Kaijun Su a, Jinzhou Du a, *, Mark Baskaran b and Jing Zhang a State Key Laboratory of Estuarine and Coastal Research, East China Normal University, Shanghai , P.R.China b Department of Geology, Wayne State University, Detroit, Michigan, , USA a State Key Laboratory of Estuarine and Coastal Research, East China Normal University, Shanghai , P.R.China b Department of Geology, Wayne State University, Detroit, Michigan, , USA 210 Po and 210 Pb disequilibrium of the PN section in the East China Sea 1

Chapter 1 Introduction  The time scale of processes in the estuary/coast/ocean can be evaluated with different half-life time radionuclides;  Dissolved Ra/Rn isotopes, is one of powerful tools to study the materials diffusion process (i.e. nutrient offshore diffusion and nutrient discharge with submarine groundwater discharg,SGD )  Particle-active radionuclides (i.e. 210 Po/ 210 Pb, and 7 Be) can be as tracers in dynamics of suspended particulate matter (SPM), POC and the concerned particle-active pollutions(POPs, PAH) Behaviors of natural radionuclides in marine environment State Key Laboratory of Estuarine and Coastal Research, East China Normal University

Sources of 210 Po and 210 Pb in the coastal waters Cycling of 210 Po, 210 Pb in coastal waters (modified from Lin and Chung, 1991) Pb sources: Atmospheric precipitation; decay from 226 Ra in the water and sediment 210 Po sources: decay from 210 Pb The half-life and affinities with particles are different between 210 Po and 210 Pb — 210 Po and 210 Pb disequilibria to trace oceanographic processes State Key Laboratory of Estuarine and Coastal Research, East China Normal University

Euphotic layer 210 Po/ 210 Pb disequilibrium 5 For example: 210 Po/ 210 Pb to assessing POC fluxes 234 Th/ 238 U disequilibrium Euphotic layer State Key Laboratory of Estuarine and Coastal Research, East China Normal University

5 Why? PN section of the East China Sea Complex of water mass structures 0.5 Gt terrestrial particulate matter(Wang, 2008) and 2-5 Mt organic matter (Wu et al., 2007) from the Changjiang river to the ECS every year. Mean water depth = 370 m Two major sources of nutrients upwelling of the Kuroshio Current’s subsurface waters (Chen et al., 1996) and the Changjiang (Yangtze) River (due to its tremendous river runoff) State Key Laboratory of Estuarine and Coastal Research, East China Normal University

The atmospheric deposition fluxes of 210 Po and 210 Pb Summer Autumn Winter Spring Summer Autumn Winter Spring In winter, there is a high correlation between the activities and rainfall. In spring, the pair possibly have different scavenging mechanisms. Correlation coefficients State Key Laboratory of Estuarine and Coastal Research, East China Normal University

The properties of Riverine input The particulate species are dominate, the same trend with TSM. The Ratio in dissolved phase: Compared with the ratio of deposition(0.22), there is another source of the excess 210 Po, possibly from the organic contaminate in the river water Yangtze River State Key Laboratory of Estuarine and Coastal Research, East China Normal University

8 Cruise time: Oct, 2013 Sampling sites: A CTD-Rosette assembly with Niskin bottles Sampling volume: 20 L 19.90~25.34 ° C 32.08~34.76 State Key Laboratory of Estuarine and Coastal Research, East China Normal University T-S of PN section of the East China Sea

9 3.33~167 mg L ~41.75 μmol C L -1 State Key Laboratory of Estuarine and Coastal Research, East China Normal University POC and TSM of PN section of the East China Sea

10 Dissolved 210 Po (DPo) 、 210 Pb (DPb) and their ratio distribution at PN section State Key Laboratory of Estuarine and Coastal Research, East China Normal University

11 Particulate 210 Po (PPo) 、 210 Pb (PPb) and their ratio distribution at PN section State Key Laboratory of Estuarine and Coastal Research, East China Normal University

12 State Key Laboratory of Estuarine and Coastal Research, East China Normal University Total 210 Po (TPo) 、 210 Pb (TPb) and their ratio distribution at PN section

13 The positive correlation between different phase of 210 Po and 210 Pb and POC concentration was found, In different phase, 210 Pb was more affinities with POC than 210 Po. Radioactivities vs POC in the PN section of ECS

14 State Key Laboratory of Estuarine and Coastal Research, East China Normal University (Kd) vs TSM in the concerned seas

15 State Key Laboratory of Estuarine and Coastal Research, East China Normal University Distribution coefficients (Kd) vs TSM in the concerned seas

One-dimension Scavenging Model Weiand Murray, 1994 Dissolv ed Particul ate Sinking with particles Scavenging rate J Po Removing rate P Po h 10 State Key Laboratory of Estuarine and Coastal Research, East China Normal University Scavenging and remove of 210Po/210Pb in the PN section

17 Assumption:  Ignoring the atmospheric deposition of 210 Po (10% of the 210 Pb depositional fluxes) comparing with the in-situ production (Lambert et al., 1982; Kim et al., 1999)  Steady state — Ignoring the physical process The vertical export fluxes of 210 Po 、 POC 、 PON in the PN section of the ECS in fall Statio n Laye r (m) Bq m -2 a -1 mg C m -2 d -1 mg N m -2 d -1 C C C C C Mean State Key Laboratory of Estuarine and Coastal Research, East China Normal University POC fluxes in the PN section

18 Using One-dimension Steady state Scavenging Model to estimate the fluxes of 210 Po, the effect of physical process always can’t be ignored. If we consider the impact of the runoff caused by Changjiang River flushing into the seawater. Station Layer (m)Bq m -2 a -1 C C C C C V=0 that POC fluxes would be increase Advection process impacts on the Po export flux

MethodsReferncesExport layer/m Depth/ m POC export flux /mg C m -2 d -1 Cruise time Sediment traps Huang et al., Aug Th/ 238 U disequilibrium Huang et al., Aug Th/ 238 U disequilibrium Bi et al., May Po/ 210 Pb disequilibrium Bi et al., Oct Po/ 210 Pb disequilibrium This study4024.6Oct POC export flux in the East China Sea State Key Laboratory of Estuarine and Coastal Research, East China Normal University

20 State Key Laboratory of Estuarine and Coastal Research, East China Normal University Third International Conference on Po and Radioactive Pb Isotopes(INCO-PoPb-2015) ， October11-14,2015 ， Kusadası,Turkey POC export flux in the other Sea(s)

21 Summary and future work  The distribution of total 210 Po/ 210 Pb was opposite to that of POC along PN section in Fall 。 Generally speaking ， the export flux of POC was higher at the nearshore than the open sea  At PN section, The average residence time of D 210 Po 、 P 210 Po and T 210 Po in the PN section of ECS in fall was 0.52, 0.32 and 0.85 a, respectively.  A simple steady state box model-based export fluxes POC and PON out of the upper waters were found to be 24.6 mg C m -2 d -1 and 26.7 mg N m -2 d -1, respectively, with a decreasing trend of POC export fluxes with increasing offshore distance.  If we consider the impact of the runoff caused by Changjiang River flushing into the seawater, the POC fluxes would be increase.  Futrue work ： Modeling… State Key Laboratory of Estuarine and Coastal Research, East China Normal University

Any questions are welcome! Acknowledgements This research was supported by the the Ministry of Science and Technology of China (No: 2011CB ）.