Using multi-radiotracer techniques to better understand sedimentary dynamics of reworked muds in the Changjiang River estuary and inner shelf of East China Sea

Sulfur and iron diagenesis in temperate unsteady sediments of the East China Sea inner shelf and a comparison with tropical mobile mud belts (MMBs)

“…A recent compilation of excess 210 Pb profiles for the ECS sediments suggests more intense reworking of surface sediments in the inner shelf than in the outer shelf [ Xu et al ., ], and MMBs are a common feature in the Yangtze estuary and along the ECS inner shelf, mainly as a result of physical reworking [ Aller et al ., ; DeMaster et al ., ; Xu et al ., ]. Thicknesses of MMB in the delta‐front estuary are between 20 and 40 cm, reaching 60–100 cm only locally; the thicknesses along the Zhejiang‐Fujian coast mud belt are typically between 10 and 30 cm and rarely up to 50 cm [ Xu et al ., ]. The thicknesses of the ECS‐MMB are generally much less than those in the Amazon shelf (50–200 cm) but similar to those in the Gulf of Papua (10–30 cm) [ Aller and Blair , ; Aller et al ., , , ; R. C. Aller et al , ].…”

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

“…With the increasing distance from land, the dominant unimodal of the frequency curves for sedimentary grain size changes from the ranges of 0–4 φ in the river channel to 4–6 φ in the mixing zone, and to 6–8 φ in the estuary. Furthermore, the low 210 Pb xs activity (42.1 ± 28.9 Bq kg −1 ) in surface sediments is strong evidence that repetitive reworking and setting processes are occurring in this region (Crockett et al, ; Xu et al, ).…”

“…The analyses of variations in sedimentary grain size, X‐radiographs, and 210 Pb xs show that the temporal variations in C org profiles could be associated with intense physical and/or biological processes, and the 210 Pb xs profiles and X‐radiographs exhibit evidence of the presence of reworked sediments. More specially, the absence of a logarithmic decrease with depth and the low 210 Pb xs activity for cores C1, C2, C3, C4, C5, and C7 indicate that no net accumulation has not occurred in the time interval captured by these cores (Miller & Kuehl, ), or increased inputs of eroded material from other sites (Sun et al, ; Xu et al, ). 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, ).…”

“…Sediments in core C3 not only display a coarsening trend with decreasing depth, but they are also enriched in δ 13 C org and δ 15 N; this reflects the significant reduction in terrestrial particles and associated C org loading. In comparison, the reversed 210 Pb xs in cores C1 and C7 indicate that the erosion and advection of older or aged sediments from other sites is caused by sedimentation, resuspension, and winnowing processes (Crockett et al, ; Xu et al, ); coarse particle‐associated low C org that is preferentially deposited could thus be responsible for these deposition patterns. It is also possible that the increased sedimentary C org in core C2 is related to biological activities induced by the remobilization of fine‐grained particles.…”

“…Filled green and yellow circles represent surface and box core sediment sampling sites, respectively. YSCC = Yellow Sea Coastal Current; YDW = Yangtze Diluted Water; ZFCC = Zhejiang‐Fujian Coastal Current; TWWC = Taiwan Warm Current (Circulation systems in panel (b) are modified according to Liu et al, , and Xu et al, ); TGD = Three Gorges Dam; DJK = Danjiangkou Dam.…”