Long-term impacts of heavy metal contamination in the East Sea-Byeong ocean dumping site, Republic of Korea

This study analyzed sediment samples from the East Sea-Byeong ocean dumping site in the Republic of Korea during three key years: during active ocean dumping (2009), just before the sewage sludge dumping ban (2015), and six years post-ban (2022). The study established regional background concentrations and contamination levels of eight heavy metals (Cr, Ni, Cu, Zn, As, Cd, Pb, and Hg). The results indicate a general reduction in contamination levels following regulatory measures and natural recovery processes. However, past dumping activities have a persistent influence on several indicators. In 2022, geo-accumulation index (I geo ) values for Hg, Cd, Pb, and Cr remain high, and the Pollution Load Index (PLI) also exceeds 1. Additionally, consistent patterns observed in Principal Component Analysis (PCA) and Hierarchical Cluster Analysis (HCA) further underscore this ongoing impact. This study underscores the need for long-term monitoring to track recovery, evaluate regulatory effectiveness, and support decisions for sustainable environmental management and ecosystem restoration. • Heavy metal contamination in sediments was assessed at ES-B site across key years. • Regional background concentrations were calculated using statistical methods. • Contamination by Hg, Pb, Cd, and Cr persisted in the resting area. • PLI values peaked at 14.2 in the 2009 red mud site and currently exceed 1 at all stations. • Station-specific dumping history was effectively captured by combining PCA and HCA.