Restoration Technology of Contaminated Sediments in Coastal Environments using Steel-making Slag in Korea

This research was conducted to investigate the possibility of applying steel-making slag as a capping (or covering) material for the remediation of polluted sea sediments and to restore the productivity in polluted marine culturing grounds and seawater quality ultimately. Steel-making slag obtained from the Kwangyang Works of POSCO were scattered in the area of 100 M x 200 M, which is located in Go-sung Bay of southern part of Korean Peninsula. The diameter of slag less than 5~8 mm was scattered using a spreading machine until the slag layer on sea sediments reached thickness between 0.5 and 1.0 cm. From these large-scale experiments for more than 12 months, PO₄-P and H₂S liberations from the polluted sediment resulted to be suppressed to the extent of above 95% and 97%, respectively. Applying steel-making slag on the seawater quality was determined to be not harmful in the view of pH and leached trace metal concentrations. Furthermore, applying steel-making slag resulted in much higher survival rate of phytoplankton than that from the original area. The beneficial effects of steel-making slag were evident in the sense of elevated population of phytoplankton in middle and lower water layer on the slag covered area. The growth indexes of oyster such as shell length, height, width, and wet weight in steel slag scattering area were also higher than those from the original area. In addition, higher contents of protein and fatty acid including EPA and DHA were found in the body of oyster cultured in slag-covered area. No evidence of secondary contamination from steel-making slag was found in the body of oyster.