Particulate Export of PAHs Firstly Traced by 210Po/210Pb Disequilibrium: Implication on the “Shelf Sink Effect” in the Arctic Ocean

Abstract

AbstractIn the changing Arctic Ocean, organic pollutants' transport and biogeochemical processes are strongly influenced by their particulate export on the broad continental shelf. To better evaluate the vertical particulate export of polycyclic aromatic hydrocarbons (PAHs), seawater samples were collected from the Bering Sea, Chukchi Sea, and Canada Basin with the first application of 210Po/210Pb disequilibrium during the summer of 2012. Dissolved PAHs (1.1–19 ng L−1, mean 5.2 ± 3.6 ng L−1) showed spatial distinctions, with high values on the Bering Shelf and low values in the Chukchi Sea, while particulate PAHs (1.0–12 ng L−1, mean 5.0 ± 3.5 ng L−1) showed high levels in the nutrient‐rich Bering Shelf Water layer. According to the 210Po/210Pb deficit on the Bering Shelf, the export fluxes of particulate PAHs ranged from 1,201 ± 276 to 3,650 ± 1,570 ng m−2 d−1, and their residence time ranged from 55 ± 23 to 133 ± 31 days. From the Bering Shelf to the Chukchi Sea, the decreased inventories of dissolved PAHs were positively related to their vertical particulate export fluxes (R2 = 0.62), suggesting the “Shelf Sink Effect” on PAHs.