DOI : 10. 1051/jp4 : 20030262 Heavy metals in Morocco Lagoon and river sediments L. G. Bellucd, B. El Moumni, F. Collavini2, M. Frignani1 and S. Albertazzi' Université Abdelmaleck Essaadi, Department of Earth Sciences and Oceanology, Tangier, Morocco 1/stituto di Ge%gia Marina, CNR, via Gobetti 101, 40129 B%gna,/ta/y 2lstituto per Io Studio della Dinamica delle Grandi Masse, CNR, 30122 Venice, ltaly Abstract. Analyses of Mn, Cd, Cr, Cu, Pb, and Zn were carried out in a short core from a salt marsh of the Nador Lagoon (north-eastem Morocco) and in surficial sediment samples collected in the Martil river, which borders the industrial town of Tétouan. Three soit samples and a reservoir sediment were also collected around the town to check the effects of atmospheric delivery of contaminants.'Cs and 2lOPb activity-depth profïles were used to establish a chronology for the core, obtaining an apparent accumulation rate of 0. 41 cm il. The concentrations of anthropogenic metals in this marsh sediment are low and probably represent natural backgrounds. A recent decrease can be an effect of changing grain size. Thé Mardi River sediments are slightly contaminated by Cu and Pb, whereas the soil samples present anomalous values of Cd and Zn. 1. INTRODUCTION Promoting a sustainable development, which is our option for the future, requires a good knowledge of the sources of contaminants, distribution mechanisms, sites where chemicals tend to accumulate, potential risk and actual danger to the human and environmental health. By analysing cores of undisturbed sediment it is very often possible to reconstruct the pollution history of an area. Furthermore, actively accreting salt marshes, due to the lack of sediment reworking, may provide a relatively high resolution chemical record of atmospheric fluxes. On the other hand, it is important to assess the degree of contamination of key areas such as lagoons and rivers. The former are highl valuable as transition environment, usually rich of biological species and important also from a socio-economic point of view. The latter usually carry to the coastal zone a significant fraction of the pollutant load released inland and may contribute to the contamination ofnear-shore marine sediment. We focused the study on two areas of the northern coastal zone of Morocco : the Nador Lagoon and the terminal tract of the Martil river, close to the industrial town of Tétouan. The purpose of the work was to obtain a first insight into the heavy metal contamination, with a special reference to the input from the atmosphere (Nador), and to assess the influence of industrial activities on the quality of the environment (Martil River and Tétouan). 2. MATERIALS AND METHODS Study areas and sampling locations are shown in Fig. 1. A short sediment core was taken from a salt marsh in the Lagoon of Nador (north-eastern Morocco) in September 2000, and analysed for Mn, Cd, Cr, Cu, Pb and Zn. Furthermore, in October 2002 other samples were collected along the terminal stretch of the Martil River, which borders the industrial town of Tétouan, three soil samples taken from the surroundings of the town and a short core from a nearby water reservoir were analysed as well. The cores were extruded and sectioned at intervals of 2 cm. Sub-samples were put in acid washed plastic vessels. Samples were then kept at 4°C until analysis. Sediment sarnples were dried at 60°C and disaggregated. Metals were extracted after a treatment of wet samples with H202 using a leaching with conc. H2NO3 under reflux. AH the detemlinations were carried out by AAS, Analytical precision and accuracy varied with metals and their concentrations, being typically 1. 6 (Zn)-6. 1 (Cr) % and 2. 7 (Cu)- 22. 5 (Cr) respectively. Alpha counting of 210po was used for 21OPb determinations, assuming secular equilibrium between the two isotopes. 210p was extracted from the sediment using hot HNO3 and H2O2,