Journal of Environmental Solutions Volume 3 (2014) 1-10 Journal of Environmental Solutions Averroes Publisher METALLIC CONTAMINATION ASSESSMENT OF THE LÉVRIER BAY (MAURITANIAN ATLANTIC COAST), USING PERNA PERNA AND VENUS ROSALINA MHAMADA Mohammed1; OULD MOHAMED CHEIKH Mohammed1; KHANNOUS Soumaya1; DARTIGE Aly2; ER-RAIOUI Hassan1* 1 Geosciences and Environment team - Department of Earth Sciences - Faculty of Sciences and techniques, Tangier, Morocco 2 Office of Sanitary Inspection of Fishery Products and Aquaculture (ONISPA) Nouadibou, Mauritania * 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: By its proximity to Nouadhibou city (the economic capital of Mauritania), Lévrier bay (Atlantic coast of Mauri- Lévrier bay tania) is closely exposed and influenced by port and industrial activities effluents. Its coastline is highly coveted Atlantic coast of Nouadhibou for the establishment of several industrial firms accompanied by a growing urban development. In this context, trace metals the present study focuses on the marine coasts evaluation of the trace metals contamination (Cd, Hg, Pb, Fe, Co, Perna perna Cr, Cu, Mn and Zn) in two different species of bivalves (mussels and clams) using ICP- AES. The results showed Venus rosalina significant coastal contamination by iron and Cd. Their recorded results have to be considered in any integrated coastal zone management in Mauritania. The trends of trace metal concentration values, recorded from 1991 to 2009, showed an undeniable increase in Cd and iron, mainly attributed to industrial and urban domestic wastes. Cd concentration values ranged from 3.9 mg/kg dry weight (dw) in 1991 to 23 mg/kg dw in 2009. On the other hand, iron concentrations increase has been found both in mussels and clams. Actually, mussels showed in- creasing concentration values ranged from 155.5 mg/kg dw in 1999 to 460 mg/kg dw in 2009 while in clams, concentration values ranged from 322 mg/kg dw in 1991 to 663.6 mg/kg dw in 2009. I. INTRODUCTION Mauritanian coasts extend over almost 720 km along the Atlantic Ocean. They are considered as an aquatic system that is more economically important than ecologically as they are hosting a wide variety of species. Thus chemical pollution of these coastal areas could have serious consequences on the balance of marine ecosystems. That is why this work focuses on the assessment of the contamination of the Lévrier bay by trace metals and the sanitary of fishery products in the maritime exclusive economic zone (MEEZ). The Lévrier bay has an exceptional potential due to both its strategic geographical position and its natural resources. It is recognized as a true "biogeographical crossroads" where the ecological characteristics of the southern and northern areas meet including those of Europe. Beside its proximity to Nouadhibou city, the economic capital of Mauritania, the Lévrier bay is intimately linked to industrial and harbour activities. Its coastline is highly coveted for setting several industrial enterprises as well as for growing urban development. In fact, it is designated to accommodate important development projects in the frame of the Mauritanian government orientations into a special economic zone (AECOM, 2011). Moreover, the bay is under increasing anthropogenic pressure due to the significant urbanization development of Nouadhibou city. This development generates important economic activities such as setting of fishing companies and flour and fish oil factories. There are also many shipwrecks as well as petroleum and ore ports that could be sources of potentially toxic substances. Table 1 sums up some examples of industrial and agricultural sources (Othmer, 1995) which may introduce chemical pollutants in the bay environment. 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 Mhamada et al. Contamination of coastal ecosystems by these hazardous substances is one of the major problems in ecotoxicology. Unlike organic pollutants, some trace metals could not be submitted to biodegradation. Thus, they could be accumulated in food chains to reach toxic thresholds (Cumont, 1984) and could generate critical and even dangerous situations (Serghini et al., 2001). In natural aquatic ecosystems, metals are found at low contents, generally in limits of nano-gram or microgram per liter. However, in recent decades, the occurrence of high trace metals levels, above than their natural contents, has become a serious problem which could be attributed to fast population growth, increased urbanization and especially expanded industrial activities. When addressing the toxicity of metals, it is necessary to distinguish between essential elements and non-essential ones. A metal is considered essential when pathological symptoms appear with decreasing concentrations or even with its absence and disappear once it is added. It also requires that the symptoms should be associated to a biochemical defection (Förstner & Wittmann, 1979). However, an essential element could be toxic when it is present in excessive concentrations. According to these criteria, 17 metals are considered essential, including four (Na, K, Ca and Mg) are present in large amounts (> 1 μmol 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 (0.001 to 1 mmol kg-1 fresh weight) or even in ultra- trace (< 1μmol kg-1 fresh weight) (Mason & Jenkins, 1995). Unlike those previous elements, non-essential metals have no currently known biological role. This is the case of Hg, Ag, Cd and Pb (Mason & Jenkins, 1995). They are considered as harmful once they are present in the environment and lead to noxious biological effects at very low concentrations. In this focus, analyzed organisms belong to bivalves; that is mussels and clams. Those bivalves are widely used as bio-indicators in the evaluation of marine environmental contamination studies, given their ability to concentrate contaminants at levels well above those found in their surroundings. Indeed, by their lifestyle and/or their metabolic and physiological characteristics, bio- accumulative species have the ability to accumulate contaminants directly from the environment (bio-concentration) or by other means (e.g. food) (bio-magnification) to levels well above the levels present in the physical environment (water and sediment). Therefore, the bio-accumulative species are frequently used in monitoring networks (bio-monitoring) of the marine environment quality (Lagadic et al., 1998; Phillips & Rainbow, 1993). Moreover, the organisms chosen for this study are sedentary and may reflect pollution levels by geographic location. This research complements previous works conducted in the northern Mauritanian zone (Sidoumou, 1991; Sidoumou et al., 1997, et 1999; Roméo et al., 2000; Dartige, 2006; Wagne et al., 2013) and shows the actual state of metal contamination of the bay of Lévrier. II. MATERIALS AND METHODS II.1. The study area The study area is located in the North Atlantic coast of Mauritania. It contains important agglomerations having different human activities as fisheries, trade and industry. Along its coast, there are four ports (oil port, fishing port, industrial port and Ore port). However, the fishing remains the main activity carried out by several industrial units located in this area. Two organisms were concerned by this study: clams (Venus rosalina) and mussels (Perna perna). The first ones were collected from five sampling points situated in the off-shore of the Cansado bay (table 2) while mussels were sampled from four sampling points from which three are located inside the Cansado bay (figure 1) and the fourth one is located outside the bay and is considered as a reference sampling point. The samples were the same age with the exception of mussels collected from the station Guerra which were smaller. The choice of sampling points was based on their abundance in mussels but also on their proximity to discharges. Cansado bay, being part of the Lévrier bay, is well known to host the majority of pollution sources of Nouadhibou city. It also accommodates many shipwrecks. • GUERA’s sampling point (used as control reference) is free from any significant pollution. It is exposed to strong waves that break on the coast area. This sampling point is located outside the bay in the north-west (20° 51' 26.09" N; 17° 01' 52.37" W); • Oil port sampling point is close to both Ore port, belonging to the National Industrial and Mining Company of Mauritania (SNIM) and Nouadhibou refinery (20° 49' 55.11" N; 17° 02' 08.34" W); • COMECA’s sampling point is located near the metallurgical company “COMECA”. This sampling point is near the oil port Cansado (20° 50’ 28.98" N, 17° 02' 03.93" W); • IMROP’s sampling point is located in the southeast bay Cansado (20° 51' 26.09" N; 17° 01' 52.37" W). This bay receives all urban wastes including Cansado effluent of domestic wastewater. Figure 1. Location map of Perna perna and Venus rosalina samples (Lévrier bay) Journal of Environmental Solutions Volume 3 (2014): 1-10 2 Mhamada et al. Regarding Venus rosalina, sampling stations are located off of the bay (figure 1), table 2 summarizes the details of the different sampling points. Table 2. Coordinates of the different sampling sites Venus rosalina Site Coordinates M5 20°19’ N 17°08’ W M6 20°13’ N 17°12’ W M7 20°12’ N 17°08’ W M8 20°15’ N 17°08’ W M9 20°18’ N 17°10’ W II.2.