In the period 1957-77 a part of 100-200 tons of mercury as industrial waste was discharged into a 10 km2 lagoon (“Pialassa Baiona”) connected to the Ravenna harbor and the Northern Adriatic Sea (Italy). Extremely high levels of Hg (up to 160 µg/g) were found in surface sediments, but the maximum values (up to 1114 µg/g) were detected in subsurface layers, down to 80 cm, close to the industrial source, and values of 1-2 µg/g were recorded in the fore-harbor, outside the lagoon. The calculation of total Hg budget in sediments gave 38 tons of Hg being stored within a contaminated area of 15 km2. The redistribution of polluted sediments would seem to be due mainly to the tidal action; more than 80% of the total Hg discharged is confined in 10% of the area, i.e. in the southern ponds close to the input point. The time necessary for a restoration of the area was estimated by using different approaches of accumulation rate calculations (210Pb, Hg peak). It appears that 40-50 years would be needed to clean the surface sediments of the Ravenna lagoon from the mercury contamination. We suggest that remedial plans should be focused on the southern ponds.
The Fate of Hg Contaminated Sediments of the Ravenna Lagoon (Italy): Final Burial or Potential Remobilization
S. Miserocchi, L. Langone, S. Guerzoni; The Fate of Hg Contaminated Sediments of the Ravenna Lagoon (Italy): Final Burial or Potential Remobilization. Water Sci Technol 1 October 1993; 28 (8-9): 349–358. doi: https://doi.org/10.2166/wst.1993.0633
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