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1.
本文报道2015年9月和2016年5月期间天然放射性核素224Ra和223Ra在吕宋海峡及周边海域表层和垂向水体的分布特征。为理解日本福岛核事故的影响，本文亦分析研究区域内人工放射性核素137Cs的分布特征。结果表明，224，223Ra和137Cs比活度水平均处于我国南海海洋天然放射性本底变化范围之内。224Ra在吕宋海峡以西南海北部海域比活度较高，在吕宋海峡以东菲律宾海域比活度较低。137Cs没有明显的分布趋势。基于三站位（LS3，LS5和LS8）224Ra、137Cs以及温盐的垂向分布特征，本文揭示224Ra和137Cs在热带表层水、次表层水和中-深层水中比活度水平和梯度变化的差异特征。彩虹台风事件扭转了整个吕宋海峡及周边海域的海流循环过程。大量以低水平224Ra为特征的西太平洋海水涌入南海，降低水体224Ra比活度水平。但是，西太平洋和南海北部海域水体137Cs比活度水平没有明显差异，台风导致的海流变化对水体137Cs比活度没有明显影响。 相似文献
2.
海洋沉积物不同相态中Sr、Nd同位素提取方法研究 总被引：1，自引：1，他引：0
海洋沉积物中Fe-Mn氧化物相和残渣态的Sr、Nd同位素组成能够敏感地指示洋流循环及物质来源,但实验室对沉积物中上述相态的Sr和Nd同位素的提取易产生过量或提取不完全,进而影响同位素测定结果的准确性,因此制定有效的提取流程显得非常重要。本文采用不同浓度盐酸羟胺(Hydroxylamine Hydrochloride,HH)与醋酸(Acetic Acid,HAc)混合溶液对中印度洋海盆深海沸石黏土、北极半深海沉积物以及安达曼海近海沉积物的Fe-Mn氧化物相进行提取,残渣态用HNO3-HF高压密闭消解法溶融,测定了各相态的主微量元素含量及Sr、Nd同位素组成,通过分析不同实验条件下得到的Fe-Mn氧化物相与残渣态的稀土元素(REE)配分模式、Al/Nd含量比值及Sr、Nd同位素组成,建立了3种不同成因类型海洋沉积物不同相态的化学提取方法。提取深海沸石黏土中Fe-Mn氧化物相的理想试剂条件为0.25 mol/L HH和15%HAc,北极半深海沉积物和安达曼海近海沉积物的试剂条件为0.5 mol/L HH和15%HAc。该方法可以准确获得沉积物中Fe-Mn氧化物相与残渣态的Sr、Nd同位素组成信息,为古海洋学的研究提供方法支持。 相似文献
3.
Naoto Takahata Yuji Sano Keika Horiguchi Kotaro Shirai Toshitaka Gamo 《Journal of Oceanography》2008,64(2):293-301
We have collected fifty-five seawater samples at seven stations at various depths in the Yamato and Japan Basins of the Japan
Sea and measured their helium isotopic ratios. The 3He/4He ratios vary from 0.997 Ratm to 1.085 Ratm where Ratm is the atmospheric ratio. The maximum 3He excesses about 8%, are observed at mid-depth (1000 m), and these values are significantly lower than those observed in
deep Pacific waters. This implies that mantle-derived helium in deep Pacific water cannot enter the Japan Sea since it is
an almost landlocked marginal sea. The observed 8% excess 3He may be attributable to the decay product of tritium. Slightly higher 3He/4He ratios in the Bottom Water were observed in the Yamato Basin than in the Japan Basin. The ventilation ages of seawater
shallower than 1000 m are calculated as about 5 to 20 years, which is consistent with the CFC ages reported in the literature.
There is a positive correlation between the apparent oxygen utilization and 3H-3He ages. The estimated oxygen utilization rate from the correlation in a layer between 500 m and 1000 m is about 3 μmol/kg/yr, which is similar to that in the eastern subtropical North Atlantic. 相似文献
4.
Understanding phosphorus dynamics in marine environment is of great importance, and appropriate tracers for phosphorus cycling in oceans are invaluable. In this study, two methods were developed for extraction, purification, and determination of naturally occurring 32P and 33P in rainwater, marine plankton and sediments using both a low-level beta counter (LBC) and an ultra-low-level liquid scintillation spectrometer (LSS). Blanks, chemical yields and counting efficiencies were quantified for both methods. The chemical purification of 32P and 33P separated by both procedures was validated by their decay curves. The absorber thickness of aluminum for LBC was assessed as 39.2 mg/cm 2 . 32P and 33P specific activities in some rain samples were determined by both methods and showed good consistent results. The advantage of the LSS over the LBC is apparent in its high counting efficiency and in determining samples with high concentration of stable phosphorus. However, when measuring environmental samples with low concentration of stable phosphorus, such as rainwater, both methods can be used and each has its distinct advantage. 相似文献
5.
JI Lihong LIU Guangshan CHEN Zhigang HUANG Yipu XING N JIANG Shan HE Ming 《海洋学报(英文版)》2015,34(10):31-35
In the present study,the analytical method for 129iodine(129I) in ferromanganese crusts is developed and129iodine/127iodine(129I/127I) ratio in ferromanganese crusts is measured by the accelerator mass spectrometry(AMS).The developed method is applied to analyze 129I/127 I ratio in two ferromanganese crusts MP5D44 and CXD08-1 collected from the Mid-Pacific Ocean.The results show that 129I/127 I ratio in MP5D44 and CXD08-1crusts varies from 7×10–14 to 1.27×10–12,with the lowest value falling on the detection limit level of AMS reported by previous literatures.For the depth distribution of 129I/127 I,it is found that both MP5D44 and CXD08-1 crusts have two growth generations,and the 129I/127 I profiles in two generations all displayed an approximate exponential decay.According to the 129I/127 I ratio,the generate age of bottom layer of MP5D44 and CXD08-1 was estimated to be 54.77 and 69.69 Ma,respectively. 相似文献
6.
The RaDeCC™ system has proved to be a robust method of measuring 223Ra and 224Ra extracted from natural waters. Samples ranging in size from < 1 to > 1000 L are first concentrated onto Mn-fiber. The Mn-fiber is partially dried and placed into a circulation system with helium as the carrier gas. Alpha decays of the radon daughters of 223Ra and 224Ra are recorded in a scintillation cell. These data are used to activate electronic gates in the delayed coincidence system, which separate events due to 223Ra from those due to 224Ra. The system combines a high detection efficiency with low background to accurately measure 223Ra and 224Ra at concentrations on the order of 5 atoms per liter. Since this system was first deployed, numerous improvements in electronics and technique have occurred. In this paper I present tests we have conducted to confirm certain assumptions and improve the overall technique of sample collection and measurement. 相似文献
7.
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
8.
9.
白令海颗粒有机物碳、氮同位素组成及其生物地球化学意义 总被引：1，自引：0，他引：1
Stable carbon and nitrogen isotopic composition of particulate organic matter(POM) were measured for samples collected from the Bering Sea in 2010 summer. Particulate organic carbon(POC) and particulate nitrogen(PN) showed high concentrations in the shelf and slope regions and decreased with depth in the slope and basin, indicating that biological processes play an important role on POM distribution. The low C/N ratio and heavy isotopic composition of POM, compared to those from the Alaska River, suggested a predominant contribution of marine biogenic organic matter in the Bering Sea. The fact that δ13C and δ15N generally increased with depth in the Bering Sea basin demonstrated that organic components with light carbon or nitrogen were decomposed preferentially during their transport to deep water. However, the high δ13C and δ15N observed in shelf bottom water were mostly resulted from sediment resuspension. 相似文献
10.
不同潮时对厦门湾水体中234Th/238U不平衡的影响 总被引：1，自引：0，他引：1
厦门海水体中^234Th/^238U不平衡的时间序列数据表明，无论是溶解态、颗粒态^234Th还是总^234Th,相对于母体^238U均严重亏损，呈现出与开阔大洋水明显不同的特征。溶解态、颗粒态^234Th的停留时间介于0．5－41d之间，其中低潮时停留时间比高潮时小2－4倍，证实近岸海域具有强烈的清除、迁出作用，且潮汐变化对海域颗粒动力学特征有重要影响。^234Th停留时间与总悬浮颗粒物浓度（TSM）、Ch1.α的关系则表明，近岸海域元素的清除、迁出作用主要受陆源颗粒物输送的影响，与生物活动关系并不密切。此外，非稳态与稳态清除模型结果的对比证明，稳态模型对于具有强烈清除、迁出作用的近岸海域是适用的。 相似文献
11.
We utilized 234Th, a naturally occurring radionuclide, to quantify the particulate organic carbon (POC) export rates in the northern South
China Sea (SCS) based on data collected in July 2000 (summer), May 2001 (spring) and November 2002 (autumn). Th-234 deficit
was enhanced with depth in the euphotic zone, reaching a subsurface maximum at the Chl-a maximum in most cases, as commonly
observed in many oceanic regimes. Th-234 was in general in equilibrium with 238U at a depth of ∼100 m, the bottom of the euphotic zone. In this study the 234Th deficit appeared to be less significant in November than in July and May. A surface excess of 234Th relative to 238U was found in the summer over the shelf of the northern SCS, most likely due to the accumulation of suspended particles entrapped
by a salinity front. Comparison of the 234Th fluxes from the upper 10 m water column between 2-D and traditional 1-D models revealed agreement within the errors of
estimation, suggesting the applicability of the 1-D model to this particular shelf region. 1-D model-based 234Th fluxes were converted to POC export rates using the ratios of bottle POC to 234Th. The values ranged from 5.3 to 26.6 mmol C m−2d−1 and were slightly higher than those in the southern SCS and other oligotrophic areas. POC export overall showed larger values
in spring and summer than in autumn, the seasonality of which was, however, not significant. The highest POC export rate (26.6
mmol C m−2d−1) appeared at the shelf break in spring (May), when Chl-a increased and the community structure changed from pico-phytoplankton
(<2 μm) dominated to nano-phytoplankton (2–20 μm) and micro-phytoplankton (20–200 μm) dominated. 相似文献
12.
Xiaolin WangWenxuan Hu Suping YaoQi Chen Xiaomin Xie 《Marine and Petroleum Geology》2011,28(5):992-1002
One hundred and ten carbon and nineteen strontium isotopic values of outcropping Cambrian Series 2 and Series 3 carbonate rocks in the Penglaiba section of the Keping area were analyzed. Effective isotopic data with little influence of diagenesis were used to address the global correlation. The δ13C values exhibit two major positive excursions (peaking at 3.1‰ and 3.3‰) and three major negative excursions (peaking at −3.0‰, −4.2‰ and −3.2‰). The carbon isotope excursions (peaking at −3.0‰ and −4.2‰) across the Cambrian Series 2-Series 3 boundary show good correlations with similar variations reported in Siberia, Laurentia, North China and South China. In contrast, the other three carbon isotope excursions (peaking at 3.1‰, 3.3‰ and −3.2‰) do not have a fairly good global correlation because of the lack of biostratigraphic data. With respect to the 87Sr/86Sr ratios, they show good correlation with those reported for Laurentia, and further support the global δ13C comparison. On the basis of these new data, it is showed that the combination of δ13C curves and 87Sr/86Sr variations serves as a powerful tool for correlation and subdivision of Cambrian strata in the Tarim Basin of northwest China, and provides new data for global correlation. 相似文献
13.
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
14.
The oxygen (δ18O) and carbon (δ13C) isotope ratios of 10 species of living Bryozoa collected from the Otago Shelf, New Zealand were analysed to assess the extent to which isotopic equilibrium (relative to inorganic equilibrium isotope fractionation) is attained during the precipitation of skeletal calcium carbonate. The data reveal that whereas eight species of Bryozoa synthesise skeletal carbonate in apparent oxygen isotope equilibrium with respect to environmental conditions, two species (Celleporina grandis and Hippomonavella flexuosa) yield δ18Ocalcite values which indicate significant disequilibrium oxygen isotope fractionation during calcification. Sufficient data are available from one species (C. grandis) to demonstrate that disequilibrium is probably related to kinetic factors associated with diffusion‐controlled transport of HCO3‐ to the site of calcite precipitation. Carbon isotope signatures indicate significant departures from inorganic isotope equilibrium in all but one bryozoan species (Hippomenella vellicata). Although greater uncertainties are associated with estimates of the isotopic composition of total dissolved inorganic carbon (δ13CSDIC), the data suggest that two factors—kinetic fractionation and incorporation of respiratory CO2—are important in controlling carbon isotope disequilibrium. Where bryozoan species exhibit evidence for disequilibrium in both oxygen and carbon isotope systems (C. grandis, H. flexuosa), it is likely that kinetic factors are primarily responsible for observed departures from carbon isotope equilibrium. In contrast, the probable explanation for those species which display evidence for carbon isotope disequilibrium only, is that skeletal carbonate is precipitated from a DIC pool modified by the incorporation of respiratory CO2. Differences between the carbon isotope composition of skeletal elements from the same species and co‐existing species living in the same community suggests that significant variations may occur in the extent to which marine DIC and respiratory CO2 are utilised during calcification. Additional studies of carbon pathways associated with calcification are required to assess the relative effects of kinetic, metabolic, and environmental factors on the carbon isotopic composition of bryozoan skeletal carbonate. 相似文献
15.
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
16.
Patrick Ollivier Christelle Claude Olivier Radakovitch Bruno Hamelin 《Marine Chemistry》2008,109(3-4):337
Submarine groundwater discharge (SGD) is now recognized as an important pathway for water and chemical species fluxes to the coastal ocean. In order to determinate SGD to the Gulf of Lion (France), we measured the activities of 226Ra and 228Ra by thermal ionization mass spectrometry (TIMS) in coastal waters and in the deep aquifer waters of the Rhone deltaic plain after pre-concentration of radium by MnO2. Compared to conventional counting techniques, TIMS requires lower quantities of water for the analyses, and leads to higher analytical precision. Radium isotopes were thus measured on 0.25–2 L water samples containing as little as 20 fg of 226Ra and 0.2–0.4 fg of 228Ra with precision equal to 2%. We demonstrate that coastal surface waters samples are enriched in 226Ra and 228Ra compared to the samples further offshore. The high precision radium measurements display a small but significant 226Ra and 228Ra enrichment within a strip of circa 30 km from the coast. Radium activities decrease beyond this region, entrained in the northern current along the shelf break or controlled by eddy diffusion. The radium excess in the first 30 km cannot be accounted for by the river nor by the early diagenesis. The primary source of the radium enrichment must therefore be ascribed to the discharge of submarine groundwater. Using a mass-balance model, we estimated the advective fluxes of 226Ra and 228Ra through SGD to be 5.2 × 1010 and 21 × 1010 dpm/d respectively. The 226Ra activities measured in the groundwater from the Rhone deltaic plain aquifer are comparable to those from other coastal groundwater studies throughout the world. By contrast, 228Ra activities are higher by up to one order of magnitude. Taking those groundwater radium activities as typical of the submarine groundwater end-member, a minimum volume of 0.24–4.5 × 1010 l/d is required to support the excess radium isotopes on the inner shelf. This has to be compared with the average rivers water runoff of 15.4 × 1010 l/d during the study period (1.6 to 29% of the river flow). 相似文献
17.
~(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
18.
Radionuclides (i.e., 7Be and 210Pb) can be used to trace particle and sediment dynamics and to quantify coastal oceanic processes with time scales ranging from a few days to a hundred years. Here, we study the settling dynamics of suspended particles and the implication by sedimentary heavy metals in the Wenjiao/Wenchang River and Wanquan River estuaries through the measurement of the particulate 7Be and 210Pb nuclides. Activity in the particulate phase had a range of 2.1–54.5 and 4.6–67.9 Bq kg−1 for 7Be and excess 210Pb (210Pbxs), respectively, in the Wenjiao/Wenchang River estuary. In the Wanquan River estuary, activity is in the range of 1.2–43.5 Bq kg−1 for 7Be and 6.2–194.5 Bq kg−1 for 210Pbxs. At the same time, activity in the dissolved phase had a range of 0.46–1.26 and 0.30–1.17 Bq m−3 for 7Be and 210Pb, respectively, in the Wenjiao/Wenchang River estuary; ranges of 0.10–2.31 and 0.09–1.87 Bq m−3 for 7Be and 210Pb, respectively, were observed in the Wanquan River estuary. The distribution coefficients (Kd) for the two nuclides decreased within increased in suspended particle matters (SPM) concentration and/or salinity in Wanquan River estuary. The residence times of particulate 7Be and 210Pbxs had ranges of 0.4–1.6 and 1.65–5.15 days, respectively, in the Wenjiao/Wenchang River estuary; and ranges of 0.02–3.2 and 0.61–4.44 days, respectively in the Wanquan River estuary. All residence times for the two nuclides increased in the seaward direction. In the Wenjiao/Wenchang River estuary, we found that 11.8–21.0% of Cu, 3.0–9.0% of Zn and 43.2–69.9% for Cd is removed from the water column and deposited into the estuary, and 24.2–34.8% for Cu, 7.2–23.8% for Zn, and 70.0–82.5% for Cd in the Wanquan River estuary, respectively. 相似文献
19.
Research on seamounts provides some of the best constraints for understanding intraplate volcanism, and samples from seamounts reveal crucial evidence about the geochemical makeup of the oceanic mantle. There are still many seamounts in the West Pacific Seamount Province(WPSP) that have not been studied, meaning their ages and geochemistry remain unknown. A better understanding of these seamount trails and their evolutionary history, investigated with age and geochemistry data, will enable better understanding of the geological processes operating underneath the Pacific Ocean Plate. Here, new ~(40)Ar/~(39) Ar ages and trace element and Sr-Nd-Pb isotopic data for seven basalt rocks from four seamounts in the WPSP are provided. Chemically, these rocks are all Oceanic Island Alkali basalt(OIA type); analysis of olivine phenocrysts shows that the magmas experienced strong olivine fractionation and changed from olivine + plagioclase to olivine + plagioclase + clinopyroxene cotectic during their evolution. Rare earth element(REE) patterns and a spider diagram of the samples in this study show OIB(Ocean Island Basalt) like behavior. The range of ~(87)Sr/~(86) Sr values is from 0.704 60 to 0.706 24, the range of ~(206)Pb/~(204) Pb values is from 18.241 to 18.599, and the range of ~(143)Nd/~(144) Nd values is from 0.512 646 to 0.512 826; together, these values indicate magma sources ranging from EMI to EMII. Finally, new ~(40)Ar/~(39) Ar age data show that these seamounts formed at ～97 and ～106 Ma, indicating that some may have undergone the same formation processes as seamounts in the eastern part of the Magellan Seamount Trail, but other seamounts likely have different origins. 相似文献
20.
We have measured helium isotopic ratios of thirty-seven Pacific water samples from various depths collected in adjacent regions
of Honshu, Japan. The 3He/4He ratios vary significantly from 0.989 R
atm to 1.208 R
atm where R
atm is the atmospheric ratio of 1.39 × 10−6. The mid-depth (750–1500 m) profile of 3He/4He ratios at ST-1 located Northwestern Pacific Ocean east of Japan (Off Joban; 37°00′ N, 142°40′ E) is significantly different
from that at ST-2 of the Northern Philippine Sea south of Japan (Nankai Trough; 33°07′ N, 139°59′ E), suggesting that these
waters were separated by a topographic barrier, the Izu-Ogasawara Ridge. Taking 3He/4He data of the Geosecs expeditions in the western North Pacific, an extensive plume of 15% excess 3He relative to the air may be traced at ST-1 over 12,000 kilometers to the northwest of the East Pacific Rise where the mantle
helium may originate. The 20% excess found at ST-2 may be attributable to the additional source of the subduction-type mantle
helium in the Okinawa Trough. A 15% excess of 3He has also been discovered at a depth of about 1000∼1500 m at ST-3 adjacent to Miyakejima Island (33°57′ N, 139°22′ E) and
ST-4 of Sagami Bay (35°00′ N, 139°22′ E). It is confirmed that mid-depth all over the western North Pacific water is affected
by the mantle helium with a high 3He/4He ratio.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献