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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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冲绳海槽海底热液喷出口附近海水中210Pb和210Po的行为 总被引：1，自引：0，他引：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210Pb和210Po浓度的垂直分布剖面.在伊平屋海岭,甲烷及222Rn的数据表明海底热液活动不强,总210Pb和210Po放射性均低于它们各自母体的放射性,210Pb和210Po在海水中的平均停留时间分别为20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210Pb含量(0.167×10-3～2.50×10-3Bq/kg)相对其母体226Ra贫乏,而总210Po含量(1.83×10-3～2.83×10-3Bq/kg)则相对其母体210Pb过剩.该处海水中的210Po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210Po过剩.210Pb/226Ra以及210Po/210Pb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210Pb被优先从海水中清除.控制南奄西海丘海水中210Pb浓度的可能机制涉及到210Pb通过扩散作用的横向输送.在热液扩散带中高210Po/210Pb放射性比值表明210Pb的耗尽及210Po从海底热液喷出口的加入. 相似文献
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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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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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本研究测定了2015年1~7月厦门市大气气溶胶中的7Be、210Pb和210Po,利用多核素联合示踪研究了相关的大气过程.结果表明7Be和210Pb在1、3和4月份具有较高的活度水平和较大的活度变化范围,在6~7月份降低到相对较低的活度水平和一个相对较小的变化范围,不同的气团来源、对流混合及清除机制是其主要的控制因素.相对于7Be,7Be和210Pb同位素对对臭氧(O3)具有更好的相关关系.基于210Pb和210Po的数据计算出厦门市大气气溶胶停留时间为21~188 d,平均值为87 d.通过辐射剂量评估发现这3种放射性核素对人体所产生的年待积有效剂量仅为5.31μSv,近似为天然辐射本底的千分之一. 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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为了研究长江水下三角洲及邻近海域沉积动力环境对长江入海输沙量减少的响应,进行了野外采样以及论文数据收集工作,利用~(210)Pb放射性同位素的测量和分析,分别比较表层和柱状沉积物的~(210)Pb活度在2003年前后的变化。结果显示,在2003年后,表层沉积物~(210)Pb活度分布特征由原来的明显梯度变化变为均一分布,同时活度值普遍降低;而柱状沉积物的~(210)Pb垂向分布曲线也由原来的稳定沉积曲线变为混合强烈的均匀分布。这说明了,在长江入海输沙量减小的背景下,研究区内的沉积动力环境随之发生改变,河口过程主导的沉积作用在不断减弱,而陆架过程主导的混合作用却在不断加强。 相似文献
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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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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
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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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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
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Sediment trap experiments were carried out in two oceans, the eastern Pacific Ocean and the Antarctic Ocean, which have very different biological productivities. The natural radionuclides,234Th,210Po and210Pb were used as tracers of reactive metals. Larger particulate fluxes of these radionuclides were found in the seas where total mass fluxes were larger, although the concentrations of these radionuclides in the settling particles were somewhat smaller. The concentrations of234Th in the settling particles varied widely and irregularly with depth, whereas the concentrations of210Po and210Pb in the settling particles steadily increased with increasing water depth. The ratios of210Po/210Pb in the settling particulates were larger than unity which the ratio of234Th/excess210Po as larger than234Th/210Po in the deep water. These results suggest that, when the particles sink through the water column, these radionuclides are being absorbed by settling particles in the order234Th>210Po>210Pb. The observed particulate fluxes of210Pb are about one eighth of those calculated from the disequilibria between226Ra and210Pb at the stations in the subtropical eastern Pacific, although the observed fluxes are the same as the calculated ones in the northern North Pacific and the Antarctic Ocean. Thus, there must be a horizontal flow carrying these reactive metals from the oligotorophic ocean to the biologically productive ocean where the metals are removed by settling particles even in deep water. 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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Quantifying relative affinities of Po and Pb in different populations of marine particulate matter is of great importance in utilizing 210Po as a tracer for carbon cycling. We collected and analyzed water samples for the concentrations of dissolved and total 210Po and 210Pb from the upper 600 m of the water column at Bermuda Time-series Study site (September 1999–September 2000) to investigate their seasonality of concentrations and their activity ratio (210Po/210Pb activity ratio, AR). Sinking particles collected in sediment traps at depths of 500 m, 1500 m, and 3200 m from the Oceanic Flux Program (OFP) time-series sediment traps were analyzed over a period of 12 months (May 1999–May 2000). The objective was to compare the deficiencies of 210Po with respect to 210Pb in the water column to that measured in the sediment traps and to assess the relative affinities of Po and Pb with different particle pools.Inventories of 210Po in the upper 500 m water column varied by a factor of 2, indicating seasonal variations of particulate flux dominated the removal of 210Po. The 210Po/210Pb ARs in the dissolved phase were generally less than the secular equilibrium value (1.0) in the upper 600 m, while were generally greater than 1.0 in the particulate phase, indicating higher removal rates of 210Po relative to 210Pb by particulate matter. The measured fluxes of 210Po and 210Pb in the 500 m, 1500 m, and 3200 m traps increased with depth, while the 210Po/210Pb ARs decreased with depth except from May–August 1999. From the measured fluxes of 210Po and 210Pb at these three traps and the concentrations of 210Po and 210Pb in the water column, this region appears to be a sink for 210Pb which is likely brought-in by lateral advection. 相似文献
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Gi-Hoon Hong Young-Ill Kim Mark Baskaran Suk-Hyun Kim Chang-Soo Chung 《Journal of Oceanography》2008,64(2):277-292
The distribution of the natural radionuclide 210Po in the water column along a horizontal transect of the continental shelf, slope and deep basin regions of the East Sea
(Sea of Japan), a marginal sea of the Northwest Pacific Ocean, was investigated, and its behavior is described here. The settling
fluxes of particulate 210Po in the deep basin along with 210Pb, 234Th and biogenic matter were also determined. 210Po inventories in the water column were observed to decrease from winter to summer in all stations, probably due to increased
influx of 210Po-poor Kuroshio Water of the Northwest Pacific Ocean during summer. Vertical profiles of dissolved and particulate 210Po along with the settling fluxes of particulate 210Po in the deep basin station have enabled us to evaluate temporal variations and residence times of 210Po. In the slope and basin, activities of dissolved 210Po generally decreased from the surface to the bottom water, with maximum activity just below the subsurface chlorophyll a maximum at 50–75 m depth in spring and summer. These subsurface peaks of dissolved 210Po activity were attributed to the release of 210Po from the decomposition of 210Po-laden biogenic particulate organic matter. In the deep basin, despite the decrease in total mass flux, the sinking flux
of particulate 210Po was higher in the deeper trap (2000 m) than in the shallower one (1000 m), probably due to scavenging of dissolved 210Po from the water column during particle descent and/or break-down of 210Po-depleted particulate matter between 1,000 m and 2,000 m depths. In general, the ratios of the particulate phase to the
dissolved phase of 210Po (Kd) increased with depth in the slope and basin stations. 210Po removal from the water column appears to depend on the primary productivity in the upper waters. There is an inverse relationship
between Kd and suspended particulate matter (SPM) concentration in the water column. From the 210Po activity/chlorophyll a concentration ratios, it appears that sinking particles arriving at 1000 m depth were similar to those in the surface waters. 相似文献