This paper reports the metals content in water, sediment, macroalgae, aquatic plant, and fish of Batang Ai Hydroelectric Reservoir in Sarawak, Malaysia. The samples were acid digested and subjected to atomic absorption spectrometry analysis for Na, K, Mn, Cr, Ni, Zn, Mg, Fe, Sn, Al, Ca, As, Se, and Hg. The total Hg content was analysed on the mercury analyser. Results showed that metals in water, sediment, macroalgae, aquatic plant, and fish are distinguishable, with sediment and biota samples more susceptible to metal accumulation. The distributions of heavy metals in water specifically Se, Sn, and As could have associated with the input of fish feed, boating, and construction activities. The accumulation of heavy metals in sediment, macroalgae, and aquatic plant on the other hand might be largely influenced by the redox conditions in the aquatic environment. According to the contamination factor and the geoaccumulation index, sediment in Batang Ai Reservoir possesses low risk of contamination. The average metal contents in sediment and river water are consistently lower than the literature values reported and well below the limit of various guidelines. For fishes, trace element Hg was detected; however, the concentration was below the permissible level suggested by the Food and Agriculture Organization.
Metals contamination has been a concern of hydroelectric development [
The construction of dam has been long challenged with the issue of elevated mercury (Hg). Upon impoundment of a dam, the naturally occurring inorganic Hg may be converted to bioavailable organic Hg by bacteria leading to bioaccumulation of Hg in fish [
Sarawak, a state in Malaysia on the island of Borneo, possesses high potential for hydroelectric development due to the abundant rainfall throughout the year [
According to Roulet et al. [
With the continuous increase of demand for aquaculture harvest and the potential of metal contamination particularly the phenomenon of mercury accumulation, the status of Batang Ai Reservoir is poorly understood. There is relatively little information on the metal accumulation in hydroelectric reservoir in this region; Barletta et al. [
Water, sediment, macroalgae, aquatic plant, and fish samples were collected from 7 stations in Batang Ai Reservoir and the Ai River as shown in Figure
Summary of species of macroalgae, aquatic plant, and fish samples.
Fish (total length (cm)) | Description | Algae/aquatic plants | Description |
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It is largely herbivorous, consuming aquatic macrophytes and submerged plants as well as algae. |
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Found at ST1. It is commonly known as macroalgae. |
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It is a migratory species where the diet consists mainly of aquatic insects. |
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Found at ST6. It is a type of floating aquatic plant. |
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It is a carnivorous species consuming mainly small fish and aquatic insects. |
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Found at ST7. It is an emergent aquatic plant. |
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It is probably a predator feeding on crustaceans and smaller fishes. | ||
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It is largely herbivorous, consuming aquatic macrophytes and submerged plants as well as algae. |
The sampling locations at Batang Ai Reservoir and the Ai River.
The samples were digested in triplicate and subjected to atomic absorption spectroscopy (AAS) for metal analyses including Na, K, Mn, Cr, Ni, Zn, Mg, Fe, Sn, Al, Ca, As, and Se. The total Hg was analysed on a mercury analyser (Perkin Elmer, FIMS 400). The water samples were analysed according to the standard method of APHA [
For biological samples, they were washed under running tap water prior to drying to remove dirt. The dorsal of fish samples was dissected whilst for aquatic plant only the part above ground is considered. The samples were oven dried at 60°C and ground. A total of 0.5 g of sediment sample was digested with 6 mL of concentrated HNO3 and 2 mL of HCl on a hotplate until the solution is colorless. The sample was cooled and filtered through 0.45
Detection limits of element analysed were Na (0.0037 ppm); K (0.0009 ppm); Mn (0.0016 ppm); Cr (0.0054 ppm); Ni (0.008 ppm); Zn (0.0033 ppm); Mg (0.0022 ppm); Fe (0.0043 ppm); Sn (0.21 ppm); Al (0.028 ppm); Ca (0.0037 ppm); As (0.12 ppm); Se (0.23 ppm); and Hg (at ppb level). Blanks were also analysed for potential contamination.
The metal contents tabulated in tables with rows corresponding to samples and columns corresponding to variables (elements) were square rooted and standardised prior to principal component analysis (PCA). The multivariate exploratory approach reveals the clustering pattern of various samples and according to sampling locations. This facilitates the interpretation of a relatively large dataset whether metal contents in various samples are distinguishable and whether respective samples can be differentiated according to sampling locations. Pearson’s correlation analysis was performed to identify the correlation between two elements where
The contamination status is evaluated based on the contamination factor (CF), the geoaccumulation index (
The geoaccumulation index,
The pollution load index (PLI) is calculated as
Metals in water, sediment, macroalgae, aquatic plant, and fish are subjected to PCA yielding a scores plot of PC2 versus PC1 in Figure
The nonzero average of metal contents in different samples.
Elements | Water |
Sediment |
Macroalgae |
Aquatic plants |
Fish |
Literature range in sediment (mg/kg) | Literature range in water |
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Na |
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nd |
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3190–6910a | — |
K |
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7550–17300a | — |
Mn |
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nd | 348–5740a; 167–915c | 4–86a; 0.038–0.239c; 0.2–10d; 0.05e |
Cr |
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nd |
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40–343a; 30.2–74.8b; 92.5–160c; 37.3f; 90g | 7-8a; 2.4–7. |
Ni | nd |
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nd | nd | nd | 11.6–64.5a; 6.2–17.8b; <0.05c; 21f; 52g | 9–18a; 1.2–5. |
Zn | nd |
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nd | nd | nd | 54–904a; 21.8–127b; 182–484c; 123f; 315g | <5a; 26–88. |
Mg |
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2400–7630a | 11200–17300a |
Fe |
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8340–25400a; 12842–53581c | 90–164a; 0.088–0.463c; 5d; 0.3e |
Sn | nd |
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nd | ||
Al | nd |
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20000–52200a; 12280–35035c | 20–98a; 0.024–0.149c; 5d |
Ca |
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16000–82100a | |
As |
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nd | nd | nd | nd | 3.2–7.4a; 34.1–112.8b | 11–14a; 13.1–47. |
Se |
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nd | nd | nd | — | |
Hg |
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0.17–0.35b | 0.01–0. |
The scores plot of heavy metal contents according to heavy metals in water, sediment, aquatic plant, macroalgae, and fish.
The occurrence of metals in water, sediment, macroalgae, aquatic plant, and fish is examined independently with PCA; the scores plots are shown in Figure
The scores plot of heavy metals in water, sediment, macroalgae, aquatic plant, and fish according to sampling stations.
Water
Sediment
Macroalgae and aquatic plant
Fish
The average metal contents in water, sediment, macroalgae, and aquatic plant according to sampling stations.
Evidently, Se is below the detection limit in most water samples except ST5 and ST6 with aquaculture activities. The presence of Se can be an indication of excessive discharge of fish feed as Se has been commonly added to animal feed including fish meal due to its importance in biological function [
Arsenic is detected in water at ST3, ST4, and ST7. This may be associated with the development and construction activity nearby as studies revealed that As is susceptible to leaching from construction debris with chromate-copper-arsenate (CCA) wood [
Sn, particularly organotin, has been widely used as a component in antifouling paint, applied as a finish coat to the submerged part of boat, and in pesticides. In this study, Sn is found in an appreciable amount in algae and plants. In fact, Sn is relatively immobile; it may exist as Sn(II) or Sn(IV) where both forms are readily precipitated under reduced conditions. The element can be profoundly accumulated in aquatic organisms. According to Thompson et al. [
Five species of fish samples were collected from the reservoir near the aquaculture farm at ST5. No well-defined separation can be interpreted based on the scores plot of PCA. Figure
The average concentrations of six prominent elements in fish according to species and parts (SP1:
The relationships of metals within samples, that is, water, sediment, and macroalgae/aquatic plant, are correlated based on the mean concentrations. Table
Correlation analysis of metal concentrations in (a) water, (b) sediment, and (c) macroalgae and aquatic plant.
Water
Na | K | Mn | Cr | Mg | Fe | Ca | As | Se | Hg | |
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Na | 1.00 | |||||||||
K | −0.34 | 1.00 | ||||||||
Mn | 0.15 | 0.61 | 1.00 | |||||||
Cr | −0.51 | 0.39 | 0.40 | 1.00 | ||||||
Mg | 0.75 | −0.71 | −0.42 | −0.65 | 1.00 | |||||
Fe | 0.25 | 0.40 |
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0.32 | −0.16 | 1.00 | ||||
Ca | 0.46 | −0.61 | −0.07 | −0.12 | 0.55 | 0.14 | 1.00 | |||
As | −0.24 | −0.51 | −0.40 | −0.32 | 0.05 | −0.33 | 0.46 | 1.00 | ||
Se | −0.35 | 0.15 | −0.39 | 0.34 | −0.18 | −0.50 | −0.62 | −0.54 | 1.00 | |
Hg |
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0.19 | 0.64 | −0.36 | 0.25 | 0.62 | 0.10 | −0.34 | −0.50 | 1.00 |
Sediment
K | Mn | Cr | Ni | Zn | Mg | Fe | Al | Ca | Se | Hg | |
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K | 1.00 | ||||||||||
Mn | 0.25 | 1.00 | |||||||||
Cr | 0.02 | − |
1.00 | ||||||||
Ni | 0.28 | 0.35 | −0.02 | 1.00 | |||||||
Zn | 0.28 | 0.35 | −0.02 | 1.00 | 1.00 | ||||||
Mg | 0.51 | 0.39 | −0.06 | − |
− |
1.00 | |||||
Fe | 0.64 | 0.34 | 0.35 | 0.39 | 0.39 | 0.43 | 1.00 | ||||
Al | 0.13 | 0.58 | 0.62 | 0.41 | 0.41 | 0.28 | 0.55 | 1.00 | |||
Ca | 0.70 | −0.04 | −0.32 | 0.46 | 0.46 | 0.64 | 0.39 | −0.34 | 1.00 | ||
Se | −0.03 | −0.39 | −0.14 | −0.17 | −0.17 | −0.18 | 0.05 | −0.51 | 0.45 | 1.00 | |
Hg | 0.64 | 0.29 | 0.17 | 0.66 | 0.66 | 0.68 | 0.63 | 0.32 | 0.68 | 0.34 | 1.00 |
Aquatic plants and macroalgae
Na | K | Cr | Mg | Fe | Al | Ca | Hg | |
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Na | 1.00 | |||||||
K | −0.47 | 1.00 | ||||||
Cr | 0.14 | 0.59 | 1.00 | |||||
Mg | − |
0.61 | 0.20 | 1.00 | ||||
Fe | −0.29 | 0.68 | 0.10 | 0.18 | 1.00 | |||
Al | 0.43 | −0.38 | −0.20 | −0.62 | 0.24 | 1.00 | ||
Ca | 0.13 | −0.23 | 0.07 | −0.21 | 0.17 | − |
1.00 | |
Hg | 0.43 | −0.70 | −0.44 | −0.46 | −0.79 | −0.11 | −0.41 | 1.00 |
Considering the metals uptake in algae and plant, macroalgae at ST1 demonstrates greater tendency of metal accumulation. According to Michalak and Chojnacka [
The contamination factors (CF) calculated for Mn, Cr, Ni, Zn, Mn, and Fe are comfortably below 1. The CF of Hg, however, is slightly above 0, at an average of 0.322, indicative of slight pollution. According to a survey of Hg present in 73 rivers of the USA, the concentrations reported range between 0.1
The findings of the study indicate that there is low risk of heavy metal contamination in the environment of Batang Ai Hydroelectric Reservoir. The aquaculture and development activities, however, may result in elevated Se, As, and Sn. The availability of the trace elements is largely governed by the redox conditions in the environment. Generally, there is no special concern of heavy metal contamination in fish; nonetheless there is a tendency of Hg bioaccumulation and continuous monitoring is necessary.
The authors declare that there is no conflict of interests regarding the publication of this paper.
The authors would like to thank the Ministry of Education for funding this project (Fundamental Research Grant Scheme: FRGS/STWN01(04)991/2013(32)). They would also like to acknowledge Associate Professor Othman Bojo and Dr. Mohd Effendi bin Wasli for their assistance in identifying the aquatic plants.