1. J. Kirk Cochran Marine Sciences Research Center State University of New York Natural and Anthropogenic Radionuclides in Coastal Systems- Examples from the Venice Lagoon

2. November 4,1966 ‘Acqua alta’ of 120 cm flooded most of Venice

3. Venice Lagoon Facts 550 km 2 surface area Average depth ~0.6 m Tidal range 60 cm Three inlets through which tidal exchange occurs Daily tidal exchange ~400 10 6 m 3 Flushing time <2 days

4. Venice Lagoon in 16 th Century Diversion of rivers

5. Venice Lagoon- Late 20 th Century Construction of industrial area- Marghera

6. Environmental issues in the Venice Lagoon Sea level rise- caused by land subsidence (ground water extraction on mainland) and eustatic sea level rise Fate of contaminants that enter the lagoon

7. 60 cm Atmospheric flux (Be-7, Pb-210, Cs-137)

9. Contaminant Inputs and Retention Contaminants -Metals -Organic Contaminants Pathways -Atmosphere -Run-off -Submarine groundwater discharge Fate (Scavenging, Accumulation)

10. Contaminant Inputs

11. Lead in lagoon sediments

12. Zinc in lagoon sediments

13. Copper in lagoon sediments

14. Scavenging Rates of Reactive Contaminants Use U/Th series radionuclides as tracers Known source Measure distributions

15. 234 Th diss 238 U 234 Th part Scavenging Decay Decay k Sinking Simplified Th Scavenging Model

16. 234 Th/ 238 U Activity Ratios and Residence Times Venice Lagoon 234 Th/ 238 U  scavenging (d) Giudecca0.00440.1 ± 0.04 Sacca Sessola0.00980.3 ± 0.1 Cona (Bocca Carozza)<0.002<0.05 Cona (La Rotta)0.0120.4 ± 0.2 Long Island Sound (Aller and Cochran, 1976) 0.041.4 Narragansett Bay (Santschi et al. 1979) 0.06 – 0.302.2 - 15 New York Bight (Kaufman et al. 1981) 0.17 – 0.807.1 - 139

17. Wetlands

18. Sea Level Curves: Venice and Trieste Source: Carbognin (1999)

19. Source: Gatto and Carbognin (1981)

20. Rates of Sea Level Rise in Venice and Trieste (mm/y) 1896- 1930 1931- 1970 1971- 1993 1896- 1993 Venice1.53.8-0.082.5 Trieste1.71.5-0.031.1 Carbognin (1999)

21. Frequency of Acqua Alta

22. Marsh Sampling Sites

23. Marsh Coring

24. Marsh Chronologies with 210 Pb

27. 210 Pb profiles in Venice marsh sediments

28. Chronology of marsh accretion Accretion rates generally have increased with time, with relative rate of sea level rise Patterns similar in northern and southern areas of lagoon

29. 137 Cs profiles in marsh sediments

30. Chronologies of 137 Cs flux to Venice marshes Chernobyl Weapons testing (atmosphere)

31. Marsh accretion linked to frequency of acqua alta

32. Acqua Alta and Accretion Rates

33. Marsh Accretion Results Accretion at sites examined driven by long-term sea level rise and frequency of flooding by acqua alta events Sites keeping pace with sea level rise (at least) But marsh area is being lost via bank erosion along periphery (waves from boat traffic)