The Open Environmental Pollution & Toxicology Journal, 2012, 3, (Suppl 1-M5) 37-46 37 1876-3979/12 2012 Bentham Open Open Access Origin and Distribution of Polycyclic Aromatic Hydrocarbons in Lagoon Ecosystems of Morocco Abdelghani Semlali *,1 , Abdelghani Chafik 1 , Mohamed Talbi 2 and Hélène Budzinski 3 1 Institut National de Recherches Halieutique, Morocco 2 Department of Chemistry, University of Hassan II, Morocco 3 Laboratoire de Physico- et Toxico-Chimie de l’Environnement (LPTC) Université de Bordeaux 1, France Abstract: Polycyclic Aromatic Hydrocarbons (PAHs) were determined in sediments and bivalves by the Gas chromatography coupled to Mass spectrometer (GC/MS). PAHs concentrations in sediments of My Bousselham and Khnifiss, Atlantics lagoons, (expressed as ∑PAH) ranged from 31 to 82 ng/g of dry weight and from 6.6 to 34 ng/g of dry weight, respectively. Concerning organisms, PAHs levels contamination ranged from 28 to 117 ng/g of dry weight for My Bousselham (Ruditapes Decussates) and from 7 to 18.5 ng/g of dry weight for Khnifiss Lagoon Oyster (Crassostrea gigas). In the Med Lag (Nador), the results obtained showed a range varying from 6 to 126 ng/g of dry weight for sediments and from 24 to 32 ng/g of dry weight for organisms (Mytilus Galoprovincialis). The origin investigation of PAHs in sediment revealed, that the process of combustion was the main source in these Lagoons, while the diagenetic source, related to the high concentrations obtained of Perylene, was established only in both Atlantics Lagoons (Khnifiss and My Bousselham). A prevalence of high molecular weight PAHs was observed, with a considerable predominance of 4-ring PAHs in sediments and organisms of the My bousselham and Nador lagoons, while, no clear predominance was observed in the compartments studied in the Khnifiss lagoon. Correlation study of individual PAH between sediments and organisms, showed that absorption by Clams of low molecular weight PAH group, of which correlation was low, could be done through the water dissolved form, while the absorption of heavier molecular weight PAHs, which showed a high correlation of their distribution between sediments and Clams, could be the absorption from particulate matter. Keywords: PAHs, Lagoons, Molluscs, Sediments, Molecular ratios. 1. INTRODUCTION Polycyclic Aromatic Hydrocarbons are among the pollutants most monitored in marine environment, particu- larely in higly stressed areas such as harbours, estuaries, and others shallow coastal zones exposed to anthropogenic inputs and natural emissions, because are widespread class of environmental chemicals pollutants contaminants in ma- rine environment. Among anthropogenic factors, petrogenic and pyrolytic sources are the most important. Whereas pyro- lytic sources, which are largely prevalent in aquatic environ- ment, include combustion processes (e.g., fossil fuel com- bustion forests fires, shrub and grass fires), the petrogenic input is closely related to petroleum products (e.g., oil spills, road construction materials) [1]. This class of compounds has been widely studied, because of its carcinogenic and mutagenic character [2]. Due to their hydrophobic character, which increases with molecular weight [3], these neutral compounds tend to rapidly adsorb to sediment particles, and therefore represent the most important reservoir of PAHs in marine environment. For that reason, sediments are of high interest in environmental assessment of aquatic ecosystems *Address correspondence to this author at the Institut National de Recherches Halieutique, Morocco; Tel: 212-5-39946586/87; Fax: 212-5- 39325139; E-mail: a_semabd@yahoo.com and can represent a useful tool for monitoring inputs of PAHs in coastal areas. The fate of PAHs in water is strongly influenced by sorption mechanisms between water and the solid phase, of which physicochemical properties may play a critical role in sorption [4]. Furthermore, sources exhibit different chemical behaviours and distribution in marine sediments. In order to distinguish between these two origins, some molecular ratios of specific hydrocarbons were developed, based on the thermodynamic stability of isomers [5-8]. Also the use of marine organisms, especially, as bio- indicators of chemical pollution, was developed for pollution monitoring programs such as the ”Mussel Watch” in the USA or the O.N.N (Observation Network National) in French, which use Mussels and Oysters to study spatial and temporal trends in coastal and estuaries zones [9-11]. This preliminary work focus on the presence, distribu- tion, and origin of several PAHs (those highlighted by the US-EPA) in superficial sediments and bivalve’s molluscs collected of three lagoons, which represent wetlands of particularly ecological and economic relevance in Morocco, and previously not studied. Two are located at Atlantic coast (Khnifiss and My Bousselham Lagoons) and the other one, in the Mediterranean coast (Nador Lagoon). Moreover, we have studied the processes affecting the introduction of these pollutants in these aquatic ecosystems, being an important