Thesis jointly supervised by the University of Western Brittany. PhD jointly supervised by: Philippe GIAMARCHI, University of Western Brittany
Committee: Gaëtane LESPES, Michel WARTEL, Philippe GIAMARCHI, René OLIER, Stéphane LE FLOCH, Jordan TESSE, Alain LE BIHAN
Abstract: This report deals with the study of the physico-chemical effects after an accidental coal immersion. Coal is a sedimentary rock mainly composed of organic matter (> 50 M %). The organic part contains humic matter, polycyclic aromatic hydrocarbons (PAHs) and sulfur compounds. The inorganic part contains major (> 0,5 %: Al, Ca, Fe, Si...), minor (0,02 -0,5%: Mg, Na ) and trace elements (<0,02%: Cd, Zn, Cr, Cu, Mn...), some of the latter being heavy metals. The PAH contents in the various coals used were determined by several extraction methods: they are 0f the order 0f 1 mg kg for the 16 most toxic PAH5. The inorganic phase was analyzed by sequential extraction apart from manganese, which is present in gypsum, the studied metals (AI, Cr, Cu, Fe, Ni, Pb and Zn) are present in insoluble minerals such as kaolinite. After mixing with seawater, fluorescence analyses by xenon and LASER excitation, along with gas chromatography and mass spectrometry were used to identify organic compounds dissolved from coal onto seawater: they are humic and fulvic acids. Neither PAHs nor sulfur compounds could be detected. The concentration in humic acid equivalent increases with increasing coal mass and agitation time and intensity, and decreases with increasing grain size. Dissolved inorganic compounds were analyzed by electrothermal atomic absorption spectroscopy: since they are included in insoluble minerals, most of the analyzed elements were not dissolved, apart from Mn which is dissolved as a sulfate. The Mn concentration increases with increasing Goal mass and agitation time and intensity, and decreases with increasing grain size. It is, in batch, higher than 1.5 g L-1, which can be considered as an environmental limit. Several experimentations were eventually conducted in open media this displayed the elimination of thin suspended particles preventing photosynthesis and the dilution of humic acids and Mn due to the continuous seawater renewal. The spreading of a coal pile submitted to a seawater flow was also studied, and it occurs that the tiniest coal particles move faster: they can be dispersed over a distance of 1 km in 10 hours. The environmental impact after an accidental coal immersion remains on the whole limited.
Bibliographical reference: www.cedre.fr/pmb/opac_css/index.php?lvl=notice_display&id=3886