Classification and risk assessment of sediment in the Karosta Canal after dredging

Abstract

Sediment samples were collected from the Karosta Canal, Liepaja, Latvia, in December 2023, shortly after dredging of the Canal. The sediments were analysed for a selection of contaminants and data was provided for the Norwegian Institute for Water Research (NIVA). Measured concentrations of heavy metals, polycyclic aromatic hydrocarbons (PAH), and oil (hydrocarbons) were classified according to classification systems used in Norway, Latvia, and HELCOM. A risk assessment of sediments, following the guidelines developed by the Norwegian Environmental Agency, were executed on the collected sediments in the Karosta Canal. Classification of the sediment samples shows that the sediment still contains high concentrations of some heavy metals, PAH compounds, and oil. The sediment in the mid and inner part of the Karosta Canal had the highest concentrations of heavy metals and oil, while the sediment in the outer part of the canal was less polluted. Sediment samples taken outside the dredged area, close to the slopes of the canal had higher concentrations of oil, PAH-compounds, and heavy metals, compared to the dredged areas. The risk assessment concludes that there is a risk of spreading contaminated sediments, a risk of harm on the ecosystem and a risk for human health if fish or shellfish from the Karosta Canal are consumed.