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Microplastic distribution surveys centered on Korea’s Gwangyang Bay and southern coastal waters. Gwangyang Bay seawater averaged 3.17 ± 1.23 particles/L, and sediments averaged 462.4 ± 143.9 particles/kg. The southern coastal seawater averaged 0.10 ± 0.09 particles/L, and the sediments averaged 50.6 ± 29.7 particles/kg. Microplastics flowing from land, through physical modeling of ocean currents in Gwangyang Bay and southern coastal waters, pass through the Yeosu Strait and flow into the southern coastal waters. At the same time, it is judged that the southern coastal waters showed somewhat lower abundance than the Gwangyang Bay waters because they move toward the Korean Strait due to the Jeju warm current water and Tsushima current water, strongly generated in summer. In addition, the seawater microplastic abundance showed a higher abundance than that on the site adjacent to the land in the southern coastal waters, which is the study area. On the other hand, the results for sediment microplastic abundance were opposite to the surface seawater microplastic results. Therefore, it is judged that entering one source of pollution does not affect the distribution of microplastics in Gwangyang Bay and southern coastal waters, but rather this occurs in different forms.

In this study, a comprehensive investigation was performed to understand the overall occurrence, relative distribution, and bioaccumulation of seven different groups of POPs, comprising 27 polybrominated diphenyl ethers (PBDEs), 76 polychlorinated biphenyls (PCBs), 23 organochlorine pesticides (OCPs), three hexabromocyclododecanes (HBCDs), and 13 perfluoroalkyl substances (PFASs) as legacy POPs, and 41 polychlorinated naphthalenes (PCNs) and 24 short-chain chlorinated paraffins (SCCPs) as emerging POPs, by monitoring crucian carp, sediment, and river water in the freshwater system. Among the targeted POPs, SCCPs were predominant in sediment and crucian carp (more than 95%), while a dominance of PFASs was observed in river water (92%). Principal component analysis revealed four different groups/patterns of POPs in all media: one for PBDEs, PCBs, and OCPs, another for HBCDs and PFASs, and the two others for PCNs and SCCPs. Also, sexually dimorphic growth-dependent accumulation of legacy POPs was observed in crucian carp such that POPs concentration increased with increasing fish size and males recorded significantly higher levels of POPs compared to females. Keywords: Persistent organic pollutants, Overall monitoring, Relative distribution, Growth-dependent accumulation, Maternal transfer

An estimation of the appropriate load reduction from point sources in Kwangyang Bay, Korea is studied using an eco-hydrodynamic model. The results suggested that wastewater discharge was the dominant pollution source of chemical oxygen demand (COD), nitrogen (TN), and phosphorus (TP) in Kwangyang Bay.