Journal of Environmental Solutions Volume 2 (Issue 1) (2013): 1-8
Journal of Environmental Solutions
Averroes Publisher
METALLIC CONTAMINATION OF THE OCCIDENTAL MEDITERRANEAN COASTS OF MOROCCO (COASTAL FRINGE “KABILA - OUED LAOU”), USING Callista chione
KHANNOUS SOUMAYA1; BOUZID SAIDA1; BENOMAR MOSTAPHA2; ER-RAIOUI HASSAN 1*
1Geosciences and Environment team - Department of Earth Sciences - Faculty of Sciences and techniques, Tangier, Morocco 2 Laboratory of Chemical Micropollutants, National Institute of Halieutic Research, Tangier, Morocco
* Corresponding author. Er-raioui Hassan E-mail: [email protected] Tel: +212 5 39 39 39 54
A B S T R A C T
Keywords: In order to study the metallic contamination of the western Mediterranean coasts of Morocco, bivalve samples metallic contamination (Callista chione) were collected during the pluvial period from five sites (Kabila, Cabo Negro, Oued Malleh, Oued Occidental Moroccan Mediterrane- Laou and Oued Laou River's mouth) and were analyzed for 6 elements (Zn, Ni, Cu, Pb, Cr and Cd) by ACP-AES. an coasts The average of metallic concentrations found (62.52 mg/kg for Zn, 16.23 mg/kg for Ni, 5.57 mg/kg for Cu, 2.21 Callista chione mg/kg for Pb, 1.50 mg/kg for Cr and 0.28 mg/kg for Cd) are far away from being considered as negligible even though industrial and harbor activities are less developed in this region compared to industrial countries. The concentrations show significant spatial variations. It seems that these variations are related to urban dis- missals from close agglomerations and from the washing of the geological formations of the back-country.
I. INTRODUCTION
The intensity of human activities in areas surrounding enclosed seas and semi-enclosed seas, such as the Mediterranean Sea, has always had a significant environmental impact resulting in coastal and marine degradation. Today, the coast of large industrial con- centrations shows the most disturbing marine forms of degradation. However, the Mediterranean coast which represents 1 % of the surface of the global ocean is a vast inland sea (Burns & Saliot, 1986). It is a fragile and vulnerable ecosystem and also corresponds to a semi-enclosed sea where the waters are renewed slowly (15 years for deep water) (Hopkins, 1978). The waterflow is greatly hampered by the Strait of Gibraltar. Such a closure worsens the impact of a rapidly expanding population. The Mediterranean coast of Morocco, economically rich, ecologically fragile, is an exceptional place for marine life by the multitude of animal and plant species that breed there. With its 512 km of coastline, it is characterized by a significant marine biodiversity, including a large amount of specific species (Belcaid, 2010). The areas at most risk are undoubtedly those located near to the Strait of Gibraltar where North and South meet and where major cities make up the Moroccan coast. The ports of Tangier, M'diq (Tetouan) and Nador with industrial releases are other sources of pollution, as well as those emissions in fishing areas. The areas receive a significant amount of both industrial and urban waste; in addition to that generated by tourism and maritime activities (Er-Raioui et al., 2012). There are many sources of water pollution and they are an ongoing problem in Morocco, which manifests particularly in irrigated perimeters and areas of economic activity. Among the causes of water pollution, are included industrial units, mainly concentrated in and around cities, and among these industries, some are recognized pollutants. Two types of industries can be distinguished: (1) those whose discharges are essentially organic and (2) those whose discharges contain toxic elements. Emissions correspond to ordinary organic substances, organic products of synthesis, hydrocarbons, minerals, heavy met- als, polychlorinated biphenyls (PCBs), chlorides, sulphates, cyanides, and arsenic salts. In summary, table 1 sums up some examples of industrial and agricultural sources which may introduce metals in the environment (Othmer, 1995).
Table 1. Industrial and agricultural sources of metals in the environment. Uses Metals Batteries and other electrical appliances Cd, Hg, Pb, Zn, Mn, Ni, Pigments and paints Ti, Cd, Hg, Pb, Zn, Mn, Sn, Cr, Al, As, Cu, Fe Alloys and solders Cd, As, Pb, Zn, Mn, Sn, Ni, Cu Biocides (pesticides, herbicides, curators) As, Hg, Pb, Cu, Sn, Zn, Mn Catalyst agents Ni, Hg, Pb, Cu, Sn Glass As, Sn, Mn Fertilizers Cd, Hg, Pb, Al, As, Cr, Cu, Mn, Ni, Zn Plastics Cd, Sn, Pb Dental and cosmetic products Sn, Hg Textiles Cr, Fe, Al Refineries Ni, V, Pb, Fe, Mn, Zn Fuels Ni, Hg, Cu, Fe, Mn, Pb, Cd 1 Khannous et al.
The coast of Tetouan (occidental Mediterranean), which is the subject of this study, is experiencing urbanization and rapid industri- alization, as well as important port and tourist activity. Domestic pollution is the main source of contamination in the area. First, the wastewater is discharged without any treatment, neither in the rivers that flow into the coastline (Oued Martil, Oued Smir and Oued Laou) nor directly into the sea. The second source of pollution comes from industrial units in the region, mainly from the industrial area of Martil. The volume of wastewater released at the coastline in question is more than 50 000 m3/day; draining more than 21.5 t/d oxidizable matter, and more than 83.85 t/d of suspended solids. These waters are also responsible for metal emission (Zn, Cu, Cd, Cr, Ni and Pb). The load is heavy in lead, cadmium, chromium and nickel, which show high concentrations in some places (Er-Raioui et al., 2012). Trace metal elements (TME) are one of the main chemicals that cause degradation of the water quality. Indeed, the contamination of the coastal ecosystem by these elements is a major problem in environmental toxicology. Unlike organic pollutants, some TME are practically not a subject of biodegradation. They can accumulate then in the food chain to reach toxic levels (Cumont, 1984) and generate critical, even dangerous situations (Serghini et al., 2001). In natural aquatic ecosystems, metals are found at low concentrations, typically in nanograms or micrograms per liter. However, in recent decades, the presence of trace metal concentrations above natural charges has become a serious problem due to the rapid population growth, the increased urbanization and the expansion of industrial activities. Regarding the toxicity of metals, it is necessary to distinguish between the essential and non-essential elements. A metal is consid- ered essential if the disease symptoms appear when its concentration decreases or is absent and disappears when it is added. It also requires that the symptoms are associated with a biochemical defect (Förstner & Wittmann, 1979). However, an essential element can be toxic when present in excessive concentrations. According to these criteria, 17 metals are considered essential, including four (Na, K, Ca and Mg) which are present in large quantities (>1 mmol.kg-1 fresh weight), while the other thirteen (As, Cr, Co, Cu, Fe, Mn, Mo, Ni, Se, Si, Sn, V and Zn) are present in trace (from 0.001 to 1 mmol.g-1 fresh weight) or ultra-trace (<1 μmol.kg-1 fresh weight) amounts (Mason & Jenkins, 1995). Non-essential metals have, unlike the essential ones, no biological role currently known. This is the case for Hg, Ag, Cd and Pb (Mason & Jenkins, 1995). They are considered harmful when they are present in the environment and cause deleterious biological effects at very low concentrations. To assess the state of metallic contamination at the coast of Tetouan for public health and protection of aquaculture areas, this pre- liminary study was carried out for some metals (Zn, Cu, Cd, Cr, Ni and Pb), primarily by use of a quality monitoring network of coastal waters using bivalve molluscs. These are used as indicators of metal pollution because of their great accumulation power. Often, it is possible to detect the presence of trace metals in molluscs, even when their concentrations in water are very low, highly variable or difficult to determine by routine chemical analysis (Mazlani et al., 1994). Molluscs have the capacity to accumulate contaminants directly from the environment (BCF) or by other means (e.g. food) to levels well above the level of contamination of the physical environment (water, sediment). Therefore, bio accumulative species are used frequently in monitoring networks (biomonitoring) for the quality of the marine environment (Amiard et al., 1998). In addition, the region has large reserves of shellfish, represented mainly by species such as Acanthocardia Tuberculata, Callista Chione, Venus and Galina Donax Trunculus. Clams represent the most sought bivalves in wide geographical distribution (Shafee, 1999). In addition, the monitoring of coastal metal contamination by bivalve organisms is a common practice in many monitoring programs around the world. For example, one famous site program called "Mussel Watch", which is the oldest continuous monitoring program of contaminants in coastal waters of the United States, uses bivalve tissues as indicators of several parameters including organic and inorganic contaminants, and trace metals in particular. In France, the National Network of Observation marine environmental quality (RNO) uses bivalve organisms to evaluate the safety of the French coast.
II. MATERIALS AND METHODS
II.1. Study area
The studied area is localized in the Northwest of Morocco at the western part of the Mediterranean Sea. It corresponds to the fringe between Kabila and Oued Laou (figure 1). From a geological point of view, the western Mediterranean coasts are bordered on both sides by alpine chains known as Rifo-Betic- Kabyle, consisting of Paleozoic detritic lands, not or slightly metamorphosed, and generally having a clay, sandy and marly nature. The area is also made up of pleated and metamorphosed ultrabasic lands, essentially formed by peridotites, kinzigites, gneiss and micaschists (Michard et al., 2006 and Suter, 1980). These lands may, by leaching, provide a material rich in heavy minerals and trace metal elements. Five stations, M’diq, Cabo Negro, Oued Malleh, Oued Laou and the mouth of Oued Laou, were chosen for the sampling (figure 1), taking into consideration: the point of discharges of sewage waters and industrial dismissals; tourism installations; harbour activity. The choice has been focused on a kind of filter feeding shellfish (Callista chione) as bioindicator of metal pollution because of: its wide distribution in the region; its capacity to accumulate contaminants; its sedentary lifestyle, its ease of collection and identification; and its exploitation by fishers and residents of neighbouring communities.
Journal of Environmental Solutions Volume 2 (Issue 1) (2013): 1-8 2 Khannous et al.
Figure 1. Map of the North Moroccan coasts showing sampling stations (Kabila, Cabo Negro, Oued Mallah, Oued Laou and Mouth of Oued Laou).
II.2. Sampling and chemical analysis
The samples of Callista chione have been taken during the humid period (February and March 2007) when continental inputs are extremely important. Two samples and two replicates were made for each site. Each sample corresponds to a lot of 12 to 15 organ- isms ranging in size from 6 to 8 cm. The sampling was accomplished with a mechanical dragnet at 500 to 800 m sea inward at a depth between -6 and -10 m. The bi- valves in question are washed by sea water at the sampling site, then wrapped in polyethylene bags. They are transported in an isotherm icebox where the temperature is maintained between 2 and 8°C and once in the laboratory they are kept at -20°C until later analysis. Entire organisms’ tissues were crushed, freeze-dried and then mineralized. The mineralization of the samples (2 g) consists in a first cold digestion of 1 hour and thereafter they are kept at 140°C for a minimum of 3 hours in 20 ml of nitric acid (HNO3) and 3 ml of concentrated sulphuric acid (H2SO4). Then 5 ml of bi-distilled water and 5 ml of hydrogen peroxide are added to every sample. The mixture is warmed to 100°C during one night. Once the samples are cooled, they are treated with 5 ml of hydrogen peroxide every hour at 140°C till the end of sample mineralized (absence of black coloration). Next, the volumes of the mineralized samples are adjusted to 100 ml with bi-distilled water. The reagents used in this analysis were obtained from Merck (Aminot & Chaussepied, 1983). The trace metals have been analysed by ICP-AES (Inductively Coupled Plasma and Atomic Broadcast Spectroscopy). The used standards correspond to Precise Mono elements of 1000 ppm. ACP-AES model “Ultima 2” of Jobin Yvon has two “High dynamics" detectors, used to optimize the sensitivity in the UV and the visible range. The device has a holographic network of high brightness (2400 turns/min.), a spectral domain of 120 to 800 nm, a linear scattering (0.21 nm/mm for 120 nm to 320 nm and 0.42 nm/mm for 320 nm to 800 nm) and a convenient resolution (5 pm for 120 nm to 320 nm and 10 pm for 320 nm to 800 nm). This device is also provided with a software ICP V5 analyst in windows 98/NT. The chosen analysis method presents the advantage to be fast and multi-elementary. The measures in ICP-AES have been done at the technical unit support to scientific research (UATRS) of the National Centre of Scientific Researches and Techniques (CNRST) in Rabat, Morocco.
II.3. Statistics
The analysis of variance (ANOVA) and principal component analysis were used to show the status of distribution of metallic ele- ments in the different sampling sites. Metal concentrations in organisms are expressed as mean (± Standard error). The difference between the concentrations’ average as a function of sampling sites was evaluated using analysis of variance (ANOVA), which pro- vides the variance through the Fisher’s parameter F and the significance level p. In order to establish correlations that may exist between the various studied elements (Zn, Cu, Cd, Cr, Ni and Pb), the Spearman method was used. Statistical analyses were per- formed using SPSS for Windows version 15.0 (2006).
Journal of Environmental Solutions Volume 2 (Issue 1) (2013): 1-8 3 Khannous et al.
III. RESULTS
Geochemical analyses were carried out on filter-feeding shellfish samples (Callista chione) widely available in the region, to deter- mine the rates of Zn, Cu, Cd, Cr, Ni and Pb. They correspond to items in the list of xenobiotic compounds discharged into the marine environment, altering marine ecosystems which can be accumulated by organisms. The results show variable rates depending on the site and are far from being negligible.
III.1. Metal contents in Callista chione
The results for the spatial average concentrations of metals in the tissues of Callista chione recorded at the different sample sites are shown in table 2.
Table 2. Metallic elements (Zn, Cu, Cd, Cr, Ni and Pb) recorded in Callista chione tissue as mg/kg dry weight at different study sites (Kb: Kabila, OM: Oued Malleh, CN: Cabo Negro, OL: Oued Lau, EOL: Mouth of Oued Laou) Standard Confidence interval at 95 % Metals Site N Average Minimum Maximum deviation lower limit upper limit Zn Kb 4 60.70 1.16 57.02 64.38 57.95 63.25 CN 4 54.44 1.57 49.44 59.45 51.38 58.50 OM 4 76.80 3.17 66.71 86.89 69.35 84.55 OL 3 66.45 1.09 61.78 71.12 64.92 68.55 EOL 3 54.18 1.19 49.08 59.29 52.05 56.15
Cu Kb 4 4.65 0.22 3.95 5.35 4.05 5.11 CN 4 5.20 0.04 5.08 5.32 5.10 5.28 OM 4 5.65 0.23 4.92 6.37 5.09 6.15 OL 3 6.90 0.11 6.44 7.37 6.75 7.11 EOL 3 5.45 0.03 5.32 5.57 5.40 5.50
Cd Kb 4 0.25 0.02 0.17 0.33 0.18 0.30 CN 4 0.30 0.03 0.19 0.41 0.20 0.35 OM 4 0.40 0.02 0.33 0.46 0.35 0.45 OL 3 0.34 0.01 0.30 0.38 0.32 0.35 EOL 3 0.13 0.02 0.05 0.22 0.10 0.17
Cr Kb 4 1.48 0.03 1.38 1.57 1.39 1.52 CN 4 1.33 0.09 1.03 1.63 1.15 1.55 OM 4 1.25 0.15 0.76 1.74 1.04 1.71 OL 3 2.18 0.09 1.78 2.58 2.00 2.30 EOL 3 1.25 0.03 1.13 1.37 1.20 1.30
Ni Kb 4 13.00 0.28 12.11 13.88 12.19 13.47 CN 4 16.18 0.25 15.39 16.97 15.75 16.85 OM 4 20.95 0.68 18.80 23.10 19.45 22.65 OL 3 17.23 0.19 16.41 18.04 16.85 17.45 EOL 3 13.80 0.50 11.63 15.97 12.79 14.35
Pb Kb 4 2.90 0.06 2.70 3.09 2.75 3.05 CN 3 1.27 0.12 0.77 1.78 1.05 1.45 OM 4 3.43 0.20 2.80 4.07 3.17 4.02 OL 3 0.94 0.09 0.53 1.34 0.75 1.05 EOL 3 2.55 0.19 1.74 3.36 2.25 2.90
Zinc (Zn): Anthropogenic inputs of zinc in the environment are due to industrial activities (mining sources, ore treatment, refining processes, iron galvanizing, roof gutters, batteries, pigments, plastics, rubber), agricultural activities (spraying, animal feeding, ma- nure), and urban activities (road traffic, garbage incineration). In port areas, zinc is introduced by the dissolution of anodes intended to protect the boat hulls against corrosion, and is present in some antifouling paints. Average Zn concentrations detected varied significantly between various stations. The variance, expressed through the F fisher parameter and the degree of significance p are quite significant (F=23.986; p=0.000). The contents vary from 54.18 ± 1.18, recorded at the mouth of Oued Laou to 76.80 ± 3.17, recorded at Oued Malleh. Copper (Cu): Cu is used in antifouling paints to replace tin and in vines and fruit tree treatments. Copper is considered to be danger- ous. Considering the lowest toxic concentrations encountered in coastal or estuarine zones, there are copper effects from 1 to 3 μg/l (Amiard-Triquet, 1989). The mean levels found range from 4.64 ± 0.22 recorded at Kabila to 6.90 ± 0.10 noted in Oued Laou. Spatial variations in concentrations are significant. Fisher parameter F is 23.162 and the significance level p is quite demonstrative (p=0.000). Cadmium (Cd): Mainly coming from industry, cadmium is found in batteries, antifouling paints for ship hulls, in rubber tires, fertiliz- ers and insecticides. The values of Cd concentrations fluctuate between 0.13 ± 0.02 recorded at the Mouth of Oued Laou and 0.40 ± 0.02, recorded at Oued Malleh. This metal shows a significant variation in space (F=14.750, p=0.000). Journal of Environmental Solutions Volume 2 (Issue 1) (2013): 1-8 4 Khannous et al.
Chromium (Cr): Intakes of chromium in inland and coastal waters mostly come from industrial effluents, cooling water, washing water and dyeing discharges. The atmosphere is also an important route of transfer to the ocean of metallurgy emissions, burning oil, and coal containing chromium (Chiffoleau et al., 2001). Spatial variations are significant at the level of the studied area (F=13.634, p=0.000). Average concentrations vary from 1.25 ± 0.15, recorded at Oued Malleh to 2.18 ± 0.09, recorded at Oued Laou. Nickel (Ni): Transport of nickel into the marine environment occurs via rivers in particulate form and via the atmosphere, coming from the use of fossil fuels and the production of non-ferrous metals (Caplat, 2001). Mean values of Ni vary from 13.00 ± 0.27 in Kabila to 20.95 ± 0.67 in Oued Malleh. The ANOVA analysis showed a significant spatial variation (F=55.427, p=0.000). Lead (Pb): Resulting from smelting activity, waste incinerators, gasoline combustion, some paints, insecticides and cable sheaths. Lead can also be introduced naturally due to volcanic activity, leaching of granitic massifs or forest fires. The average concentrations obtained show a well-marked variation between different stations. Variance expressed through the Fisher parameter F and the de- gree of significance p are quite significant (F=53.065, p=0.000). Levels vary from 0.94 ± 0.09 at Oued Laou to 3.43 ± 0.19 at Oued Malleh.
III.2. Studies of correlations between metals
The correlation matrix between the analysed elements shows significantly positive coefficients (table 3).
Table 3. Matrix of correlations between the metals analyzed in Callista chione taken from the coastal region of Tetouan Zn Cu Cd Cr Ni Pb Zn 1.000 Cu 0.500 1.000 Cd 0.900 0.600 1.000 Cr 0.205 0.051 0.103 1.000 Ni 0.700 0.800 0.900 -0.154 1.000 0.000 Pb 0.300 -0.300 0.100 -0.616 0.000 1.000
• Zn, Cd and Ni show positive correlations of great significance. The correlation coefficients vary from 0.700 to 0.900. • Cu and Cr show a significant positive correlation (r=0.600). • Cu and Ni show a significant correlation. The correlation coefficient is 0.800. This can sometimes translate the same origin. These correlations require a study of the existing relations between the studied metals. In this sense, a statistical PCA analysis has been done. The obtained results are represented in figure 2.
III.3. Principal Component Analysis
The results presented in figure 2 are derived from a PCA with six variables (Zn, Cu, Cd, Cr, Ni and P) and five terms (sampling sites). The first two axes represent respectively 51.35 % and 35.15 % of the information; summing 86.5 % of the total variability which leads to the adoption of a bi-dimensional representation (figure 2).
Figure 2. PCA diagram showing the correlation between different trace metals (Zn, Cu, Cd, Cr, Ni and Pb) and sampling sites (Kb: Kabila OM: Oued Malleh CN: Cabo Negro, OL: Oued Lau, EOL: Mouth of Oued laou).
IV. DISCUSSION
This study reveals some interesting results concerning the accumulation rates of trace metals in Callista chione’s tissue. Generally, the bioaccumulation behaviour in Callista chione seems to follow the descending order Zn> Ni> Cu> Pb> Cr> Cd. The spatial analysis of metals indicates that the stations of Oued Malleh and Oued Laou are showing the highest concentrations. Samples from Oued Malleh record maximum levels of Zn, Ni and Pb. River inputs in the considered area, often loaded with organic matter and minerals, could be responsible for this charge. These metallic elements exhibit similar patterns of spatial variation. It indicates that the station Oued Malleh, located 3 km north from Oued Martil, drains the urban and industrial discharges of different
Journal of Environmental Solutions Volume 2 (Issue 1) (2013): 1-8 5 Khannous et al. cities of Tetouan and industrial units installed along the river to the sea without prior treatment. The intervention of the ocean cur- rents in the redistribution of certain quantities of metals is obvious. The area is known by the drift of water bodies from South to North (El Moutchou, 2002). This may explain the routing of inputs to both Oued Martil and Oued Malleh stations. However, samples from Oued Laou recorded maximum levels of Cu. The element Cd represents important and relatively similar concentrations in both sites. Oued Laou station is located in a rural area and directly receives the waters of the rivers loaded by ter- restrial inputs characterizing biotopes and their sources. Moreover, the importance of natural and the effects of urban effluents load- ed with industrial and household pollutants are confined to sediment sites located in the vicinity of the sampling point and could play the role of a real vector from these metals to aquatic organisms (Pempkowiak et al., 1999). The bottom sediments are known for their ability to accumulate heavy metals introduced into the seas and oceans through industrial and urban effluents direct, riverine inputs and atmospheric leaching of soils (Försner & Wittmann, 1979). A study of the marine surface sediments of the coastal fringe shows the predominance of Zn, Ni, Cr, Cd and Pb in the area of Martil (Benomar, 2010). Indeed, the enrichment factor (EF), which assesses human or natural origins of trace metals in sediments (Taylor & McLennan, 1985; Hofmann, 1988), demonstrates low contamination levels of Cu, Cr and Ni (1.92
Table 4. Comparison of trace metal concentrations in Callista chione obtained in this study with literature data from other Moroccan sites (mg/kg dry weight): Norms (EC) Metal present study literature data Organisms Sampling region References mg/kg (dw) Mouth of Moulouya river 54.52 – 172 Chamelea gallina (Zegmout et al., 2011) (Moroccan Mediterranean) Zn 54.17 – 76.8 Jorf lasfar – El Jadida 118.23 -2 92.45 Mytilus galloprovincialis (Merzouki et al., 2009) Moroccan Atlantic ocean Mouth of Moulouya river 1.11 – 3.32 Chamelea gallina (Zegmout et al., 2011) (Moroccan Mediterranean) Cu 4.65 – 6.90 Jorf lasfar – El Jadida 5.36 – 237.41 Mytilus galloprovincialis (Merzouki et al., 2009) Moroccan Atlantic ocean Pb 0.85 – 3.42 2.57 – 11.64 Mytilus galloprovincialis coast of Casablanca (Bouthir et al., 2004) 7.5
Cr 0.25 – 2.17 6.40 – 18.71 Mytilus galloprovincialis coast of Casablanca (Bouthir et al., 2004)
11.9 Mytilus galloprovincialis South of Morocco (Chafik et al., 2001)
Cd 0.12 – 0.40 Mouth of Moulouya river 5 0.1 - 3.8 Chamelea gallina (Zegmout et al., 2011) (Moroccan Mediterranean)
Compared with the results reported in other studies, it should be noted that there are few data in the literature concerning metal accumulation in Callista chione. Comparing the rates of Pb, Cu, Zn, Cd, Cr and Ni found in Callista chione in this study, with other stud- Journal of Environmental Solutions Volume 2 (Issue 1) (2013): 1-8 6 Khannous et al. ies carried out along the Mediterranean and Atlantic coast in Morocco and elsewhere, they show a relatively low to moderate con- tamination (table 4) (Zegmout et al., 2011; Merzouki et al., 2009; Bouthir et al., 2004; Shafik et al., 2001). For example, at the mouth of Oued Moulouya, located in the extreme north-east of Morocco, the levels of Zn and Cd in Chamelea gallina clams reach alarming levels. These levels highlight the polluting effect of the Moulouya river that drains in its passage the leachate ponds where residents held an important agricultural activity. In addition, polluted releases, industrial units, and untreated domestic discharges contribute to the pollution of Oued Moulouya with significant quantities of metals, inevitably ending up in the Mediterranean Sea (table 4) (Zegmout et al., 2011). The same situation is observed at the French Mediterranean coast and at the French islands in the Caribbean where bivalve molluscs (Mytilus spp. and Isognomon alatus) show varying metal concentrations as a consequence of both urban and industrial diffused or punctual pollution (sewage or industrial areas) loaded mainly with cadmium, copper, lead, mercury, nickel and zinc (MEDDTL-DGPR, 2009) (table 5).
Table 5. Comparison of results obtained in this study with those cited in literature relating to the French coast from 2000 to 2004, expressed in mg/kg dry weight Metal concentration (mg.kg-1) present study Atlantic Manche Mediterranean Antilles Mini-Maxi Callista chione Crassostrea gigas Mytilus spp. Mytilus spp. Isognomon alatus Zn 54.17 - 76.8 425 - 7030 36 - 409 43 - 357 973 - 13450 Ni 13.00 - 20.95 0.34 - 4.83 0.45 - 6.00 0.47 - 8.41 0.31 - 7.24 Cu 4.65 - 6.90 6.72 - 2208 4.0 - 23 3.8 - 67 5.4 - 83 Pb 0.85 - 3.42 0.4 - 6.1 0.4 - 9.6 0.1 - 27.7 0.1 - 18.3 Cr 1.25 - 2.17 0.15 - 14.1 0.32 - 9.21 0.12 - 3.77 0.23 - 19.3 Cd 0.12 - 0.40 0.43 - 56.3 0.17 - 3.03 0.20 - 10.0 0.13 - 1.15
At the Moroccan Atlantic ocean, the coast of the Great Casablanca is subject of strong human impact (releases of metallurgical indus- tries, chemicals and related). The rates of Pb and Cr identified in the mussel Mytilus galloprovincialis are highest and range from 2.57 to 11.64 and 2.57 to 11.64 mg/kg respectively (Bouthir et al., 2004). The rate of Cr accumulated in the tissues of the Mytilus galloprovincialis mussel growing on the Mohammadia coast shows Cr concen- trations of 18.71 mg/kg, attesting to the influence of domestic sewage and textile industries (Bouthir et al., 2006). Nearby the indus- trial area of Ain Sebâa (north of Casablanca port), the Cr rates are 14.41 mg/kg reflecting the impact of iron and steel industries, chemical and surface treatment, as well as agri-food and textile activity (Bouthir et al., 2006). On the Atlantic coast of El Jadida, the Mytilus galloprovinciali mussels from the industrial stations of Jorf-Lasfar site are significantly more contaminated, with 118.23 to 292.45 mg/kg Zn, 5.36 to 237.41 mg/kg Cu and 3.35 to 62.62 mg/kg Cd. Those metals most likely come from the phosphate complex of the region, knowing that they are phosphate ores by-products (Merzouki et al., 2009). Further south, at the coast of Safi, the rates of Cu and Cd found in the Mytilus galloprovinciali tissues are respectively around 7 and 25 mg/kg (Shafik et al., 2001). The relationship between Cd concentrations in mussels and phosphate concentrations in the water sug- gests that the processing of phosphate ores in these two sites is the source of this contamination. Also, Banaoui et al. (2004) noted a high level of cadmium (6 μg.g-1 dry weight) in the Perna perna mussel,, despite the absence of pollution sources in the south area of Cape Juby in Morocco, This could be explained by the regular presence of dissolved cadmium in this area, probably due to the intense upwelling between Cape Ghir and Cape Juby. In Mauritania, the Atlantic coast of Nouadhibou has an important submarine fauna and fishing sites considered to be very produc- tive. It is the core of urban waste and important port activities. The review of the contamination state through the analysis of heavy metals in bivalves and fish products shows high concentrations of Cd particularly in clams (3696-11543 μg.g-1). These results reflect the impact of urban discharges and port activities at the level of Lévrier Bay, characterized by a low hydrodynamic and intense evap- oration and at the exclusive economic zone of Mauritania (EEZ) subjected to a hydroclimate which leads to a high risk of pollutants dispersion (Mhamada et al., 2011). On the coast of Senegal, the analysis of metals in bivalve molluscs (Crosspostera gasar and Cardita ajar) collected from the coast reveals high concentrations of cadmium, respectively 6.82 ± 0.54 and 13.77 ± 0.80 mg cd/kg (dw). The results suggest that cadmium may be present in high concentrations in Senegalese waters where upwelling occurs (Sidoumou et al., 2006). On the French Atlantic coast, metal contamination in mussels (Mytilus edulis) located at Goury port and the Reels cove (Manche) and oysters (Crassostrea gigas), reveal for the period from 2000 to 2004 important values for Zn (36 – 7030 mg/kg dw), Cu (4-2208 mg/kg dw), Pb (0.4 - 9.6 mg/kg dw), Cr (0.15 - 14.1 mg/kg dw) and Cd (0.17 - 56.3 mg/kg dw) (table 5). This reflects the pollution that flows through rivers and pollutants which are added from areas close to the sea that may have diffuse sources (mainly agricul- tural) or punctual (industrial or urban purification plants) loaded with heavy metals (MEDDTL-DGPR, 2009). Results of 2007 show a stable situation compared to previous years. A decreasing trend in the concentration of metals is primed for lead, nickel and chromi- um that display maximums of 1.1 mg/kg, 1.4 mg/kg and 1 mg/kg, respectively.
V. CONCLUSIONS
The Assessment of metal concentrations (Cr, Cu, Ni, Zn, Pb and Cd) in Callista chione collected in the coastal region of Tetouan can focus on variation in metal concentrations in space. The highest concentrations of Zn, Ni, Cd and Pb were detected at the Oued Malleh station which is under the effect of domestic and industrial untreated sewage discharges of Tetouan city. Lead is also related to the Kabila station that contains a yacht harbour, which suggests an anthropogenic origin related to the use of fuel containing high con- centrations of lead. Oued Laou station recorded high levels of Cu and Cr, this may be related to agricultural activities. Metal concen- trations recorded in Callista chione are far away from being negligible, although industrial and port activities are relatively less de- veloped comparing with industrialized countries. Fortunately they do not seem to lead to important contamination.
Journal of Environmental Solutions Volume 2 (Issue 1) (2013): 1-8 7 Khannous et al.
REFERENCES
Amiard J-C., Caquet T., Lagadic L. & Ramade F., 1998. L'utilisation de biomarqueurs pour la surveillance de la qualité de l'environnement. Eds. Tec & Doc, Paris, 320 p. Amiard-Triquet C., 1989. Bioaccumulation et nocivité relatives de quelques polluants métalliques à l’égard des espèces marines. Bull. Ecol. 20(2): 129-151. Aminot A. & Chaussepied M. 1983. Manuel des analyses chimiques en milieu marin. CNEXO, France, 395 p. Banaoui A., Chiffoleau J.F., Moukrim A., Burgeot T., Kaaya A., Auger D. & Rozuel, E., 2004. Trace metal distribution in the mussel Perna perna along the Moroccan coast. Mar. Pollut. Bull. 48(3-4): 385-390 Belcaid S., 2010. Biodiversité dans la zone maritime détroit de Gibraltar et Méditerranée occidentale, Journée mondiale de la terre, Tanger Benomar M., 2010. Etat de la contamination des côtes ouest de la Méditerranée marocaine par les métaux lourds: frange littorale M’diq-Djaouen. Thèse de Doctorat, Université AbdelMalek Essaâdi, Maroc. 243 p. Bouthir F.Z., Chafik A., Benbrahim S., Souabi S., El Merdhy H., Messoudi A. & Sifeddine M., 2004. Qualité physico-chimique des eaux côtières du littoral de la Wilaya du grand Casablanca (océan Atlantique marocain) utilisant la moule Mytilus galloprovincialis comme indicateur de la contamination métallique, Mar. Life 14 (1-2): 59-70 Bouthir F.Z., Souabi S., Chafik A., Benbrahim S. & Sifeddine M., 2006. Impact des rejets industriels sur l’environnement: cas de l’accumulation du chrome dans les différents compartiments aquatiques le long du littoral Casablanca – Mohammadia. Water Qual. Res. J. Canada, 41(4): 418–426 Burns K.A. & Saliot A., 1986. Petroleum hydrocarbons in the Mediterranean Sea: a mass balance. Mar. Chem. 20: 141-57 Caplat C., 2001. Caractérisation géochimique de sédiments fins du littoral du Calvados (Baie de Seine) – Comparaison de matériaux portuaires contaminés à des matériaux non contaminés de la baie des Veys, Université de Caen. Th. Univ. Sci. Terre & Univ., 182 p. Chafik A., Cheggour M., Cossa D., Benbrahim S. & Sifedine M., 2001. Quality of Moroccan Atlantic coastal waters: water monitoring and mussel watching. Aquat. Living resour. 14: 239-249 Chiffoleau J-F., Claisse D., Cossa D., Ficht A., Gonzalez J-L., Guyot T., Michel P., Miramand P., Oger C. & Petit F., 2001. La contamination métallique. Fasicule nº8 du programme scientifique Seine-Aval. Eds. Ifremer, Plouzané, France. 39 p. Cumont G., 1984. La contamination des aliments par le mercure. Ann. Fals. Exp. Chem. 77: 309-320 El Moutchou B., 2002. Dynamique côtière et évolution spatio-temporelle de la frange littorale méditerranéenne entre Fnideq et Martil (Province de Tétouan, Maroc). CIESM Workshop, Série n°18: Erosion littorale en méditerranéen occidentale-Tanger, p. 35-37 Er-Raioui H., Khannous S., Ould Mohamed Cheihk M., Mhamada M. & Bouzid S., 2012. The Moroccan Mediterranean Coastline: A Potential Threatened by the Urban Discharges. The Open Environmental Pollution & Toxicology Journal 3(Suppl 1-M4) 23-36 Förstner U. & Wittmann G.T.W., 1979. Metal Pollution in the Aquatic Environment. Springer-Verlag, New York, 469 p. Hofmann A.W., 1988. Chemical differentiation of the earth: The relationship between mantle, continental crust, and oceanic crust. Earth Planet. Sci. Lett. 90(3): 297-314 Hopkins T.S., 1978. Physical processes in the Mediterranean basins. In: Kjerfve B. (Ed.) Estuarine transport processes. University of South Caroline Press, South Carolina, Columbia: p. 269-310 JOCE, 2006. Décision n° 1881/2006/CE du Parlement européen et du Conseil du 19 décembre 2006. Fixation de teneurs maximales pour certains contaminants dans les denrées alimentaires, Annexe, Teneurs maximales pour certains contaminants dans les denrées alimentaires. Section 3: Métaux. Off. J. Euro. Comm., L 364, ANNEXE, Section 3. Mance G., 1987. Pollution threat of heavy metals in aquatic environments. Els. App. Sci. Pub. LTD., 372 p. Mason A.Z. & Jenkins K.D., 1995. Metal detoxification in aquatic organisms. In: Tessier A. & Turner D.R. (Eds.) Metal speciation and bioavailability in aquatic systems. International Union of Pure and Applied Chemistry series (IUPAC), Wiley, J., Sons Ltd, London, p. 479-609 Mazlani S., Maarouf A., Rada A., El Meray M. & Pihan J.C., 1994. Étude de la contamination par les métaux lourds du champ d’épandage des eaux usées de la ville de Marrakech (Maroc). Rev. Sci. Eau 7 (1): 55-68 MEDDTL-DGPR, 2009. Ministère de l'Écologie, du Développement durable, des Transports et du Logement - la direction générale de la prévention des risques. Indicateur: arrêtés de catastrophe naturelle dans les communes littorales, Traitements: SOeS (Observatoire du littoral). Merzouki M., Talib N. & Sif J., 2009. Indice de condition et teneurs de quelques métaux (Cu, Cd, Zn et Hg) dans les organes de la moule Mytilus galloprovincialis de la côte d'El Jadida (Maroc) en mai et juin 2004, Bull. Inst. Sci, Rabat, section Sciences de la Vie, 31 (1): 21-26 Mhamada M., Ould-Mohamed-Cheikh M., Dardige A. & Er-raioui H., 2011. Etat de la contamination des côtes atlantiques de Nouadhibou par les métaux lourds (Mauritanie). Conférence Méditerranéenne Côtière et Maritime, édition 2, Tanger, Maroc Michard A., Negro F., Saddiqi O., Bouybaouene M.L., Chalouan A., Montigny R. & Goff´e B., 2006. Pressure-temperature-time constraints on the Maghrebide mountain building: evidence from the Rif-Betic transect (Morocco, Spain), Algerian correlations, and geodynamic implications. C. R. Geosci. 338: 92-114 Mukai H., Tanaka A., Fuji T., Zeng Y., Hong Y. & Tang J., 2001. Regional characteristics of sulfur and lead isotope ratios in atmosphere at several Chinese urban sites. Environ. Sci. Technol. 1064: 35-71 Nriagu J.O., Blankson M.L. & Ocran K., 1996. Atmospheric lead pollution in Kwa- Zulu/Natal, South Africa. Sci. Total Environ. 181: 93-100 Othmer K., 1995. Encyclopaedia of Chemical Technology. 4th edition, vol. 15. New York, Wiley Intersci. Publ., p. 69-157 Pempkowiak J., Sikora A. & Biernacka E., 1999. Specification of heavy metals in marine sediments vs their bioaccumulation by mussels. Chemosphere 39: 313-321 Rouhi A., Sif J., Ferssiwi A. & Chemaa A., 2007. Bioaccumulation de quelques éléments métalliques par deux espèces d’Annélides Polychètes du littoral de Jorf Lasfar (région d’El Jadida, Maroc). Bull. Inst. Sci., Rabat, section Sciences de la Vie 29: 81-87 Serghini A., El Abidi A., Idrissi L., Mouhir L., Fekhaoui M. & Zaid E.H., 2001. Evaluation de la contamination métallique des sédiments du complexe zone humides de la ville de Mohammedia (Maroc). Bull. Inst. Sci., Rabat, section Science de la Vie 23: 77-81 Shafee M.S., 1999. Etude de la pêche des bivalves sur la côte méditerranéenne marocaine. IAV Hassan II. Rapport pour le FAO-COPEMED ALICANTE, Espagne, 57 p. Shanker A.K., Cervantes C., Loza-Tavera H. & Avudainayagam S., 2005. Chromium toxicity in plants. Environ. Int. 31: 739-753 Sidoumou Z., Gnassia-Barelli M., Siau Y., Morton V. & Roméo M., 2006. Heavy metal concentrations in molluscs from the Senegal coast. Environ. Int. 32(3): 384-387 SPSS, 2006. Logiciel SPSS 15.0. SPSS Inc Chicago, III. Suter G., 1980. Carte géologique et structurale de la chaîne rifaine 1/500000. Notes et Mm. Serv. géol. Maroc 188: 71-74 Taylor S.R. & McLennan S.M., 1985. The continental crust: its composition and evolution. Blackwel Sci. Pub. ed., Oxford, 311 p. Xue H.B., Sigg L. & Gächter R., 2000. Transport of Cu, Zn and Cd in a small agricultural catchment. Water Res. 34: 2558-2568 Zegmout M., Eladdouli J., Chahlaoui A., Demnati S. & Chafi A., 2011. Bioaccumulation de quelques métaux lourds (Zn, Fe, Cu, Pb, Cd) chez la petite praire au niveau de l’Embouchure de la Moulouya (Maroc Nord Oriental), ScienceLib Eds. Mersenne 3: 111-212
Journal of Environmental Solutions Volume 2 (Issue 1) (2013): 1-8 8