The Impact of Grain Size Composition and Organic Matter Content on Magnetic Susceptibility of Anthropogenically Transformed Bottom Sediments, as Exemplified by the Former Naval Harbour in Hel

The article presents the results of an analysis of the surface layer of bottom sediments in the naval harbour in Hel. During field work conducted in June 2013, 54 sediment samples were collected. The aim of the study was to examine magnetic susceptibility of harbour sediment as a parameter determining the degree of anthropopressure. As part of laboratory tests, grain size analysis was performed in order to determine organic matter content and magnetic susceptibility of the sediment. The study also measured the impact of environmental factors on fluctuations in the other studied parameters. The results demonstrate increased dynamics of sedimentary environment in the open part of the naval harbour, better sediment sorting and reduced percentage share of <0.063 mm grain size fraction. Variability in magnetic susceptibility values measured in isolated parts of the harbour correlates with increased percentage share of the fine fraction and LOI%. A significant impact on the accumulation of pollutants in surface sediments is exerted by the harbour’s closed hydrodynamic conditions.