Contaminant fate and transport in the Venice Lagoon: Results from a multi-segment multimedia model

Abstract

a b s t r a c tContaminant loadings to the Venice Lagoon peaked from 1950s-1980s and although they have since declined, contaminant concentrations remain elevated in sediment and seafood. In order to identify the relative importance of contaminant sources, inter-media exchange and removal pathways, a modified 10-segment fugacity/aquivalence-based model was developed for octachlorodibenzodioxin/furan (OCDD/F), PCB-180, Pb and Cu in the Venice Lagoon. Results showed that in-place pollution nearby the industrial area, current industrial discharges, and tributary loadings were the main sources of contaminants to the lagoon, with negligible contributions from the atmosphere. The fate of these contaminants was governed by sediment-water exchange with simultaneous advective transport by water circulation. Contaminants circulated amongst the northern and central basins with a small fraction reaching the far southern basin and the Chioggia inlet. As a consequence, we estimated limited contaminant transfer to the Adriatic Sea, trapping the majority of contaminants in the sediment in this ''average'' circulation scenario which does not account for periodic flooding events.

Persistent organic pollutants in sediments from the Lagoon of Venice—a possible hazard for sediment-dwelling organisms

“…This trend, as previously underlined for PCBs, may be due to activities to improve the environmental quality of the area around the industrial zone of Porto Marghera. Moreover, as already highlighted for pesticides, the higher concentrations measured in the northern basin could be due to contaminant circulation among central and northern basins (Sommerfreund et al 2010) and/or the intense clam and mussel harvesting, during which there are continuous new inputs of hydrocarbons from more than 600 small boats equipped with mechanical dredges, used to resuspend and to catch mussels ). In addition, further sources of PAHs could be individualized in the maritime traffic for goods and people that characterize the whole Lagoon.…”

“…This lack of differences could be due to the fact that sediments and the bound contaminants (above all the finest fraction) were resuspended by clam rearing, water turbulence and other practices, recirculating throughout the Lagoon by advective transport in the water column (Sommerfreund et al 2010). We can only point out that the northern area showed higher levels of these industrial organochlorine compounds, with average values (4.8±3.4 ng g −1 d.w.) about twofold higher than those measured in the other zones.…”

“…The moderate DDT levels measured in the central basin, with the peak of Fusina (44.31±2.00 ng g −1 d.w.), can be due to the contaminant circulation that follows the pattern of water circulation. In fact, extensive water exchange occurs among the northern and the central basins (net flow range from 5 to 70 m 3 s −1 ) as explained by Sommerfreund et al (2010) by a multi-segment multimedia model. Differently, the DDTs pollution found in the southern sites of Valle di Brenta (84.46±22.48 ng g −1 d.w.) could be due to possible local sources as tributaries that cross many Venetian rural zones.…”

“…The consequent decline of the macroalgae Ulva rigida coverage in the Lagoon (Sfriso and Marcomini 1996) favors the tide-or wind-induced resuspension of surface sediments and bound POPs. Moreover, since 1994, clam harvesting has been done using hydraulic and mechanical dredges that cause sediments resuspension and reworking down to 30 cm below the surface (Sommerfreund et al 2010) causing the upset of sedimentation patterns (Facca et al 2002;Sfriso et al 2003). The consequence of this particular fishing practice was that about 24 million m −3 year −1 of sediments were resuspended (Pessa and Sfriso 2002).…”

Harmful Elements in Estuarine and Coastal Systems

“…Coccioni et al (2009) indicated that the lagoon is affected by trace element pollution (Cd, Cu, Ni, Pb, Zn and Hg) with the highest concentrations in its inner part, which corresponds to the Porto Marghera industrial area, and also revealed a strong relationship between trace elements (in particular Mn, Pb and Hg) and the occurrence of abnormalities in tests with foraminifera. In addition, a study by (Sommerfreund et al 2010) showed that the current industrial discharges are the main cause of the pollution nearby the industrial area, but they also pointed out the role of tributary loadings as a source of contaminants to the lagoon. Apitz et al (2009) used statistical methods to separate natural background and anthropogenic concentrations of trace elements in radio-chronologically selected surface sediments of the Venice Lagoon.…”