Tesis doctoral de Saioa Elordui-zapatarietxe Del Aguila
To date, most studies on the environmental consequences and fate of marine oil spills and pollution have been undertaken in coastal areas, probably as a result of the impact of spills in local economies and the vulnerability of coastal ecosystems to such events. This fact, together with analytical and technical difficulties, may explain why, in contrast, there is an apparent shortage of studies on the distribution and fate of oil hydrocarbons in open ocean waters. In fact, given the increasing exploitation of oilfields in the high seas, and the intensification of maritime traffic, in the last decades, oil pollution of the marine environment beyond the continental platforms is increasing. In addition, new sources of pollution are being recognized. Thus, in recent years it has been noted that the high number of sunken vessels scattered in the oceans sea floor are potentially a present and future source of oil spills. in this thesis, the accident of the prestige tanker in 2002 off the galician coast is investigated as a case study of a deep sea spill in open ocean waters. Although part of the cargo carried by the tanker was released at the surface, more than 57,000 tonnes of heavy fuel oil remained in the vessel when it sank and the great majority of them were spilled from the deep ocean. In addition, the area near the galician bank, where the prestige wrecks are located, is hydrodynamically complex. The water column is comprised by five main water masses from different origins and physico-chemical properties, which may contribute to actively spread the oil released from the prestige in different and distinct ways. in this context, the main aim of this study has been to determine the importance of the prestige shipwrecks as a source of oil pollution in the waters near the galician bank several years after the accident took place. In addition, it has been investigated the role of the different water masses in the sinking area in the transport and distribution of hydrocarbons. These objectives have been tackled by a combination of laboratory and field studies. First of all, several sets of experiments were carried out under controlled temperature and salinity conditions which provided information about the potential dissolution of the prestige fuel oil in seawater. In addition, two oceanographic cruises were undertaken in march and october 2006, near the wrecks location and surrounding areas, to collect seawater samples. Aliphatic and polycyclic aromatic hydrocarbons (pahs) were determined in the suspended particulate matter (spm) and dissolved phase (dp) in the water column of three stations. One was located above the prestige wrecks, and the other two 73 nautical miles north and south of the prestige incident area. hydrocarbons concentrations from petrogenic sources in the spm above the wreck and surrounding areas in march 2006 were within the range of abundances previously reported for similar compounds in the north atlantic and other marine locations, but much higher in october 2006. The concentrations of pahs found in the dp were, both in march and october 2006, well above any expected background levels. The chemical fingerprint of the hydrocarbons indicated that in october 2006 the oil at the prestige station originated from the wrecks. This, together with the unusually high relative concentration of hydrocarbons in the dp at the prestige station in march 2006, indicates that the prestige wrecks had been releasing oil for several years after the accident. However, despite the widespread occurrence of oil hydrocarbons in the three stations and throughout their water columns, it could not be concluded that the prestige was the main source of pollution in the area near the galician bank, which most likely has multiple origins. In fact, different water masses contain distinct contents of hydrocarbons in the spm and the dp, which in some instances may have remote sources. This is especially likely for the hydrocarbons in the mediterranean water mass. the study conducted can be viewed as an example of the potential of a sunken wreck in the deep north atlantic as a source of pollution. Apparently a deep spill from a wreck would have initially a much localized impact, more noticeable in the dissolved hydrocarbon fractions. Eventually, the chemical signature from a deep spill cannot be easily disentangled from the background concentrations of oil pollutants after the spill is over. Although each potentially polluting shipwreck represents a singular case, knowledge obtained about the temporal and spatial distribution of hydrocarbons after the accident of the prestige could be applied to deal with other deep spills in the future.
Datos académicos de la tesis doctoral «Hydrocarbons in the open ocean waters near the galician bank after the deep sea spill from the prestige wrecks«
- Título de la tesis: Hydrocarbons in the open ocean waters near the galician bank after the deep sea spill from the prestige wrecks
- Autor: Saioa Elordui-zapatarietxe Del Aguila
- Universidad: Autónoma de barcelona
- Fecha de lectura de la tesis: 03/06/2009
Dirección y tribunal
- Director de la tesis
- Antoni Rosell Melé
- Tribunal
- Presidente del tribunal: pere Masqu barri
- josep María Bayona termens (vocal)
- (vocal)
- (vocal)