Removal of top-layer sediment

Removal of active top layer of sediment – Southwest Finland ELY Centre

Janne Suomela taking samples.

Removal of organic, oxygen consuming top layer of bottom sediment was planned to be tested at two pilot sites in Finland and the effect and efficiency of the method was to be evaluated. The main objective is to remove nutrients from the seabed, but also to deplete the organic oxygen consumption in the sediment and, consequently, decrease the leakage of phosphorus from anoxic sediment to the watercourse. Implementation of sediment surface layer removal using slow flow technique, or comparable, to avoid sediment resuspension and turbulence, was beyond the SEABASED project budget. Therefore, the project decided to carry out an experiment in a laboratory to study probable effects of sediment removal to sediment oxygen demand and nutrient fluxes between the sediment and the overlying water. The suitability and potential of the measure in Baltic Sea protection was evaluated, especially for coastal anoxic bottom areas that have been historically under high nutrient load, with little possibilities of significant flora or fauna to survive without restoration measures.

Results

Results from this pilot were presented in the SEABASED Final Webinar on January 26th, 2021. See the presentation behind this link. Read the final report of this pilot behind this link and the study on the incubation of the sediment behind this link (the study is in Finnish).

Anoxic sediment (gyttja clay) from Archipelago Sea.

Well oxygenated sediment surface.

For more information, please contact

Pekka Paavilainen, Senior Officer

Janne Suomela, Chief Specialist

Varsinais-Suomen ELY-keskus (Centre for Economic Development, Transport and the Environment for Southwest Finland)
firstname.lastname@ely-keskus.fi