Rapid response of the Changjiang (Yangtze) River and East China Sea source-to-sink conveying system to human induced catchment perturbations

Gao, Jian; Shi, Yong; Song, Hui; Kettner, Albert J.; Yang, Yang; Jia, Jian Jun; Wang, Ya Ping; Jun, Li; Chen, Yining; Zou, Xinqing; Gao, Shu

doi:10.1016/j.margeo.2019.05.003

Cited by 52 publications

(22 citation statements)

References 70 publications

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“…With respect to the significant decrease in SARs in the distal mud of the Yangtze, relating to the decreased fluvial sediment supply from the Yangtze River, there is currently no direct evidence to indicate that a significant accretion‐erosion transition of sedimentary C org has occurred in this region. This result is in accordance with previously mentioned findings that a stable environment in the distal mud of the Yangtze River is beneficial for the accumulation of sedimentary C org (Cao et al, ), trace metals (Sun et al, ), and 210 Pb (Gao et al, ). The differences between the depositional states of sedimentary C org in the proximal and distal deposits of the Yangtze delta may be explained by the differences in the fine‐grained sediment supply.…”

Section: Discussionsupporting

confidence: 93%

“…This contrasts with the high SARs (2–5.4 cm year −1 ) and low mixing coefficients occurred in the YRE prior to the 1980s (DeMaster et al, ; Mckee et al, ; Nittrouer et al, ). It is of note that similar results were reported by Gao et al (, ), based on the 210 Pb xs profiles in 73 sediment cores; their study found the occurrence of sediment redistribution in the YRE after 2003 (TGD) in response to intensified material mixing processes, and their results further indicated that the decreased sediment load from the Yangtze River probably altered the natural balance between the hydrodynamics and the sediment supply (Dai & Lu, ). These results show that the occurrence of low SARs and evidence of energetic physical reworking has resulted in redistribution of fine‐grained particles and associated C org in these settings.…”

Section: Discussionsupporting

confidence: 84%

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Fate of Organic Carbon Burial in Modern Sediment Within Yangtze River Estuary

et al. 2020

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Large river‐dominated margins play a potential key role in regulating global carbon cycle and budget due to high terrestrial organic carbon (Corg) inputs and sediment accumulation rates. Here bulk elements (Corg and TN), isotopic compositions (δ13Corg and δ15N), radioisotope 210Pb, sedimentary grain size, pH, Eh, and physicochemical properties were analyzed on samples from the Yangtze River Estuary to determine the mechanism involved in transporting sedimentary Corg offshore. In addition, nine box‐cores were analyzed to further reveal the potential effects of the declining sediment load on the modern depositional pattern of Corg. The statistical analyses indicate that the hydrodynamically driven sediment composition exerts a significant control on the transport, mobilization, and accumulation of sedimentary Corg from the river to the estuary, with respect to the redistribution of fine‐grained sediments. Furthermore, X‐radiographs and 210Pb indicate that reworked environment dominates carbon burial in the Yangtze proximal deposit, while a stable sedimentary environment of Corg (3.50–5.58 g cm−2 year−1) is observed in the Yangtze distal mud. Notably, the enhanced erosional inputs that contain terrestrial plant debris (mainly the coarse fractions) have tended to become important sources for Corg. Although reworked sediments in the Yangtze River Estuary are frequently exposed to oxygen during physical and biological processes, there appears to be a high potential for long‐term sedimentary Corg storage, due to its association with sediment particles (mainly the clay fractions) that provide physical protection against its degradation.

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Section: Discussionsupporting

confidence: 93%

Section: Discussionsupporting

confidence: 84%

Fate of Organic Carbon Burial in Modern Sediment Within Yangtze River Estuary

et al. 2020

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“…Previous studies have demonstrated that surface sediment grain size in the CSD has been obviously coarsened due to human‐induced catchment changes and that the CSD has shifted from accretion to erosion (Dai et al, ; Luo et al, ; Yang et al, ). Grain‐size variations from 1982–2014 showed that sediment coarsening occurred not only in the Changjiang Estuary but had also expanded to the entire estuarine‐inner shelf areas (Gao et al, ). Previous studies also demonstrated that material deposited in the estuarine‐inner shelf regions of the ECS was likely to lag behind changes in the Changjiang River catchment by about 3 years (Gao et al, ; Hu et al, ).…”

Section: Resultsmentioning

confidence: 99%

Shifts in the Distribution and Fate of Sedimentary Polycyclic Aromatic Hydrocarbons Within the Estuarine‐Inner Shelf Areas of the East China Sea: Response to Human‐Induced Catchment Change

et al. 2020

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Human-induced changes in river catchments, such as damming, can affect estuarine depositional settings and further affect the transport of sediments and associated pollutants. Polycyclic aromatic hydrocarbons (PAHs) in surface sediments from the East China Sea (ECS) at two time nodes (2006 and 2018) were compared to understand the response of PAHs to human-induced catchment changes. PAH concentrations in the ECS ranged from 8-414 ng g −1 (dry weight), with a mean value of 112 ± 77 ng g −1 , relatively low than that in 2006 (38-308 ng g −1 , with a mean of 122 ± 60 ng g −1 ). Sharp decreases in sediment loads have triggered erosion in subaqueous delta and changed the distribution of sediment components, which may eventually influence the distribution pattern of PAHs. The obvious spatial differentiation of PAHs between 2006 and 2018 suggested that the depositional center of PAHs shifted from the estuary to the inner shelf area. PAH deposition patterns in the ECS were primarily influenced by riverine input before 2006 but are now dominated by winnowing processes related to long-distance transport due to sharply decreased sediment loads. Dam construction in the river catchment intercepted large amounts of sediments and PAHs, shifting the Changjiang-derived PAH depositional center from the ocean to reservoirs. Overall, depositional patterns of PAHs in the ECS were largely altered by human-induced catchment changes, which may cause significant impacts on the region's biogeochemical cycles and ecosystem health. Plain Language SummaryCoastal oceans are usually considered important sinks of terrestrial materials, especially river-dominated coastal margins. However, river-derived terrestrial materials have decreased drastically in the last several decades worldwide, due to intensified human activities that have changed the local sedimentary environment. In this study, changes in the surface sediment grain size within the East China Sea from 2006 to 2018 indicated that the sedimentary environment in this region was clearly altered. Similarly, the distributions and compositions of PAHs in surface sediments changed from 2006 and 2018. Based on combined analysis of grain size and PAHs, we found that PAH dynamics in this region were primarily influenced by riverine inputs before dam construction in the Changjiang (Yangtze) River basin but are now dominated by winnowing processes related to long-distance transport due to sharply decreased sediment loads. Therefore, intensified human-induced catchment changes have significant influenced the fate of PAHs in the East China Sea.

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“…Sediment load in the upper and middle Yangtze had been decreasing along with the decreasing water discharge, which is possibly due to water diversion for intensive agriculture (Chen et al 2001). Gao et al (2019) analyzed the siltation and erosion state of the estuary-shelf depositional systems by combining the spatial distribution of deposition rates, types of vertical distribution profiles of 210 Pb activity, and distribution of grain size composition in surficial sediments and discussed the response intensity and timing of the depositional system in the Yangtze subaqueous delta and mud belt area. Their results showed that the abrupt reduction in the sediment discharge to the estuary disturbed the equilibrium among the estuarine, coastal, and shelf depositional systems following operation of the Three Gorges Dam in 2003, modifying the siltation-erosion balance and seabed sediment types (Gao et al 2019).…”

Section: Discussionmentioning

confidence: 99%

Provenance changes in fine detrital quartz in the inner shelf sediments of the East China Sea associated with shifts in the East Asian summer monsoon front during the last 6 kyrs

Wang

Tada

Zheng

et al. 2020

Prog Earth Planet Sci

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The inner shelf sediments of the East China Sea (ECS) preserve valuable information regarding climatic changes on land through detrital material discharged from large rivers, particularly the Yangtze River. In this paper, we examine the provenance changes of fine-grained detrital quartz preserved in the sediment of the MD06-3040 core retrieved from the mud belt on the inner shelf of the ECS during the last 6 kyrs. The provenance of the fine silt fraction (4-16 μm) of the sediments, which is considered to represent the suspended particulate matter (SPM) from the Yangtze River, is estimated based on the electron spin resonance (ESR) signal intensity and crystallinity index (CI) of quartz. By comparing the ESR signal intensity and CI of quartz in the fine silt fraction of sediments to those from different parts of tributaries in the modern Yangtze River drainage, we can discriminate the SPM sourced from the northwestern and southeastern tributaries of the Yangtze River. Shifts in the East Asian summer monsoon (EASM) front are monitored by changes in the main precipitation areas which are manifested as changes in source rock ages and types implied from the ESR signal intensity and CI of quartz in the fine silt fraction of the studied sediments discharged from the Yangtze River. Temporal changes in provenance of the fine silt fraction through time suggest that shifts in the main location of EASM precipitation (most likely representing the EASM front) occurred at a multi-centennial-to-millennial scale with the deepest northwestward penetration of the EASM precipitation front (an enhanced EASM) occurring during the period 3.5-2.0 kyr BP and a southeastward retreat (a weak EASM) occurring during the periods 6.0-4.1 and 2.0-0 kyr BP.

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Rapid response of the Changjiang (Yangtze) River and East China Sea source-to-sink conveying system to human induced catchment perturbations

Cited by 52 publications

References 70 publications

Fate of Organic Carbon Burial in Modern Sediment Within Yangtze River Estuary

Fate of Organic Carbon Burial in Modern Sediment Within Yangtze River Estuary

Shifts in the Distribution and Fate of Sedimentary Polycyclic Aromatic Hydrocarbons Within the Estuarine‐Inner Shelf Areas of the East China Sea: Response to Human‐Induced Catchment Change

Provenance changes in fine detrital quartz in the inner shelf sediments of the East China Sea associated with shifts in the East Asian summer monsoon front during the last 6 kyrs

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