CHEMICAL SPECIATION OF SOME PARTICULATE ELEMENTS IN THE ENGLISH-CHANNEL, AND IMPACT OF HUMAN ACTIVITIES ON THE MAGNETIC-BEHAVIOR OF SUSPENDED MATTER

Environmental studies necessitate the knowledge of the various characteristics of suspended matters/sediments to identify predominant controls. To address these problems, we have analysed marine particles collected in the English Channel by means of several techniques: 1. graphite-furnace atomic absorption spectroscopy and inductively coupled plasma atomic emission spectroscopy to determine total chemical composition; 2. Fe-57 Mossbauer spectroscopy to identify the various types of iron and their oxidation states; and 3. electron spin resonance spectroscopy and mass-susceptibility balance to know the magnetic behaviour of particles. We have undertaken the chemical speciation of some particulate elements (Ca, Al, Fe, Mn, Cu, V, Ti, and Cr) and determined their total concentration in the particles. These elements were chosen because of either their use as reference elements (Ca, Al) or their importance in biological/environmental processes or their toxicity. Unfortunately, it has not been possible: 1. to apply the sequential extraction procedure to suspended matter because its use has yielded approximately constant speciation pattern (even for particles collected at sites presumably perturbated by human activities); and 2. to use Al or Sc for particulate-element normalization because these metals are discharged by local industries. However, the combined use of the above techniques has allowed suspended matter from several marine regions in the English Channel to be distinguished not only geographically and/or sedimentologically, but also anthropogenically in polluted zones. In addition, we have used the Random-Walk numerical model to predict the transport of suspended matter along the French coast. The impact of polluted seawaters derived from Boulogne-sur-Mer on the Gris-Nez Cape area has thus been surveyed and discussed.