This work reports a comprensive characterization study of refractory organic matter forms including the so called Black Carbon (BC) in reference materials and recent marine sediments from the Gulf of Cadiz (South West Iberian Peninsula), by usinf elemental analysis and spectroscopic and chromatographic techniques. Marine sediment samples were collected in the Southwest Atlantic coast of Spain, a site of geological and environmental interest. A two step procedure, consisting in a chemical oxidation with sodium chloride of the demineralised sediments followed by integration of the aromatic C region in the remaining residues by solid-state 13C Nuclear Magnetic Resonance (NMR) spectroscopy, was used to estimate the refractory organic matter (ROM), including BC, in marine sediments of the area under study. Measured contents of BC-like material ranged between 3.0 and 45.7% of total organic carbon. Higher relative BC contents were found in riverine sediments close to urban areas, showing an input of anthropogenic organic material. The BC-like material content in the offshore marine sediments (5.5-6.1%) were well in the range to values previously reported for this kind of samples. However, NMR and pyrolisis-GC/MS of the islated ROM reveals that abundant refractory aliphatic organic material remains in most of the marine samples after chlorite oxidation. We suggest that this pool of aliphatic carbon may play an important role as a stable carbon pool within the global C cycle. This work also includes a new methodology for BC quantification by using thermogravimetric techniques, which was successfully applied in most of the reference samples.

El presente trabajo se ha realizado en el marco del proyecto titulado "Distribución y composición molecular del "Black Carbon" y otras formas de materia orgánica refractaria en sedimentos del litoral Suratlántico. Implicaciones en el secuestro de carbono y el cambio global" (REN 2002-04602-CO2) del Plan Nacional de I+D (CYCIT), dentro del Programa Nacional de Formación de Personal Investigador (FPI).

196 páginas, 317 referencias. Realizada en el Departamento de Bioquímica y Geodinámica del IRNAS-CSIC. Leída el 22 de junio de 2007.

Peer reviewed