mining activ-
ities contribute mercury to the aquatic environment.
Limited number of samples was also tested. Mercury
released into river systems during gold ore-processing is
likely to be transformed into the highly toxic
S. O. B. Oppong R. B. Voegborlo (&)
S. E. Agorku A. A. Adimado
Department of Chemistry, Kwame Nkrumah University
of Science and Technology, Kumasi, Ghana
Present Address:
S. O. B. Oppong
Department of Maritime Engineering,
Regional Maritime University, Accra, Ghana
Bull Environ Contam Toxicol (2010) 85:324–329
DOI 10.1007/s00128-010-0059-0
methylmercury and becomes accumulated through
biomagnification in aquatic food chains, particularly in
fish. In spite of the considerable global concern about
mercury contamination of fish and fishery products, infor-
mation on mercury contamination of fish in freshwaters in
Ghana is scanty. This research sought to determine the
levels of mercury in different fish species, soil and surface
sediments from the River Pra Basin in Southwestern Ghana
and attempt to determine if any trend of increasing mercury
concentrations along the river as it flows downstream could
be established due to contributions from the tributaries
where there is a concentration of small scale mining
River Pra is one of the main rivers in which intense
fishing activities are carried on. Topographical features
demonstrate that river Pra has its source from the conflu-
ence of river Ofin and river Brim. Dunkwa, a small mining
town, is located along river Ofin just before it enters river
Pra. After this confluence, the river Pra then proceeds
through Awisam, Twifo Praso, Twifo Mampong in the
Central Region and down through Daboase and Beposo in
the Western Region and finally joins the Gulf of Guinea at
Shama also in the Western Region of Ghana (Fig. 1). Since
artisanal gold mining activities using mercury are carried
out close by the rivers it is likely that mercury could be
carried along the river Pra. Aquatic species like fish may be
affected by this contamination and eventually affecting
living organisms that may also feed on these aquatic
Materials and Methods
Fish samples were obtained from River Pra at Awisam,
Twifo Praso, Twifo Mampong, Daboase and Beposo
between August 2005 and January 2006 from fishermen.
Soil and sediments were also collected within the same
period. Surface sediments were collected by the grab
method and soil samples were taken about 200 m away
from the bank of the river in each town. The samples were
placed in clean plastic bags. Fish and sediment samples
were stored on ice in an ice chest. All the samples were
immediately transported to the laboratory. Sediment sam-
ples were sieved through 2 mm mesh, air-dried and
homogenized by grinding using mortar and pestle. Soil
samples were air-dried and sieved through 2 mm sieve.
The fish samples were stored in the freezer after they had
been sorted out and identified at the Theoretical and
Applied Biology Department of the Kwame Nkrumah
University of Science and Technology. They were later
removed and allowed to thaw. The weight and total length
of each fish were measured. A portion of edible muscle
tissues were removed from the dorsal portion and stored in
a freezer until analysis.
Fig. 1 Map of Southwestern
Ghana showing the various
sampling sites
Bull Environ Contam Toxicol (2010) 85:324–329 325
All glassware were soaked overnight in a detergent
solution; rinsed and soaked in 10% (v/v) HNO
overnight. They were rinsed with distilled water followed
by 0.5% KMnO
solution and rinsed again finally with
distilled water before use. All reagents used were of ana-
lytical reagent grade (BDH Chemicals Ltd, Poole,
England) unless otherwise stated. Double distilled water
was used for the preparation of all solutions. Fish, sedi-
ments and soil samples were digested for total mercury
determination by an open flask procedure developed at the
National Institute for Minamata Disease (NIMD) in Japan
by Akagi and Nishimura (1991) and reported earlier
(Voegborlo et al. 2004). Total mercury concentrations were
determined in all the digests by cold vapour atomic
absorption spectrophotometry using an automatic Mercury
Analyzer Model HG-5000 (Sanso Seisakusho Co., Ltd.,
Japan) developed at NIMD. The reducing reagent used in
mercury analysis was 0.5 mL of 10% (w/v) SnCl
1 M HCl. Quality assurance samples analyzed included
procedural blanks, replicate samples and post-digestion
spikes. The accuracy of the procedure was determined by
analysis of certified reference material (Dogfish muscle,
DORM-2) from the National Research Council (NCR) in
Canada and Fish Homogenate Certified Reference Material
IAEA-407 from International Atomic Energy Agency,
Vienna. Recovery studies were performed by adding
increasing amounts of mercury chloride standard solution
to samples of two different fish species, which were taken
through the digestion procedure. The resulting solutions
were analyzed for mercury concentration.
Results and Discussion
Total Hg concentrations were determined in soil, sediments
and fish species from River Pra at Awisam, Twifo Praso,
Twifo Mampong, Daboase and Beposo. A total of one
hundred and sixty (160) fish samples covering six (6) dif-
ferent species, five (5) soil and five (5) sediment samples
were analysed. Results of mercury (Hg) concentration,
fresh weight of fish are presented in Table 1. Mean results
for soil and sediments are given in Table 2.
The validity of the method used in this study has been
proved by the agreement between the measured concen-
tration (mean =4.67 lg
,n=3) which lies within the
certified (range of 4.38–4.90 lgg
) concentrations in the
dogfish muscle (DORM-2) and concentrations obtained for
the measured (mean =0.215 lgg
,n=3) was in
agreement with the certified values (0.216–0.228 lgg
for IAEA-407.
Recoveries were between 98.08% and 103.8%. Mercury
concentrations in fish from Twifo Praso ranged from
0.040 to 0.083 lgg
wet weight for Labeo coubie
(mean: 0.057), 0.033–0.011 lgg
wet weight for Tilapia
zilii (mean: 0.059), from 0.093 to 0.257 lgg
weight for Chrysichthys sp. (mean: 0.187), from 0.143 to
0.187 lgg
wet weight for Heterobranchus longifillis
(mean: 0.165) and from 0.025 to 0.069 lgg
wet weight
for Alestis imberi (mean: 0.041). The highest Hg concen-
tration was recorded in Chrysichthys sp. (0.257 lgg
weight) and the lowest Hg concentration was recorded in
Alestis imberi (0.025 lgg
wet weight). Burger et al.
(2001) reported site-specific differences in muscle tissue
mercury levels in fish from the Savannah River and found
that mercury concentrations generally reflected trophic
levels. Fish species at high trophic levels showed higher Hg
concentrations whereas those at lower trophic levels
recorded low Hg levels. A similar trend was observed in
this study. Hg concentrations increased with trophic levels.
Fish species have been categorized into numerical trophic
values where top predators were assigned a value of 5 and
above; between 4.00 and 4.99 fish are classified as high
level carnivores; middle level carnivores are assigned 3.00
to 3.99. The omnivores, herbivores or dentritivores are
assigned values between 2.00 and 2.99 (Froese and Pauly
2009). Thus from Twifo Praso, Labeo coubie at trophic
level 2.0 (Froese and Pauly 2009) recorded Hg concen-
tration that ranged between 0.040 and 0.083 lgg
weight (mean: 0.057) whereas Chrysichthys sp., at trophic
level 3.4 (Froese and Pauly 2009) recorded Hg concen-
tration range of 0.092–0.257 lgg
wet weight (mean:
0.187). Lange et al. (1994) also showed that mercury
concentration varies with fresh weight of fish and total
length. High correlation between mercury concentration
and total length and fresh weight of fish are normally
observed among carnivorous species whereas poor corre-
lations are observed among herbivorous species. Among
the fish species studied at Twifo Praso, there was a poor
correlation between Hg concentration and fresh weight of
fish for Labeo coubie (r
=0.1076, trophic level =2.0),
Tilapia zilli (r
=0.1219, trophic level =2.0), Chrysich-
thys sp.(r
=0.1456, trophic level =3.4), Heterobran-
chus longifillis (r
=0.3864, trophic level =3.7) and
Alestis imberi (r
=0.0042, trophic level =3.2). Mercury
concentrations ranged between 0.018 and 0.057 lgg
(mean: 0.042) wet weight for Alestis imberi from Twifo
Mampong and between below 0.001 and 0.136 lgg
(mean: 0.071) wet weight for Labeo coubie from Awisam.
There was poor correlation between mercury concentration
and total length (r
=0.0404) and fresh weight (r
0.0453) for Alestis imberi. Labeo coubie from Awisam
showed good correlation between mercury concentration
and fresh weight (r
=0.697). This is in agreement with
other authors who reported similar findings for carnivorous
species (Lange et al. 1994). Mercury concentrations in the
muscle tissue of fish from Beposo ranged from 0.014 to
326 Bull Environ Contam Toxicol (2010) 85:324–329
0.216 lgg
(mean: 0.065) wet weight for Alestis imberi,
from 0.104 to 0.370 lgg
(mean: 0.152) wet weight for
Chrysichthys sp., from 0.035 to 0.043 lgg
0.039) wet weight for Labeo coubie and from 0.019 to
0.163 lgg
(mean: 0.052) wet weight for Tilapia multi-
fasciata. Hg concentrations were higher for fish at higher
trophic levels. For samples from Daboase, Hg concentra-
tion ranged from 0.020 to 0.037 lgg
wet weight for
Labeo coubie (mean: 0.029), 0.019–0.041 lgg
weight for Tilapia zilli (mean: 0.028), 0.013–0.042 lgg
wet weight for Tilapia multifasciata (mean: 0.026) and
0.069–0.315 lgg
wet weight for Chrysichthys sp.
(mean: 0.165). There was good correlation between Hg
concentration and fresh weight (r
=0.8038) and total
length (r
=0.8449) for Tilapia zilli. There was however,
poor correlation between Hg concentration and total length
and fresh weight for Labeo coubie,Tilapia multifasciata
and Chrysichthys sp. The mean Hg concentration recorded
for river sediments ranged from 0.390 to 0.707 lgg
the highest being recorded at Daboase and the least at
Twifo Praso whereas for soils the levels ranged from 0.042
to 0.145 lgg
with the highest being recorded at Beposo
and the lowest at Twifo Praso.
In an earlier study of mercury levels in sediments and
soil within the river Pra basin, lower concentrations were
reported (Donkor et al. 2006). For sediments a range of
0.007 to 0.057 lgg
(mean =0.026) was reported for
the lower Pra basin and a range of 0.013 to 0.023 lgg
(mean =0.018) for the upper Pra basin. For soil, mercury
levels ranged 0.003–0.202 (mean =0.076) and 0.012–
0.034 (mean =0.025) for the lower and upper Pra basins
respectively. The difference could be attributed to differ-
ent sampling periods, seasons, locations with respect to
the mining areas, volume and flux of waterways and
particle size distribution of the sediments (Larceda and
Salomons 1991). When our results were compared with
levels reported for elsewhere, differences were observed.
The levels obtained for sediment from the Brazilian
Madeira river (0.030–0.350 lgg
; mean =0.130) and
from Brazilian Tapajos river (0.170–0.430 lgg
mean =0.290) were lower than values reported in this
study. Far higher values were however reported for sedi-
ments from Philippines Mindanao island (0.920–66.470;
mean =21.030). On the other hand mercury levels
reported for soil in this study were lower than levels
reported for Brazil Madeira river (0.270–0.540 lgg
mean =0.390) and for Brazil Tapajos river (0.180–
0.360 lgg
). Recent mercury accumulation rate in sed-
iments is reported to increase with concentrations in fish.
Hunter et al. (1987) reported that more than 90% of the
surface sediments of the Onondaga Lake contained mer-
cury concentrations greater than 0.1 ppm. In the same
year, mercury levels in fish were also found to exceed
0.5 ppm, the maximum permissible levels established by
the World Health Organisation (WHO).
Table 1 Total mercury concentrations (lgg
) in muscle tissue of fish samples from River Pra Basin, Southwestern Ghana
Species Sample site Sample
size (n)
Fresh weight
range (g)
weight (g)
Hg concentration
Mean Hg
Labeo coubie Twifo Praso 17 9.0–379.2 204.9 0.040–0.083 0.057
Awisam 19 108.1–373.3 244.6 \0.001–0.136 0.071
Beposo 4 137.0–500.6 340.0 0.035–0.043 0.039
Daboase 5 126.1–950.7 391.7 0.020–0.037 0.029
Tilapia zilli Twifo Praso 11 43.3–602.5 359.3 0.033–0.109 0.059
Daboase 5 77.4–201.5 124.7 0.019–0.041 0.028
Tilapia multifaciata Beposo 5 113.4–290.4 181.7 0.019–0.163 0.053
Daboase 10 96.3–184.3 138.2 0.013–0.046 0.026
Chrysichthys sp Twifo Praso 6 161.7–427.5 262.2 0.092–0.257 0.187
Beposo 12 126.7–270.1 201.9 0.104–0.370 0.153
Daboase 10 69.7–660.2 291.6 0.069–0.315 0.166
Heterobranchus longifillis Twifo Praso 3 253.3–301.4 279.3 0.142–0.187 0.165
Alestes imberi Twifo Praso 32 139.3–431.1 235.4 0.025–0.069 0.041
Twifo Mampong 15 173.5–385.3 242.6 0.018–0.057 0.042
Beposo 6 191.5–440.4 258.3 0.014–0.216 0.065
Table 2 Mean mercury concentrations (lgg
) in sediments and
soil from River Pra Basin
Samples Sampling Sites
Awisam Twifo
Daboase Beposo
Sediment 0.507 0.390 0.500 0.707 0.575
Soil 0.078 0.042 0.079 0.075 0.145
Bull Environ Contam Toxicol (2010) 85:324–329 327
The levels obtained for fish by Hunter et al. (1987) are
higher than the levels recorded in the fish species under this
study even though high levels were obtained for the sedi-
ments. Mercury concentrations in bed sediments are not
necessarily correlated with concentrations in fish tissues
(Rose et al. 1999). The results of this study appeared to
follow a similar trend as poor correlation was observed
between mercury concentration in fish and sediments at all
the sampling sites. The relationship between mercury
concentrations of fish and sediments vary as a function of
factors that affect sediment methylation rates and mercury
bioavailability. Although some studies have shown that
sediments can be a sink for mercury (Rudd and Turner
1983; Sorensen et al. 1990), mercury accumulation by fish
depends on the combined effect of the abundance of
available inorganic mercury in sediments/water column,
trophic interaction and the rate at which microflora trans-
form mercury into methylmercury in addition to the spe-
cies-specific accumulation and seasonal variations (Jackson
1990). That mercury concentrations in soil from similar
areas were far lower than concentrations in sediments
suggests that atmospheric deposition was not significant.
River Pra has three main tributaries namely, River
Anum, River Oda and Fumso River. Small scale artisanal
gold mining activities are widespread along these rivers.
The low mercury concentration in all the species studied in
River Pra can be ascribed to low input of Hg into the
environment from artisanal gold mining which involves the
use of Hg; and factors affecting methylation of mercury
were probably not favourable. Human activities such as
agriculture that employs the use of mercurial compounds
could be minimal. An attempt to determine any trend of
mercury accumulation along the main river Pra will require
the use of an indicator obtained at all the sampling loca-
tions. But, no specie of fish was obtained at all the sam-
pling locations. Labeo coubie was available at four out of
the five locations and was therefore used as the indicator.
Even though generally, good correlation between mercury
concentrations and fish fresh weight was not obtained,
mercury concentration was normalized in order to reduce
any effect of variable size composition of the samples.
Labeo coubie did not show any consistent trend along
the main river as it flows downward toward the
sea (Awisam =0.290 lg; Twifo Praso =0.277 lg;
Daboasi =0.073 lg; Beposo =0.115 lg). Similarly, no
trend was exhibited for the sediments. All the fish samples
from the five locations along the Pra River recorded mer-
cury concentrations below the World Health Organisation’s
threshold value of 0.5 lgg
. The results obtained in this
study therefore showed that fish from River Pra does not
constitute any significant methylmercury exposure to the
public through fish consumption from the studied areas.
Whereas the mean values for soil in this study were below
the US-EPA value of 0.2 lgg
, the mean values for
sediment exceeded it.
Acknowledgments The authors would like to thank Mr. Munir
Abdullah Dawood of Pure and Applied Biology Department, Faculty
of Biosciences, Kwame Nkrumah University of Science and Tech-
nology for identifying the fish species.
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... According to the FAO [44], fish accounts for as much as 60 percent of animal protein in the average Ghanaian diet, and 22.4 percent of household food expenditures. Studies in Ghana have shown a mean Hg concentration up to 0.187 µ g/g fish muscle tissue, depending on fish species and the location where the fish is caught [45,46]. These concentrations are well below the European Union recommendation for Hg in fish for human consumption (<0.5 mg/kg). ...
... According to the FAO [44], fish accounts for as much as 60 percent of animal protein in the average Ghanaian diet, and 22.4 percent of household food expenditures. Studies in Ghana have shown a mean Hg concentration up to 0.187 µg/g fish muscle tissue, depending on fish species and the location where the fish is caught [45,46]. These concentrations are well below the European Union recommendation for Hg in fish for human consumption (<0.5 mg/kg). ...
Full-text available
The aims of this study were to assess serum concentrations of per- and polyfluoroalkyl substances (PFASs) in selected populations from Ghana, including workers engaged in the repair of electronic equipment (ERWs), and to elucidate PFAS concentrations in relation to blood mercury concentrations (B-Hg) as a biomarker of seafood consumption. In all, 219 participants were recruited into the study, of which 26 were women and 64 were ERWs. Overall, the PFAS concentrations were low. The most abundant components were perfluorooctane sulfonate (PFOS) and perfluorohexane sulfonic acid (PFHxS). Women had generally lower PFAS concentration than men. The ERWs had statistically significantly higher concentrations of perfluorooctanoate (PFOA), which was associated with the concentration of tin in urine. This could indicate exposure during soldering. The concentration of B-Hg was associated with several of the PFASs such as PFOA, PFOS and perfluoroheptane sulfonate (PFHpS). Additionally, the concentrations of perfluorodecanoic acid (PFDA) and perfluoroundecanoate (PFUnDA) were highly associated with the concentrations of B-Hg. It is noteworthy that the linear isomer of PFHxS was strongly associated with B-Hg while the branched isomers of PFHxS were not. In conclusion, the PFAS concentrations observed in the present study are low compared to other populations previously investigated, which also reflects a lower PFAS exposure within the Ghanaian cohorts. ERWs had significantly higher PFOA concentrations than the other participants. Several PFASs were associated with B-Hg, indicating that seafood consumption may be a source of PFAS exposure.
... Data on mercury concentration in whole small fish as food for humans is scarce in the scientific literature, which limits the basis for comparison. However, scientific reports on mercury concentrations in fish fillet from the Gulf of Guinea and Ghana have reported mercury concentrations of 0.19 mg/kg up to 0.61 mg/kg in fillet of local marine and freshwater fish [34,115,120,127]. The aforementioned studies found higher concentrations of mercury than in the present study, even though the water content was reduced by processing. ...
... The aforementioned studies found higher concentrations of mercury than in the present study, even though the water content was reduced by processing. Due to illegal gold mining, freshwater fish from surrounding watersheds are likely to be contaminated by mercury at higher levels [115,127]. All samples analyzed in this study were below the limit given by the Ghanaian Standards Authority and European Commission of 0.5 mg/kg [107,109]. ...
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The triple burden of malnutrition is an incessant issue in low- and middle-income countries, and fish has the potential to mitigate this burden. In Ghana fish is a central part of the diet, but data on nutrients and contaminants in processed indigenous fish species, that are often eaten whole, are missing. Samples of smoked, dried or salted Engraulis encrasicolus (European anchovy), Brachydeuterus auritus (bigeye grunt), Sardinella aurita (round sardinella), Selene dorsalis (African moonfish), Sierrathrissa leonensis (West African (WA) pygmy herring) and Tilapia spp. (tilapia) were collected from five different regions in Ghana. Samples were analyzed for nutrients (crude protein, fat, fatty acids, several vitamins, minerals, and trace elements), microbiological quality (microbial loads of total colony counts, E. coli, coliforms, and Salmonella), and contaminants (PAH4 and heavy metals). Except for tilapia, the processed small fish species had the potential to significantly contribute to the nutrient intakes of vitamins, minerals, and essential fatty acids. High levels of iron, mercury and lead were detected in certain fish samples, which calls for further research and identification of anthropogenic sources along the value chains. The total cell counts in all samples were acceptable; Salmonella was not detected in any sample and E. coli only in one sample. However, high numbers of coliform bacteria were found. PAH4 in smoked samples reached high concentrations up to 1,300 μg/kg, but in contrast salted tilapia samples had a range of PAH4 concentration of 1 μg/kg to 24 μg/kg. This endpoint oriented study provides data for the nutritional value of small processed fish as food in Ghana and also provides information about potential food safety hazards. Future research is needed to determine potential sources of contamination along the value chains in different regions, identify critical points, and develop applicable mitigation strategies to improve the quality and safety of processed small fish in Ghana.
... In Ghana, toxins of fungal origin (mushroom toxins and mycotoxins) are another commonly reported causative agent of food poisoning (Apetorgbor et al., 2006;Kortei et al., 2019;Osemwegie et al., 2014) and the rare cases of severe food poisoning can be linked to consumption of other toxins such as phytotoxins and phycotoxins (cyanogenic glycosides which occur in cassava a staple widely consumed in Africa) (Kwaansa-Ansah et al., 2017;Nhassico et al., 2008;Opoku-Nkoom et al., 2013). Furthermore, contamination of aquatic foods (mostly fishes) with methyl mercury has been reported (Gbogbo et al., 2018;Kortei et al., 2020;Oppong et al., 2010). Methyl mercury (methyl derivative) that is formed by bacterial action in an aquatic environment may result in high toxicity (Dolan et al., 2010). ...
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Background: Natural Food Toxins (NFTs) are poisonous substances produced by the biological processes of living organisms. This study aimed to evaluate the knowledge and attitude of tertiary students of the Volta Region of Ghana about NFTs. Methods: During March to June 2020, semi-structured questionnaires were used to examine knowledge and attitudes about NFTs among 252 tertiary students from various institutions of the Volta Region of Ghana. Data were statistically analyzed using IBM SPSS Statistics version 20.0. Results: A majority (90.48%) of students were aware of the NFTs. The male students showed significantly (p<0.05) greater knowledge than the females. Totally, 190 out of 252 (75.40%) respondents had prior-to-the-study knowledge about NFTs. Also, 245 out of 252 (97.22%) respondents desired to learn more about NFTs. Conclusion: From this study, it was observed that tertiary students from the various institutions in the Volta Region of Ghana had enough knowledge and attitude about NFTs; but there are still slight deficits in the knowledge of students about types of NFTs. Hence, there is a need for more sensitization of the subject among the students and throughout the general public.
... In 2010, Oppong et al. reported that Hg levels in six fish species from the River Pra Basin in south-western Ghana, where activities of ASGM are prominent, were below the WHO permissible limit (Oppong et al. 2010). The authors further observed no obvious trend of increasing Hg levels along the main river as it flows downward towards the sea. ...
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Reduction or possible elimination of Hg from artisanal and small-scale gold mining (ASGM) is one of the main goals of the Minamata Convention on Mercury, which has been signed by many countries involved in ASGM, including Ghana. This article provides a recent overview of ASGM gold production and Hg use in Ghana. In addition, in order to highlight the impacts of Hg use in Ghana, a review was conducted on research studies investigating Hg pollution in waterbodies, soils, fish, and humans caused by ASGM over the past two decades. The continued use of Hg in Ghana’s growing ASGM sector has resulted in reportedly high Hg levels found in water, sediments, crops, and miners, which exceed international guidelines. A subsequent ASGM ban and increased monitoring of illegal mining activities in Ghana have not ultimately been successful at significantly reducing Hg use and its associated impacts caused by rampant use in the country. Moreover, Hg alternatives in the ASGM sector are limited in Ghana, with little funding, support, education, and training in place to promote their implementation. As gold produced by ASGM continues to increase annually, clear policy reforms targeting Hg use are vitally needed, as well as efficient strategies to remediate Hg-contaminated areas.
... Fishery products from the Senegalese coasts, that of the Dakar region, are overexploited and marketed locally, in the absence of analyses of mercury and its derivatives [8]. In contrast, in African countries, such as Ghana, the presence of mercury has been assessed in some species of fish and environmental samples [9][10][11][12][13]. ...
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Liberia is endowed with an impressive stock of mineral reserves and has traditionally relied on mining, namely iron ore, gold, and diamonds, as a major source of income. The recent growth in the mining sector has the potential to contribute significantly to employment, income generation, and infrastructure development. However, the development of these mineral resources has significant environmental and health impacts that often go unnoticed. The method used in this research was a cross-sectional study design. A questionnaire 0f 16 questions were prepared and used to collect data. The survey was sent to the focus group participants in the research communities via electronic devices (Mobile phones and tablets). The replies to the questionnaire were gathered and analyzed using KOBO TOOL and Excel. The questions were closed-ended questions and 56 persons were expected to participate in the survey. A total of 50 persons participated in this research survey from both communities. The 50 participants completed the study questionnaire (100% response rate), including 25 (50%) men and 25 (50%) women; which makes this research gender-sensitive, most of the participants were below 44 years of age. All the participants are from both study areas (Kartee Village 27% and Gbankona Village 23%). Heavy metals as a long-term threat it is critical to improve the knowledge of the communities on the effect of heavy metals on the environment and human health. Educational interventions, medications & Vaccines if necessary are urgently needed to reach all community members beyond borders, and further studies are warranted. 2 1. INTRODUCTION Environmental pollution of heavy metals is increasingly becoming a problem and has become of great concern due to the adverse effects it is causing on human health. These inorganic pollutants are being discarded in waters, soils and into the atmosphere due to the rapidly growing mining activities and improper waste disposal during mining activities. Liberia is estimated to hold reserves ranging from between two to five billion metric tons of iron ore and three million ounces of gold. Heavy metals contamination of food has become a prominent concern in the world due to its toxicological effects on humans. These metals naturally exist in soil, air, and water and are rapidly dispersed by human activities such as urbanization, waste disposal, mining, and other activities. Mining causes serious accidents such as fires, explosions, or collapsed mine tunnels that affect miners and people living in communities near mines. Even in places where mining happened long ago, people can still be exposed to health threats from mining waste and chemicals that remain in the soil and water. Mining damages health in many ways, Dust, chemical spills, harmful fumes, heavy metals, and radiation can poison workers and cause lifelong health problems as well as allergic reactions and other immediate problems. Mining uses large amounts of water and leaves large amounts of waste, contaminating water sources and the people who depend on them. While all mining operations tend to pollute water, big companies usually cause the biggest problems. Surface water and groundwater in mining areas may remain contaminated for many years. Water loss can leave the land barren and unusable for farming or raising animals. The long-term damage of water contamination will last much longer than the short-term economic gain from mining. Based on the current development trend, this paper aims to conduct a systematic review of the current water use-related challenges in the Liberian mining sector, particularly the water management issues, and mining regulatory frameworks. Results from the review will be used to recommend policy strategies that promote sustainable water resources management in the mining sector.
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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.
This chapter aims to discuss the social, health and environmental impacts of artisanal and small-scale gold mining (ASGM) in Ghana in the context of sustainability vis-à-vis voluntary sustainability standards (VSS). Mining has played a crucial role in the development of human civilisation; in part by providing precious metals such as gold and silver, which are coveted by many cultures. Such was the value placed upon them that they were used as a universal currency for almost three millennia, stimulating global trade growth (Hruschka and Echavarría 2011).
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Bioaccumulation of 203Hg and 75Se by several members of the food chain, including fish, was followed in large in situ enclosures in the presence and absence of organic-poor sediment. When the sediment was absent, 203Hg was bioaccumulated 8- to 16-fold faster than when it was either suspended in the water or present on the bottom of the enclosures. Mercury-contaminated and uncontaminated sediments were equally effective at reducing the rate of radiolabeled mercury bioaccumulation, apparently by binding the mercury to fine particulates making it less available for methylation and/or bioaccumulation. Based on these results, a mercury ameliorating procedure involving semicontinuous resuspension of organic-poor sediments with downstream deposition onto surface sediments is suggested. The presence of sediments, in the water or on the bottom of enclosures, also reduced radiolabeled selenium bioaccumulation. The degree of inhibition (2- to 10-fold) may have been related to the concentration of organic material in the predominantly inorganic sediments. Implications of this research with respect to mercury–selenium interactions in aquatic ecosystems are discussed.
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To obtain the basic information on human exposure to mercury (Hg) due to gold mining activities in Amazon, total mercury (T-Hg) and methylmercury (MeI Ig) were determined for human hair, blood and/or urine samples collected from populations living in gold mining area and fishing villages upstream of the Tapajos River basin. Abnormally high levels of T-Hg were observed in hair and blood from all fishing villages investigated and more than 90% of T-Hg was in the form of MeHg in both samples, whereas in goldrnining area the value were much lower and the %MeHg values varied widely (20–100%) with individuals even in blood samples. Urine from gold shop workers contained Hg mostly in inorganic form at 165g/g creatinine on the average, with the range of 20 to 450g/g creatinine. A good correlation between Hg in hair and blood was found in fishing villages and the ratios of hair Hg to blood Hg were very close to 250, generally established for MeHg. T-Hg and inorganic Hg levels in urine from gold shop workers were also significantly correlated with inorganic Hg in blood.
Despite a large number of investigations concerning the distribution of mercury in the aquatic environment, our understanding of the overall dynamics of environmental mercury is still unsatisfactory. This may be mainly because little information is available on the distribution of mercury in the methylated form that is more biologically available for aquatic organisms. Hence, the work reported here was undertaken to establish a highly sensitive and reliable method for the determination of methylmercury as well as total mercury in various biological and non-biological environmental samples by the combination of dithizone extraction and ECD-gas chromatography. These samples include natural water containing mercury down to parts per trillion levels. The method for methylmercury is based on the fact that methylmercuric dithizonate in the final sample solution is converted into methylmercuric chloride as soon as it is subject to ECD-gas chromatography. The differences in the composition of the samples determine the pretreatment of the sample for the highest extraction efficiency. Thus, the biological sample, suspended solids and sediment were treated with KOH in ethanol, whereas the water sample was treated with KMnO4 and sulfuric acid. After pretreatment, methylmercury in the sample was extracted with dithizone in benzene and then back-extracted into alkaline Na2S solution. The excess sulfide ions were removed by acidification with HC1 and purging with N2 and methylmercury was re-extracted with a small portion of dithizone in benzene. The extract was washed with NaOH solution and subjected to the conventional ECD-gas chromatography.
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.
Enlargement of northern Manitoba lakes to form hydroelectric reservoirs caused a rise in the Hg content of walleye (Stizostedion vitreum), northern pike (Esox lucius), lake whitefish (Coregonus clupeaformis), yellow perch (Perca flavescens), and spottail shiner (Notropis hudsonius) owing to stimulation of Hg methylating microbes by submerged terrestrial organic matter. However, an increase in the supply of organic substrates beyond a critical amount mitigated this effect, apparently by promoting Hg demethylation and production of Hg-binding agents such as sulfides. Fish species, even at the same trophic level, differed markedly in their Hg content, Hg – fork length relationships, and regional and temporal variations in Hg content; this is ascribed to differences in habitat preference, metabolic rate, age, growth rate, size, biomass, diet, and excretory pathways, and hence different responses and degrees of exposure to spatially varying conditions influencing Hg speciation and availability. Whitefish had an anomalously weak tendency to accumulate CH3Hg+ and a high ratio of liver CH3Hg+ to muscle CH3Hg+, suggesting a special mechanism of excretion. Only walleye Hg correlated significantly with CH3Hg+ production in offshore mud, indicating the value of walleye for whole-lake Hg bioassays and the validity and utility of the methods used to quantify CH3Hg+ production.
In light of increasing fish consumption advisories in several states, a comprehensive multimedia database was created to answer a variety of questions. Mercury concentrations in precipitation, lake water and sediment, zooplankton, and fish were measured and analyzed together with extensive watershed and lake chemistry data for 80 lake watersheds in the study region of northeastern Minnesota including the Superior National Forest, Voyageurs National Park, and Boundary Waters Canoe Area Wilderness. Atmospheric deposition of mercury, transport, water column lifetimes, and sedimentation in lakes are determined. The factors relating mercury concentrations within the lake watershed components are analyzed and discussed. The notable correlates with mercury residue levels in northern pike of a standard length and weight (55 cm, 1.0 kg) were mercury concentrations in zooplankton and water, total organic carbon concentration, and pH. The primary source of mercury was found to be of atmospheric origin.
The sediment, water, and three species of fish from 24 of Massachusetts' (relatively) least-impacted water bodies were sampled to determine the patterns of variation in edible tissue mercury concentrations and the relationships of these patterns to characteristics of the water, sediment, and water bodies (lake, wetland, and watershed areas). Sampling was apportioned among three different ecological subregions and among lakes of differing trophic status. We sought to partition the variance to discover if these broadly defined concepts are suitable predictors of mercury levels in fish. Average muscle mercury concentrations were 0.15 mg/kg wet weight in the bottom-feeding brown bullheads (Ameiurus nebulosus) (range = 0.01–0.79 mg/kg); 0.31 mg/kg in the omnivorous yellow perch (Perca flavescens) (range = 0.01–0.75 mg/kg); and 0.39 mg/kg in the predaceous largemouth bass (Micropterus salmoides) (range = 0.05–1.1 mg/kg). Statistically significant differences in fish mercury concentrations between ecological subregions in Massachusetts, USA, existed only in yellow perch. The productivity level of the lakes (as deduced from Carlson's Trophic Status Index) was not a strong predictor of tissue mercury concentrations in any species. pH was a highly (inversely) correlated environmental variable with yellow perch and brown bullhead tissue mercury. Largemouth bass tissue mercury concentrations were most highly correlated with the weight of the fish (+), lake size (+), and source area sizes (+). Properties of individual lakes appear more important for determining fish tissue mercury concentrations than do small-scale ecoregional differences. Species that show major mercury variation with size or trophic level may not be good choices for use in evaluating the importance of environmental variables.
Samples of soils, plantain (Musa paradisiaca), water fern (Ceratopteris cornuta), elephant grass (Pennisetum purpureum), cassava (Manihot esculenta) and mud fish (Heterobranchus bidorsalis) were collected from Obuasi and its environs, which is the most active gold mining town in Ghana. The distribution of mercury and arsenic in these samples from fourteen sampling sites was determined. The annual average surficial soil concentrations of As and Hg from 14 sampling sites have the mean and SD of 12.92 17.48 (range = 2.11–48.87 mg kg–1 d.w.) and 0.93 0.58 (range = 0.29 – 2.52 mg kg–1 d.w.), respectively. The annual average concentrations of As and Hg from plant and grass samples show the mean and SD of 9.05 17.50 (range = 0.49 – 78.71 mg kg–1 d.w.) and 1.85 2.04 (range = 0.12 – 9.68 mg kg–1 d.w.), respectively. Plant/soil concentration ratios of As and Hg showed elevated values for the grass samples, especially from sites within 4 km of the Pompora Treatment Plant. The high bioaccumulation ratios of fern reflected both soil and air sources of pollution. The results substantiated a mercury and arsenic concentration gradient in the area, thereby indicating that the local environment is contaminated by mining activities.