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1.
讨论了在冲绳海槽伊平屋海岭和南奄西海丘两处海底热液喷出口附近海水中的铀系子体放射性核素2 10 Pb和2 10 Po浓度的垂直分布剖面 .在伊平屋海岭 ,甲烷及2 2 2 Rn的数据表明海底热液活动不强 ,总2 10 Pb和2 10 Po放射性均低于它们各自母体的放射性 ,2 10 Pb和2 10 Po在海水中的平均停留时间分别为 2 0和 2～ 5a ,而在以“黑色烟雾”为特征的海底热液活动强烈的南奄西海丘 ,在”烟雾”中的总2 10 Pb含量 ( 0 1 6 7× 1 0 -3～ 2 50× 1 0 -3Bq/kg)相对其母体2 2 6Ra贫乏 ,而总2 10 Po含量 ( 1 83× 1 0 -3～ 2 83×1 0 -3Bq/kg)则相对其母体2 10 Pb过剩 .该处海水中的2 10 Po的放射性高于东海陆架区及冲绳海槽其他海区 ,并且显示了2 10 Po过剩 .2 10 Pb/ 2 2 6Ra以及2 10 Po/ 2 10 Pb放射性比值的范围分别为 0 1～ 0 4和 1 1～ 7 8.在热液扩散带中2 10 Pb被优先从海水中清除 .控制南奄西海丘海水中2 10 Pb浓度的可能机制涉及到2 10 Pb通过扩散作用的横向输送 .在热液扩散带中高2 10 Po/ 2 10 Pb放射性比值表明2 10 Pb的耗尽及2 10 Po从海底热液喷出口的加入 . 相似文献
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Vertical profiles for the uranium-series radioisotopes 210Pb and 210Po were obtained at thetwo hydrothermal vent sites, the Iheya Ridge and the Minami-Ensei Knoll, in the Mid-Okinawa Trough in 1993 and 1994, respectively. In 1995, both radioisotopes were measured at the Minami-Ensei Knoll a-gain. At the Iheya Ridge, where the hydrothermal activity is not active as reflected by the CH_4, and 222Rn data, both the total 210Pb and 210Po activities show deficiency relative to their parents, and the mean residence time of 210Pb and 210Po is approximately equal to 20 and 2-5 a, respectively. At the Minami-Ensei Knoll, which is characterized by black smokers, the total 210Pb(0.167 × 10~(-3)-2.5 × 10~(-3)_ Bq/kg) around the plumes is deficient relative to 226Ra but the total 210Po activities (1.83 × 10 ~(-3) - 2.83 × 10~(-3) Bq/kg) are in excess relative to 210Pb. The 210Po activities are higher than those in the East China Sea and the Okinawa Trough and excess 210Po has been found. The 210Pb/226Ra and 210Po/ 相似文献
3.
为揭示中国东南沿海地区210Po和210Pb的大气沉降时空变化特征，探讨该地区气溶胶的停留时间，于2013年1月至2014年12月对厦门地区210Po和210Pb的大气沉降通量进行了时间序列研究。结果发现，210Po和210Pb的平均日沉降通量分别为（65.38±4.79） mBq/（m2·d）（n=54）和（0.78±0.09） Bq/（m2·d）（n=54），表现出明显的周年变化。东北季风期间，210Po和210Pb的沉降通量较高，而西南季风期间其通量较低。2013年和2014年，210Po的年沉降通量分别为19.29 Bq/（m2·a）和9.25 Bq/（m2·a），210Pb的年沉降通量分别为159.2 Bq/（m2·a）和189.6 Bq/（m2·a）。两核素的年沉降通量表现出不同程度的年际差异。210Po与210Pb沉降通量之间存在显著的线性正相关关系，揭示了大气中210Po和210Pb具有相同的迁出机制，降雨和大气中核素含量是影响210Po和210Pb沉降通量的主要因素。该研究结果可以为探求台湾海峡海水中210Po与210Pb的收支平衡提供大气来源项。 相似文献
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对北太平洋亚热带环流区表层水中溶解态(＜0.2 μm)和颗粒态(≥0.2 μm)210 Po、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210 Po、210Pb的分馏起着一定的作用. 相似文献
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对南海和厦门湾表层水中210Po和210Pb的粒级分布特征进行了研究.结果表明,南海海水中210Po和210Pb在不同粒级颗粒物中的体积比活度高低顺序为:(＜0.4μm)＞(0.4～2.0 μm)＞(2.0～10 μm)＞(＞10μm).210Po、210Pb主要存在于＜2.0 μm粒级颗粒物中.厦门湾210Po体积比活度高低顺序为:(2.0～10 μm)＞(＜1.2μm)＞(＞10μm)＞(1.2～2.0 μm),210Po主要存在于＞2.0μm粒级颗粒物中.南海不同粒级颗粒物中210Pb的质量比活度差异不大,0.4～2.0 μm和2.0～10 μm粒级210Po质量比活度约为10μm粒级210Po比活度的3倍.厦门湾210Po的质量比活度比南海相应粒级210Po低约1个数量级,且各粒级间差异不大,表明不同粒径颗粒物在210Po和210Pb清除过程中的作用不同.210Po和210Pb的固-液分配系数(Kd)及分馏因子(α)进一步证实南海0.4～2.0 μm粒级颗粒物对210Po的清除能力比其它粒级颗粒物更强,而＞10μm粒级颗粒物对210Pb的清除能力比其它粒级颗粒物更强.不同粒级颗粒物中210Po与210Pb之间的不平衡状况揭示了不同粒级颗粒物不同的来源,为210Po/210Pb不平衡示踪颗粒物来源提供了依据. 相似文献
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世界大洋表层水中的210Pb 总被引：2，自引：0，他引：2
本工作获得了西太平洋,东印度洋和南大西洋15个站位表层水中的溶解态210Pb和颗粒态210Pb的浓度.溶解态210Pb的浓度范围为西太平洋0.71～3.80Bq/m3;东印度洋0.42～2.15Bq/m3;南大西洋0.97～1.78Bq/m3.210Pb最大值3.80Bq/m3是在27°18′N,125°40′E(北太平洋)测得的,而最小值0.42Bq/m3是在远离澳大利亚西岸的25°18′S,111°38′E(东印度洋)测得的.在26°56′S,166°07′E(南太平洋)观测到颗粒态210Pb浓度的最大值0.35Bq/m3,而在东南印度洋颗粒态210Pb的浓度都小于0.03Bq/m3.表层水中溶解态210Pb含量一般呈现出地理性变化,其随纬度的变化与文献报道的结果很相符. 相似文献
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冲绳海槽中部南奄西海丘海底热液活动的若干特征 总被引：1，自引：0，他引：1
冲绳海槽中部南奄西海丘海底热液活动为弧后盆地型热液活动。在水深 ６５０～７７０ｍ处发育有活烟囱，喷出的热液温度（２７０℃）临近当地沸点（２７５℃），热液 中富含ＣＯ２气泡。稳定同位素研究表明，热液活动与岩浆活动有关。根据热液沉积 物的矿物学及化学特征可将其划分为４种类型，它们是富硅热液沉积物、富硫酸盐 热液沉积物、块状富硫化物热液沉积物和碎屑状富硫化物热液沉积物。热液沉积物 中至少含有２７种矿物，并富集了Ｚｎ，Ｐｂ，Ｃｕ，Ａｇ等成矿元素。 相似文献
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大气输送的放射性核素7Be、210Po和210Pb,可以作为研究北冰洋大气沉降通量、海洋现代沉积以及海冰中物质传输的重要示踪剂,已被广泛应用于包括气团运动、土壤侵蚀以及水系统中颗粒物循环过程的研究。本文报道了2018年北极高纬度浮冰区表层积雪中7Be、210Po和210Pb的活度特征。7Be、210Po和210Pb的比活度变化范围分别为33.6～632.68 mBq/L、36.2～87.5 mBq/L、30.9～194.49 mBq/L。本文的研究发现,北冰洋表层积雪中7Be和210Pb比活度小于中纬度大陆地区。研究区域表层积雪中7Be的比活度随着纬度的增加而增加。此外,表层积雪中210Po/210Pb活度比值范围为0.70～1.48 (平均为0.93),210Po与210Pb活度已基本达到平衡,表明积雪样品年龄可能较“老”。 相似文献
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通过分析第十次北极考察楚科奇海、白令海考察区表层沉积物样品中放射性核素~(210)Pb和~(137)Cs,获得表层沉积物(0～8 cm)中~(210)Pb和~(137)Cs在不同断面和不同层的比活度范围和分布。楚科奇海陆架区R断面表层沉积物(0～2 cm层)~(210)Pb比活度范围为44.80～117.45 Bq·kg~(-1);~(137)Cs检出主要分布在表层沉积物(2～4 cm和4～6 cm层),比活度范围为未检出～2.23 Bq·kg~(-1)。白令海BL和BR断面表层沉积物(0～2 cm层)~(210)Pb比活度范围分别为29.93～141.35 Bq·kg~(-1)和40.78～620.43 Bq·kg~(-1);BL和BR断面~(137)Cs比活度范围分别为未检出～2.48 Bq·kg~(-1)和未检出～2.08 Bq·kg~(-1)。其中在白令海考察区南端陆坡区深海站位出现~(210)Pb比活度高值;结合表层沉积物垂向分层数据揭示水体中~(210)Pb随颗粒物移除沉降到海底,随海底深度增加而显著升高;各站位的表层沉积物年沉积率随海底深度增加而降低。深海区域站位表层沉积物~(210)Pb比活度随海底深度增加而增加现象说明,颗粒物沉降过程的吸附作用是主要原因。也表明表层沉积物~(210)Pb比活度与海水深度的比值作为~(210)Pb均化因子(HF),可指征颗粒物中~(210)Pb比活度从水体上层至海洋底层随沉降过程的平均变化。研究结果表明楚科奇海陆架区部分站位表层沉积物~(210)Pb存在明显的扰动情况,楚科奇海陆架区、白令海陆架区表层沉积物中~(137)Cs在沉积物各层深分布不均匀。 相似文献
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~(210) Po and ~(210) Pb are increasingly used to constrain particle dynamics in the open oceans, however they are less used in coastal waters. Here, distributions and partitions of ~(210) Po and ~(210) Pb were examined in the Taiwan Strait, as well as their application to quantify particle sinking. Activity concentrations of dissolved ~(210) Po and ~(210) Pb(0.6 μm)ranged from 1.21 to 7.63 dpm/(100 L) and from 1.07 to 6.33 dpm/(100 L), respectively. Activity concentrations of particulate ~(210) Po and ~(210) Pb varied from 1.96 to 36.74 dpm/(100 L) and from 3.11 to 38.06 dpm/(100 L). Overall,particulate ~(210) Po and ~(210) Pb accounted for the majority of the bulk ~(210) Po and ~(210) Pb. 210 Po either in dissolved or particulate phases showed similar spatial patterns to 210 Pb, indicating similar mechanisms for controlling the distributions of ~(210) Po and ~(210) Pb in the Taiwan Strait. The different fractionation coefficients indicated that particles in the Zhemin Coastal Current(ZCC) inclined to absorb 210 Po prior to 210 Pb while they showed an opposite effect in the Taiwan Warm Current(TWC). Based on the disequilibria between ~(210) Po and ~(210) Pb, the sinking fluxes of total particulate matter(TPM) were estimated to range from –0.22 to 3.84 g/(m2·d), showing an overall comparable spatial distribution to previous reported sediment accumulation rates. However, our sinking fluxes were lower than the sedimentation rates, indicating a sediment resuspension in winter and horizontal transport of particulate matter from the Taiwan Strait to the East China Sea. 相似文献
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210Pb was measured during the 3rd Chinese National Arctic Research Expedition cruise to investigate its spatial pattern in the western Arctic Ocean, as well as its relation with the thermocline in the Canadian Basin. The specific activities varied from 0.04 to 2.72, 0.013 to 4.37, and 0.1 to 4.85 Bq/m3 for dissolved, particulate, and bulk 210Pb, respectively, corresponding to respective averages of 0.65, 0.43, and 1.08 Bq/m3. In the Canadian Basin, the minimum 210Pb activities occurred in the thermocline, which was characterized by low temperature of-1.52°C and salinity of 33.1. Combining the spatial distribution of 210Pb and hydrographical characteristics in the western Arctic Ocean, this scenario was ascribed to the effective scavenging of 210Pb when the Pacific water flowed across the Chukchi Shelf. Quantitatively, this interpretation was supported by both the shorter residence times and higher scavenging efficiencies(SE) of dissolved 210Pb over the Chukchi Shelf. The highest SE values were observed in the Herald Shoal and bottom waters over the slope. 相似文献
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南极长城站附近企鹅栖息地粪土沉积地层放射性核素210Pb定年 总被引：1，自引：0，他引：1
用γ谱方法测定了南极长城站附近特有生物群落栖息地沉积物中放射性核素含量,地表沉积物中40K,137Cs,210Pb,226Ra,228Ra,228Th.和238U平均比活度,分别为143,7.56,24.1,3.65,5.36,4.15和6.5Bq/kg.同时测试了阿德雷岛企鹅栖息地粪土沉积地层中放射性核素含量,利用其中的210Pb比活度,210Pbex垂向变化特征,推演沉积物的沉积速率和地质历史年代:其中AD1-a柱样时间跨度约为74a(1928~2002年),据此计算了沉积速率为0.063mm/a(r=0.794),并讨论了在南极特定条件下,放射性核素示踪对定年影响以及与区域现代气候环境变化的内在联系. 相似文献
14.
210Po, 210Pb, and 234Th were determined in water columns of the East China Sea (ECS) to investigate their biogeochemical behaviors during a severe red tide event. Dissolved 210Po, 210Pb, and 234Th accounted for large fractions of the total phases. The abnormally high concentrations of dissolved 210Pb were observed. Partition behaviors of these radionuclides were influenced by particle content effect and particle composition based on distribution coefficient (Kd) vs. total suspended matter (TSM) content and Kd vs. ratios of particulate organic carbon and total suspended matter contents (POC/TSM content ratios). The peaks of mass specific activities of 210Po, 210Pb, and 234Th indicated that degraded particles could have an intensified enrichment ability for radionuclides compared with the surficial suspended matters. Fractionation factor of 210Po and 210Pb (FPo/Pb) (>1) and fractionation factor of 210Po and 234Th (FPo/Th) (>1) were much higher at algal blooming regions than that at non-blooming stations, indicating that algal blooms promoted the fractionation of 210Po against 210Pb and 234Th, and proving that 210Po exhibited a stronger affinity for biogenic particles than 210Pb and 234Th when POC content increased in the sea. POC/210Po, POC/210Pb and POC/234Th ratios (content/activity ratios) sharply decreased with depth in both algal bloom and non-bloom stations. The outbreak of algal bloom promoted the complexity of suspended particles and increased the variability of POC/tracer ratios (content/activity ratios) in the different depth of the shallow seas. More considerations should be taken to the difficulty of the selection of export interface and the suitable tracers when algal blooming occurs. 相似文献
15.
本文利用放射化学分析法测定了长江口及其邻近陆架沉积物中~(226)Ra和~(210)Pb的含量。结果表明,在该海区的沉积物中,~(226)Ra含量的水平分布随经度增加而直线下降,而~(210)Pb含量的水平分布则随经度增加而直线上升,二者形成明显的同步反向分布。 相似文献
16.
南海东北部表层沉积物天然放射性核素与137Cs 总被引：4，自引：2，他引：4
用HPGeγ谱仪测定了南海东北部表层沉积物中的放射性核素.结果给出7种核素的平均比活度分别为40K:538Bq/kg,210Pb:116Bq/kg,226Ra:27.7Bq/kg,228Ra:4.49Bq/kg,228Th:42.0Bq/kg,238U:35.4Bq/kg和137Cs:1.16Bq/kg,210Pb的比活度随离岸距离增大,226Ra比活度随离岸距离没有明显变化,其余核素比活度随离岸距离减小.与对我国近海其他海域报道的沉积物放射性核素含量相比,40K和137Cs稍低于其他海域,其余核素为中等水平. 相似文献
17.
Vertical profiles of dissolved and particulate 210Po and 210Pb were measured across the redox transition zone at Station F1 in Framvaren Fjord, Norway. In this fjord, a sharp decrease in pH above the O2/H2S interface facilitates the aerobic dissolution of MnO2. In contrast, Fe(II) concentrations begin to increase only at the O2/H2S interface depth. Activity profiles reveal that dissolved 210Po and 210Pb are sequestered efficiently by particulates in surface waters. As polonium-210 and lead-210 activities descend down into the aerobic manganese reduction (AMR) zone, they are remobilized during the reductive dissolution of the carrier phase oxyhydroxides. Both 210Po and 210Pb are highly enriched at the O2/H2S interface where an active community of microbes, such as anoxygenic phototrophs (e.g., Chromatium, Chlorobium sp.), thrives. The coincident peaks in 210Po, 210Pb and microbial biomass suggest a strong biological influence on the behavior of these radionuclides. There is a strong covariance between the vertical distribution of Mn and Pb, indicating that their redox cycling is closely coupled and is likely microbially mediated. 相似文献