Contamination of rare earth elements in coastal seawaters from nearby industrial complexes, Korea

With the rapid expansion of high-tech industries, demand for rare earth elements (REE) has surged, leading to the emergence of anthropogenic REE as a novel class of marine pollutants. This study investigates the spatial distribution of REE across various environmental media-including seawater (dissolved and particulate phase), sediments, and road dust-within the Oehwang River estuarine and coastal zone, a region characterized by dense petrochemical and non-ferrous metal industrial complexes in South Korea. Our analysis revealed unprecedented concentrations of dissolved lanthanum (dLa) (up to 35.0 μg/L) and a pronounced positive La anomaly throughout the water systems adjacent to the industrial complexes. This enrichment is likely associated with wastewater discharge from petrochemical activities involving fluid catalytic cracking (FCC) catalysts, as suggested by its positive association with vanadium (V) and nickel (Ni). Anthropogenic dLa (dLa_anthr) exhibited a predominantly conservative mixing behavior within observed salinity range between 18 and 33 ‰ with physical dilution along the estuarine salinity gradient. These industrial signals dispersed into coastal waters, persisting across the continental shelf seawater tens of kilometers away from the source. Ecological risk assessment, conducted using the Risk Quotient (RQ) based on the Predicted No-Effect Concentration (PNEC) for La, classified a broad area as "High Risk", indicating the potential for adverse ecological effect. This study underscores the significant influence of industrial REE pollution on adjacent marine environments and highlights the urgent need for environmental policy standards for systematic management.