Nearshore scavenging phenomenon elucidated by 234th/238u disequilibrium in the coastal waters off Western Taiwan

Wei, Ching-Ling; Tsai, Jing-Ru; Wen, Liang-Saw; Pai, Su‐Cheng; Tai, Jung-Hsiang

doi:10.1007/s10872-009-0014-z

Cited by 9 publications

(2 citation statements)

References 54 publications

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“…To understand the behavior of 234 Th in a dynamic environment, where advective transport may significantly control the distribution of 234 Th, the model should account for physical mixing processes (Benitez-Nelson et al 2000;Buesseler et al 2006). Similar to the model used by Wei et al (2009), assuming a steady-state, the mass balance of 234 Th d and 234 Th p are described by the following equations,…”

Section: Discussionmentioning

confidence: 99%

Scavenging Phenomenon Elucidated from 234Th/238U Disequilibrium in Surface Water of the Taiwan Strait

Wei¹,

Tsai²,

Hou³

et al. 2010

Terr. Atmos. Ocean. Sci.

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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.

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Section: Discussionmentioning

confidence: 99%

Scavenging Phenomenon Elucidated from 234Th/238U Disequilibrium in Surface Water of the Taiwan Strait

Wei¹,

Tsai²,

Hou³

et al. 2010

Terr. Atmos. Ocean. Sci.

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“…This unique distribution pattern observed over a large area along the west coast off Taiwan could be attributed to desorption of Cd from SPM transported by mountainous rivers. In general, SPM concentrations were higher in the northern regime (Wei et al 2009) and Cd tends to desorb from particles' surfaces in coastal waters when high Cl concentrations from seawater are present (Stumm and Morgan 1996), thus resulting in low particulate Cd concentrations (Fig. 4f).…”

Section: Sources Of Trace Metalsmentioning

confidence: 97%

Spatial and Temporal Distribution of Trace Metals (Cd, Cu, Ni, Pb, and Zn) in Coastal Waters off the West Coast of Taiwan

Jiann¹,

Wen²,

Wei³

2014

Terr. Atmos. Ocean. Sci.

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Surface water samples were collected along the west coast of Taiwan during two expedition cruises which represent periods of different regional climatic patterns. Information on hydrochemical parameters such as salinity, nutrients, suspended particulate matter (SPM), and Chlorophyll a concentrations were obtained, and dissolved and particulate trace metal (Cd, Cu, Ni, Pb, and Zn) concentrations were determined. Spatial variations were observed and the differences were attributed to (1) influence of varying extents of terrestrial inputs from the mountainous rivers of Taiwan to the coast, and (2) urbanization and industrialization in different parts of the island. Geochemical processes such as desorption (Cd) and adsorption to sinking particles (Pb) also contributed to the variability of trace metal distributions in coastal waters. Results showed temporal variations in chemical characteristics in coastal waters as a consequence of prevailing monsoons. During the wet season when river discharges were higher, the transport of particulate metals was elevated due to increased sediment loads. During the dry season, lower river discharges resulted in a lesser extent of estuarine dilution effect for chemicals of anthropogenic sources, indicated by higher dissolved concentrations present in coastal waters associated with slightly higher salinity.

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Terrestrial and marine POC export fluxes estimated by 234Th–238U disequilibrium and δ13C measurements in the East China Sea shelf

Zhong,

Huang,

Wang

et al. 2024

Biogeochemistry

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The use of 234Th–238U disequilibrium has been widely employed to estimate the sinking flux of particulate organic carbon (POC) from the upper sea and ocean. Here, the deficits of 234Th relative to 238U in the water column and the carbon isotope signature (δ13C) of POC in the East China Sea (ECS) Shelf were measured, which was used to distinguish the fraction of marine and terrestrial POC export fluxes. In the ECS Shelf, very strong deficits of 234Th relative to 238U were observed throughout the water column, with 234Th/238U activity ratios ranging from 0.158 ± 0.045 to 0.904 ± 0.068 (averaging 0.426 ± 0.159). The residence times of particle reactive radionuclide 234Th (τTh–T) in the ECS shelf water varied between 9 and 44 days, which is significantly shorter than that in the continental slope area or the basin area. This phenomenon indicates that there is a more rapid particle scavenging process in the ECS shelf water compared to the continental slope and basin upper water. By applying a two-end-member mixing model based on the δ13C, the fraction of terrestrial POC was estimated to be 0 to 74% (mean: 30 ± 22%) and the fraction of marine POC was in the range of 25% to 100% (mean: 70 ± 22%). Fluxes of marine and terrestrial POC settling to the seafloor exhibited significant spatial differences among different stations, ranging from 11 to 129 mmol C/m2/day and from 2.6 to 38 mmol C/m2/day, respectively. The averaged terrestrial POC fluxes in the southern and northern ECS Shelf were similar (~ 21 to 24 mmol C/m2/day), while the marine POC fluxes in the north (86 ± 37 mmol C/m2/day) were approximately four times higher than those in the south (26 ± 20 mmol C/m2/day). Interestingly, the estimated export flux of both marine and terrestrial POC were approximately one order of magnitude higher than the previously reported burial fluxes of POC (ranging from 1.1 ± 0.1 to 11.4 ± 1.1 mmol C/m2/day) in the underlying bottom sediments, indicating that the majority (> 90%) of both terrestrial and marine POC exported from the upper water column are degraded in the sediments of the ECS Shelf. This “carbon missing” phenomenon can greatly be attributed to rapid decomposition by other processes (including microbial reworking, cross-shelf transport, and possible consumption by benthic organisms). Our findings highlight the dynamic nature of carbon cycling in the continental shelf and the need for further research to understand these processes and improve carbon budget assessments.

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Nearshore scavenging phenomenon elucidated by 234th/238u disequilibrium in the coastal waters off Western Taiwan

Cited by 9 publications

References 54 publications

Scavenging Phenomenon Elucidated from 234Th/238U Disequilibrium in Surface Water of the Taiwan Strait

Scavenging Phenomenon Elucidated from 234Th/238U Disequilibrium in Surface Water of the Taiwan Strait

Spatial and Temporal Distribution of Trace Metals (Cd, Cu, Ni, Pb, and Zn) in Coastal Waters off the West Coast of Taiwan

Terrestrial and marine POC export fluxes estimated by 234Th–238U disequilibrium and δ13C measurements in the East China Sea shelf

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