Sources and degradation of sedimentary organic matter in the mud belt of the East China Sea: Implications from the enantiomers of amino acids

摘要: Abstract Total organic carbon (TOC), total N (TN) and amino acids (AAs, including the bacterial biomarker D-AAs) were determined in sediment cores from mud belt of East China Sea (ECS). The concentration hydrolyzable AAs (THAAs) ranged 3.35 to 13.44 µmol/g dry wt (dw) sedimentary matter (SOM), exhibiting a decreasing trend downcore. Major constituents THAAs glycine (Gly), L-serine (L-Ser), L-alanine (L-Ala), L-glutamic acid (L-Glu) L-aspartic (L-Asp), whereas D-aspartic (D-Asp), D-glutamic (D-Glu), D-serine (D-Ser) D-alanine (D-Ala), along with non-protein (γ-aminobutyric β-alanine) together accounted for ca. 7% THAA pool. Given C/N ratio values, OM three was predominantly marine origin. Based on D-Ala yield, represented average 18% TOC 30% TN. C-normalized THAAss (THAA-C%) sensitive indicator SOM diagenetic alteration upper 40 cm sediment. However, degradation index (DI) reactivity (RI) values did not exhibit any definite trend, which may indicate that these two indicators early stage degradation. Negative correlation between D/L Ala THAA-C% suggested close coupling extent accumulation and/or selective preservation material sediments. In addition, clay content fine grained particles played an important role affecting quality SOM.