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The Distribution And Influencing Factors Of Terrestrial Organic Matter In The Typical Systems

Posted on:2016-10-09Degree:DoctorType:Dissertation
Country:ChinaCandidate:Z Q LiFull Text:PDF
GTID:1220330461974114Subject:Estuarine and coastal science
Abstract/Summary:PDF Full Text Request
The land sends massive terrestrial organic carbon (TOC) to the river, and the river takes part of the TOC to the marginal sea. During the transit, most of the TOC are trapped in the river sediments or oxidized to CO2 and released to the atmosphere. The part of the TOC delivered to marginal sea is buried as the sink of carbon in the sediment and takes part in the global carbon cycle in a geological timescale. Therefore, the behavior of TOC in the river system and marginal sea is important component of the global carbon cycle. Recently, the frequency of floods and other natural disasters increased due to the global change, and they make the TOC varying in flux and composition. Moreover, the human activity, such as dam building would make the suspend material being trapped in the river. It will intensify the erosion in the lower reaches of the river, and it will change the flux and composition of the TOC. At the same time, the TOC buried in the marginal sea contains the information from the drainage basin. Although the results about the river-marginal sea system are often reported, there are no systemic summary about the different typical river-marginal sea systems. In this thesis, we collected the sedimentary samples in the Red River delta in the sub-tropic area, the Changjiang and East China Sea system, the Bohai channel and the Svalbard and Iceland in the Arctic region, and analyzed the bulk properties and biomarkers to those samples, for tracing the source and composition of TOM in those areas. We also try to unscramble the information of climate change and human activity in the drainage basin based on the profiles of TOM in the marine sediments. At last, we would like to summarize the law of distribution and composition of TOC in different typical systems.The OC, TN and lignin insurface sediments in the red river delta were controlled by the grain size of those sediments, and the marine phytoplankton and soil contributed most of the organic matter to the sediments. The percentages of TOC based on different terrestrial and marine two endmembers were different (N/C,δ13C and A8). However, there are positive correlations between the results. The lignin the red river delta was moderately degraded and the C/V and S/V rations indicated that the no-woody angiosperm were the sources of lignin in the red river delta, and it was in according with the plant type in the river drainage basin..There were spatial variation in the distribution and composition in the Changjiang bed sediments. In the main channel and north tributaries, the TOC were controlled by the grain size, but this correlation was not observed in the south tributaries. In the north tributaries, the addition of fresh plants might destroyed the correlation between organic matter and grain size. Soil, plant debris and rock contributed to the organic matter in the Changjiang bed sediments, and phytoplankton was potential source. Generally, the soil contributed most of the sedimentary organic matter, and rock carbon was the major source of organic matter in the low OC stations. The composition of GDGTs in the main channel of Changjiang was different from the upper reaches to lower reaches. The distinction was because the mean air temperature and pH of the source area. The cluster analysis and principal component analysis indicated that GDGTs in Shigu might from the plateau soils, and the mixture source in other stations. The iGDGTs in the bed sediments were mostly from in situ production of archaea in the Changjiang.The organic matter sources of P4 core in the continental shelf of the East China Sea were majorly marine phytoplankton and terrestrial organic matter. The lignin composition in P4 core was much different from that in Huanghe basin, and the Changjiang contributed most of the lignin to P4 core. The lignin content (E8) was positively correlated with the strength of Indian Summer Monsoon. The lignin composition of lignin, such as C/V, S/V, LPVI and DHB A indicated the extreme draught events in the Changjiang basin. Moreover, the variation of lignin composition after 1880 A.D. indicated the strength of human activity and land use change in the Changjiang basin, especially in the upper reaches.The organic matter in T4 sediments collected in Bohai Strait were from a mixture source, including C3 plants, C4 plants and marine phytoplankton. The lignin content varied with the grain size profile. In T4 core, the grain size and lignin content recorded the variation of Huanghe, and the increased human activity in the drainage basin. The diversions of Huanghe in 1194-1855 A.D. and 1938-1947 A.D. made the small grain size in T4 core, and they made the high lignin content. The abrupt increasing human activity in Northern Song Dynasty leaded to the strong erosion in the Loess Plateau, and made a more contribution of plant debris to the P4 core.The results of soils and sediments collected around "Huanghe Station in Arctic" showed that the organic matter was low in this region. The 813C was in agree with the previous report. The lignin around "Huanghe Station" was from the mixture of vascular plants and moss. The low value of PON/P indicated the animal and bacteria contributed part of the organic matter around the "Huanghe Station". The core GA306-4 contained high percentage of organic matter, which was majorly from marine phytoplankton. Moreover, the terrestrial ecosystem also contributed part of the total organic matter, which came from the moss in the Iceland.To compare the TOC between different typical systems, it was found that the natural conditions and human activity had impact on the content and composition of TOC. In different region, there were big differences in the TOC, and the differences were caused by the natural change or human activity. How to distinguish the signals of natural change and human activity would be the next step of this research.
Keywords/Search Tags:sediments, terrestrial organic matter, lignin, river, marginal sea, humanactivity, natural change
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