【作者】 孙蕴婕；

【导师】 吴莹；

【作者基本信息】 华东师范大学 ， 海洋化学， 2011， 硕士

【摘要】 河流系统能携带颗粒物将陆源物质输送到近岸和海洋,是陆海作用的重要媒介。因此研究河流体系沉积物中有机物的来源和归宿对于了解全球碳循环有着重要意义。脂肪酸与正构烷烃是两种有代表意义的有机生物标志物。可通过其组成来判断沉积物中的有机物是来自于陆地、水体还是人类活动。还可通过生物标志物的时空变化,判断同一地区的历史环境变化和不同地区的自然环境差异。本文以脂肪酸与正构烷烃为研究手段,结合有机碳、总氮、碳稳定同位素和脂肪酸单体碳稳定同位素等参数初步探究了海南岛八门湾红树林柱状样、老爷海泻湖柱状样、八门湾和万泉河口表层沉积物及中国东部若干入海河流表层沉积物中有机物的来源和转化。海南八门湾生态保护区内红树林沉积物柱样的调查结果显示了当地丰富的微生物活动和浮游植物对有机物的贡献。表层沉积物有机碳与总氮比值(OC/TN)值、碳稳定同位素值(δ13C)及脂肪酸标志物组成表明浮游植物与细菌来源是当地有机质的重要组成。当地微生物对有机质的改造,可能是导致正构烷烃缺失奇偶优势的原因。有机物在短柱中呈现选择性降解,脂肪酸标志物：多不饱和脂肪酸(PUFAs)、单不饱和脂肪酸(MUFAs)和支链脂肪酸(BFAs)在5cm以上就有了很大程度的降解,而长链脂肪酸(LCFAs)由于其化学结构稳定而得以较好保存。正构烷烃总体比较稳定,没有明显降解。烷烃指标,碳优势指数(CPI)和平均碳链长度(ACL)显示,随着埋藏深度加深,有机物经历的改造越发显著。CPI、ACL与LCFAs有较好的对应关系,显示了陆源植物输入量对降解程度有一定影响。此外,柱样底层25cm的δ13C、粒度与OC/TN值的变化反映了当时有机质来源的改变。老爷海柱样沉积物中OC/TN及δ13C结果显示,有机物来源主要为浮游植物。从30cm深度开始观察到OC、TN值增大,说明有机物输入逐渐增多,δ15N值的增加说明水体生物活动繁茂,推测这一时期开始繁荣的养殖业使得水体生产力增加。15cm处脂类生物标志物显示有大量浮游植物来源的有机物,记录了水华爆发。通过对表层沉积物有机物参数对比发现老爷海泻湖富营养化现象较为严重的地区在东北部,其沉积物中有机物含量较高,不饱和脂肪酸所占比重较大。脂肪酸标志物和正构烷烃分析结果显示,黑龙江、海河、长江和珠江水系陆源植物机质对总有机质贡献较大。较低的碳稳定同位素值δ13C和较高的浮游生物源脂肪酸(多不饱和脂肪酸)含量以及较低的长链与短链烷烃比值(H/L)显示,黄河及东南沿海及海南河流沉积物则以浮游生物贡献为主。东南诸中河某些河流的人为污染比较严重：钱塘江、曹娥江、飞云江几个站点有石油烃类污染。同时在长江的南京、大通站也发现了石油烷烃的贡献。使用单体稳定同位素手法研究了八门湾地区及万泉河地区表层沉积物。长链脂肪酸浓度及其稳定碳同位素结果显示八门湾地区某些站点的有机物来自于红树林、河流、海洋的三端源的输入；而万泉河口主要以河流、海洋贡献为主。细菌源脂肪酸单体碳同位素值与浮游生物稳定同位素值接近,推测细菌在湾口优先利用浮游生物有机质。从湾口到湾内细菌源脂肪酸碳稳定同位素值逐渐变负,说明细菌所利用的有机物基质的改变。UCM与CPI结果显示八门湾地区受人文活动影响较大。更多还原

【Abstract】 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.更多还原