Scavenging phenomenon elucidated from~(234)Th/~(238)U disequilibrium in surface water of the Taiwan Strait

摘要

Concentrations of dissolved (~(234)Th_d) and particulate (~(234)Th_p) ~(234)Th in surface water at 38 stations in the Taiwan Strait were determined for samples collected in May 2006. The spatial distribution of ~(234)Th in the Taiwan Strait is controlled by advective input of Kuroshio Branch Water via the Peng-Hu Channel and fast removal due to the high input of riverine particulates from the Cho-Sui River. A scavenging model involving physical transport was applied to the ~(234)Th_d and ~(234)Th_p data to estimate scavenging and removal rates of ~(234)Th. Estimated scavenging rate ranges from 32 to 703 dpm m~(-3) d~(-1) and the removal rate ranges from 24 to 560 dpm m~3 d~(-1). Using ~(234)Th as a proxy of particulate organic carbon, we estimate that the removal rate of POC from surface water of the Taiwan Strait ranges from 0.3 ± 1.5 mmol-C m~(-3) d~(-1) off southwestern Taiwan to 10.2 ± 3.5 mmol-C m~3 d~(-1) in the central Taiwan Strait.