Application Of Sedimentary Organic Biomarkers As Sources Tracer And Environmental Change Indicator

Rivers play important roles of land-ocean interactions, they can carry particles and transport them to near shore and ocean. In order to understand global carbon cycle it's important to study the source and fate of ogranic matters in river systems. In recent years human impact is more and more activated which has far-reaching influence on river and costal. Fatty acid and alkane are very useful and widely used organic biomarkers. It could be used to identify the source from terrestial marine or anthropogenic. It could be also used to indentify the environmental changes and regional disparity of sediment through it's spatial and temporal variations. In this paper, fatty acids and alkanes were used combined with organic carbon, total nitrogen and stable isotope parameters to study the surface sediments of core sediments of Bamen Bay mangroves Hainan China and core sediments of Laoye Lagoon, and also the surface sediments of east china land rivers.OC/TN value,δ13C value indicated the organic source of Laoye lagoon came from phytoplankton. In down core 30cm OC% and TN% were rased indicated the load of organic matters. In down core 15cm biomarkers indicated a mass of phytoplankton derived organic matters, which documented the alga bloom. Through the comparation of surface sediments, it seems that eutrophication was more serious in north east of Laoye Bay. In north east of Laoye Bay, the OC% and PUFAs fraction was much more higher than anyother sites.Through the investig ation of Bamen Bay mangroves we found high portions of bio-source organic matters were derived from micro-organism, with large contributions of bacteria and plankton derived fatty acids, judged from it's low OC/TN value, lowδ13C value. Polyunsaturated fatty acids (PUFAs) with high degradation rate were lost fastest during decomposition. Long chain fatty acids (LCFAs) were relatively stable and shown no significant difference during degradation. The carbon preference index (CPI) and the n-alkane average chain length (ACL) indicated organic matter generally became more mature in deeper sediments. Moreover theδ13C value, grain size and OC/TN change in 25cm down core implied of the shift of organic sources.Rivers of eastern China have different latitude characteristics and source differences. This paper used biomarkers to trace the sources of the these rivers and detected the impact of human activity. Laoye Lagoon Has had suffered serious eutrophication and algal blooms, this paper used organic biomarkers to study the changes of the local environment, and investigated the phenomenon of eutrophication. Bamen Bay has unique mangrove eco-environment and has high productivity. We used biomarkers to probe the change of the fatty acids and n-alkanes in sediments during 100-year time scales.The result of fatty acid and alkane biomarkers indicated that the north river, Yangtse River and Pearl River were dominated by terrigenous vegetation organic sources.δ13C value, PUFAs and low H/L value indicated that Yellow River, small rivers in hainan and the small rivers in south east china were dominated by istu organic source. Futermore the pulltion of Qiantang Jiang, Caoe Jiang and Feiyunjiang is pretty serious. We also found oil pulltion in Nanjin and Datong site of Yangtse River.We analyzed the stable carbon isotopic ratios in surface sediment cores collected from Bamen Bay and Wanquan estuary. The end member results shows that the organic matters in Bamen Bay came from mangrove rivers and marine sources, while the organic matters in Wanquan estuary came from river and marine sources. Fatty acids stable carbon isotopic ratios of bacteria source were similar to that of plankton in Bamen Bay, which shows bacteria use plankton source organic matter in estuary. The isotopic ratios of bacteria fatty acid deplected with distance from estuary to bay, show shift of organic matter bacteria used from marine source to terrestial. UCM and CPI shows some spot in Bamen bay were polluted by human activities.