Fig 4 - uploaded by Zhi-Gang Chen
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The distribution of 226 Ra (Bq/m 3 ) in the surface seawater of Prydz Bay and its adjacent sea area ▲, • represent the sampling stations of the 13 th and the 19 th CHINARE respectively, the numbers near them represent their 226 Ra specific activity; numbers in italics denote mean water depths (m).
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During the 13th (1996–1997) and the 19th (2002–2003) Chinese National Antarctica Research Expeditions, we collected 60 discrete surface seawater samples along the cruise from the Chanjiang River (Yangtze) estuary (30°59′S, 122°26′E) through Taiwan Strait, the South China Sea, and the Eastern Indian Ocean to Prydz Bay, Antarctica (69°10′S, 74°30′E),...
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Citations
... We examined Ra behavior from the CJR system to the ECS by combining data from the drainage basin, the CJE and the ECS in the literature (Elsinger and Moore, 1984;Nozaki et al., 1991;Zhang, 2007;Men et al., 2010;Chen et al., 2011;Xu, 2011;Gu et al., 2012). Overall, the 228 Ra activity concentrations are higher than 226 Ra throughout the continuum from river to ocean. ...
... Water samples are collected by utilizing a submerged pump at~0.5 m below the surface water for the measurement of radium isotopes (19 stations) and nutrients (32 stations). Additionally, datasets from Nozaki et al. (1991), Zhang (2007), Liu et al. (2010a), Men et al. (2010), Chen et al. (2011), andXu (2011) are collected to extend the study area. The high Ra data points much close to the Yangtze and Qiantang River estuary are excluded. ...
Advection and diffusion are recognized as two important processes in the mixing and exchange of coastal waters and associated nutrients. In this study, Ra isotopes (226Ra and 228Ra) are surveyed in the East China Sea (ECS) to investigate the advection and diffusion processes. Both one-dimensional (1D) and two-dimensional (2D) advection–diffusion models are applied to estimate the cross-shore and along-shore eddy diffusivities and advection velocities. The advection velocity is basically small in magnitude, suggesting its secondary role in transport. The cross-shore 1D model gives promising results on the diffusivity by 4.93 × 105 cm2 s− 1. Sensitivity analysis shows that the cross-shore diffusivity is less sensitive whereas the along-shore diffusivity is quite sensitive to advection velocity. Introducing benthic Ra flux in the model decreases the eddy diffusivity. A quisi-2D method generates an along-shore diffusivity by 2.50 × 107 cm2 s− 1, which is within the sensitivity range thus reliable. Based on the estimated diffusivity and advection velocities, we calculate the offshore nutrient fluxes (mol m− 2 d− 1) by 0.44 for dissolved inorganic nitrogen (DIN), 0.012 for dissolved inorganic phosphorous (DIP) and 0.26 for dissolved inorganic silicates (DSi). The along-shore fluxes (mol m− 2 d− 1) are 6.44 for DIN, 0.10 for DIP and 2.92 for DSi. Compared with nutrient inputs from other sources, e.g. river, sediments, and ocean, the horizontal mixing-derived nutrient fluxes contribute only < 4% N, < 1% P and < 2% Si to the nutrient requirements for primary productivity in the study area. This study stresses the role of advection and diffusion in the material transport, i.e. nutrients and stoichiometry in the ECS.
