| Terrigenous organic matter (TOM) is not only an important pool of carbon in the global carbon cycling, but also a huge source of ocean carbon. As a transition zone with strong land-sea interaction, the continental shelf is important region for migration and burial of terrigenous materials, and an important area for the global carbon cycle. The East China Sea (ECS), with a broad shelf area, is one of the largest marginal seas in the world. Because of the unique ecological environment resulting from its specific geography, the ECS has become a key area of research on the land-sea interaction and flux of materials in coastal ocean zones. In this thesis, we used lignin as a biomarker of TOM, combining witseveral conventional parameters such as the total organic carbon (TOC) and C/N ratio, to discuss the source, migration and degradation of TOMs in surface sediments from the two mud areas in the ECS. We also presented a preliminary result on the changes of organic matter and the environmental implication for alteration of terrestrial vegetation in a short-time scale.TOC contents in the surface sediments from mud areas of inner shelf and southwest of Cheju Island ranged from0.41%to0.99%, with an average of0.76%; the C/N ratios were between5.00and7.50. These results indicated that most of organic matters in surface sediments of ECS were marine originated. TOC concentration in the mud area southwest off Cheju Island was higher than that in the mud area of inner shelf along the shoreline. On the contrary, the concentration of lignin concentration was higher in the inner shelf area (an average of E8was0.35mg/10gdw for the mud area of inner shelf along the shoreline and was0.12mg/10gdw for southwest off the Cheju Island). The spatial distribution of concentrations of E8, A8and TOC are similar in the mud area of inner shelf along the shoreline. From the north to the south of reseach area, the contrations increased first, then decreased in the central area and increased again in the southern region. We suggested that this distribution trend was controlled by Zhejiang Coast Current (ZCC) and Taiwan Warm Current (TWC), and are affected by input of continental runoff along the shoreline. The vertical distributions of TOC and lignin concentrationsin the three cores RA7, ZA6, ZB7indicated that the input of terrigenous organic matter in the ECSdecreased gradually, especially organic matter from higher plants. The most important reason is that the terrestrial ecosystem has been seriously deteriorated, resulting in greatly reduced forest coverage and river runoff.Vegetation parameters, S/V-C/V and LPVI, indicated that lignin in sediments of the continental shelf of the ECS were from various types of terrestrial plants, including angiosperm and gymnosperm, with an angiosperm dominance overall in the two mud areas.The lignin degradation parameters showed that terrigenous organic matters in surface sediments of ECS had a relatively high level of degradation rate, and were mainly degraded via demethylation/demethoxylation (the average of P/(V+S) is0.85). Lignin degradation changed insignificantly with time (depth), implying that degradation of lignin was mainly occurred in soil and water column, and lignin can be preserved for a long time after deposition. In addition, degradation may vary depending on the location, most probably because of the depositional environment. Demethylation/demethoxylation and oxidation might occur concurrently under one circumstance (such as at RA7station), and they might dominate alternately with time under another circumstance (such as at ZA6station), and still, one of them might control under other circumstance (such as oxidation at ZB7station). |
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