Produced formation waters: A preliminary study on chemical characterization and acute toxicity by using fish larvae (Dicentrarchus labrax L.,1758)

This paper illustrates a preliminary toxicological assessment of the produced formation waters (PFW) including analytical determinations and acute toxicity bioassay by using the European sea bass (Dicentrarchus labrax L., 1758) fish larvae. To accomplish this goal, PFW samples were collected from an off-shore gas platform located in the Central Adriatic Sea (Italy), and characterized by chemical analysis. The chemical characterization, concerning inorganic and organic compounds, was carried out using filtered (0.45 mum Millipore filters) and non-filtered PFW samples, but also the PFW solid fraction. The inorganic elements (Fe, Cu, Ni, Mn, Pb, Zn, Cd, Hg) were found to be linked only to the solid fraction. The aromatic hydrocarbons (C<12) and phenols, which are petroleum volatile fractions, were absent in all the matrices analysed. The toxicological bioassay was performed by using 30 days old fish larvae. The test results, expressed as PFW LC(50)(24h) (lethal dilution percentage), were 18.1 % for filtered and 17.7 % for unfiltered samples. Nevertheless, during the first five hours of acute test phase the response time to PFW toxicity of larvae resulted to be shorter in unfiltered samples than in filtered ones. This observed response might be related to chemical compounds linked to the solid PFW fraction or, more simply, to the ingestion and absorption of particulate matter by test organisms.