Dispersion of metal contaminants from the coast to offshore on the southeastern coast of Korea.

Coastal industrialization has led to the accumulation of metal and metalloid contaminants in marine sediments, particularly in semi-enclosed harbors. This study investigates the distribution and enrichment of contaminants in surface sediments along the southeastern coast of the Korean Peninsula, encompassing the industrialized ports of Busan and Ulsan. A total of 282 surface sediment samples were collected from the southeastern coastal and offshore areas of the Korean Peninsula. Geochemical and grain size analyses, including Cs-normalized element concentrations and factor analysis, revealed elevated levels of Cu, Zn, Cd, Sn, Sb, and Pb in harbor sediments, especially near industrial complexes and shipyards. The dispersion of contaminants toward offshore areas, based on the Cu/Zn ratio, could be resolved by high resolution samples, which indicated that most contaminants do not disperse significantly beyond the harbor headwaters, despite historical industrial contamination, due to the blocking effect or rapid dilution of contaminants by a nearby current system. Despite restricted contaminant mobility beyond breakwaters, metal accumulation in port sediments remains a long-term environmental concern. These findings underscore the importance of high-resolution sediment monitoring and improved port management to mitigate offshore contamination risks, particularly in regions like Ulsan with direct coastal industrial discharge.