PORE WATER ANALYSIS

The geochemical analyses of both the pore water and the sediment aim at improving the understanding of fluid migration in chosen location in the Sea of Marmara. Fig.13 shows the methodology. A particular interest was given to the Western High as gas hydrates have been recovered there during the R/V L'Atalante 2007 Marnaut Cruise. The work proposed here in as continuation of the pore water analysis done by M.K.Tryon from samples recovered during the already mentioned Marnaut Cruise TRYON2010.

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Figure 13: The RHYZON methodology for pore water extraction.

• Bottom sea water sampling. From the CTD casts, the sea waters near the seafloor have been sampled in 5 stations in order to compare with the pore-water profiles. Plastic bottles were rinsed several times with water of the Rosette Bottle, filled and stocked in deep freezer at -20 C. Three of them were filtered.

• Pore-water sampling. After recovery, the gravity cores were immediately cut into segments of 1 m length. The whole round sediment sections were capped and transported to the shipboard laboratory for pore water extraction. The pore waters have been sampled for chemical analysis using the Rhizon soil moisture samplers. This is an innovative water extraction technology. The sampler consists of a hydrophilic, porous polymer tube of 2.5 mm in diameter. The tube is permanently connected to the soil surface from one end, and to a connector for attaching a vacuum tube of 10 mL from the other end where the samples are collected. The pore waters pass trough a filter 0.1 $\mu$m diameter, therefore no further filtration is required. The samplings were performed with a resolution of about 30 cm in depth. In few hours following the sampling, the pore waters were analysed to determine their alkalinity by titration, using the 716 DMS Titrino and 728 Stirrer by Metrohm. This measurement has not been carried on the core recovered on the Western High. A number of 10 cores ware sampled for a total of 108 analysis on subsamples.

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Figure 14: .Pore-water sampling from a core section using Rhizon technology