title: 210Po and210Pb disequilibrium at the PN section in the East China Sea.
abstract: Lead-210 and210Po have been widely used as tracers for quantifying particulate scavenging in the upper layer of the oceanic water column. In this study, we investigated the210Po/210Pb disequilibrium in the water column of the PN section in the East China Sea (ECS) during autumn 2013. In most of the water column, a deficiency of210Po was observed with respect to its parent nuclide210Pb (i.e., a210Po/210Pb activity ratio < 1.0). The (210Po/210Pb)dissolved, (210Po/210Pb)particulateand (210Po/210Pb)totalactivity ratios ranged from 0.29 to 0.71 (average: 0.53 ± 0.13, n = 27), 0.31 to 1.42 (average: 0.70 ± 0.27, n = 27) and 0.22 to 0.62 (average: 0.50 ± 0.12, n = 27), respectively. The distribution coefficients (Kd) of210Po and210Pb were 12.1× 104ml g-1and 8.8× 104ml g-1, with an average (210Po/210Pb)totalactivity ratio of (0.50 ± 0.12, n = 27). However, over the continental shelf, planktonic detritus and fecal pellets appear to be the main carriers for210Po, which preferentially scavenges210Po and produces a lower (210Po/210Pb)totalactivity ratio (0.49 ± 0.12, n = 22) with a Kdfor210Po of 13.8× 104ml g-1in the water column. The variations in the fractionation factor (1.48 ± 0.66) of210Po/210Pb reveal distinct differences between the distribution and scavenging of210Po and210Pb by particulate matter in different marine environments: in the estuarine zone (a high turbidity area), terrigenous suspended particulate matter scavenges210Pb from the water column, while in areas dominated by biogenic particular matter,210Po is preferentially scavenged from the water column. Using the210Po/210Pb disequilibrium in the water column, we estimated the removal fluxes of POC from the upper waters downward to be 25.0 mg C m-2d-1, comparable to those in other marginal seas. Moreover, a decreasing trend of POC removal fluxes was observed with increasing distance offshore.
authors: State Key Laboratory of Estuarine and Coastal Research, East China Normal University, Shanghai 200062, PR China; Institute of Radiation Medicine, Chinese Academy of Medical Sciences and Peking Union Medical College, Tianjin 300192, PR China.
authors: Kaijun
authors: K
authors: Su
authors: State Key Laboratory of Estuarine and Coastal Research, East China Normal University, Shanghai 200062, PR China. Electronic address: jzdu@sklec.ecnu.edu.cn.
authors: Jinzhou
authors: J
authors: Du
authors: Department of Geology, Wayne State University, Detroit, MI 48202-3622, USA.
authors: Mark
authors: M
authors: Baskaran
authors: State Key Laboratory of Estuarine and Coastal Research, East China Normal University, Shanghai 200062, PR China.
authors: Jing
authors: J
authors: Zhang
mesh_terms: D002681:China; D007856:Lead Radioisotopes / Q000032:analysis*; D011059:Polonium / Q000032:analysis*; D011834:Radiation Monitoring; D014875:Water Pollutants, Radioactive / Q000032:analysis*
chemical_list: D007856:Lead Radioisotopes; D014875:Water Pollutants, Radioactive; D011059:Polonium
keywords: (210)Po/(210)Pb disequilibria; East China Sea; POC flux; Scavenging