Depositing of Dredged Material in the Baltic Sea
The total amount of material deposited at Baltic Sea area is highly variable between years, depending widely on the occurrence of larger capital dredging operations. Total amount of material deposited in 2016 was around 7 million tonnes which is approximately one third of the amount in 2015, mainly due to reduction of capital dredging operations. Dredged material was deposited at 101 depositing sites in 2016.
In 2016 most of the material deposited at sea originated from maintenance rather than capital dredging. Maintenance dredging produced 4.8 million tonnes of the deposited material, which constitutes 68% of all dredged material deposited at sea in 2016. This amount is slightly less than the amount reported in 2015 but exceeds the amounts reported in 2013 and 2014. Most of the maintenance dredging in 2016 was reported by Denmark, Latvia, Lithuania, Poland and Russia.
Capital dredging in 2016 contributed 2.2 million tonnes, which constitutes about 32% of all dredged material deposited at the Baltic Sea. This amount is much less than what was reported in the previous three years and almost one eighth of the amount reported in 2015. The main contributors in 2016 were Denmark, Finland, Poland and Sweden.
73% (5.1 million tonnes) of the material deposited at sea in 2016 originates from harbours or river estuaries.
There were six major contaminants reported by countries in 2016: four heavy metals (mercury, lead, cadmium and copper), tributyltin and polyaromatic hydrocarbons. Most of the contaminants reported in 2016 originate from dredging operations in harbours and river estuaries. The proportion of TBT and PAHs in sediments from harbours/rivers is about 98% out of total amount. The same concerns lead, cadmium and copper, the proportion of which in dredged material from harbours/rivers is about 76% from the total amount deposited at sea. Mercury demonstrates the opposite distribution character in 2016; about 88% of this pollutant originates from dredging operations at open sea.
The total amount of reported priority pollutants was lowest in 2016 for the period of 2013-2016.