Anthropogenic Metal Delivery in Sediments of Porto Marghera and Venice Lagoon (Italy)

Abstract

This paper exemplifies the search for historical information on sources, levels, and trends of anthropogenic metals in a zone that has been subject to the influence of multiple industrial sources. Four cores from the canals of the industrial area and one in the lagoon just outside the industrial zone were studied in order to assess the temporal trends of Ag, As, Ba, Cd, Hg, Pb, and Zn. Maximum values were found in the Brentella Canal (4.0, 2315, 41, 5367, 34259 μg g⁻¹ for Ag, As, Cd, Pb, and Zn, respectively). High values also characterize the North Industrial Canal (2.2, 120, 70, 49, 929, 8295 μg g⁻¹ for Ag, As, Cd, Hg, Pb and Zn) and the Salso Canal. Hg and Ba, the first used as cathode in chlor-alkali plants and the other as a catalyst in the production of trielin, show very high downcore maxima in the Lusore-Brentelle Canal (4901 and 9399 μg g⁻¹, respectively). Lagoon sediments show much lower concentrations, with maximum downcore values that are from 11 (Cd) to 2188 (Hg) times lower than within the industrial canals. Chronologies, based on ²¹⁰Pb and ¹³⁷Cs activity-depth profiles, show that the highest fluxes occurred in the 1970s and early 1980s and that the input of metal contaminated materials is now decreasing. The correlation of some metals with dioxins and furans within the 1st Industrial Area suggests that both these inputs originated from the same series of production processes, active in the first half of the 20th century and starting from pyrite roasting for the production of sulphuric acid.

Keywords:

• chronology
• contaminant sources
• industrial pollution
• sediments
• toxic metals
• Venice Lagoon

Acknowledgements

This study was funded by EniChem SpA, Stabilimento di P.to Marghera. G. Marozzi made X-radiographs, M. Mengoli grain size analyses and E. Lipparini ²¹⁰Po extractions. M. Zago helped in the analyses of trace metals. This is contribution n. 1660 from the CNR-ISMAR, Sede di Bologna.

Notes

* lower than the true value.