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Fate of Organic Carbon Burial in Modern Sediment Within Yangtze River Estuary
Author(s) -
Sun Xueshi,
Fan Dejiang,
Liao Huijie,
Tian Yuan
Publication year - 2020
Publication title -
journal of geophysical research: biogeosciences
Language(s) - English
Resource type - Journals
eISSN - 2169-8961
pISSN - 2169-8953
DOI - 10.1029/2019jg005379
Subject(s) - estuary , sedimentary depositional environment , sedimentary rock , sediment , total organic carbon , geology , sedimentary budget , environmental science , geochemistry , hydrology (agriculture) , environmental chemistry , sediment transport , oceanography , geomorphology , chemistry , geotechnical engineering , structural basin
Large river‐dominated margins play a potential key role in regulating global carbon cycle and budget due to high terrestrial organic carbon (C org ) inputs and sediment accumulation rates. Here bulk elements (C org and TN), isotopic compositions (δ 13 C org and δ 15 N), radioisotope 210 Pb, 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 C org 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 C org . The statistical analyses indicate that the hydrodynamically driven sediment composition exerts a significant control on the transport, mobilization, and accumulation of sedimentary C org from the river to the estuary, with respect to the redistribution of fine‐grained sediments. Furthermore, X‐radiographs and 210 Pb indicate that reworked environment dominates carbon burial in the Yangtze proximal deposit, while a stable sedimentary environment of C org (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 C org . 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 C org storage, due to its association with sediment particles (mainly the clay fractions) that provide physical protection against its degradation.