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International audience; This study examined the potential metal pollution induced by the accidental spill of different acids into seawater. The acids sink to the bottom according to their densities and subsequently react with marine sediments. The acids selected for this study were acetic, hydrochloric, nitric, sulfuric, and phosphoric acids; the metallic elements selected were Cr, Cu, Fe, Mn, Pb and Zn. The sediment was collected in Brest Harbour. The percentages of metals released from this sediment in the presence of various concentrations of acids in seawater were important; concentrations of approximately 7 mg L(-1) for Mn and 60 mg L(-1) for Zn were observed under our experimental conditions. We also examined the rate of release of these metals from the sediment into the seawater in the presence of the different acids and under different experimental conditions. We found that most of the metallic elements were released from the sediments into the seawater during the first fifteen minutes of exposure. After this time, a high degree of pollution was induced if acids leached into seawater were not rapidly diluted.

International audience; Coal is currently becoming an increasingly interesting fossil energy resource and that is the reason why its maritime transport, and hence the risk of collier accidents, increase. In this work, the environmental impact of an accidental coal immersion at sea is studied: the physicochemical effects are estimated using innovative experimental setups--a laboratory seawater canal called "polludrome" is used to evaluate the behaviour of coal particles submitted to a seawater flow, and a specifically designed tub is used to study the physicochemical consequences induced when coal is introduced into continuously renewed seawater. When coal is introduced into seawater, the most easily visible consequences are physical: fine coal particles reduce the daylight penetration up to 100% and move along with the flow, and coal chunks accumulate on the floor. Chemical effects are also measured: humic matters are dissolved from coal into seawater (up to 2 mg L(-1)), but no release of polycyclic aromatic hydrocarbons is evidenced. Some inorganic compounds are dissolved, among which manganese, whose concentrations can reach 1 microg L(-1). Fortunately, the results show that the environmental impact of this type of accident would remain limited.