Temporal and spatial changes of PAH concentrations in Mytilus galloprovincialis from Ria de Vigo (NW Spain)

The aim of this study was to establish the temporal trends and spatial distribution of Polycyclic Aromatic Hydrocarbons (PAHs) in Ria de Vigo by means of studying the PAH burden in wild mussels. The samples were collected in eight sites along the margins of the Ria de Vigo during November from 1998 to 2008 and Polycyclic Aromatic Hydrocarbon contents were determined using high performance liquid chromatography-fluorescence derivatization (HPLC-FLD). Quality of chemical analysis was guaranteed by participation in QUASIMEME intercalibration exercises carried out during the period of analysis. The concentrations for the sum of 13 PAHs were in the range 24-480 mu g/kg dw, typical of an urban and industrialized area (50-500 mu g/kg dw) except for a punctual input in La Guia in 1998 that led to a concentration above 1,000 mu g/kg dw. In general, the sites in the outermost section of the estuary (ria) showed the lowest values, with an increasing gradient in the medium and inner parts of the ria. Temporal patterns show, in general, a downward trend. The relative proportion of 3 and 4 ring PAHs also varies with the site, the former being predominant in the outermost area and the latter in the medium and inner parts of the ria. This is consistently related with the sources and processes taking place in different areas of the estuary.