Assessing the Potential Marine Environmental Impacts of Heavy Metal Leaching from Ship Cleaning Residues

Antifouling paint is periodically applied to prevent the fouling of marine organisms that increase friction on the ship operations and fuel consumption. However, the process of cleaning the surface of ships in coastal areas results in the introduction of alien species, and a large amount of heavy metals, such as Cu and Zn, which are toxic substances in antifouling paints, are discharged. Mixed antifouling sludge paint obtained from the cleaning process of various ships was used for the experiment. The leaching rates of copper (Cu) and zinc (Zn) discharged from sludge paint and powdered paint were measured and their impact on the marine environment was predicted. The concentrations of Cu and Zn in the dried sludge paint were 15.5% and 31.7%, respectively. The leaching rates of Cu and Zn were found to decrease rapidly over time, and the predicted environmental concentrations (PECs) of Cu and Zn were calculated to be 0.099 μg/L and 0.822 μg/L, respectively. Although the PEC values for both metals were well below the long-term standard for the protection of marine ecosystems, Cu had a PEC value similar to the predicted no effect concentration (PNEC), suggesting that it may be environmentally harmful under certain conditions. The physicochemical and behavioral properties of antifouling toxic chemicals, as well as the hydraulic characteristics of the cleaning area, should be considered for a more accurate prediction of ecological impacts and to provide treatment standards for ship cleaning.