长江口水体混合过程中的水/粒作用地球化学——微量元素及同位素地球化学研究

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	长江口水体混合过程中的水/粒作用地球化学——微量元素及同位素地球化学研究
	王中良
	2001
学位授予单位	中国科学院地球化学研究所
学位授予地点	中国科学院地球化学研究所
学位名称	博士
学位专业	地球化学
关键词	长江口水体混合溶解态酸溶态颗粒态锶同位素稀土元素重金属元素水／粒作用分配分异析出絮凝解絮吸附解吸再悬浮
摘要	近几年来，随着水体地球化学研究的逐步深入，人们发现表生水体中许多微量元素利同位素的水体地球化学行为都与水体颗粒物的行为密切相关，水／粒相互作用过程越来越引起研究者的关注。河口是连接河流与海洋两大不同性质水体的过渡地带，其水体的理化性质及化学组成在短时内会发生显著变化，使得河口环境成为研究表生水体水／粒相互作用过程的优势场所。本文首先对稀土和重金属元素以及锶同位素等化学组分在世界河口水体混合过程中的地球化学行为进行了综述。并在综述和调研的基础上，选择世界大河之一的长江口作为研究区域，通过对水体溶解相、酸溶相、和颗粒物中稀土和重金属元素以及水体锶同位素地球化学的研究，系统了解了长江口表层水体中微量元素和同位素的迁移转化规律，并对发生在河口区的水与颗粒物以及水与沉积物的相互作用过程进行了分析，并得出以下初步结论：1．在长江口，表层水体的混合不是以均匀方式进行的，盐度及主离子浓度在空间剖面上显示非连续性变化。这是由于长江口属于潮汐分汊河口，儿股径流相互穿插所致。但在盐度剖面上，主离子浓度都随盐度增加而线性变化，显示明显的化学保守性。2．长江口水体颗粒物的含量和pH值都比较高，使得溶解态物质的迁移转化规律相对特殊，尤其是水／粒相互作用过程比较强烈。3.长江及长江口水体的~(87)Sr／~(86)Sr比值(0.7105)相对较低，而Sr元素浓度(约150ppb)相对较高。Sr及~(87)Sr／~(86)Sr在长江口水体混合过程中显示保守行为，基本不受水/粒相互作用及其它地球化学过程的影响，只与水体端员的化学组成有关，所以锶同位素是河口研究中确定水体端员的良好指标。4.本文首次测定了长江口表层水体中溶解态REE的浓度。利世界大多数河口相比，长江口溶解态REE的浓度相对较低，仅为0.1～10ppt左右，比其它河口低了近10到100倍。溶解态REE在长江门盐度剖面上的分布规律也比较特殊，显示了自低盐度向高盐度的整体升高趋势，而不是通常的随盐度降低趋势。5.溶解态重金属元素Fe、Co、Ni、Cu、Pb、Zn、Cd等在长江口表层水体混合过程中显示了各不相同的地球化学行为。受胶体絮凝过程的影响，溶解态Fe利Zn的浓度在河口低盐度区显著降低；溶解态Ni和Cu则显示住低盐度区的强烈解吸过程；Co和Pb的行为主要受水体颗粒物吸附作出的控制；溶解态Cd显示随盐度增加的全过程解吸行为。6．本文对江口表层水体中酸溶态利颗粒态微量元素的浓度也进行了测定。结果显示，酸溶态微量元素的行为主要受水体颗粒物行为的控制，但在一定程度上又受到盐度等水化学因素的影响，所以用酸溶态微量元素的行为讨论水/粒相互作用过程比颗粒物全样更为有效。颗粒态微量元素在水体混合过程中的行为相对惰性，除受粒度效应的影响外，基本不受其它物化参数及水／粒相互作用过程的影响，只与其物质来源有关。7．在江口表层水体中，发生着广泛的水／粒相互作用以及水与沉积物相互作用过程。住河口低盐度区以胶体絮凝作用为主，但同时又因离子交换反应而使某些元素(Cu和Ni)发生解吸过程。在河口中高盐度区广泛发生有沉积物再悬浮和颗粒物解吸及解聚过程，从而造成酸溶态及部分溶解态微量元素浓度的升高。8．水／粒相互作用过程明显影响到微量元素长江的入海通量，对解释东中国海及西太平洋的微量元素及同位素地球化学也有比较重要的意义。
其他摘要	Based on largely and increasingly accumulated results of aquatic geochemcal studies in recent years, more and more researchers find that the behaviors of trace elements in surface waters is markedly affected by the signatures of suspended matter and so, water-particle interaction processes have attracted much interests of researchers. Estuaries are buffers between two distinct water columns, river and ocean, and the properties and constitute of the estuarine waters change rapidly in a short time. Therefore, the estuaries are good locations for study the water-particle interaction processes. We chose the Changjiang Estuary, one of the biggest estuary of the word, as our study area based on the review of geochemical behaviors of rare earth elements, heavy metals, and Sr isotope in estuarine mixing processes. In this study, the dissolved, acid-soluble and particular trace elements including heavy metals and, 'are earth elements were determined. Measurements of Strontium isotopic compositions was also involved. The water-particle and water-sediment interactions that happened in the Changjiang Estuary are discussed. From the results of this study, we get the following conclusions: 1. Water mixing is not uniformity at the Changjiang Estuary, because the salinity and the concentrations of main ions show discontinued spatial distributions from the river to the ocean. This is because the Changjiang Estuary is a tidal and branched estuary, and several flows interlarded each other. However, the concentrations of those main ions changes linearly along the salinity gradient, implying the conservative behaviors of those constitute during estuarine mixing. 2. The Changjiang estuarine waters have high pH and high concentration of particular matter, which makes the transportation and transition of estuarine substance very special, especially the water-particle interaction processes frequently occur. 3. The Changjiang and Changjiang estuarine waters have low ~(87)Sr/~(86)Sr ratios (0.7105) and high Sr concentration (about 150ppb). The Sr and its isotopes show conservative behaviors in estuarine mixing, seldom affected by water-particle interaction and other geochemical processes. 4. The first data of dissolved REE concentrations were determined in this study. Comparing with the other estuaries of the world, the concentrations of dissolved REE in the surface waters of the Changjiang Estuary are very low, only about 0.1 to 10ppt, 10 or 100 fold lower than other estuaries. The distribution of dissolved REE at the Changjiang Estuary is also very special, which show increasing trend with the salinity increasing. 5. In the surface waters of the Changjiang Estuary, the dissolved Fe, Co, Ni, CCu, Pb, Zn, Cd show different distribution behaviors from each other. At the low salinities, the dissolved Fe and Zn are removed markedly but the dissolved Ni and CCu show desorption behaviors. The concentrations of dissolved Co and Pb decrease when the salinity increase, due to adsorption by the suspended particles. Complexed by Cl~-, the dissolved Cd shows desorbption behavior at all salinities. 6. In this study, the concentrations of trace metals in the acid-soluble and particular phases were also determined. The result shows that the behavior of acid-soluble trace elements are mainly controlled by the behavior of suspended matter, and subordinately controlled by salinity. Besides "particle effects", the particular trace metals are immobile in estuarine mixing, only controlled by its origins. 7. The water-particle and water-sediment interactions intensely occurred in surface waters of the Changjiang Estuary, which involve fiocculation and desorption processes at low salinities, and desorption and defiocculation and resuspension processes at middle and high salinities. 8. The water-particle interactions is important processes that control the flux of dissolved trace elements from the Changjiang River to the ocean, and are also significant for interpreting geochemistry of the trace elements of the East China Sea and the West Pacific.
页数	92
语种	中文
文献类型	学位论文
条目标识符	http://ir.gyig.ac.cn/handle/352002/3560
专题	研究生_研究生_学位论文环境地球化学国家重点实验室
推荐引用方式 GB/T 7714	王中良. 长江口水体混合过程中的水/粒作用地球化学——微量元素及同位素地球化学研究[D]. 中国科学院地球化学研究所. 中国科学院地球化学研究所,2001.

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