近海溶解态硒及其同位素的生物地球化学过程

发布时间：2018-01-03 21:18

本文关键词：近海溶解态硒及其同位素的生物地球化学过程　出处：《华东师范大学》2017年博士论文　论文类型：学位论文

【摘要】：痕量元素在海洋生态系统中起着举足轻重的作用,是海洋科学乃至全球环境变化研究的重点领域,而且非传统稳定同位素也是国际上同位素研究的一个前沿领域。硒是多种生物必需的营养元素,浓度高时会产生毒性效应,而且能够沿食物链传递富集。研究海洋中硒的分布及其沿食物链的传递行为,对于认识硒的生物地球化学循环过程及其对海洋生态系统的影响尤为重要。本论文针对长江口、东海和黄海桑沟湾(养殖海湾)开展了多次野外观测,基于不同价态硒的浓度和硒同位素组成,系统地认识了研究区域内溶解态硒的时空分布格局和迁移转化规律,以及硒沿食物链的传递行为特征,初步探讨了我国近海硒的生物地球化学循环过程。硒稳定同位素的分馏效应大,是一种潜在的地球化学示踪剂,但是目前海水中的硒同位素组成尚未见报道。本论文采用新型巯基树脂预富集和纯化海水样品,将氢化物发生技术结合去溶剂装置与多接收电感耦合等离子体质谱仪联用,建立了海水中溶解态硒同位素组成的分析方法。δ82/78Se、δ82/77Se和δ82/76Se的长期精密度分别为0.07‰、0.10‰和0.16‰(2sd,n=24),优于文献报道值,多个硒标准溶液的测定结果与国际同行接近(p=0.4),而且加标海水经巯基树脂分离前后也无明显的硒同位素分馏。在长江口,夏季(2011年7月)和春季(2012年3月)的溶解态无机硒(Dissolved Inorganic Selenium,DISe = Se(Ⅳ)+Se(Ⅵ))浓度范围分别为 0.35～4.39 nmol/L和0.49～4.75nmol/L,其中Se(Ⅵ)为溶解态无机硒的主要存在形态。DISe浓度水平分布格局呈现口内向口外逐渐降低的特点,受长江淡水、台湾暖流和黄海沿岸流三个水团的共同控制,各水团皆具有特征性的Se(Ⅳ)/Se(Ⅵ)比值。冬季时DISe、Se(Ⅳ)和Se(Ⅵ)呈严格的保守性行为,而夏季时则呈非保守性行为。在咸淡水混合的基础上,浮游植物利用和悬浮颗粒物吸附是长江口 DISe被清除的主要原因,而且Se(Ⅳ)被清除的程度大于Se(Ⅵ)。东海陆架夏季(2013 年 8 月)的δ82/76DISe 平均值为 0.82‰(-1.14‰～1.66‰),是全球第一组海水中溶解态硒同位素数据。春季(2011年5月)和夏季(2013年8月)DISe浓度范围分别为0.30～2.3 nmol/L和0.26～2.2 nmol/L,较为接近,其中Se(Ⅵ)为溶解态无机硒的主要存在价态。DISe浓度分布受到长江冲淡水、台湾暖流和黑潮水的共同控制,呈现近岸高、离岸逐渐降低的特点。初步收支估算显示台湾暖流和黑潮水入侵陆架是东海DISe的重要来源,共计输入约90%的DISe。冲绳海槽区域的δ82/76DISe值随水深从1.59‰逐渐降低至0.41‰,真光层内轻质硒同位素被浮游植物优先利用,导致水体δ82/76DISe偏重,而深层水体生源有机质降解,轻质同位素被优先释放到水体中,是δ82/76DISe值逐渐偏轻的可能机制。长江口近底层缺氧水体中82/76DISe值明显偏负(-0.66‰),偏轻约1‰t～2‰,可能发生了微生物异化还原Se(Ⅵ)。在黄海桑沟湾,2013年的3次调查(4月、7月和10月)发现表层水体中DISe浓度范围为0.21～1.36nmol/L,其中Se(Ⅵ)为溶解态无机硒的主要存在形态。DISe和Se(Ⅳ)浓度存在明显的季节差异,夏季低而春、秋季高,而且受湾内大面积密集养殖藻类和贝类以及浮游生物的影响,还呈现出明显的水平梯度变化特点。初步估算了桑沟湾内DISe的收支模型,表明最主要的源是黄海与桑沟湾的水交换,其次是地下水输入;而最重要的汇是生物移除,共计移除约53±12%的DISe。桑沟湾2015年5月表层水体中溶解态总硒(Total Dissolved Selenium)同位素组成(TDSe=DOSe+DISe,DOSe 为溶解态有机硒,Dissolved Organic Selenium)的范围为0.38‰到1.06‰,其中δ82/76DISe值相对偏负(-2.77‰到-2.05‰)。湾内生物的硒同位素组成范围较宽(-3.26到3.46‰),其平均δ82/76Se值的顺序为:鱼类肌肉(-1.11±2.02‰)浮游动物(0.76±0.17‰)≈浮游植物(0.80±0.10‰)牡蛎肌肉(1.24±0.30‰)扇贝肌肉(1.67±0.23‰)龙须菜(1.88±0.21‰)海带(3.19±0.22‰)。若不考虑人为饵料等的影响,桑沟湾湾内,相较于水体中的溶解态无机硒,浮游植物和大型藻类均明显富集重质硒同位素;湾内贝类与悬浮颗粒物和浮游植物相比,富集重质硒同位素;鱼类的δ82/76Se值随着硒含量、δ15N值增加而增加,逐渐富集重质硒同位素。本论文针对我国长江口、东海陆架和黄海桑沟湾内硒浓度和同位素组成的研究成果表明,我国近海区域溶解态硒受水团混合、生物利用、悬浮颗粒物吸附和氧化还原环境变化等多种因素控制,而且硒同位素沿食物链传递时会产生明显的同位素分馏,为硒同位素成为有效的地球化学示踪因子提供了依据。
[Abstract]:Trace elements play an important role in the marine ecosystem, is the focus of research in the field of marine science and global environmental change, but also a frontier field of traditional non stable isotope is also the isotope research. Many biological selenium is required, the high concentration would produce toxic effects, but also along the food chain enrichment Study on the distribution of selenium in the ocean. And along the transfer behavior of the food chain, is particularly important for the biogeochemical cycle of selenium and its impact on the marine ecosystem. Aiming at the mouth of the Yangtze River, the East China Sea and the Yellow Sea in Sanggou Bay (Bay aquaculture) to carry out a number of field observations, the concentration and composition of different valence selenium isotopes se based on the systematic understanding of the temporal and spatial patterns of migration and transformation rules of the distribution of dissolved selenium and selenium in the region, along the food chain transfer line features And discussed the biogeochemical cycle in coastal waters of China. The selenium fractionation effect of selenium isotopes, is a potential geochemical tracer, but the selenium isotopic composition of ocean water has not been reported. This paper adopts novel sulfhydryl resin preconcentration and purification of seawater samples, will combine to device and solvent multi collector inductively coupled plasma mass spectrometry combined with hydride generation technique, an analytical method of dissolved selenium isotopic composition in seawater. The delta 82/78Se, Delta 82/77Se and delta 82/76Se of the long-term precision of 0.07 per thousand respectively, 0.10 per thousand and 0.16 per thousand (2sd, n=24), better than the reported values, the determination results of multiple selenium the standard solution and close to the international counterparts (p=0.4), and the spiked seawater before and after sulfhydryl resin separation has no obvious. Selenium isotope fractionation in the Yangtze River Estuary, the summer (July 2011) and spring (March 2012) dissolved The inorganic selenium (Dissolved Inorganic Selenium, DISe = Se (IV) +Se (VI)) concentration range was 0.35 ~ 4.39 nmol/L and 0.49 ~ 4.75nmol/L, including Se (VI) is the main form of.DISe concentration distribution pattern appeared to the outside mouth gradually reduced characteristics of dissolved inorganic selenium, the Yangtze River water, common control of the Taiwan warm current and the Yellow Sea coastal water flow, the water masses are the characteristics of the Se (IV) /Se (VI) ratio. In the winter of DISe, Se (IV) and Se (VI) is strictly conservative behavior, while the summer is a non conservative behavior. On the basis of mixed salt and fresh water the use of phytoplankton and suspended particles, adsorption is the main reason for the mouth of the Yangtze River DISe is cleared, and the Se (IV) removed is greater than that of Se (VI). The East China Sea shelf in summer (August 2013) of the delta 82/76DISe average value of 0.82 per thousand (-1.14% ~ 1.66 per thousand), is the world's first group in seawater Dissolved selenium isotope data. In spring (May 2011) and summer (August 2013) DISe concentration range was 0.30 ~ 2.3 nmol/L and 0.26 ~ 2.2 nmol/L, which is close to that of Se (VI) for dissolved inorganic selenium mainly has the valence of.DISe concentration distribution by the Changjiang River, the common control of Taiwan warm current and the Kuroshio. Present, coastal, offshore characteristics gradually reduced. Preliminary estimates indicate that the balance of Taiwan warm current and the Kuroshio the continental shelf is an important source of DISe in the East China Sea, about 90% of the total input of 82/76DISe. DISe. in the Okinawa trough area value with depth from 1.59 per thousand gradually reduced to 0.41 per thousand, within the euphotic zone light selenium isotope by phytoplankton is preferred use, resulting in water and deep water on the delta 82/76DISe, biogenic organic matter degradation, light isotope is preferentially released into water, 82/76DISe values is small. The possible mechanism gradually in the Changjiang Estuary near the bottom of. 82/76DISe oxygen in water was significantly negative (-0.66%), partial light about 1 ~ 2 T%%, possible microbial dissimilatory reduction of Se (VI) in the Yellow Sea. In Sanggou Bay, 3 2013 Survey (April, July and October) found the concentration of DISe in surface water is 0.21 ~ 1.36nmol/L. The Se (VI) is the main form of.DISe and Se dissolved inorganic selenium (IV) concentration varied with season, summer is low and high in autumn and spring, but also by the large area of intensive farming algae and plankton and shellfish, also showing a level gradient characteristic. Budget model of mulberry the DISe ditch was preliminarily estimated that the main source of the Yellow Sea and the Sanggou Bay water exchange, followed by the groundwater input; and the most important biological sinks is removed, total dissolved removed about 53 + 12% DISe. in Sanggou Bay in May 2015 in the surface waters of total selenium (Total Dissolved Seleniu M (TDSe=DOSe+DISe, DOSe) isotopic composition of dissolved organic selenium, Dissolved Organic Selenium) in the range of 0.38 per thousand to 1.06 per thousand, the 82/76DISe values of relative partial negative (-2.77% to -2.05%). The biological selenium isotope composition of a wide range (-3.26 to 3.46 per thousand), the average 82/76Se values. Order: fish muscle (-1.11% + 2.02 (0.76 + 0.17) planktonic animal%) = phytoplankton (0.80 + 0.10 per thousand (1.24 + 0.30) oyster muscle muscle Scallop in Shell%) (1.67 + 0.23 per thousand (1.88 + 0.21)%) of Gracilaria kelp (3.19 + 0.22 per thousand). Without considering the effect of artificial bait the Sanggou Bay Bay, dissolved inorganic selenium compared to water, phytoplankton and macroalgae were significantly enriched in heavy isotopes of selenium; the shellfish and suspended particulate and phytoplankton in heavy enriched selenium isotope; Delta 82/76Se fish value with the Se content, 15N values increased gradually. The enrichment of heavy isotopes of selenium gradually in our country. This paper research the mouth of the Yangtze River, the East China Sea shelf and the Yellow Sea Bay and Sanggou selenium isotopic composition indicate that dissolved selenium coastal region of our country by water mixing biological utilization, suspended particle adsorption and redox environment of many factors such as control, and selenium isotope along the food chain will produce significant isotopic fractionation, provide the basis for the effective factors of geochemical trace selenium isotopes become.

【学位授予单位】：华东师范大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：P736.4

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