Bioavailability-based ecological risk assessment of metals in coastal sediments from industrial bays in South Korea: Insights from geochemical fractionation and source identification.

In this study, the levels, geochemical fractions, sources, and bioavailable ecological risks of 11 metals in coastal sediments from four industrial bays (Gwangyang, Jinhae, Busan, and Ulsan) in South Korea were investigated. The mean concentration of Σ11 metals ranged from 60.6 to 92.0 g/kg, and Al, Fe, and Mn accounted for 99.5% of the total concentration. Spatial distributions were closely associated with industrial complexes, with Cd concentrations two times higher in Jinhae than in other bays, Cu and Zn concentrations highest in Busan near port facilities, and As concentrations elevated in Ulsan near a petrochemical complex. The residual fractions of Al, As, Cr, Fe, Ni, and V exceeded 60%, indicating predominantly lithogenic origins. In contrast, Cd, Cu, Mn, Pb, and Zn were characterized by elevated non-residual fractions (65%). The exchangeable fractions were particularly high for Cd (26%) and Mn (36%). Principal component analysis (PCA) of total concentrations identified three distinct metal groups: As, Cr, Ni, and V associated with natural crustal sources; Cd, Pb, and Zn affected by industrial emissions; and Cu related to port activities. PCA of non-residual fractions separated the sources more clearly, with samples clustering more distinctly according to their origins. The modified comprehensive potential ecological risk index (MRI) was highest in Jinhae (428), indicating considerable risk, and Cd contributed 80.8% of the MRI across all bays. Bioavailable ecological risks were high at five stations in Jinhae and one station in Busan. These severe site-specific pollution patterns indicate the need for remediation efforts in these industrial bays.