【作者】 胡利民；

【导师】 郭志刚；

【作者基本信息】 中国海洋大学 ， 海洋地球化学， 2010， 博士

【摘要】 大河控制性影响下的陆架海是海岸带陆海相互作用(LOICZ)研究的关键区域。全球排名前10位的大河向其邻近陆架区输送的淡水和颗粒物质约占全世界这一总量的40%,全球80%的有机碳埋藏也主要发生在河口-陆架地区。因此,陆架海沉积有机质的“源-汇”作用是海洋碳循环和陆海相互作用研究中不可或缺的重要一环。渤、黄海是我国东部典型封闭--半封闭的陆架海,这里有黄河这一世界级大河的输入,其历史上每年携带高达10亿吨以上的泥沙入海,沉积物输送量排在世界第二位。此外,这里又处于东亚季风的下风带,接受了大量的来自于大气沉降输入的人为污染物,陆海相互作用活跃。由于相对封闭的海洋环境、大河物质的输入加之特有的陆架环流动力体系使得该区存在固有的物质“汇”特性。本论文以受黄河入海物质影响巨大的渤海、黄海陆架区域为研究靶区,重点研究了这一区域沉积有机质及其有机污染物的“源-汇”过程及环境效应,揭示了研究区有机碳的埋藏量及其在全球海洋碳储库中的意义,并评估了人类活动在这一陆海相互作用强烈区域的环境影响。论文首先通过在渤海湾及其邻近海域41个站位取得的155个样品的颗粒有机碳(POC)和颗粒氮(PN)的分析数据,分析了该区夏季POC和PN的空间分布特征、影响因子与有机碳物源。结果表明,POC与PN的空间分布特征一致,呈现近岸高,远岸低,表层低,底层高的特点。生物作用、水体温盐跃层和总悬浮颗粒物(TSM)是影响研究区POC空间分布的重要原因。POC与TSM之间具有正相关关系,不同来源的TSM是控制水体中POC浓度高低的重要因素。POC/PN这一物源指标的应用受到海水中颗粒无机氮(PIN)的影响。通过建立POC和PN的一元线性回归模型,估算了样品中PIN的含量。扣除样品中PIN的影响后,显示POC除了以海洋生物为主要来源外,周边河流的陆源输入也有重要贡献。这一成果对认识中国近海的POC物源具有一定的参考价值。通过对渤海表层和柱样沉积物中的总有机碳(TOC)、总氮(TN)、有机质碳稳定同位素(δ13C)及饱和烃的分析和研究发现,总有机碳、氮的空间分布一致,有机碳的高值区分布在近岸和渤海中部,这与细颗粒沉积物的分布相一致。通过有机质的C/N、613C等物源指标,认为该区有机质主要受陆源输入和海洋生物的共同作用。研究区正构烷烃主要呈现出单峰和双峰的分布特征,表明正构烷烃主要来源于陆源输入和海洋自身贡献。所有样品的气相色谱图中均不同程度的出现了鼓包(hump),显示样品中含有“色谱不能分辨”组份(UCM),这意味着沉积物受到了不同程度石油烃的污染。黄河口及其邻近海区是河流输入陆源有机碳的主要“汇”。这与世界上其它大河控制影响下的大陆边缘海地区(RiOMar)的物质“汇”作用具有可比性和一致性,意味着这些大河控制下的陆架浅海的有机碳埋藏是全球碳循环过程中的重要一环。柱样岩芯沉积物中的有机质主要受陆源和海洋自生来源作用的影响；柱样上层沉积物中UCM组份含量明显高于下层样品,上层沉积物样品中的藿烷和甾烷等生物化合物的分布特征也反映出其沉积有机质的成熟度高于下层,这可能跟人为活动导致的石油烃的输入有关。结合测年资料发现,自上世纪70年代后期开始,柱样沉积物样品的粒度明显变粗,且沉积有机质C/N比值也随之降低,这可能跟黄河1976年改道有一定的关系,导致供应该区的陆源物质不断减少。基于正构烷烃分子组成特征的证据,探讨了黄海陆源沉积有机质的运移,结果表明,沉积物中正构烷烃的分布也受到水动力条件的影响,细颗粒沉积区的含量最高,且北黄海正构烷烃含量明显高于南黄海,与TOC的相关性也更强,这可能跟不同海区沉积物的粒度和陆源有机质的贡献差异有一定的影响。泥质区内陆源有机质的绝对含量和相对百分含量都有明显的升高趋势,显示黄海陆架中部泥质区是陆源沉积有机质的主要“汇”。PCA分析也显示出现代黄河入海物质供应的陆源沉积有机质在波浪、潮流等综合水动力条件的影响下可以通过一定的方式在陆架运移,并在远离其输入地的弱动力区域进行沉积、埋藏。这与世界其它边缘海地区陆源沉积有机质的“源-汇”过程具有一定的可比性。渤、黄海陆架上受特有水动力条件形成的细颗粒泥质区成为有机碳的主要沉降区,是有机碳的“汇”。把渤、黄海视为一个整体,可得到本区单位面积有机碳的堆积量约为13.5 tC/km2/yr,有机碳的年埋藏累积量约为5.9 Mt。考虑到现代黄河的入海物质主要集中在渤海,故单独估算得到渤海单位面积有机碳和正构烷烃的埋藏堆积量分别为28 tC/km2/yr,17.2 kg/km2/yr,高于渤、黄海整体的平均水平。渤海有机碳的年埋藏累积量约为2.1 Mt,这与世界上其它大河控制影响下的边缘海地区(RiOMar)具有一定的可比性,说明渤海具有和世界上其他大河控制下的陆架浅海及高生产力海区相当的碳汇效应。黄河这一世界级大河的输入,带来了巨量的陆源颗粒物质,加之相对封闭的海区环境、特有的水动力环境等因素条件共同决定了其相对较高的碳汇效应。研究结果对于认识大河控制性影响下的陆架海在全球碳循环中的角色和作用具有重要的意义。对渤海55个表层沉积物样品进行了有机氯农药分析,结果表明：DDTs和HCHs两大类化合物是本区最重要的两类有机氯污染物,母体DDT在大部分样品中发生了明显的降解。在近岸区域DDT输入(如：三氯杀螨醇)主要与农业生产活动,化工企业的生产废水和防腐油漆的使用有关。主成分分析的结果可以区别出近岸区域不同农药的历史贡献和当前输入状态,并指出近期DDT和工业氯丹的使用是环境中有机氯农药的重要来源；早期输入的有机氯农药化合物的分布除了受到输入来源的影响外,在二次搬运、分选等作用下,也受到了沉积物中有机质分布的影响。通过对本区沉积物进行质量风险评价发现,DDT和chlordanes两类化合物在本区具有较高生态影响,尤其是在渤海湾等近岸区域。渤海柱样岩芯中PAHs的垂向变化趋势受其低环化合物组份的影响较大。渤海热解PAHs的来源主要为燃煤贡献,石油等产物的输入对本区低环PAHs化合有重要影响,考虑到渤海受大河控制性影响,高等植物来源对于低环PAHs化合物的贡献也不可忽视。DDTs的垂向沉积记录与80年代农药的禁止生产、使用及随后90年代的城市化进程的加快和土地利用方式的改变有一定的对应关系。黄海中部泥质区沉积柱中16种PAHs的垂向变化趋势与中国社会经济发展和工业化进程有着较好的阶段性响应关系。黄海沉积柱中的PAHs主要以燃煤贡献为主,其主要输入方式为大气沉降。通过对不同地区之间的PAHs沉积记录进行比较,可反映出东西方国家之间不同的经济发展和能源结构的演变历程。更多还原

【Abstract】 The river-dominated continental shelves could serve as a key role for the study of land-ocean interaction in the coastal zone (LOICZ) in the context of the global change. Worlds 10 largest rivers transport-40% of fresh water and particulate matter into its associated marginal shelves, and over 80% of the global carbon burial occurs in these systems (Berner,1982; Hedge and Keil,1995). The sedimentary organic matter in the shelf settings should be an important process in the global cycle of carbon and land-ocean interaction.With large inputs of particulate materials and anthropogenic pollutants via rivers (e.g. Yellow River-the second largest sediment-load river in the world) and atmospheric deposition, the Bohai and Yellow Sea located in East China are the typical enclosed-semienclosed shelf seas with active land-Ocean interaction. The relative enclosed setting, large river inputs and typical shelf hydrodynamics forced the sink characteristics in this region. In this work, the soures and sinks of sedimentary organic matter (SOM) as well as the organic pollutant materials were examined in order to better characterize the importance of organic carbon burial in these shelf regions around the world, and also to evaluate the human influence in these shelf regions.Based on the analyses of particulate organic carbon (POC) and particulate nitrogen (PN) in the Bohai Bay and its adjacent sea, the results show that the spatial distribution patterns of POC and PN are similar in the study area. The concentrations of POC and PN in the coastal regions are higher than those in the outer shelf, and the concentrations of POC and PN are higher at the bottom water layers than those at the surface water layers. Biological effect, thermocline and concentration of TSM are the main factors affecting the spatial distribution of POC. The POC/PN ratio to evaluate the sources of POC is influenced by the presence of particulate inorganic nitrogen (PIN). Removing the content of PIN in the samples, the POC/PON ratio suggested that the terrestrial input originating from the nearby rivers is also an important source of POC, in addition to the major contribution from the marine primary production. This method could be applied to identify the sources of POC in other coastal areas of China.According to the analysis of total organic carbon (TOC), total nitrogen (TN), stable carbon isotopic composition and aliphatic hydrocarbons in the surface and cores sediment samples from the Bohai Sea, the results indicate that TOC showed a direct relationship with sediment grain size with the finest sediment having the highest TOC, suggesting that the hydrodynamics in Bohai was the main driving force in the accumulation of SOM.δ13C, the corrected TOC/ON ratios and TAR of n-alkanes indicated a mixed marine/terrestrial source for the SOM. The ubiquitous presence of UCM, composition patterns of hopanes and steranes, and PCA results indicated that the petroleum contamination in Bohai. The Huanghe River Estuary (HRE) and its adjacent area is the main sink for the Huanghe river-derived OC. This draws a similarity with other large river-dominated ocean margins (RiOMar) in the world, suggesting that the preservation of terrestrial OC in these large river-dominated coastal margins should be an important process in the global cycle of carbon. For the core samples, the C/N ratio of the bulk organic matter and the composition of the n-alkanes suggested that the sedimentary organic matter (OM) was of mixed marine and terrestrial sources. The presence of unresolved complex mixtures (UCM) in the surface layers and the patterns of biomarkers (hopanes and steranes) indicated more petroleum-derived inputs in recent years due to oil exploration and heavy traffic in Bohai. The coarser sediment grain size and decreasing C/N ratios since the mid of 1970s could be attributed to the relocation of the Yellow River course into the sea from the central Bohai to the south Bohai to decrease the influence of Yellow River-derived sediments and associated OM on the central Bohai.Based on the molecular composition feature of n-alkane in surface sediments, the dispersal of terrestrial organic matter (TOM) in the YS was identified. The results indicated that the distribution of n-alkanes content was influenced by the hydrodynamics, with the highest content found in the fine-grained mud area. The concentration of n-alkanes in the northern YS together with the correlation with TOC was higher than that of the southern YS, which could be related with the different sediment grain size and contribution of TOM in various regions. The concentrations and relative abundance of TOM in shelf mud areas increased distinctly, suggesting the central mud areas in the middle shelf of YS could be the main sink for the TOM. The PCA analysis also revealed that the riverine TOM from Huanghe could transport along the shelf under the special hydrodynamics, and then deposit and accumulate in the regions far distance from the original entrance. This source to sink process draws similarity with TOM in other shelf margins in the world.The fine-grained mud areas induced by the specific hydrodynamic conditions on the shelves of the Bohai and Yellow Seas are important sink for the organic carbon (OC). The weighted average accumulation rates of OC and alkanes in Bohai Sea were calculated as approximately 28 tC/km2/yr and 17.2 kg/km2/yr, respectively, which is higher than the mean values of the whole areas of the Bohai and Yellow Sea. The total OC budget for the entire Bohai could be estimated as 2.1 Mt/yr. This average OC accumulation rate in Bohai Sea draws similarity with other river-dominated ocean margins (RiOMar) in the world, suggesting the regional OC burial in the Bohai Sea could serve as an important role in the carbon sink by comparing with other RiOMar and coastal systems with high primary production preservation. The large riverine inputs of the terrestrial organic matter; relatively enclosed marine environments and special hydrodynamic conditions could serve as the key factor in maintaining the high carbon sink in this region, which are essential for the understanding of the role of large rivers and associated margins in the global cycles of carbon.Fifty-five surface sediment samples covering virtually the entire Bohai Sea (Bohai) were analyzed for organochlorine pesticides (OCPs). The results showed that DDTs and HCHs could be the most two important pesticides contaminants in Bohai. (DDE+DDD)/DDT ratios indicated that the degradation of the parent DDT occurred significantly. High concentrations of DDTs were observed in the coastal areas especially the isolated sites neighboring the harbor or port regions, suggesting the recent DDT inputs from wastewater derived from agriculture activity (e.g. dicofol) and chemical plant as well as the usage of antifouling paint. The contribution of the previous and current input of pesticides in the coastal areas was distinguished by means of principal component analysi. And the distribution of these relatively "old" accumulated pesticides could also be influenced by the distribution of organic matter due to the post-depositional sorption in addition to the input sources. DDTs and chlordanes are the two-main species of pesticides with more ecotoxicological concern in Bohai.The vertical distribution patterns of total PAHs in the two cores in Bohai was mainly dominated by the abundance of the low-molecular weight component, which influenced by the petroleum-related contributions. The pyrogenic PAHs in Bohai two cores were mainly from the incomplete combustion of coal or biomass burning. In addition, in the context of the large river dominated conditions, the biogenic contribution from higher plants for the low molecular PAH compounds could be inevitable. The vertical record of DDTs could reflected the official ban of the production for these chemicals in 1980s and the large-scale land use transformation and citifying process in the following 1990s. The 16 PAHs variation in the sediment core in the central mud of southern Yellow Sea follows closely with the stage features of historical economic development in China. The historical profile of PAH distributions in this region is different from those in the United States and Europe, owning to the different evolution course of energy structures between these western and oriental countries.更多还原