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A multiproxy analysis of sedimentary organic carbon in the Changjiang Estuary and adjacent shelf
Author(s) -
Yao Peng,
Yu Zhigang,
Bianchi Thomas S.,
Guo Zhigang,
Zhao Meixun,
Knappy Chris S.,
Keely Brendan J.,
Zhao Bin,
Zhang Tingting,
Pan Huihui,
Wang Jinpeng,
Li Dong
Publication year - 2015
Publication title -
journal of geophysical research: biogeosciences
Language(s) - English
Resource type - Journals
eISSN - 2169-8961
pISSN - 2169-8953
DOI - 10.1002/2014jg002831
Subject(s) - total organic carbon , estuary , sediment , environmental chemistry , chemistry , carbon fibers , lignin , sedimentary rock , composition (language) , mineralogy , geology , oceanography , geochemistry , geomorphology , organic chemistry , materials science , linguistics , philosophy , composite number , composite material
Surface sediments from the Changjiang Estuary and adjacent shelf were analyzed using a variety of bulk and molecular techniques, including grain size composition, sediment surface area (SSA), elemental composition (C, N), stable carbon isotopic composition ( δ 13 C), n ‐alkanes, lignin phenols, and glycerol dialkyl glycerol tetraether lipids to obtain a more comprehensive understanding of the sources and fate of sedimentary organic carbon (SOC) in this dynamic region. Bulk N/C ratios of 0.09 to 0.15, δ 13 C of −24.4‰ to −21.1‰, branched/isoprenoid tetraether index of 0 to 0.74, n ‐alkane content of 0.02 to 0.37 mg g −1 organic carbon (OC), and lignin content (Λ 8 ) of 0.10 to 1.46 mg/100 mg OC and other related molecular indices in these samples indicate a mixed source of marine, soil, and terrestrial plant‐derived OC in the study area. A three‐end‐member mixing model using principal component analysis (PCA) factors as source markers and based on Monte Carlo (MC) simulation was constructed to estimate the relative contributions of OC from different sources. Compared with traditional mixing models, commonly based on a few variables, this newly developed PCA‐MC model supported bulk and biomarker data and yielded a higher‐resolution OC inputs to different subregions of this system. In particular, the results showed that the average contributions of marine, soil, and terrestrial OC in the study area were 35.3%, 47.0%, and 17.6%, and the highest contribution from each OC source was mainly observed in the shelf, inner estuary, and coastal region, respectively.