1. 210 Pb as tracer of contaminant transport in a complex canyon-channel system (Gulf of Cagliari, South Sardinia, Western Mediterranean Sea) Barsanti M. 1, Delbono I. 1, Schirone A. 1, Conte F. 1, Delfanti R. 1, Del Core M. 2, Tamburrino S. 2, Sprovieri M. 2 1 ENEA, Marine Environment Research Centre, La Spezia, Italy 2 CNR, IAMC UOS Capo Granitola, Campobello di Mazara (TP), Italy

2. Study area Sarroch Gulf of Cagliari (Sardinia, IT) Many submarine canyons Continental shelf ~ 15 km wide StationWater depth (m) Location A2TM625S. Elia–Foxy Canyon A3TM636Sarroch Canyon A4TM907Carbonara Canyon A6TM787Pula Canyon

3. Methods 0.5 cm 1 cm Box-corer Sub-cores with PVC tubes (10cm Ø) Sub-cores sliced on board (0.5cm in the top 3 cm and 1cm thereafter) 210 Pb and 137 Cs -> Gamma spectrometry with four high resolution ORTEC HPGe Trace elements -> Inductively coupled plasma optical emission spectrometry (ICP-OES; iCAP 6000)

4. 625 m depth 210 Pb and 137 Cs profiles Sarroch CF-CS 0.24±0.01 g cm -2 y -1 0.33 ± 0.01 cm y -1 1963 ± 2 1945 ± 2

5. 636 m depth Sarroch CF-CS 0.18 ± 0.01 g cm -2 y -1 0.26 ± 0.02 cm y -1 1983 ± 3 210 Pb and 137 Cs profiles 1956 ± 5 C ostant R ate S upply

6. 907 m depth Sarroch 210 Pb and 137 Cs profiles 210 Pb xs

7. 787 m depth Sarroch 210 Pb and 137 Cs profiles

9. Grain size composition A2TM A3TM

10. Grain size composition A6TM A4TM

11. 210 Pb and 137 Cs profiles normalised to clay fraction A6TM

12. Al-normalised trace elements vs depth A2TM A3TM A4TM Ni, Pb, Cr, V, Zn and Hg Co, Ni, Pb, Cr, V, Zn and Hg Pb, Cr, V, Zn and Hg As and Pb Pb, Cr and Zn As and Hg Pb, Cr, V and Hg Hg V and Hg Pb and Hg Ni, Pb, Cr, V, Zn and Hg A6TM

13. Al-normalised trace elements vs time 2005 1983 1953 1943 2006 1988 1967 A2TMA3TM

14. Enrichment Factor – (EF Al ) vs time A2TM A3TM 1953-1956 1943 1983 1988 2004-2008 1967 Identified and selected the TE values before the '20s along A2TM and A3TM cores as geochemical natural background to calculate the Enrichment Factor.

15. Conclusions Four sediment cores were collected in 2014 from the Gulf of Cagliari in the thalwegs of submarine canyons (depth range 600-900m). 210 Pb and 137 Cs dating for A2TM and A3TM cores provides the pollution history of the most populated and industrialised area of Sardinia. Regional natural background levels for trace elements are defined for the first time: Pb = 25 mg/kg, As = 13 mg/kg, Hg = 0,03 mg/kg. Highest Enrichment Factors values were observed for Pb, As and Hg with an increasing trend starting from the 1970s for the A3TM core and from the 1940s for the A2TM core, pointing out a significant anthropogenic input.