The benthic boundary layer (BNL) largely regulates the source and fate of some elements in the ocean. However, the processes occurred in BNL have been poorly understood due to the very dynamic environments. Here, radioactive ²¹⁰Po and ²¹⁰Pb were analyzed, together with the total particulate matter (TPM), particulate organic carbon and nitrogen (POC and PN), and particulate black carbon (PBC), to examine the sediment resuspension and its influence on the cycling of particulate carbon in the northern South China Sea. A line of evidence, including the elevated TPM content, lower POC/TPM signals, and higher ²¹⁰Po/²¹⁰Pb ratios in the bottom water, evidenced the prevalent sediment resuspension on the northern shelf. The deficits of ²¹⁰Po in the water column overall balanced the excess of ²¹⁰Po in sediments, indicating the locally resuspension and supporting the application of the non-physical mass balance model of ²¹⁰Po-²¹⁰Pb. Based on a proposed resuspension-including model, the resuspension flux of ²¹⁰Po varied from 4 dpm m^-2 d^-1 to 30 dpm m^-2 d^-1 with an average of 13 ±7 dpm m^-2 d^-1 (mean ± SD), accounting for 25% to 70% of the total ²¹⁰Po sinking fluxes (avg.: 43 ± 6%). This magnitude indicated that resuspension plays an important role in regulating the sinking and fate of particulate matter in the shelf region. Combing particulate components, the estimated resuspension fluxes of POC and PBC varied from 0.9 to 12.7 mmol m^-2 d^-1 and from 0.10 to 1.61 mmol m^-2 d^-1, averaging 3.8 ± 1.8 and 0.44 ± 0.26 mmol m^-2 d^-1, respectively. The resuspended PN flux averaged 0.4 ± 0.8 mmol m^-2 d^-1. The preliminary study highlighted the overlooked recycling of organic matter in the BNL in the South China Sea. To learn the capacity of the South China Sea in sequestering carbon dioxide, the processes in the BNL are crucial to constrain carbon cycling and other trace elements.

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