Sediment Quality Assessment in a coastal lagoon (Pialassa Baiona, Italy)

The Pialassa Baiona is a shallow coastal lagoon covering a surface of about 1100 ha, which lies parallel to the Northern Adriatic Sea shoreline, approximately 10 km north of the town of Ravenna. Natural and man-made changes over the time lead to existing physical features resulting in a number of different basins of less than 1 m in depth, broad and irregular in shape, separated by levees and crossed by a network of artificial channels. From the fifties, the delicate balance of life in Pialassa Baiona lagoon has been threatened by the presence of a petrochemical industrial complex, fuel oil power generation, inland intensive agriculture, as well as to the close contact with the densely populated town and coast, and human negligence. As industrial and urban development increased, so did the input of chemical contamination in the lagoon. During the last decades, various chemicals from municipal and industrial wastewaters, and agriculture runoff have been discharged into the lagoon, depending upon treatment levels, chemicals common to the time period (i.e. DDT, mercury). These sediment-borne chemicals, may, in turn, cause toxicity to aquatic organisms. As a part of an on-going study, sediment quality within Pialassa Baiona (Italy) was investigated to determine the incidence and spatial patterns of toxicity in sediments, elutriates and porewaters, and the concentration and distribution of potentially toxic anthropogenic chemicals. To this end sediments samples were synoptically collected at selected stations within the lagoon along a gradient of chemical contamination, and evaluated by a set of sediment toxicity assays using amphipods (Corophium volutator), rotifers (Brachionus plicatilis), and luminescent bacteria (Vibrio fisheri). In addition, sediment grain size and organic carbon content, total and bioavailable metals, as well as priority pollutants such as polycyclic aromatic hydrocarbons and chlorinated biphenyls (PAHs and PCBs) were determined in the sediment samples. As a result, sediment toxicity and chemistry data were analysed by means of multivariate analysis (e.g. principal component analysis, PCA) in order to establish site-specific Sediment Quality Guidelines (SQGs) for the area of study. These guidelines are generally intended as informal (non-regulatory) guidelines to interpret chemistry data, but could also be a useful tool in the assessment of sediment quality in the case of dredging activities that are likely to occur in the studied area. In particular, two numerical guideline values were established for each chemical: (1) the Effect-Range Low (ERL), indicative of concentrations below which adverse biological effects rarely occurs, and the Effect Range-Median (ERM) value, representative of concentrations above which effects frequently occur. The ERL values were not intended as concentrations that are always predictive of toxicity, but rather intended as estimates of the concentrations below which toxicity is least likely.