Geochemical behaviors of 210Po and 210Pb and their application in the China Marginal seas

本研究通过对北部湾湾口、南黄海、东海、南海北部海域进行的共计10个航次的调查、采样及分析，对海水中210Pb和210Po活度浓度的时空分布特征进行研究，并利用模型估算出210Po的清除迁出速率、停留时间、垂向迁出通量以及POC输出通量。得到主要结果如下： 1）、北部湾溶解态和总210Pb活度浓度春、夏季较秋、冬季高，颗粒态刚好相反，春、夏季低于秋、冬季。溶解态和总210Po活度浓度秋季最低，其余三个季节变化较小，但夏季各层次之间活度浓度变化比较明显；颗粒态210Po活度浓度秋季最高，冬季最低，春、夏季居中，且二者相接近。各站位近底层溶解态210Pb活度浓度随离岸距离的增加而增加，颗粒态210...Activity concentrations of 210Pb and 210Po in China marginal seas, including the Beibu Gulf, the southern Yellow Sea, the East China Sea and the northern South China Sea, were determined. The spatial and temporal distribution of them was depicted. The scavenging and removal rates, residence times, removal flux of 210Po and POC export flux were calculated by steady-state (SS) and non-steady-state (...学位：理学博士院系专业：海洋与环境学院海洋学系_海洋化学学号：2242006015333

Particle transport and export in the north Pacific and the western Arctic Ocean as revealed by radionuclides

234Th、210Po和210Pb均为颗粒活性核素，已被广泛应用于海洋颗粒物及其所携带生源要素的循环与输出的研究。本论文以西北冰洋的234Th-238U不平衡，热带与亚热带北太平洋的210Po-210Pb不平衡为对象，开展海洋颗粒动力学方面的研究。得到如下结果与认识： （1）基于234Th/238U不平衡获得西北冰洋颗粒有机碳输出通量的空间分布特征。西北冰洋大部分研究站位上层水柱中总234Th相对于母体238U呈亏损状态，表明研究海域存在颗粒物清除、迁出作用，西北冰洋颗粒动力学特征仍显活跃。234Th迁出通量和颗粒有机碳输出通量由陆架区向深海盆地呈减少态势，而234Th停留时间呈现增加趋势，...234Th，210Po and 210Pb are particle-reactive radionuclides and have been widely used to study particle transport and export in marine environments. In this thesis, 234Th/238U disequilibrium and 210Po/210Pb disequilibrium have been used to study the particle dynamics in the western Arctic Ocean and in the tropical and subtropical North Pacific, respectively. The major results as follows: （1） Region...学位：理学硕士院系专业：海洋与环境学院海洋学系_海洋化学学号：20022701

近40年北太平洋亚热带环流区生态系变化的~(226)Ra证据

利用1999年7～10月和2003年10～12月实测的北太平洋亚热带环流区表层水~(226)Ra含量,结合文献所报道的历史数据,发现自20世纪60年代至今,北太平洋亚热带环流区表层水体~(226)Ra含量呈下降趋势,反映出全球变化导致该海域生态系结构的变化.全球增暖一方面导致了该海域水体层化作用的加强,进而导致上层水体Ra补充量的减少;另一方面,全球增暖导致海域生物生产力的升高,进而导致Ra迁出量的增加.~(226)Ra含量的上述变化与文献报道的该海域叶绿素a、硅酸盐、磷酸盐含量与初级生产力的历史变化趋势相吻合,确证北太平洋亚热带环流区在全球变化背景下正发生着可观测的生态系统变化.在上层海洋层化作用加强的情况下,为维持海域升高的生物生产力,其“新”氮可能的来源是海洋的固氮作用

MnO_2 precipitation and direct beta counting technique for determining ~(234)Th in small-volume seawater

探讨了MnO2共沉淀直接β计数测定小体积海水中234Th方法在固体闪烁α/β计数仪上实现的可能性,对实验流程空白、流程化学回收率、仪器探测效率、MnO2共沉淀量对全程回收率的影响以及检测核素的特征性等进行了研究.结果表明,该方法具有稳定的流程空白和全程回收率、高的探测效率和化学回收率,且所检测核素与234Th的理论半衰期基本吻合.将该流程应用于亚热带北太平洋表层水中234Th的分析也得到了令人满意的结果.与传统方法相比,该方法具有流程简单、所用水样体积小、快速获得结果等特点,适合于船载分析,由此可实现高时空分辨率数据的获取,为海洋颗粒有机碳输出通量以及颗粒物迁移速率的研究提供了更好的分析手段. 【英文摘要】 A method for ~(234)Th determination in small-volume seawater was established by using the alpha/beta counter with scintillating solid detectors. This method is based on the coprecipitation of thorium with Mn oxides followed by direct beta counting of the precipitation. A series of experiments were conducted in order to examine the blank, chemical yield, detector efficiency of the procedure. Besides, the effect of the amount of MnO_2 precipitation on total yields was tested. Half-life determination was used ...中国大洋矿产资源研究开发协会国际海底区域研究开发计划资助项目(DY1050204;DY1050201);; 国家自然科学基金资助项目(项目90411016)

~(210)Po/~(210)Pb disequilibria in the surface waters of the North Pacific Subtropical Gyre

对北太平洋亚热带环流区表层水中溶解态(<0.2μM)和颗粒态(≥0.2μM)210PO、210Pb的含量、分布、停留时间及其在颗粒物清除迁出过程中的分馏效应开展了研究,结果表明,研究海域表层水中溶解态210PO、210Pb的比活度分别介于0.14~3.75和1.41~6.87 bQ/M3之间;颗粒态210PO、210Pb的比活度分别介于0.35~2.49和0.18~3.18 bQ/M3之间.溶解相和颗粒相中的210PO/210Pb不平衡状态呈现截然不同的特征,溶解相中210PO相对于210Pb呈亏损状态,而在颗粒相中则呈过剩状态,反映出210PO与210Pb生物地球化学行为的差异,210PO具有更强的颗粒(生物)活性.由稳态不可逆模型计算出溶解态和颗粒态210PO的平均停留时间分别为0.28、0.27 A;溶解态和颗粒态210Pb的平均停留时间分别为0.88、0.15 A.由清除速率常数法计算得到的溶解态210PO、210Pb在颗粒清除过程中的平均分馏因子为4.73,且该分馏因子随颗粒氮含量的增加呈增加的趋势.停留时间的差异以及明显大于1的分馏因子均表明,210PO、210Pb在颗粒清除过程中发生了明显的分馏,而分馏因子与颗粒氮(Pn)之间存在的正相关关系则显示含氮组分对210PO、210Pb的分馏起着一定的作用.Dissolved(< 0.2 μm) and particulate(≥0.2 μm) 210Po and 210Pb in surface waters collected from the North Pacific Subtropical Gyre were analyzed to understand their distribution,residence times and fractionation during particle scavenging.The activity concentrations of dissolved 210Po and 210Pb fell in a range of 0.14~3.75 Bq/m3 and 1.41~6.87 Bq/m3 respectively,and those of particulate 210Po and 210Pb ranged from 0.35 to 2.49 Bq/m3 and from 0.18 to 3.18 Bq/m3,respectively.The disequilibria between 210Po and 210Pb showed different characteristics in the dissolved and the particulate phases.210Po was deficient in the dissolved phase but excess in the particulate phase relative to 210Pb,indicating their different biogeochemical behaviors and a more particulate(or biologically) reactive 210Po.The residence times of dissolved and particulate 210Po estimated from an irreversible steady-state model were 0.28a and 0.27a,respectively;and those of dissolved and particulate 210Pb were 0.88a and 0.15a respectively.The consistently high fractionation factors(4.73) calculated by scavenging rate constants suggested that a significant fractionation occurred between 210Po and 210Pb during their scavenging from solution to particles.Furthermore,the fractionation factors increased with the increasing contents of particulate nitrogen,indicating that the fractionation between 210Po and 210Pb was influenced by N-containing components.国家自然科学基金杰出青年基金资助项目(41125020); 国家海洋局大洋专项资助项目(DY125-13-E-01); 福建省自然科学基金杰出青年基金资助项目(2009J06026

Distribution of Primary Production in the Yellow Sea and the East China Sea in Summer

利用14 C示踪法实测了黄、东海海域2006年6—8月的初级生产力,结果表明,积分初级生产力介于378.65~6 403.47Mg/(M2.d)之间,平均为2 059.56Mg/(M2.d)。初级生产力的空间变化表现出3个特点:1)东海的积分初级生产力明显高于黄海;2)受黑潮水影响,海域的初级生产力比陆架区明显低;3)长江口东南海域和济州岛西南海域存在较高的初级生产力。对初级生产力和环境因子的关系进行分析表明,初级生产力的高值大多出现在水温为21~26℃的水体中,光强和营养盐共同调控着黄、东海海域初级生产力的分布。受黑潮水影响,海域初级生产力较低与其贫乏的营养盐有关,而长江冲淡水和冷涡输送的丰富营养盐维持着长江口东南海域和济州岛西南海域较高的初级生产力。Primary production supports substantial biomass and higher trophic level organisms in the coastal waters,but the mechanisms regulating primary production in coastal waters are still difficult to assess.In this study,primary production in the Yellow Sea and the East China Sea was measured via 14C tracer in summer 2006 to reveal their distribution features and the impact factors.Our results showed that the depth-integrated primary production ranged from 378.65 to 6 403.47 mg/(m2·d) with an average of 2 059.56 mg/(m2·d).The distribution of primary production indicated that(1) primary production in the East China Sea was higher than those in the Yellow Sea;(2) primary production in sea areas influenced by the Kuroshio waters was significantly lower than those in the shelf regions;and(3) high primary production was observed in the southeastern region of Changjiang estuary and the southwestern region of Jelu Island.The relationship between primary production and environmental factors suggested that high primary production mostly occurred in seawaters with temperature of 21-26 ℃,and the primary production was regulated by the availability of nutrients and lights.The low primary production in the regions influenced by the Kuroshio waters was ascribed to the low nutrients,and the high primary production in the southeastern region of Changjiang estuary and the southwestern region of Jelu Island was ascribed to the abundant nutrients supplied by the Changjiang river and the cold eddy.国家重点基础研究发展规划项目课题“典型水域生源要素循环及浮游植物多样性对海洋物理环境演变的响应”(2005CB422305);国家自然科学基金杰出青年基金项目“同位素海洋化学研究”(41125020

Radium-226 as a tracer for the source and movement of water masses in the Prydz Bay of Antarctica

中国第22次南极科学考察航次(2005年12月至2006年1月)期间,利用Mn-纤维富集大体积表层海水中的rA同位素,并通过222rn直接射气法测量226rA的比活度,结果表明,普里兹湾表层水的226rA比活度变化为0.92--2.09 bQ/M3,平均值为1.61 bQ/M3,在深海区域表现出226rA含量高的特征。从空间分布看,表层水226rA比活度呈现出由湾内向湾外增加的反常态势,反映出不同rA含量水团的混合影响2。26rA比活度与盐度的关系证实研究海域表层水的rA含量主要受三种端元水体的混合所控制:其一为具有镭含量高、盐度高特征的南极夏季表层水;其二为低镭、低盐特征的冰融水;其三为高盐、中等镭含量的普里兹湾中深层水,该水体的226rA纯粹由海底沉积物间隙水向上扩散所维持。结合S-226rA示踪体系及上述三端元混合模型,计算出各组成水体的比例并描绘出它们的空间分布。南极夏季表层水的份额由湾外向湾内逐渐降低,并且在68°E断面向南影响范围较大;冰融水的比例由湾内向湾外降低,并且在湾内东部的高温水体中具有最大贡献;普里兹湾中深层水中受沉积物镭来源影响比较显著的区域出现在湾内西北部,其影响向湾外逐渐降低。冰融水与普里兹湾中深层水份额分别于普里兹湾湾顶东、西部出现高值的分布特征证实埃默里冰架前沿海流东进、西出的运移规律。Surface waters were collected from the Prydz Bay of Antarctica for measurements of 226Ra activities during the 22nd China's antarctic research expedition(from December 2005 to January 2006).226Ra in large volume waters was extracted by Mn-fibers and measured by a 222Rn emanation method.Results show that 226Ra activity in the Prydz Bay ranges from 0.92 to 2.09 Bq/m3 with an average of 1.61 Bq/m3.High contents of 226Ra were observed at deep open-ocean stations,which induced an offshore increase of 226Ra activity.This unique distribution pattern in the Prydz Bay was ascribed to the influence of water masses with different 226Ra signals.Based on the relationship between 226Ra activity and salinity,three water masses were identified:(1) the antarctic summer surface water(AASSW) with a characteristics of high salinity and high content of 226Ra;(2) the ice-melted water(IMW) with a characteristics of low salinity and low content of 226Ra;and(3) the Prydz Bay deep water(PDW) with a characteristics of high salinity and intermediate content of 226Ra.226Ra in the Prydz Bay deep water was assumed to be maintained only by the supply from the seabed sediments.The fractions of the above three water masses were estimated by mass balance calculation of salinity and 226Ra activity.Results show that the AASSW fractions decrease from the deep open ocean to inshore,while the IMW and PDW fractions increase.The maximum fractions of the IMW and the PDW occur in the eastern and the western regions along the front of the Amery ice shelf,respectively,testifying the major flow into the shelf occurs at the eastern end and exits from the west.国际极地年中国行动计划项目;国际海底区域研究开发“十一五”项目(DYXM-115-02-4-06);福建省自然科学基金杰出青年基金项目(2009J06026