Some Progresses On Organic Geochemistry Study Of Bohai, The Yellow Sea, The East China Sea And Large Estuaries

This report is focused on the research carried out during postdoctoral period, emphasizing on the study of biomarkers (n-alkanes, fatty acids and PAHs) in the samples of Bohai, Yellow Sea and the East China Sea and some large river/estuary systems. The tool of biomarkers is succeeded to trace the origin of organic matter, recycling and degradation of organic materials.(1) Hydrocarbons are the most useful molecular markers. They were used as the tracers in many aspects, such as source indication; the degradation of organic matter; diagensis process; environmental pollution and paleooceanic study etc.(2) Surface sediment samples collected in May and October 1998 in the Yellow Sea and the Bohai were analyzed for ?alkanes (ALK) and fatty acids (FA). Concentrations of ALK in the surface sediments from Yellow Sea (YS) and Bohai (BH) varied from 1.3-17.8 ug/g (C]4-C33), the level of FA was 4.2-ll.Oug/g. Compared with the developed area, such as the Rhone River and the Mediterranean, the concentrations were considered modestly lower. However, the level of ALK and FA of the Bohai was higher than that of the Yellow Sea. Terrestrial inputs were dominated for organic materials in YS and BH's surface sediments. By using clustering and factor analysis of the raw data, it is found that the major terrestrial contribution of organic mater in BH is from the Huanghe, the situation of organic materials is more complex in YS. Three different sources contribute to the organic matter in YS, one is from the Changjiang, one is from the Huanghe and the third comes from the detritus of the abandoned Huanghe Estuary. The exchange of organic matter happens between YS and BH via Bohai Strait along with the water circulation.(3) Core sediments in the Bohai have been analyzed to assess the sources and diagenesis of organic matter. The variation of H/L ration along the core could reflect the change of the Yellow River in the history. The observation of the reduced CPI value may suggest the dryness and dams over the Yellow River in these days. With the ratio of BrC15/nC15and 18:1/18:0 of fatty acids, it is elucidated that fatty acids could be easily degraded in the anoxic than the oxide environment. Thirteen compounds of PAHs were identified by GC in the core sediments of Bohai Straight (S44 and T4 Stations ) . From the indicators such as Pen/Anth and Fluo/Pyr etc. the dominated origin of PAHs in S44 Station is pyrolytic origins. However, in T4 Station, a mixture of pyrolysis and petroleum origin is suggested in this area. The distribution of PAHs in the core sediments also could be a good indicative of the contribution of human activity.(4) Three core sediments (YSA10, YSB7 and YSC5) were collected from the Yellow Sea to determine the composition of w-alkanes and PAHs by GC. Riverine input seems to be the major contribution of n-alkanes compared with atmospheric deposition. Atmospheric input plays an important role of anthropogenic PAHs in the core sediments. Legal curbs of industrial and vehicle emissions should be done to prevent the increasing contamination of PAHs in the Yellow Sea.(5) Particulate samples from the Yangtze River were examined in order to assess the biogeochemsitry of hydrocarbon and fatty acids. The biomarker approach has been clearly identified autochthonous and allochthonous lipids in the particulate samples, which showed a roughly equivalent contribution of these sources. The predominant even carbon numbered n-alkanes ranging between C14 and C32 have been found in the most samples. Combinations of microorganisms (bacteria, fungi and yeast) and some special high plant may account for the n-alkanes occurrence. The biogeochemistry of organic matter in a macrotidal estuary, the Yalujiang River. Two techniques have been used: carbon isotopic ratio determination and analysis of lipid biomarker signatures in the n-alkanes and fatty acids series. The characteristics of the distribution of organic matter (continental in nature in the inner estuary and pure marine...