Monitoring dissolved aromatic hydrocarbon in Rias Baixas embayments (NW Spain) after Prestige oil spills: Relationship with hydrography

The established weekly monitoring of the oceanographic conditions at 37 oceanographic stations in Rias Baixas (NW Spain) was used to study the dissolved aromatic hydrocarbons (DAHs) and dissolved and dispersed aromatic hydrocarbons (DDPAHs) in the water column, after the Prestige oil spills. They were performed in situ with an ultraviolet fluorimeter (UVF) attached to a CTD probe and with the analysis of discrete samples of seawater by spectrofluorimeter, respectively, along the year 2003. Temporal distribution of aromatic hydrocarbons pointed out the presence of two main periods: the first part of the year characterised by recurrent oil spots detected at the mouth of rias, and the second part of the year characterised by occasional spots. Maximum values, only detected in the surface layer, were found at the mouths of Rias Baixas especially at the southernmost Ria de Vigo. These maxima were registered with moderate to strong southerly coastal winds, which introduce outer surface water into these large embayments. The nature of oil detected, inferred from the shape of synchronous excitation spectra, indicates the presence of other oils besides Prestige oil.