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(449) Mapping the ecological risk for benthic community in the Venetian lagoon sediments. Marcomini, Antonio1, Critto, Andrea1, Carlon, Claudio1, 1 ABSTRACT- Pollutants stored in the sediments represent a potential risk for benthic and fish communities mainly through bioaccumulation processes. A screening Ecological Risk Assessment (ERA) based on quotient method (sediment exposure profiles against benchmarks for benthic organism; US-EPA, 1998) was developed to characterise potential risk for benthic community. The exposure to different classes of pollutants (metals, chlorinated organic compounds and polynuclear aromatic hydrocarbons) was investigated taking into account ca. 100 sediment stations distributed across the whole lagoon open to the tidal exchange (418 Km2). Application of geostatistic techniques (variography and kriging; Isaak and Srivastava, 1989) showed a strong spatial correlation for most chemicals of potential ecological concern. Moreover, GIS tools (MapInfo© and Surfer©) allowed to draw the exposure maps and estimate the pollutants loading in the 15 cm top lagoon sediment (e.g., 6100 ton zinc and 50 ton mercury). The internal loading was compared with external lagoon loadings (e.g., atmospheric depositions, river inflows and wastewater discharges). A map of spatial distribution of estimated risk for benthic community was finally drawn. The highest risk, found in the areas near the sources of contamination (industrial zone of Porto Marghera and the river mouths), arose mainly from mercury (40% of sampling stations showed exposure levels greater than probable effect level [MacDonal, 1994]). To aid interpretation, the relative contribution of chemicals to the cumulative risk in several sites was represented by pie charts in a GIS framework. Key words: Geographic Information System, Ecological Risk Assessment, contaminated sediment, geostastic techniques |
