长江口邻近海域缺氧区营养盐及痕量金属的生物地球化学过程研究

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	长江口邻近海域缺氧区营养盐及痕量金属的生物地球化学过程研究
其他题名	Biogeochemical processes of nutrients and trace metals in the hypoxia zone in the adjacent area of Yangtze Estuary
	邹建军
学位类型	博士
	2008-06-12
学位授予单位	中国科学院海洋研究所
学位授予地点	海洋研究所
关键词	痕量金属营养盐早期成岩缺氧长江口
摘要	长江口邻近海域夏季底层水体存在世界上面积最大的缺氧带。这为研究河口区氧化还原敏感元素的生物地球化学过程提供了天然的实验场所。为了理解长江河口缺氧带存在的生物地球化学过程，本文以长江口邻近海域缺氧带上覆水体、沉积物及间隙水为研究对象，并对其营养盐及重金属进行研究，目的在于揭示长江口邻近海域缺氧带可能存在的生物地球化学过程，为理解长江河口区的物质循环提供科学证据。通过研究得出如下结论：（1）在水体中盐度是影响营养盐分布的主要因素，在高浊度带存在营养盐释放的现象；（2）底层水存在两种显著不同的生物地球化学过程：当盐度<33 PSU时，营养盐与AOU之间为负相关，影响底层海水营养盐分布的主要因素可能为流场；而当盐度>33 PSU时，营养盐与AOU之间存在正相关，影响营养盐分布的主要因素为颗粒有机质的矿化；（3）溶解态痕量金属存在保守型（Mo、U、Ni）和混合型(Fe、Mn、Cu、Pb、Zn)的分布规律，盐度、浮游生物及溶解氧都是影响溶解态痕量金属分布的重要因素；剔除浊度大于20 NTU的数据，分配系数与浊度为显著正相关；（4）间隙水Fe、Mn剖面表明，长江河口表层沉积物存在剧烈的Fe、Mn还原现象；成岩模型模拟结果显示间隙水Mn的模拟剖面与实际观测剖面吻合较好。间隙水U剖面显示，控制U分布的主要因素与Fe有关，但是其它因素如有机质含量对U、Mo的分布也有影响；（5）间隙水营养盐剖面显示近岸与远岸存在两种不同的生物地球化学过程：远岸海域，间隙水营养盐部面主要受早期成岩的控制；而在近岸海域其它过程如氨化及吸附可能是控制间隙水氮剖面分布的主要因素；模拟剖面与NH4+的实测剖面趋于一致，但是同时暗示表层沉积物受到生物扰动；通量计算结果显示，Si、N、P分别占浮游生物每日所需要营养盐数量的15%、10%及0.1%；（6）对痕量金属的黄铁矿化程度进行了分析，发现长江河口痕量金属的黄铁矿化程度异常低，黄铁矿不是影响痕量金属分布的主要因素；导致低黄铁矿化度的原因与长江河口高沉积速率、贫硫、低有机质有关。
其他摘要	The hypoxia zone in the bottom water in the adjacent area of Yangtze estuary is one of the largest in the world. As a natural laboratory, studies of the Yangtze Estuary maybe provide insight into for examining biogeochemical processes of redox sensitive elements in hypoxia environments. In order to understand the biogeochemical processes in the hypoxia zone in Yangtze Estuary, we investigated the distributions of nutrients and trace metals (Fe, Mn, U, Mo, Cr, Ni, Cu, Zn) in water column, sediments and interstitial water. Results showed that the distribution of nutrients in the water column is mainly controlled by salinity. Nutrients release in the high turbidity zone were observed. In the bottom water, two different biogeochemical processes can be identified. When the salinity is less than 33 PSU, the negative correlation between nutrients and apparent oxygen utilization (AOU) is observed. When the salinity is more than 33 PSU, the positive correlation between nutrients and AOU can be observed. The causes can be ascribed to current and the mineralization of particulate organic matter, respectively. Trace metals can be grouped into conservative-type (Mo, U, Ni) and mixing-type (Fe, Mn, Cu, Pb, Zn).The distribution of dissolved trace metals are controlled by salinity, dissolved oxygen and plankton. There exists significant positive correlation between turbidity and distribution coefficient when the turbidity values more than 20 NTU are eliminated. Interstitial Fe and Mn profiles indicated that there exist strong iron and manganese reduction phenomenon in Yangtze estuary. Two-layer diagenetic model are used to fit the interstitial iron and manganese profiles. The fitting results coincides with the observed profiles for Mn, but mediocre for iron. Interstitial uranium profiles suggested that iron is the main factor that controlled the distribution of uranium. And what’s more, other factor such as organic matter content also can affect the distribution of the uranium and molybdenum. Interstitial nutrients profiles suggested that there exist two different biogeochemical processes in Yangtze estuary. In the offshore area, the interstitial nitrogen profiles is controlled by organic matter diagenetic processes, while in the nearshore area, other processes, such as adsorption and ammnox, influence the interstitial nitrogen profile. Diagenetic fitting curves for NH4+ matched well with the observed interstitial NH4+ profiles. Moreover, the fitting curves indicate that there exist bioturbation phenomena in the surface sediments. The calculated nutrients fluxes indicated that the fluxes of silicate, nitrogen and phosphorus for plankton need daily only account for 15%, 10% and 0.1%, respectively. Pyritization of trace metals in the Yangtze estuary is much lower, which suggests that pyrite is not the sink for trace metals in Yangtze estuary. The reasons that cause the lower degree of pyritization can be ascribed to the high sedimentation rate, the poor organic matter and sulfur concentrations in Yangtze Estuary sediments.
页数	111
语种	中文
文献类型	学位论文
条目标识符	http://ir.qdio.ac.cn/handle/337002/1473
专题	海洋环流与波动重点实验室
推荐引用方式 GB/T 7714	邹建军. 长江口邻近海域缺氧区营养盐及痕量金属的生物地球化学过程研究[D]. 海洋研究所. 中国科学院海洋研究所,2008.

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