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Using rare earth elements to constrain particulate organic carbon flux in the East China Sea

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ABSTRACT

Fluxes of particulate organic carbon (POC) in the East China Sea (ECS) have been reported to decrease from the inner continental shelf towards the outer continental shelf. Recent research has shown that POC fluxes in the ECS may be overestimated due to active sediment resuspension. To better characterize the effect of sediment resuspension on particle fluxes in the ECS, rare earth elements (REEs) and organic carbon (OC) were used in separate two-member mixing models to evaluate trap-collected POC fluxes. The ratio of resuspended particles from sediments to total trap-collected particles in the ECS ranged from 82–94% using the OC mixing model, and 30–80% using the REEs mixing model, respectively. These results suggest that REEs may be better proxies for sediment resuspension than OC in high turbidity marginal seas because REEs do not appear to undergo degradation during particle sinking as compared to organic carbon. Our results suggest that REEs can be used as tracers to provide quantitative estimates of POC fluxes in marginal seas.

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Sampling locations in the East China Sea.Blue dots represent the surface sediment stations and the sediment trap deployment station in summer in 2013. Station E1 was in November 2013. (The map was created using Surfer software v.12 Surfer (Golden Software) http://www.goldensoftware.com/home/terms-of-use).
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f1: Sampling locations in the East China Sea.Blue dots represent the surface sediment stations and the sediment trap deployment station in summer in 2013. Station E1 was in November 2013. (The map was created using Surfer software v.12 Surfer (Golden Software) http://www.goldensoftware.com/home/terms-of-use).

Mentions: The East China Sea (ECS) (Fig. 1) has been regarded as a sink (10–30 Mt C yr−1, where 1 Mt = 1012 g) for atmospheric carbon dioxide based on observations of CO2 air–sea exchange7891011. Model-estimated organic carbon (OC) burial on the broad ECS shelf (0.4 × 106 km2) is 7–10 Mt C yr−1. The net imbalance of OC fluxes in the ECS amounts to approximately 10–20 Mt C yr−1 based on the difference between this input and burial. The estimated amount of OC transported offshore, which ranges from 2 to 12 Mt C yr−1 412, seems to be insufficient to account for the deficit, which raises the question as to the fate of the extra carbon. Sinking particle fluxes of POC have been calculated in the inner and middle shelves of the ECS131415, but direct observations of POC fluxes are limited11315.


Using rare earth elements to constrain particulate organic carbon flux in the East China Sea
Sampling locations in the East China Sea.Blue dots represent the surface sediment stations and the sediment trap deployment station in summer in 2013. Station E1 was in November 2013. (The map was created using Surfer software v.12 Surfer (Golden Software) http://www.goldensoftware.com/home/terms-of-use).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5037389&req=5

f1: Sampling locations in the East China Sea.Blue dots represent the surface sediment stations and the sediment trap deployment station in summer in 2013. Station E1 was in November 2013. (The map was created using Surfer software v.12 Surfer (Golden Software) http://www.goldensoftware.com/home/terms-of-use).
Mentions: The East China Sea (ECS) (Fig. 1) has been regarded as a sink (10–30 Mt C yr−1, where 1 Mt = 1012 g) for atmospheric carbon dioxide based on observations of CO2 air–sea exchange7891011. Model-estimated organic carbon (OC) burial on the broad ECS shelf (0.4 × 106 km2) is 7–10 Mt C yr−1. The net imbalance of OC fluxes in the ECS amounts to approximately 10–20 Mt C yr−1 based on the difference between this input and burial. The estimated amount of OC transported offshore, which ranges from 2 to 12 Mt C yr−1 412, seems to be insufficient to account for the deficit, which raises the question as to the fate of the extra carbon. Sinking particle fluxes of POC have been calculated in the inner and middle shelves of the ECS131415, but direct observations of POC fluxes are limited11315.

View Article: PubMed Central - PubMed

ABSTRACT

Fluxes of particulate organic carbon (POC) in the East China Sea (ECS) have been reported to decrease from the inner continental shelf towards the outer continental shelf. Recent research has shown that POC fluxes in the ECS may be overestimated due to active sediment resuspension. To better characterize the effect of sediment resuspension on particle fluxes in the ECS, rare earth elements (REEs) and organic carbon (OC) were used in separate two-member mixing models to evaluate trap-collected POC fluxes. The ratio of resuspended particles from sediments to total trap-collected particles in the ECS ranged from 82–94% using the OC mixing model, and 30–80% using the REEs mixing model, respectively. These results suggest that REEs may be better proxies for sediment resuspension than OC in high turbidity marginal seas because REEs do not appear to undergo degradation during particle sinking as compared to organic carbon. Our results suggest that REEs can be used as tracers to provide quantitative estimates of POC fluxes in marginal seas.

No MeSH data available.


Related in: MedlinePlus