7 trace metal levels

West African Journal of Applied Ecology, vol. 16, 2009 75

IntroductionThe presence of toxic metals such as lead(Pb) and cadmium (Cd) in environmentalmatrices is one of the major concerns ofpollution control and environmental agenciesin most parts of the world. This is mainlydue to the health implications of these toxicmetals since they are non-essential metals

of no benefit to humans (Borgman, 1983).Their presence in aquatic ecosystems,mainly due to anthropogenic influences hasfar-reaching implications directly to the biotaand indirectly to man. Trace metals havebeen referred to as common pollutants, whichare widely distributed in the environmentwith sources mainly from the weathering of

Trace Metal Levels in Water and Sediment from the SakumoII and Muni Lagoons, Ghana

C. K. Tay*, Ruby Asmah and C. A. BineyCSIR-Water Research Institute, P. O. Box AH 38, Achimota, Accra, Ghana*Correspondence author; E-mail: [email protected] or [email protected]

AbstractTrace metal (Cu, Zn, Pb, Mn, Fe and Cd) levels were determined in water and sediment from the Sakumo II andMuni lagoons and the Mamahuma and Gbagbla Ankonu feeder streams, which feed the Sakumo II lagoon overa 1-year period, and their occurrences compared. Some physical parameters (temperature, pH and electricalconductivity) were also investigated. The aim of the study was to establish the pollution status of the twolagoons, as well as investigate whether the feeder streams of the Sakumo II lagoon have any influence (in termsof trace metal pollution) on the Sakumo II lagoon. Results showed that upper mean values in water andsediment were Zn ( 0.160 ± 0.01 mg/l, 48.7 ± 0.93 mg/kg), Pb (0.057 ± 0.03 mg/l, 29.2 ± 3.2 mg/kg), Mn (0.798± 0.07 mg/l, 668.2 ± 6.3 mg/kg), Cu (0.158 ± 0.01 mg/l), Fe (1.32 ± 0.73 mg/l, 3075 ± 14.7 mg/kg), respectively,for Sakumo II lagoon. Cd levels in water and sediment ranged from 0.004 ± 0.001 to 0.009 ± 0.001 mg/l and <0.002 to 0.88 ± 0.05 mg/kg respectively, in the Sakumo II lagoon. Compared to the maximum contaminant level(MCL) of 0.005 mg/l, the Cd levels in water from the Sakumo II lagoon may be detrimental to the ‘health’ ofthe aquatic ecosystem and, consequently, consumers of fish products from the Sakumo II lagoon. Water andsediment in the Muni lagoon had trace metal concentrations with upper mean values as Cd (< 0.002 mg/l, 0.325± 0.01 mg/kg), Pb (0.033 ± 0.01 mg/l, 1.46 ± 0.18 mg/kg), Mn (0.434 ± 0.02 mg/l, 63.8 ± 1.50 mg/kg), Zn (0.077± 0.001 mg/l, 13.7 ± 0.18 mg/kg), Cu (0.013 ± 0.001 mg/l) and Fe (1.085 ± 0.26 mg/l, 3198.4 ± 3.51 mg/kg),respectively. Generally, trace metal levels detected in sediment from the Mamahuma ( Zn: 10.4 ± 4.10 mg/kg,Pb: 10.6 ± 1.84 mg/kg, Mn: 63.7 ± 4.5 mg/kg, Fe: 7487 ± 23.5 mg/kg, Cd: < 0.002), and from the GbagblaAnkonu ( Zn: 155 ± 13.9 mg/kg, Pb: 37.4 ± 3.07 mg/kg, Mn: 298.2 ± 2.5 mg/kg, Fe: 3209 ± 50.5 mg/kg, Cd: 0.70± 0.05 mg/kg) feeder streams were relatively higher than those in the Sakumo II lagoon. Sediment from thefeeder streams, therefore, provided a deeper insight into the long- term pollution state of the feeder streamsand, consequently, the Sakumo II lagoon. The streams could, thus, be described as potential sources of tracemetal pollution to the Sakumo II lagoon. Trace metal levels were also found to be more concentrated insediment from the mid-section of the Muni lagoon than those from the northern and southern sections, whilethe northern section had more trace metal concentrations in water than those from the mid- and southernsections. The study also showed that trace metal levels detected in both water and sediment from the SakumoII lagoon were higher relative to those from the Muni lagoon. The Sakumo II lagoon could be described asrelatively more polluted with trace metal load.

West African Journal of Applied Ecology, vol. 16, 200976

minerals and soils (Merian, 1991). However,the level of these metals in the environmenthas increased tremendously during the pastdecades as a result of human inputs andactivities (Prater, 1975; Merian, 1991).

The Sakumo II and Muni lagoon Ramsarsites are both havens for migratory birds.They are, however, located in two distinctareas. The Sakumo II lagoon is located inan urban area and receives large volumesof untreated waste discharges fromdomestic, agricultural and industrialactivities. The Muni lagoon, on the otherhand, is located in a rural area (a relativelyless populated area) and, therefore, receivesless waste discharges. Fish farming is adominant economic activity in bothcatchments. Obviously, the chemical statusof the waters and sediments in these lagoonswould have their influence on aquaticspecies, which might possibly reflect on thefish products.

The pH of a water body influences theconcentration of many metals by alteringtheir availability and toxicity. Metals suchas zinc (Zn) and cadmium (Cd) are mostlikely to have increased detrimentalenvironmental effects as a result of loweredpH (DWAF, 1996b). Temperatures at whichenvironmental samples are collected and atwhich physico-chemical measurements aremade are important for data correlation andinterpretation. For instance, for domestic use,high temperatures may increase the toxicityof many substances such as trace metals inwater. In addition to microbial activitieswithin an aquatic medium, temperature andpH are two important factors that governthe methylation of elements such as lead(Pb) and mercury (Hg) (Van Loon, 1982).Electrical conductivity (EC) is a useful

indicator of mineralization in a water bodywhich correlates with the total dissolvedsolids (TDS) in the water body.

Trace metals have been determined inpotable water (Garcia et al., 1999) and freshand marine waters (Hall et al., 2002).Although water is commonly employed as apollution indicator by trace metals, sedimentcan also provide a deeper insight into thelong-term pollution state of the water body.Sediment has been described as a ready sinkor reservoir of pollutants including tracemetals, where they concentrate accordingto the level of pollution (Onyari et al., 2003).The need to assess the state and quality ofwater and sediment from the Sakumo II andMuni lagoons, as well as the Mamahumaand Gbagbla Ankonu streams that feed theSakumo II lagoon, in terms of their tracemetal loads, becomes imperative due to thehealth implications that cut across the foodstrata, since these lagoons serve as sourcesof fish not only to people living in bothcatchments but also commercially availableto the larger community.

Previous studies on pollution of coastallagoons in Ghana covered physico-chemicalcharacteristics (Biney, 1986), limnology(Biney, 1995) and monitoring the pollutionstatus of coastal lagoons (Biney et al.,1998). These studies, however, did not coverall trace metals with detrimental effects onhuman health.

The paper seeks to identify andcharacterize the levels of trace metals (Fe,Cu, Mn, Pb, Cd and Zn) in water andsediment from the Muni and Sakumo IIlagoons, as well as the Mamahuma andGbagbla Ankonu feeder streams which feedthe Sakumo II lagoon, in order to establishthe trace metal loads and, subsequently,


determine whether the Mamahuma andGbagbla Ankonu feeder streams arepotential sources of trace metal pollution tothe Sakumo II lagoon.

Materials and methodsStudy areasThe Sakumo II lagoon occupies an area of3.5 km2 and lies between latitude 5o 36I Nand 5o 41I N and longitude 0o 01I W and 0o

04I W, about 3 km west of Tema (Fig. 1).The lagoon was a typical closed lagoon(Kwei, 1974) until pipes were laid under thesand bar to enable the construction of theAccra-Tema (Beach) road. The lagoon isnow permanently kept open to the sea bytwo parallel culverts each 70 m long and 1.4m in diameter; thus, representing a transitorystage between a closed and an open lagoon.

There are two rainy seasons, a majorseason which starts in March and peaks inmid-July and a minor season which beginsin mid-August and ends in October. Themean annual rainfall is about 753 mm.Relative humidity varies an average of 65%in mid afternoon to 95% at night. Meanmonthly temperatures range from aminimum of 24.7 oC in August to a maximumof 28.1 oC in March. The lagoon and itssurrounding wetlands have been designatedas one of the five Ramsar sites in Ghana,where important migratory birds may befound. Seventy species of water birds havebeen recorded at the site with estimatedmaximum numbers of some 30,000 birds(Birdlife International, 2003).

Two main streams, the Mamahuma andthe Gbagbla Ankonu, feed the lagoon. Bothstreams have been dammed to providewater for crop and livestock farming but havebecome polluted due to industrial anddomestic activities. The sampling point on

the Mamahuma feeder stream (FDS1) isabout 10 m away from the Ashaiman-Nungua main road, and the portion aroundthe sampling point was used by somecommercial drivers as a washing bay duringthe entire sampling period. The land area(about 10 m2) away from this sampling pointhouses a refuse dump, while the samplingpoint on the Gbagbla Ankonu feeder stream(FDS 2) is about 15 m away from the Accra-Tema Motorway. It was observed during theentire sampling period that the sampling point(FDS2) and its surrounding areas hadbecome chocked with refuse and the entirestream became almost stagnant. TheSakumo II lagoon and the feeder streamsare downstream of the major industries (e.g.Coca Cola Bottling, Printex and KasaprekoCompany Ltd) in the catchments as well asresidential areas.

The Muni lagoon covers an area of 4.5km2, located 1 km west of Winneba and 67km from Accra, and lies between latitude 5o

19I N and 5o 21I N and longitude 0o 38I W and0o 40I W (Fig. 2). The lagoon is shallow, ofaverage depth 0.6 m, and closed to the seafor most parts of the sampling period. It isfed by two rivers, Muni and Pratu. Thelagoon adjoins the Yenku Forest Reserve,which, together with the adjacent forest,form the traditional hunting grounds for thepeople of the area. Marine and lagoonfishing, livestock rearing, residential facilities,forest reserve, fuel wood harvesting, farmingand hunting are the major land-use activitiesalong the Muni lagoon (Biney et al., 1995).Salt winning activity was on-going at thenorthern section of the lagoon (Fig. 2).

Samples and sampling stationsSampling stations for water and

sediments from the Sakumo II and Muni


Fig. 1. Map showing the Sakumo II Lagoon , the Feeder Streams and the sampling points

SAKUMONO

NUNGUA

0 1 2 Km.

Road

Marshy Area

River/Stream

Railway

Sampling Point

L E G E N D

LASHIBI

T E M A

N

G H A N A


Fig. 2. Map showing the Muni lagoon and the sampling points

Mpaho

WINNEBA

Sankor

0 500 1000 15000 m.

Settlement

Road

River/Stream

Lagoon

N

Marsh

G H A N A

L E G E N D

Sampling Point

lagoons are presented in Fig. 1 and 2,respectively. Water and sediment sampleswere collected from the lagoons betweenNovember 2003 and October 2004. Fivesites were selected from the Sakumo IIlagoon; three from parts of the lagoonmarked SS, MS and NS (Fig. 1) referred toas South-Sakumo, Mid-Sakumo and North-Sakumo, respectively, one from theOnukpawahe stream, a tributary of theMamahuma, and one from Gbagbla Ankonumarked FDS1 and FDS 2 (Fig. 1), referredto as feeder stream 1 and feeder stream 2,respectively. Three sites were selected fromthe Muni lagoon, marked SM, MM and NM

referred to as South-Muni, Mid-Muni andNorth-Muni respectively (Fig. 2).Thesampling stations on the lagoons and thefeeder streams were selected on the basisof the different activities in the catchments,which are likely to affect the quality of thelagoon waters.

Sample containers were thoroughlywashed with detergent, rinsed with waterfollowed by distilled water before soakingin 5% HNO

3 for about 24 h. Sampling

protocols, described by Claasen (1982) andBarcelona et al. (1985), were strictlyadhered to during sample collection.Samples were collected in 4-litre acid-


washed polypropylene containers below (10cm) the surface of the lagoon. Watersamples were kept on ice in an ice-chestand transported to the Council for Scientificand Industrial Research-Water ResearchInstitute (CSIR-WRI) laboratory and storedat < 4 oC until analyzed (normally within 1week). Water samples for dissolved metaldetermination were filtered through 0.45 µmpore size on acetate cellulose filters andacidified to 1% acid with 65% analyticalgrade HNO

3. Sediment samples were

collected with an Eckman grab sampler, keptfrozen at -19 oC in polyethylene bags untilanalyzed (normally within 1 week). Thesediment samples were put on watch glassesand placed in an oven at 60 oC until dry. Thedried sediments were homogenized andpassed through a sieve of pore size 0.5 mm.

Dry sediment of grain size < 0.5 mm wasweighed (0.2 g) into a 60 ml Teflon vesseland digested under pressure with 2 mlconcentrated nitric acid (HNO

3) by slow

heating to 110 oC for 1 h, followed by rapidheating to 150 oC for 7 h. The samples werethen allowed to cool to room temperature.Digested samples were transferred intopolypropylene graduated tubes and made upto 25 ml with double-distilled water foranalysis (Canadian National Laboratory forEnvironmental Testing, 1994). Treatment andanalysis of samples took place within 1 weekof collection. Trace metal concentrations inwater and sediment were determined byflame atomization (UNEP, 1984b) usingUNICAM 969 flame atomic absorptionspectrometer.

Physical parameterspH, temperature and electrical

conductivity of the water samples weremeasured in situ using WTW-Multiline P4

universal meter before preserving with 5 mlconcentrated HNO

3.

Statistical analysisAnalysis of variance (ANOVA) was used

to compare means of trace metalconcentrations in water and sediment fromthe lagoons and feeder streams. Com-parisons of trace metal concentrations inwater and sediment were done between theSakumo II lagoon and the feeder streams,and Sakumo II and Muni lagoons todetermine whether the differences in tracemetal concentrations were significant orotherwise.

Results and discussionThe mean values of trace metals in water(mg/l ± SD) from Sakumo II lagoon andsome physical parameters, and mean valuesof sediment (mg/kg ± SD) from Sakumo IIlagoon are presented in Tables 1 and 2,respectively, whilst the mean values of tracemetals in water (mg/l ± SD) from Munilagoon, and some physical parameters andmean values of trace metals in sediment(mg/kg ± SD) from Muni lagoon arepresented in Tables 3 and 4, respectively.Tables 5 and 6 present the statisticalcomparison between the mean concentra-tions of trace metals in water and sedimentfor Sakumo II and Muni lagoons, and thefeeder streams.

The detection limits for trace metals usingflame photometry atomic absorptionspectrophotometer (FAAS) were Fe, 0.01;Mn, 0.005; Pb, 0.005; Cd, 0.002; Cu, 0.002and Zn, 0.005 for water and Fe, 2.8 µg/g);Mn, 33.5 µg/g; Pb, 0.55 µg/g; Cd, 0.25 µg/gand Zn, 4.5 µg/g; for sediment. Limits ofdetection of the analyzed metals weredetermined as three times the standard


TA

BL

E 1

Mea

n va

lues

of t

race

met

als

in w

ater

(m

g/l ±

SD)

from

Sak

umo

II la

goon

wit

h ot

her

phys

ical

par

amet

ers

Sam

plin

gC

uZ

nP

bM

nF

eC

dpH

Tem

p. oC

E

Cst

atio

n(µ

S/cm

)

FD

S 1

0.26

8 ±

0.0

60.

113

± 0

.01

0.02

0 ±

0.0

00.

942

± 0

.06

0.71

5±

0.0

3<

0.0

027.

5229

.034

38

FD

S 2

0.09

9 ±

0.0

10.

099

± 0

.01

0.03

7 ±

0.0

00.

777

± 0

.05

1.65

± 0

.20

0.00

6 ±

0.0

017.

4729

.316

84

SN0.

124

± 0

.01

0.12

1 ±

0.0

20.

032

± 0

.01

0.24

7 ±

0.0

11.

82 ±

0.6

30.

004

± 0

.001

8.61

29.8

1067

4

MS

0.15

8 ±

0.0

10.

160

± 0

.01

< 0

.005

0.79

8 ±

0.0

70.

888

± 0

.22

0.00

9 ±

0.0

018.

5929

.815

740

SS0.

112

± 0

.02

0.07

7 ±

0.0

10.

057

± 0

.03

0.24

0 ±

0.0

11.

32 ±

0.7

30.

004

± 0

.001

8.54

29.5

1810

2

Num

ber o

f sam

ples

(n) c

olle

cted

at e

ach

site

= s

even

, FD

S 1

= F

eede

r str

eam

1, F

DS

2 =

Fee

der s

trea

m 2

, SN

= S

akum

o -N

orth

, MS

= S

akum

o -M

id-

stre

am, S

S =

Sak

umo

–Sou

th a

nd S

D =

Sta

ndar

d de

viat

ion

TA

BL

E 2

Mea

n va

lues

of t

race

met

als

in s

edim

ent (

mg/

kg ±

SD

) fr

om th

e Sa

kum

o II

lago

on

Sam

plin

g st

atio

nZ

nP

bM

nF

eC

d

FD

S 1

10.4

± 4

.10

10.6

± 1

.84

63.

7 ±

4.5

7486

.9 ±

23.

5<

0.25

FD

S 2

155.

2 ±

13.

937

.4 ±

3.0

729

8.21

± 2

.532

08.6

± 5

0.5

0.70

± 0

.05

SN27

.1 ±

1.7

11.8

4 ±

2.0

420.

7 ±

44.

130

74.6

± 1

4.7

0.3

± 0

.09

MS

48.7

± 0

.93

29.2

± 3

.266

8.2

± 6

.330

53.5

± 1

9.42

<0.

25

SS16

.3 ±

2.6

3.79

± 0

.715

3.1

± 1

9.4

563.

2 ±

22.

30.

88 ±

0.0

5

Num

ber o

f sam

ples

(n) c

olle

cted

at e

ach

site

= s

even

, FD

S 1

= F

eede

r str

eam

1, F

DS

2 =

Fee

der s

trea

m 2

, SN

= S

akum

o-N

orth

, MS

= S

akum

o -M

id-

stre

am, S

S =

Sak

umo

–Sou

th a

nd S

D =

Sta

ndar

d de

viat

ion


TA

BL

E 3

Mea

n va

lues

of t

race

met

als

in w

ater

(m

g/L

± S

D)

from

Mun

i lag

oon

wit

h ot

her

phys

ical

par

amet

ers

Sam

plin

gC

uZ

nP

bM

nF

eC

dpH

Tem

p. oC

EC

stat

ion

(µS/

cm)

NM

0.01

3 ±

0.0

010.

077±

0.0

010.

033

± 0

.01

0.43

4 ±

0.0

201.

085

± 0

.260

< 0

.002

8.17

28.1

3906

4

MM

< 0

.002

0.05

4 ±

0.0

03<

0.00

50.

015

± 0

.004

0.50

6 ±

0.0

20<

0.0

028.

2827

.842

367

MS

< 0

.002

0.02

4 ±

0.0

04<

0.00

50.

143

± 0

.027

0.30

7 ±

0.0

21 <

0.00

28.

2328

.0 3

8333

Num

ber

of s

ampl

es (

n) c

olle

cted

at

each

sit

e =

sev

en, N

M =

Mun

i-N

orth

, MM

= M

uni

Mid

-str

eam

and

SM

= M

uni-

Sou

th, a

nd S

D =

Sta

ndar

d

devi

atio

n.

TA

BL

E 4

Mea

n va

lues

of t

race

met

als

in s

edim

ent (

mg/

kg ±

SD

) fr

om M

uni l

agoo

n

Sam

plin

g st

atio

nZ

nP

bM

nF

eC

d

NM

4.47

2 ±

0.3

21 0

.556

± 0

.02

33.5

± 0

.74

2344

.8 ±

2.8

10.

325

± 0

.01

MM

3.7

± 0

.18

1.46

± 0

.18

63.8

± 1

.50

3198

.4 ±

3.5

< 0

.25

MS

4.33

± 0

.18

0.56

9 ±

0.0

245

.3 ±

0.3

41

2546

.5 ±

6.7

1<

0.2

5

Num

ber

of s

ampl

es (

n) c

olle

cted

at

each

sit

e =

sev

en,

NM

= M

uni-

Nor

th,

MM

-Mun

i M

id-s

trea

m a

nd S

M =

Mun

i-S

outh

and

SD

= S

tand

ard

devi

atio

n.


TABLE 5Comparison between the mean concentrations of trace metals in water (mg/l) for Sakumo II and Muni

lagoons and the feeder streams.

Comparison of lagoons and Cu Zn Pb Mn Fe Cdfeeder streams

FDS1 Sakumo II ns ns ns P < 0.01 ns P < 0.05

FDS2 Sakumo II ns ns P < 0.001* ns ns ns

Sakumo II Muni ns ns ns Pf<f0.01 ns P < 0.001*

ns = not significant (P< 0.001), * = highly significant

TABLE 6Comparison between the mean concentrations of trace metals in sediment (mg/kg) for Sakumo II and Muni

lagoons and the feeder streams

Comparison of lagoons and Zn Pb Mn Fe Cd feeder streams

FDS1 Sakumo II ns ns P < 0.05* ns ns

FDS2 Sakumo II P < 0.001* P < 0.001 ns ns ns

Sakumo II Muni P< 0.001* ns P < 0.01 ns ns

ns = not significant (P < 0.001), * = highly significant

deviation (3Ã) of their lowest detectableconcentrations by FAAS from the mean ofsix replicate analyses. Good linearity wasobtained from the calibration curvesprepared from 1000 mg/l of each metalstandard from BDH laboratory, England.

Physical parametersMean water pH of Sakumo II lagoon

ranged from 7.47 to 8.61 (Tables 1 and 2),while those from the Muni lagoon rangedfrom 8.17 to 8.28 (Tables 2 and 3). This isan indication that, while the Sakumo II lagoonis neutral to basic in character, the Munilagoon is basic in character. The meanconductivity values varied from 1684 to18102 µS/cm and 38333 to 42367 µS/cm for

Sakumo II and Muni lagoons, respectively.This is a reflection of the higher salinity ofthe waters of the Muni lagoon than theSakumo II lagoon. The mean watertemperatures varied from 29.0 to 29.8 oCand 27.8 to 28.1 oC for Sakumo II and Munilagoons, respectively. This is typical ofshallow coastal waters in Ghana, whereambient temperatures remain within anarrow range of 25–35 oC (Biney, 1990).

Cadmium. Cadmium (Cd) is one of themost toxic elements with widespreadcarcinogenic effects in humans (Goering etal., 1994) and is widely distributed in theaquatic environment. The mean Cdconcentrations in water from Sakumo IIlagoon varied from 0.004 ± 0.000 to 0.009 ±


0.001mg/l, and was highest at the mid-sectionand lowest (similar concentration) at boththe northern and southern sections (Fig. 3).The high Cd value recorded at the mid-section of the Sakumo II lagoon could bedue to industrial and domestic effluents andurban storm-water runoff containing Cd-laden materials. Mean Cd concentrations inwater from feeder streams 1 and 2 variedfrom < 0.002 to 0.006 ± 0.001 mg/l, withfeeder stream 2 recording the highest Cdlevel (Fig. 3), suggestive of the relativelyhigher weathering of minerals and soils,discharge of domestic effluents and urbanstorm-water runoff containing Cd-ladenmaterials in feeder stream 2. In the watersof Muni lagoon, mean Cd concentrationswere all below detection limit ( Fig. 4, Table3), indicative of the absence of industrializa-tion and urbanization, which are associatedwith the discharge of industrial and domesticeffluents and urban storm-water runoffcontaining Cd-laden materials.

The mean Cd concentrations in sedimentfrom Sakumo II lagoon varied from < 0.002

to 0.88 ± 0.05 mg/kg, highest at the southernsection and lowest at the mid-section (Fig.5). Results from the study conforms to earlierfindings that sediments can be described asa ready sink or reservoir of pollutantsincluding trace metals where theyaccumulate according to the level of pollution(Onyari et al., 2003), since Cd concentrationin sediment from the southern section of theSakumo II lagoon was three times that fromthe northern section, even though thesouthern section recorded the least Cdconcentration in the waters of the SakumoII lagoon (Fig. 3). In the case of the feederstreams 1 and 2, mean Cd concentrations insediment varied from < 0.002 to 0.70 ± 0.05mg/kg, with feeder stream 2 recording thehighest Cd value (Fig. 5). This could be dueto weathering of minerals and soils,discharge of industrial and domesticeffluents and urban storm-water runoffcontaining Cd-laden materials in feederstream 2.

In sediments from Muni lagoon, mean Cdconcentrations varied from < 0.002 to 0.325

00.20.40.60.8

11.21.41.61.8

2

North S

akum

o

Mid

Saku

mo

South

Sakum

oFD

S 1FD

S 2

Cu

Zn

Pb

Mn

Fe

Cd

Fig. 3. Mean values of trace metals in water from Sakumo II lagoon and the feeder streams

Con

cent

rati

on (m

gl)

Sampling station


0

0.2

0.4

0.6

0.8

1

1.2

North

Mun

i

Mid

Mun

i

South

Mun

i

Cu

Zn

Pb

Mn

Fe

Cd

Con

cent

rati

on (m

gl)

0

1000

2000

3000

4000

5000

6000

7000

8000

North S

akum

o

Mid

Sakum

o

South

Sakum

o

FDS 1FDS 2

Zn

Pb

Mn

Fe

Cd

Con

cent

rati

on (m

gl)

Fig. 4. Mean values of trace metals in water from the Muni lagooon

Fig. 5. Mean values of trace metals in sediment from Sakumo II lagoon and the feeder streams

Sampling station

Sampling station


± 0.01 mg/kg, with the northern sectionrecording the highest Cd value (Fig. 6). Thehigh Cd value in this section of the Munilagoon could be attributed to the result ofweathering of minerals and soils due to thesalt winning activity in the vicinity. Thedifferences in Cd detected in water fromFDS1 and Sakumo II lagoon was significantlyhigh (P < 0.05), whilst the difference in Cdvalues for FDS2 and Sakumo II lagoon wasnot significant (Table 5). This suggests thatthe Sakumo II lagoon could be serving as aready sink for Cd pollution. Cd levelsdetected in both water (significantly higherat P < 0.001) and sediment (difference notsignificant) from the Sakumo II lagoon wererelatively higher than those detected in theMuni lagoon. This may be due to thecontribution from industrial and domesticwaste water runoffs and urban storm-waterrunoff. The mean Cd level detected in waterfrom the middle-section of Sakumo II lagoon(0.009 ± 0.001mg/l) and feeder stream 2(0.006 ± 0.001 mg/l) were higher than the

maximum contaminant level (MCL) of 0.005mg/l (USEPA, 1986a) above which theremay be detrimental effects to the ‘health’of the aquatic ecosystem and, consequently,consumers of fish products from theSakumo II lagoon.

Possible Cd effects in human includeaccumulation mainly in the kidney and liver.High concentrations have been found to leadto chronic kidney dysfunction, inducing cellinjury and death by interfering with calcium(Ca) regulation in biological systems, toxicityto fish and other aquatic organisms(Woodworth & Pascoe, 1982), and itsinvolvement in endocrine disrupting activities,which could pose serious health problems.However, concentrations of cadmium inwater are only likely to be of health concernin environments where pH is less than 4.5(WHO, 2004).

The mean Cd levels detected in sedimentfrom feeder stream 2, (0.70 mg/kg), thenorthern (0.3 mg/kg) and southern (0.88 mg/kg) sections of the Sakumo II lagoon (Table

0

500

1000

1500

2000

2500

3000

3500

North M

uni

Mid

Mun

i

South

Mun

i

Sampling station

Zn

Pb

Mn

Fe

Cd

6. Mean values of trace metals in sediment from the Muni lagoon


2) and from the northern section (0.225 mg/kg) of the Muni lagoon (Table 4) were higherthan the guideline value (0.11 mg/kg) ofunpolluted marine sediments (GESAMP,1982; Salomons & Froster, 1984; IAEA,1989).

Zinc. Zn is one of the earliest known tracemetal and a common environmental pollutant,which is widely distributed in the aquaticenvironment. It has been found to have lowtoxicity effect in man. However, prolongedconsumption of large doses can result insome health complications such as fatigue,dizziness and neutropenia (Hess & Schmidt,2002). Studies have also shown that Zn couldbe toxic to some aquatic organisms such asfish (Alabaster & Lloyd, 1980). In the watersof the Sakumo II lagoon, mean Znconcentrations varied from 0.077 ± 0.007 to0.160 ± 0.01 mg/l, with the mid-sectionrecording the highest Zn value (Fig. 3). Thiscould be attributed to natural sources,resulting from the weathering of mineralsand soils (Merian, 1991) and atmosphericdeposition from refineries. In feeder streams1 and 2, mean Zn concentrations varied from0.099 ± 0.011 to 0.113 ± 0.013 mg/l, withfeeder stream 1 recording the highest Znvalue (Fig. 3). The relatively high Zn levelin feeder stream 1 is suggestive of theinfluence of refuse dump and domesticsewage sources. It could also be attributedto industrial effluents (Asami, 1974).

Results also showed that the waters ofSakumo II lagoon recorded higher Zn valuesthan the feeder streams (differences notsignificant) (Table 5). The Sakumo II lagoonmay be acting as a ready sink which isreceiving metal loads including Zn from thefeeder streams. The waters of the Munilagoon recorded mean Zn concentrations

varying from 0.024 ± 0.004 to 0.077 ± 0.010mg/l, with the northern section recording thehighest Zn value (Fig. 4), This could beattributed to the weathering of minerals andsoils as a result of the salt winning activityin this section of the lagoon. In the case ofsediments, the mean Zn concentrations fromthe Sakumo II lagoon varied from 16.3 ±2.6 to 48.7 ± 0.93 mg/kg, with the mid-sectionrecording the highest Zn value (Fig. 5),suggestive of high domestic and industrialsewage discharge.

In sediment from the feeder streams themean Zn concentrations varied from 10.4 ±4.10 to 155.2 ± 13.9 mg/kg, with feederstream 2 recording the highest Zn value (Fig.5). The high Zn value recorded in sedimentfrom feeder stream 2 might be due to theweathering of minerals and soils anddomestic effluents, since feeder stream 2receives domestic effluents from Ashaimanand its environs, which is densely populated.Results also showed that sediment fromFDS1 had Zn values which were notsignificantly higher than those from theSakumo II lagoon, whilst sediment fromFDS2 had higher Zn levels (highly significantat P < 0.001) relative to those from theSakumo II lagoon (Table 6). Possible sourcesof Zn in sediment from the feeder streamsinclude industrial effluents, urban storm-water runoff and domestic effluents.

Mean Zn concentrations in sediment fromthe Muni lagoon varied from 4.33 ± 0.18 to13.7 ± 0.18 mg/kg, with the mid-sectionrecording the highest Zn value (Fig. 6). Aprobable reason for the high Zn value insediment from the mid-section of the Munilagoon may be increased weathering ofminerals and soils. The study showed thatlevels of Zn detected in both water


(differences not significant) (Table 5) andsediment (differences highly significant at P< 0.001) (Table 6) from the Sakumo II lagoonwere relatively higher than those detectedin the Muni lagoon. This suggests the intenseanthropogenic influence due to industrializa-tion and urbanization within the catchmentsof the Sakumo II lagoon as against theabsence of industries and low population(rural setting) in the Muni lagoon catch-ments. Results from the study showed thatsediments from both lagoons were withinthe recommended value (95 mg/kg) ofunpolluted sediments (Salomons & Foster,1984), except those from feeder stream 2(155.2 mg/kg).

Copper. Copper (Cu) is intimately relatedto the aerobic degradation of organic matter(Das & Notling, 1993) and has been shownto cause acute gastrointestinal discomfortand nausea at concentrations above 3 mg/l(WHO, 2004). In the waters of Sakumo IIlagoon, mean Cu concentrations varied from0.112 ± 0.009 to 0.158 ± 0.012 mg/l, withthe mid-section recording the highest Culevel (Fig. 3). The high Cu levels in thissection of the Sakumo II lagoon could beattributed to the presence of relatively highoxygen and organic matter, thereby,enhancing the process of aerobic degrada-tion of organic matter which, invariably, isintimately related to the deposition of Cu(Das & Notling, 1993). The waters offeeder streams 1 and 2 recorded mean Cuconcentrations varying from 0.099 ± 0.010to 0.268 ± 0.006 mg/l, with feeder stream 1recording the highest Cu value (Fig. 3). Thissuggests that the waters of feeder stream 1may be relatively more oxygenated and maycontain more organic matter than feederstream 2, thus, enhancing aerobic

degradation of organic matter and, thereby,depositing Cu in the waters (Das & Notling,1993) of feeder stream 1.

In the case of the Muni lagoon, mean Cuconcentrations in water varied from < 0.002to 0.013 ± 0.001 mg/l. The highest Cuconcentration recorded in the waters of theMuni lagoon was recorded in the northernsection (Fig. 4). Results showed that levelsof Cu detected in water from feeder streams1 and 2 (differences not significant) wererelatively higher than those from the SakumoII lagoon (Fig. 3), suggesting that the feederstreams may be relatively more oxygenatedand may contain relatively more organicmatter. The feeder streams are, therefore,potential sources of Cu contamination to theSakumo II lagoon. Cu levels in water fromthe Sakumo II lagoon were relatively higher(differences not significant) (Table 5) thanthose detected in the Muni lagoon. This isan indication of intense industrial anddomestic influence as a result ofindustrialization (the presence ofmanufacturing industries such as Printex,Coca Cola Bottling, Kasapreko CompanyLtd, etc.) and urbanization (residentialfacilities) in the Sakumo II lagoon catchmentsresulting in production of high organic matterwhich could possibly enhance the processof aerobic degradation (in the presence ofoxygen) of organic matter (Das & Notling,1993).

Lead. The United States EnvironmentalProtection Agency has classified lead (Pb)as being potentially hazardous and toxic tomost forms of life (USEPA, 1986a). Pb hasbeen found to be responsible for quite anumber of ailments in humans, such aschronic neurological disorders especially infoetuses and children. A concentration of


Pb > 0.1 mg/l is detrimental to foetuses andchildren with possible development ofneurological problems.

In the Sakumo II lagoon, mean Pbconcentrations detected in water varied from< 0.005 to 0.057 ± 0.003 mg/l, with thesouthern section recording the highest Pbvalue (Fig. 3). The waters of the feederstreams recorded mean Pb concentrationsvarying from 0.020 ± 0.00 to 0.037± 0.00mg/l, with feeder stream 2 recording thehighest Pb value (Fig. 3). A probable sourceof Pb could be due to its persistence in theenvironment and from used dry-cell batteriesresulting from the refuse dump around thearea. Results from this study showed thatthe Sakumo II lagoon waters (Fig. 3) hadhigher Pb levels relative to the feederstreams (differences in Pb levels betweenSakumo II lagoon and FDS1 not significant,whilst those between Sakumo II lagoon andFDS2 were highly significant at P < 0.001).

The study also showed that sediment fromthe feeder streams had relatively high(differences not significant between SakumoII lagoon and FDS1, whilst that betweenSakumo II lagoon and FDS2 was significantat P < 0.001) (Table 6) Pb values than thosefrom the Sakumo II lagoon. Since sedimentsprovide a deeper insight into the long-termpollution state of a water body, the feederstreams could be described as potentialsources of Pb pollution to the Sakumo IIlagoon.

In the case of the Muni lagoon, the watershad mean Pb concentrations ranging from< 0.005 to 0.033 ± 0.001 mg/l with thenorthern section recording the highest Pbvalue (Fig. 4). High Pb values in the northernsection of the Muni lagoon may be due toatmospheric deposition resulting from its

persistence in the environment. Results fromthe study showed that the waters of bothSakumo II and Muni lagoons may not bedetrimental to foetuses and children withpossible development of neurologicalproblems since Pb levels in these waterswere < 0.1mg/l. In the case of sediments,the Sakumo II lagoon had mean concen-trations of Pb varying from 3.79 ± 0.7 to29.2 ± 3.2 mg/kg, with the southern sectionrecording the highest Pb value (Fig. 5). Thefeeder stream waters had mean Pbconcentrations varying from 10.6 ± 1.84 to37.4 ± 3.07 mg/kg, with feeder stream 2recording the highest Pb value (Fig. 5). Thisconfirms earlier suggestion that Pbpersistence in the environment might beresponsible for the high Pb levels in thewaters of feeder stream 2 since Pb levels insediment from feeder stream 2 (Fig. 5) wasfour times that in sediment from feederstream 1 as against the two times that intheir waters (Fig. 3). The high Pb levels insediment from the feeder streams could bethe result of flocculation of the waters inthese streams resulting in the sedimentationof particulate Pb.

For sediment from the Muni lagoon, meanconcentrations of Pb varied from 0.556 ±0.02 to 1.46 ± 0.18 mg/kg, with the mid-section recording the highest Pb value (Fig.6). The high levels of Pb in the mid-sectionof the Muni lagoon relative to the northernand southern sections could be due tosewage effluent and runoff of waste sincethis portion of the lagoon is close to humansettlements. Results from the study haveshown that the levels of Pb detected in waterand sediment from the Sakumo II lagoonwere relatively higher (differences notsignificant) than those from the Muni lagoon,


suggestive of possible impact of dischargeof industrial and sewage effluents anddomestic wastewater into the Sakumo IIlagoon.

Results also showed that Pb levelsdetected in water (differences in valuesbetween Sakumo II and FDS1 notsignificant, whilst those between Sakumo IIand FDS2 were highly significant at P <0.001) and sediment (differences in valuesbetween Sakumo II and FDS1 notsignificant, whilst those between Sakumo IIand FDS2 were significant at P < 0.001) fromthe feeder streams relative to those fromthe Sakumo II lagoon were higher (Fig. 3and 5). This suggests that the feeder streamscould be serving as potential sources of Pbcontamination to the Sakumo II lagoon. Thestudy also showed that sediment from themid-section of Sakumo II lagoon (29.2 mg/kg) and the feeder stream 2 (37.2 mg/kg)(Fig. 5) were outside the recommendedvalues (19.00 mg/kg) of unpolluted sediments(Salomons & Froster, 1984).

Manganese. Mn is an element of lowtoxicity having considerable biologicalsignificance and one of the more biogeo-chemical and active transition metals inaquatic environment (Evans et al., 1977).Mn occurs in surface waters that are low inoxygen and often does so with Fe. Mnaccumulates in certain species of fish (Uthe& Blish, 1971). The health based guidelinevalue is 0.4 mg/l (WHO, 2004).

Mean Mn concentrations in water fromthe Sakumo II lagoon varied from 0.240 ±0.016 to 0.798 ± 0.073 mg/l, with the mid-section recording the highest Mn value (Fig.3). In the waters of the feeder streams, meanMn concentrations varied from 0.777 ± 0.05to 0.942 ± 0.069 mg/l, with feeder stream 1recording the highest Mn value (Fig. 3). A

probable source of airborne inorganicmanganese pollutant in urban centres is thecombustion of methylcyclopentadienylmanganese tricarbonyl (MMT), particularlyin areas of high traffic density (Sierra et al.,1998). MMT is neutral in charge andcontains organic groups, which makes ithighly lipophilic and soluble in petrol. Duringvehicle combustion, weak bonds betweenthe central metals and the organic groupsreadily break down in hot car engineenvironment. Combustion of MMT leads tothe emission of manganese phosphates,manganese sulfate and manganese oxidesthat include manganese tetroxide as a minorcomponent (Zayed, 2001; WHO, 2004). Thehigh Mn levels in the mid-section of SakumoII lagoon and feeder stream 1 could,therefore, be due to MMT, an anti-knockingagent present in petroleum products whichhas Mn as an active component.

Mean Mn concentrations in water fromthe Muni lagoon varied from 0.015 ± 0.004to 0.434 ± 0.02 mg/l, with the northernsection recording the highest Mn value (Fig.4). Mean Mn concentrations in sedimentfrom the Sakumo II lagoon varied from 153.1± 19.4 to 668.2 ± 6.3 mg/kg, with the mid-section recording the highest Mn value (Fig.5). In the case of sediment from the feederstreams, mean Mn concentrations variedfrom 63.7 ± 4.5 to 298.21 ± 2.5 mg/kg, withfeeder stream 2 recording the highest Mnvalue (Fig. 5). This suggests that there couldbe flocculation of the waters in Sakumo IIlagoon and FDS2 resulting in thesedimentation of particulate Mn, since Mnlevels in sediment from feeder stream 2 wasfive times that from feeder stream 1 (Table2), whilst, in contrast, Mn levels in the watersof feeder stream 1 (0.94 mg/l) was onlyslightly higher than feeder stream 2 (0.78


mg/l) (Table 1). Sediment from the Munilagoon had mean Mn concentrations varyingfrom 33.5 ± 0.74 to 63.8 ± 1.50 mg/kg., withthe mid-section recording the highest Mnvalue (Fig. 6). This might be due toflocculation resulting in sedimentation of Mnin this section of the Muni lagoon.

Results showed that the levels of Mndetected in water from the feeder streamsrelative to those from Sakumo II lagoonwere higher (differences in values betweenSakumo II and FDS1 was significant at P <0.001, whilst those between Sakumo II andFDS2 were not significant) (Table 5),suggesting that the feeder streams couldserve as sources of Mn contamination tothe Sakumo II lagoon. However, sedimentfrom the Sakumo II lagoon had higher Mnlevels relative to those from the feederstream (differences in values betweenSakumo II and FDS1 was highly significantat P < 0.05, whilst those between SakumoII and FDS2 were not significant) (Table6). This confirms the ability of sediment toserve as a ready sink or reservoir forpollutants including trace metals (Onyari etal., 2003). The Muni lagoon had relativelylower Mn values for both water (differencesin values significant at P < 0.01) (Table 5)and sediment (differences in valuessignificant at P < 0.01) (Table 6). This couldbe attributed to the relatively less impact ofhuman activity in the catchments of the Munilagoon. Results (Tables 2 and 4) showedthat Mn levels in sediments from bothlagoons were within the recommendedvalues (777.0 mg/kg) of unpolluted sediments(Salomons & Froster, 1984).

Iron. Iron (Fe) has frequently been usedas an indication of natural changes in thetrace metal carrying capacity of sediments( Rule, 1986), and its concentration has been

related to the abundance of metal reactivecompounds supposedly not significantlyaffected by man’s action (Luoma, 1990). Feis found in natural fresh- and groundwater,but have no health-based guideline value,although high concentrations give rise toconsumer complaints due to its ability todiscolour aerobic waters at concentrationsabove 0.3 mg/l (WHO, 2004). The mean Feconcentrations in water from the Sakumo IIlagoon varied from 0.888 ± 0.22 to 1.82 ±0.63 mg/l, with the northern section recordinghighest Fe value (Fig. 3). In the waters ofthe feeder streams, mean Fe concentrationsvaried from 0.715 ± 0.03 to 1.65 ± 0.20 mg/l, with feeding stream 2 recording the highestFe value (Fig. 3). This may be due to naturaloccurrence, since the feeder streams arefreshwaters which are produced fromaquifers within which geochemical andbiochemical processes take place, thereby,releasing Fe (WHO, 2004). The waters ofthe Muni lagoon recorded mean Feconcentrations varying from 0.307 ± 0.021to 1.085 ± 0.260 mg/l (Table 3), with thenorthern section recording the highest Fevalue (Fig. 4). Results (Tables 1 and 3)showed that Fe values in water from theSakumo II and the Muni lagoons, as well asthe feeder streams, were all above themaximum limits (0.3 mg/l) beyond whichthere could be the discolouration of aerobicwaters (WHO, 2004).

In the case of sediment, mean Feconcentration detected from the Sakumo IIlagoon varied from 2563.2 ± 22.3 to 3074.6± 14.7 mg/kg (Table 2), with the northernsection recording the highest Fe value.Probable sources of Fe in sediment fromthe northern section of the Sakumo II lagooncould be natural, as a result of naturalgeochemical and biochemical processes


with the aquifers. In the feeder streams,mean Fe concentrations in sediment variedfrom 3208.6 ± 50.5 to 7486.9 ± 23.5 mg/kg(Table 2), with feeder stream 2 recordingthe highest Fe value. The high Fe level infeeder stream 2 could be related to theabundance of metal reactive compoundssupposedly not significantly affected byman’s action (Luoma, 1990). In the case ofsediment, mean Fe concentrations in theMuni lagoon varied from 2344.8 ± 2.81 to3198.4 ± 3.51 mg/kg, with the mid-sectionrecording the highest Fe value (Table 4).

The levels of Fe in water (differences invalues not significant) from the Sakumo IIlagoon were higher than those from the Munilagoon (Table 5). This may be due to naturalsources as a result of the geochemical andbiochemical processes in the aquifers withinthe catchments. However, Fe levels insediment from the Muni lagoon wererelatively higher (differences in values notsignificant) (Table 6) than those from theSakumo II lagoon. This could be attributedto natural occurrence. Fe levels in sedimentfrom the feeder streams were relativelyhigher (differences in values not significant)(Table 6) than those from the Sakumo IIlagoon (Fig. 5), suggesting that the feederstreams could be considered as potentialsources of Fe contamination to the SakumoII lagoon. Results (Tables 2 and 4) showedthat Fe levels in sediments from bothlagoons were within the recommendedvalues (41000.00 mg/kg) of unpollutedsediments (GESAMP, 1982; Salomons &Froster, 1984).

ConclusionThe study showed that the mid-section ofthe Sakumo II lagoon had higher trace metallevels than the southern and northern

sections, indicative of the influence of intenseanthropogenic activities in this section of theSakumo II lagoon. The Mamahuma and theGbagbla Ankonu streams, which feed theSakumo II lagoon, serve as potential sourcesof trace metal pollution to the lagoon. Tracemetal levels in sediment from the mid-sectionof the Muni lagoon were relatively higherthan the southern and northern sections.However, the northern section of the Munilagoon had higher trace metal levels in water.This suggests the relatively intenseanthropogenic impact due to the salt winningactivity in the northern section of the Munilagoon. The levels of trace metals detectedin sediment from the lagoons and the feederstreams were higher than those in water,thus, sediment could be described as a readysink or reservoir of trace metals contami-nation in both the lagoons and the feederstreams. The study also showed that tracemetal levels detected in both water andsediment from the Sakumo II lagoon wererelatively higher than those from the Munilagoon. Thus, the Sakumo II lagoon couldbe described as relatively more polluted withtrace metal loads.

AcknowledgementFinancial support for the study was providedby the Government of Ghana. Facilitiesprovided by the Environmental ChemistryDivision, CSIR-Water Research Institute arehereby acknowledged. The authorsgratefully acknowledge the immenseassistance of Mr Michael Dorleku, PrincipalTechnical officer, CSIR-Water ResearchInstitute, for his participation in the samplingand analysis of the water samples. They alsoacknowledge the assistance of Mr John RexSappah and Mr Harrison Komladjei, Chief


and Principal Draughtsmen, respectively,CSIR-Water Research Institute, for drawingthe maps of the study areas.

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7 trace metal levels

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