Occurrence, Distribution, and Fate of Polychlorinated Biphenyls (PCBs) in Multiple Coral Reef Regions from the South China Sea: a Case Study in Spring-summer

Abstract Concentrations of 24 PCBs were simultaneously determined in air, seawater, and corals from the South China Sea (SCS) in spring-summer for understanding their distribution and fate in multiple coral reef regions. The ∑24PCBs (6.8 – 294 pg m-3) were mainly influenced by air mass origins in air samples. Southeast monsoon caused higher ∑24PCBs (mean: 61 pg m-3) than the southwest (mean: 19 pg m-3). ∑24PCBs in seawater (2.8 – 7.7 pg L-1) was equally distributed from the nearshore to offshore regions under low flow velocity and swirling state of the ocean current. Significantly higher air-water gas exchange deposition fluxes (3.5 – 29 ng m-2 d-1) than dry deposition (0.14 – 2.0 ng m-2 d-1) indicated that diffusion of PCBs from the atmosphere into seawater was the governing process in the SCS. PCBs in corals are strong bioaccumulative (Log BAFs: 2.49 – 7.86). The distribution of ∑24PCBs in coral tissues (nd – 42.9 ng g-1 dw) was significantly correlated with that in air samples, suggesting PCBs may have a migration pattern of atmosphere-ocean-corals in the SCS. Compared to a previous risk assessment study, the ∑24PCBs in corals from the SCS may cause potential risks to corals by reducing zooxanthellae density, chlorophyll-a (Chl-a) and chlorophyll-C2 (Chl-C2) in corals.