Heavy Metal Concentrations in the Bivalve Corbicula fluminalis Shells from Shatt Al-Arab River  

M.H. Al-Jaberi
Geology department, Science College, Basrah University, Basrah - Iraq
Author    Correspondence author
International Journal of Marine Science, 2015, Vol. 5, No. 39   doi: 10.5376/ijms.2015.05.0039
Received: 22 Apr., 2015    Accepted: 26 May, 2015    Published: 10 Jun., 2015
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This article was first published in Mesopot. J. Mar. Sci., 2014, 29(1): 23-28, and here was authorized to redistribute under the terms of Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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Al-Jaberi, 2015, Heavy metal concentrations in the bivalve Corbicula fluminalis shells from Shatt Al-Arab River, International Journal of Marine Science, Vol.5, No.39 1-4 (doi: 10.5376/ijms.2015.05.0039)

Abstract

This study was to investigate the contamination in the Shatt Al-Arab River by determining the heavy metals in the limnic bivalve Corbicula fluminalis, a sentinel species. The results showed that the values of Ba, Zn, Pb, Ni, Co, Cr, Sr, Cu, Mn and Fe in Corbicula fluminalis shells increased significantly from the beginning point toward the central part of Shatt Al-Arab River. This increase may be explained from the high incidence of pollution from sewage, development, and industry in the central part of Shatt Al-Arab River compared to the northern parts.

Keywords
Corbicula fluminalis; Shells; Pollution; Shatt Al Arab River; Heavy metals

The tolerance and adaptability of the bivalve molluscs have made them a preferred organism as indicator of the quality of ecosystems (Conti and Cecchetti, 2003). Trace metal contamination level in a given organism results from the net balance between the processes ofmetal uptake and metal loss (Goodfriend and Magaritz, 1989). Chemical analysis of hard body parts can yield vital information on the processes involved in biomineralisation and the interaction between the organism and the surrounding environment.
Trace elements are incorporated into bioic systems at significantly lower quantities (~0.1wt%) than elements in the surrounding environment (Dalbeck, 2008). Even though these elements do not form crystal phases, their presence can be used to provide a better understanding of biomineralisation processes.
Trace element composition can allow insight to the conditions in which mineralisation occurred, how these ‘foreign’ elements can affect growth of hard body parts, and growth of the individual, as well. Concentration of trace elements in hard body parts depends on the acceptability of the elements (Dodd, 1965; Afaj and Al-Dabbas, 1998).
In the Shatt Al-Arab River, there is high concentration of population and industries. Most of domestic sewage and industrial effluents with high organic matter are discharged untreated. This extra organic matter has caused several biogeochemical changes, both in small side streams and in the river proper, which is a source of heavy metals in these water bodies. A number of authors have studied the heavy metals in Corbicula fluminalis shells as a pollution indicator, such as the work of Mustafa (1989) and Salman (2007) in the Shatt Al-Arab River, Al-Bassam (1999) in the Euphrates River, and the study of Al-Saady (2008) in the Hor Al-Chekka River. The main objective of the present study was to determine the concentration of metals in specimens of the limnic bivalve Corbicula fluminalis shells.
Study Area
The study area was located on the banks of Shatt Al-Arab River north of and within the area of Basrah city, south Iraq (Figure 1).


Figure 1 Study area with location of sampling sites

1 Materials and Methods
Eight Corbicula fluminalis shells were chosen for analysis. These shells were tested by scanning electron microscope-EDAX, Inductively Coupled Plasma-Atomic emission spectrometry (ICP-AES), and Inductively Coupled Plasma-Mass spectrometry (ICP-MS).
Shell samples were first separated from living soft tissues, washed with distilled water, exposed to ultrasonic radiation for 2 h to remove possible foreign materials, and then air-dried, crushed to get particles of size less than 2 microns. Processed shells were assayed for Ca, Ba, Zn, Pb, Ni, Co, Cr, Sr, Cu, Mn and Fe elements.
Subsequently, graphite coated the bulk of shells prior to scanning electron microscope (SEM-EDAX) examination.
2 Results and Discussion
Bivalves were chosen for this study because they meet many of the requirements of a good biological sentinel (Phillips, 1980). They are somewhat sedentary, regionally abundant, and are long lived. They readily accumulate many metals and bioaccumulate contaminants.
Consequently, such organisms have been largely used in both salt and fresh water monitoring programs (Farrington, 1983). Chemical analyses of molluscs shells provide more information about the environment in which these organisms lived.
Ba, Zn, Pb, Ni, Co, Cr, Sr, Cu, Mn and Fe are the main trace elements in Corbicula fluminalis shells (Figure 2 and 3). These elements in our target organism increased significantly towards the central parts of Shatt Al-Arab River (Table 1) as a result of untreated sewage discharge in the river from industrial facilities and hospitals that spread in the north and center part of Basrah city. This demonstrates that C. fluminalis may be used locally as an indicator of contamination by trace metals.


Figure 2 Picture and spectrum of Corbicula fluminalis shells under scaning electron microscope-EDAX, scale bar 100 μm


Figure 3 Picture and spectrum of Corbicula fluminalis shells under scanning electron microscopr-EDAX, scale bar 20 μm


Table 1 Calcium the main trace elements in Corbicula fluminalis shells from the Shatt Al-Arab River

Table 2 shows a comparison between heavy metals that accumulated in C. fluminalis shells from this study and previous studies in the Shatt Al-Arab, Euphrates, and Hor Al-Chekka rivers. Zinc, copper, chromium, iron, and manganese were higher in the present study compared with the previous studies. This indicates the contamination of the Shatt Al-Arab River is increasing during the last few years as a result of increased anthropogenic and industrial activities.


Table 2 Comparison of the mean heavy metals (ppm) in Corbicula fluminalis shells between the present study and previous studies

References
Afaj A.H., and Al-Dabbas M., 1998, Some geochemical aspect of the sediments and mollusk shells from Khor Al-Zubair/south Iraq. The 6th Jordanian Geological Conference, 6: 35-40
Al-Basam K.S., 1999, Content and distribution of heavy metals in molluscs shells in Euphrates river, Geoserve, 24 pp (In Arabic)
Al-Saady Y.I., 2008, Environmental geochemistry and mineralogy of Hor Al-Chekka southern of Al-Msharrah River within Missan governorate. M.Sc thesis, Baghdad University, 208 pp (In Arabic)
Conti, M. and Cecchetti, G. 2003. A biomonitoring study: trace metals in algae and molluscs from Tyrrhenian coastal areas. Environ. Res., 93: 99-112
http://dx.doi.org/10.1016/S0013-9351(03)00012-4
Dalbeck, P.C. 2008. Crystallography, stable isotope and trace element analysis of Mytilus edulis shells in the context of ontogeny. M.Sc thesis, University of Glasgow, 235pp
Dodd, J.R. 1965. Environmental control of strontium and magnesium in Mytilus. Geochimica Et Cosmochimica Acta., 29: 385-398
http://dx.doi.org/10.1016/0016-7037(65)90035-9
Farrington, J.W. 1983. Bivalves as sentinels of coastal chemical pollution: The mussels (and oysters) watch. Oceans, 20(2): 18-29
Goodfriend, G. and Magaritz, M. 1989. Stable isotope composition of land snail body water and its relation to environmental waters and shell carbonate. Geochimica et Cosmochimica Acta., 53(12): 3215-3221
http://dx.doi.org/10.1016/0016-7037(89)90102-6
Mustafa, Y. 1989. Corbicula fluminea (Muller, 1774) as indicator to heavy pollution metals in Shatt Al-Arab river. Un-published MSc thesis, Basrah University, 131pp. (In Arabic)
Phillips, D.J.H. 1980. Quantitative aquatic biological indicators: Applied Science Publishers, London

Salman, K.H.K. 2007. A Study of the Environmental Situation at Al-Basrah Governorate. Unpublished Ph.D. thesis, Baghdad University, 180pp. (In Arabic)

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