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Les caracteristiques geochimiques des sediments adjacents a trois plates-formes de production (par 22 a 150, d'eau) dans le nord-ouest du golfe du Mexique ont ete determinees a partir de la presence de l'ouvrage, de la quantite et du type de materiaux liberes par l'ouvrage, et du contexte hydrographique local. Les sediments proches des plates-formes ( 80 m), les concentrations des metaux a l'etat de traces dans les sediments n'ont pas varie pendant des annees. Il s'est avere que quelques metaux (Pb, Cd) se sont constamment accumules dans les sediments depuis la mise a l'eau de la plate-forme.

Volatile organic compounds (VOC) discharged into northwestern Atlantic slope waters at a deep ocean dumpsite were dispersed to background levels within 24 h. The main VOC (>85%) of the waste was toluene, with a large mercaptan component. Several trichlorobenzenes were present in trace amounts. Initial dilution from wake dispersion reduced the waste levels by a factor of 1300. Mixing processes and evaporative loss to the atmosphere further reduced surface water concentrations of VOC by a factor of 1000 in 9 h and to background levels within 24 h. The rapid loss of volatiles from the dumpsite waters results from the very volatile nature of the dumped material and physical mixing processes. The presence of the edge of a large, anticyclonic, warm-core Gulf Stream eddy (ring) in the dumpsite area probably increased local mixing processes which resulted in the rapid dispersion of the waste. The presence of the ring water in the dumpsite area could also account for the low background concentrations observed in the dumpsite.