Magnetometry as a Tool to Estimate the Pollution of Marine Environment Around Small Shipwrecks (Gulf of Gdańsk) — Preliminary Results

Magnetic properties of deposits around the shipwrecks (“Munin” and “Abille”) in the Gulf of Gdańsk were investigated. Values of magnetic susceptibility (χ) are relatively low; however, they reveal significant differences between investigated sites. The values of χ around “Abille” wreck were 5-8×10-8 m3/kg. Around “Munin” wreck results were more diversified reaching value of χ between 3.07×10-8m3/kg and 12.92×10-8 m3/kg. The spatial variability of χ coincided with near-bottom water currents distribution in the Gulf of Gdańsk. Magnetic minerals were identified by thermomagnetic analysis. Around “Abille” wreck we have found magnetite with small amount of maghemite or hematite. The “Munin” sediments include only one magnetic phase; in several samples it is magnetite, in the others — maghemite. Day—Dunlop plot shows that “Abille” set is shifted towards lower magnetization ratio and higher coercivity ratio. The correlation between the distribution of χ and hydrodynamic condition around shipwrecks allows to determine the direction of contaminant transport.