Sinking fluxes of 210Pb and 210Po in the deep basin of the northern South China Sea

Publication date: August 2017
Source:Journal of Environmental Radioactivity, Volume 174
Author(s): Ching-Ling Wei, Chao-Yuan Chia, Wen-Chen Chou, Wen-Huei Lee
Vertical fluxes of total mass (Fmass), particulate organic carbon (FPOC), particulate inorganic carbon (FPIC), ²¹⁰Pb (FPb-210), and ²¹⁰Po (FPo-210) were determined by sediment traps deployed at two depths, 2000 m and 3500 m, at SEATS (South East Asian Time-series Study, 116°00°E, 18°00°N) in the northern South China Sea during June 2008–June 2009. The Fmass ranges from 12.2 to 55.1 mg m⁻² d⁻¹ and from 89.3 to 250.8 mg m⁻² d⁻¹, at 2000 m and 3500 m, respectively, and shows seasonal and inter-annul variation. The temporal variation of FPOC, FPIC, and FPb-210 were in phase with the Fmass, which was coupled with the seasonal cycles of primary production in the euphotic layer. The FPb-210 ranges from 5 to 48 dpm m⁻²d⁻¹ and from 38 to 105 dpm m⁻²d⁻¹, at 2000 m and 3500 m, respectively. Contrasting with ²¹⁰Pb, the FPo-210 shows poor correlation with Fmass. The FPo-210 ranges from 3 to 146 dpm m⁻²d⁻¹ and from 50 to 309 dpm m⁻²d⁻¹, at 2000 m and 3500 m, respectively. Episodic events of the settling of biological particles from the surface layer and the regeneration processes the deep layer control the ²¹⁰Po removal in the water column of the South China Sea. Strong correlations of the flux and source ratio of ²¹⁰Pb, (F/P)Pb-210, and the particulate carbon fluxes were found, which give relationships of FPOC (μg cm⁻²y⁻¹) = 26.8 + 371.0 (F/P)Pb-210 and FPIC (μg cm⁻²y⁻¹) = −1.4 + 533.1 (F/P)Pb-210.



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