“中国糖碳标准”的标定

一、前言 ~(14)C在大气上层以某一恒定速度不断产生,同时又按自身的放射性蜕变速度(T_(1/2)=5730年)蜕变。~(14)C的产生和蜕变,几十万年以来处于自然平衡,自然交换碳的~(14)C具有平衡浓度。~(14)C年代就是根据标本目前的~(14)C比度同其原始的平衡比度比较而定的。然而,标本原始~(14)C平衡比度无法直接测定,但它对应于1850年以前树木含的~(14)C浓度。因此,~(14)C年代测定工作需要定一个统一的“现代碳标准”。     

~(14)C定年和示踪数据计算与报道形式的新进展

近些年,随着~(14)C分析技术的发展,~(14)C定年与示踪研究在考古学、海洋学、大气科学甚至生物医学等领域都有新的拓展,随着我国多台加速器质谱的引进,必将引起一股~(14)C研究的热潮。然而,新的研究领域产生了一些新的~(14)C数据计算方法和报道形式,尚未有系统的归纳和介绍,使得新接触~(14)C的研究人员以及使用~(14)C数据的科研人员易产生困惑甚至导致最终结果的错误表达。本文针对近些年来~(14)C研究的新方向并结合传统的~(14)C计算原理,总结了其中常见的和较为重要的~(14)C数据计算原理及报道形式,尤其是对其中容易引起误用和混用的参数和定义进行了详尽的说明。期望本文能对我国新接触~(14)C的相关科研人员迅速而准确地了解~(14)C定年和示踪数据的计算原理和报道形式有所帮助。     

放射性~(14)C年代法在冰川冻土研究中的应用

放射性~(14)C的天然存在是由W.F.利贝发现的,1948年正式用于年代测定。此后~(14)C年代法发展很快。由于它能用来测定五六万年以来含碳样品的年龄,而这正是第四纪晚更新世和全新世时期,因此能在地球化学、第四纪地质学、古地理、古气候、考古学以及冰川冻土研究等方面得到应用。早在五十年代国外就对冰川冰进行了~(14)C年代测定。对冰川沉积物的测定更为普遍。近几年来对冰雪和地下水的测定技术也有了发展。冻土研究中测定冻土~(14)C年龄同样也是可行的。在第八、九、十、十一次国际碳十四会议上,冰的~(14)C年龄测定技术及应用方面的论文占有相当比重。我所近几年来已经用~(14)C年代法为冰期划分及冻土年代等方面研究提供了一些数据。     

A New Attempt to Evaluate the Renewable Capacity of A Typical Karst Groundwater System by Using 13C and 14C——A Case Study of Karst Groundwater in Pingyi-Feixian County, Shandong Province

正Objective The renewable capacity is an important attribute of groundwater resources.Most previous studies have focused on the porous aquifer systems by the measurement and analysis of isotopes deuterium(D),oxygen-18(~(18)O),tritium(~3H),and carbon-14(~(14)C)(Chen     

稳定碳同位素在天然气地质中的应用

了解石油、天然气及生油气源岩的同位素组成及其变化,是研究油气生成环境、演化、运移和圈闭条件的重要手段。天然气中,甲烷和乙烷的碳同位素(~(13)C、~(12)C)、二氧化碳的碳同位素(~(13)C、~(12)C)、甲烷的氢同位素(D、H)、氮气的氮同位素(~(15)N,~(14)N)、硫化氢的硫同位素(~(34)S、~(32)S),稀有气体氩的同位素(~(40)Ar、~(36)Ar)等,在油气地质研究中都不同程度得到运用,其中碳同位素应用较广。自然界的稳定碳同位素有两种,即~(12)C和~(13)C。~(12)C的平均丰度为98.893％,质量12:0     

第十三届国际~(14)C会议概况

第十三届国际~(14)C会议于1988年6月20日—25日在南斯拉夫的杜布罗夫尼克召开。与会共202位科学工作者。会议由南斯拉夫鲁德博斯科维克研究所~(14)C及氚实验室的D.Srdoc教授主持。会议提交论文157篇,内     

云南兰坪盆地古近系云龙组上段沉积环境研究——来自碳、氧同位素的证据

云南兰坪盆地古近系云龙组地层记录了盆地由淡水湖泊→盐湖、干盐湖→淡水湖泊沉积的一个完整的Ⅰ级韵律。在云龙组上段沉积了一套灰岩地层,上覆于云龙组上段含盐层之上,对此套灰岩共取样25个,测试结果显示,δ~(13)C和δ18O均为负值,δ~(13)C介于–13.13‰~–6.67‰之间,均值为–11.57‰,δ18O介于–15.55‰~–13.90‰之间,均值为–15.02‰,δ~(13)C和δ~(18)O具有较小相关性(0.57),表明当时湖泊封闭性较差。根据Z值和δ~(13)C表明,当时为陆相淡水或微咸水湖泊沉积,含盐度较低。根据经验公式计算所得温度为35.5~44.3℃,平均为41.4℃。相对于现代湖水温度,当时水体温度较高,可能与PETM事件有关。因此,整个云龙组沉积时期气候炎热干旱,造成蒸发岩沉积中断的主要原因为湖泊的封闭性降低。     

加速器质谱14C分析石墨制备技术研究进展

加速器质谱(AMS)是进行~(14)C同位素分析的主要技术手段,而高精度低本底加速器质谱~(14)C分析主要受样品制备技术限制,因此探讨如何提高石墨制备的稳定性和控制碳污染降低本底将有助于产出高质量~(14)C分析数据,突破~(14)C测年上限(约5.0万年),进一步拓宽~(14)C年代学和同位素示踪的应用范畴。本文详细阐述了催化还原法(H_2/Fe法、Zn/Fe法和Zn-TiH_2/Fe法)制备石墨样品的真空装置和主要工作原理,指出了微量样品石墨制备过程中同位素分馏、石墨产率、束流强度以及精密度与样品量之间存在严重的依赖关系及其抑制方法。着重探讨了石墨制备技术实验条件(还原剂、催化剂、温度等)的优化选择及其与石墨产率、同位素分馏、束流性能之间的内在联系,总结分析了碳污染来源并探寻合适的碳污染控制技术。目前的研究表明最佳实验条件为:H_2/Fe法宜采用还原剂H_2/CO_2(体积比2～2.5),催化剂为源自氢还原单质铁粉(-325目球粒,Fe/C=2～5),温度500～550℃;Zn/Fe法宜采用还原剂Zn/C(质量比50～80),催化剂为源自氢还原单质铁粉(-325目球粒,Fe/C=2～5),Zn反应管温度400～450℃,Fe反应管温度500～550℃。碳污染来源于制备过程中的各个方面,除采用高温除碳的方式外还可采用适当的数学模型加以校正,但还需要更多详细的实验工作来加强现有认识,以期更好地消除碳污染对测试结果的影响。对测年目标组分不稳定的样品(如地下水中的溶解无机碳)应避免样品直接暴露于大气,以减少野外采样过程中现代大气CO_2对测量结果的影响。     

我国科学家在海洋最深处生物体内发现人类核爆~(14)C信号——揭示最遥远海洋生态系统与人类活动之间的密切关系

<正>美国《Geophysical Research Letter》杂志2019年4月8日发表了中国学者领衔的~(14)C示踪海沟物质来源研究的最新进展。在马里亚纳海沟(海洋最深处)的钩虾体内发现人类核爆~(14)C信号,揭示了马里亚纳海沟并非预想中的"遥不可及",各种人为污染物(如放射性物质、持久有机污染物和微塑料等)可以通过食物链快速侵入海洋最深处,     

中国东北地区新生代火山岩的年代学研究

用常规K-Ar、~(40)Ar-~(39)Ar、~(14)C等方法系统测定了东北地区新生代火山岩的年龄,获得近百个有效年龄数据。其精度和准确度都很高,与地质背景相当吻合。对于玄武岩中超镁铁质岩色体也进行了年龄测定尝试、发现包体中含继承氩,并可能存在~(36)Ar过剩。在阶段加热过程中,样品中氩的释放有两个高峰,一个在低温阶段(450—620℃),另一个在高温阶段(>1000℃),约50％的放射成因~(40)Ar在低温阶段释放。     

The history of the mangrove vegetation in Bénin during the Holocene: A palynological study

Pollen analysis of three core samples,YEV-I, GOHO.00 and DO.00, taken in the coastal area of Bénin shows the existence of mangrove during the Holocene. This mangrove underwent many physiognomic changes from the middle to the late Holocene. In the course of the middle Holocene (from 7500 to 2500 years before present (BP)), it stretched over a large area from the littoral inland. It was tightly closed and almost monospecific, dominated by Rhizophora. During the late Holocene, this mangrove started to regress around 3000 years BP and disappeared about 2500 years BP from the studied sites. It has been replaced by swamp meadows dominated by Paspalum vaginatum Sw. and a fresh water environment colonised by taxa such as Persicaria, Typha, Ludwigia, and Nymphaea.     

The history of the mangrove vegetation in Bénin during the Holocene: A palynological study

Pollen analysis of three core samples,YEV-I, GOHO.00 and DO.00, taken in the coastal area of Bénin shows the existence of mangrove during the Holocene. This mangrove underwent many physiognomic changes from the middle to the late Holocene. In the course of the middle Holocene (from 7500 to 2500 years before present (BP)), it stretched over a large area from the littoral inland. It was tightly closed and almost monospecific, dominated by Rhizophora. During the late Holocene, this mangrove started to regress around 3000 years BP and disappeared about 2500 years BP from the studied sites. It has been replaced by swamp meadows dominated by Paspalum vaginatum Sw. and a fresh water environment colonised by taxa such as Persicaria, Typha, Ludwigia, and Nymphaea.     

Holocene climate variability in Sicily from a discontinuous stalagmite record and the Mesolithic to Neolithic transition

Fabric and stable isotopic composition of a Holocene stalagmite (CR1) from a cave in northern Sicily record changes in paleorainfall in the early Holocene. High δ¹³C stable isotope values in the calcite deposited from ca. 8500 to ca. 7500 yr ago are interpreted as reflecting periods of high rainfall. The wet phase was interrupted by two periods of multi-century duration characterized by relatively cool and dry winters centered at ca. 8200 and ca. 7500 yr ago, highlighted by low δ¹³C and δ¹⁸O values. A high variability of δ¹³C values is recorded from ca. 7500 to ca. 6500 yr ago and indicates that the transition from a pluvial early Holocene to the present-day climate conditions was punctuated by decadal-scale periods of relatively dry winters. In northern Sicily, the traditional elements of the Neolithic appear at ca. 7700 yr ago. It is possible that changes in rainfall influenced the passage from hunter-gathering to farming and sheep-herding economies.     

Evidence from wavelet analysis for a mid-Holocene transition in global climate forcing

A strong mid-Holocene transition has been identified by wavelet analyses in several sea ice cover records from the circum-Antarctic area, ice core records (Taylor dome, Byrd) and tropical marine records. The results are compared with those previously published in a synthesis of North Atlantic records and with 4 new records from the Norwegian and Icelandic seas and from a coastal site in Ireland. These new records confirm the previous pattern for the North Atlantic area, extend this pattern nearly to the Arctic Circle, and include a continental record. We further tested the possibility of extending this scheme using continental records from South America. The Holocene pattern proposed here confirms the importance of external forcing during the Early Holocene (solar activity: 1000 years cyclicity and 2500 years during the entire Holocene), even if the signal is disturbed by meltwater fluxes. The second part of the Holocene is then marked by the gradual appearance of internal forcing (thermohaline circulation around 1500 years), associated with a stabilisation of the signal. Coupling between ocean and atmosphere seems to play a fundamental role in the observed frequencies which vary accordingly in the Atlantic, circum-Antarctic and Pacific areas. The North Atlantic area seems to be the instigator of thermohaline circulation as shown by its sensitivity to meltwater discharges during the Early Holocene, even though each sector is independent with regards to its frequency content (around 1600 years for Atlantic Area; around 1250 years for Antarctica). The Holocene methane pattern, still under debate [Ruddiman, W.F., 2003a. Orbital insolation, ice volume and greenhouse gases. Quaternary Science Review 22, 1597–1629; Ruddiman, W.F., 2003b. The anthropogenic greenhouse era began thousands of years ago. Climatic Change 61, 261–293], could be explained by a more efficient thermohaline circulation around the mid-Holocene with an anthropogenic effect initiated at 2500 BP as shown by the inter-hemispheric gradient.     

海南岛南岸全新世珊瑚礁的发育

海南岛南岸的珊瑚礁,是我国全新世珊瑚岸礁最为发育的地区之一,仅次于台湾岛南端的恒春半岛沿岸。前人从生物学^[1-5]、地貌学^[6-8]和地质学^[9-12]角度对海南岛南岸的珊瑚礁进行过较为广泛的研究。作者报道过崖县鹿回头水尾岭剖面珊瑚礁样品的C¹⁴年代测定结果^[13,14]。1979年底至1980年初,作者在海南岛南岸东起小东海沿岸西至西瑁岛西岸地区进行了野外调查与采样。根据野外和室内分析资料,本文公布了一批新测试的C¹⁴年代数据,并进一步讨论了全新世珊瑚礁的发育历史及其与海岸变迁、海面变化和地壳运动的关系等问题。     

中国西部全新世历史气侯的变化

本文在收集冰川、地质、沙漠、湖泊、树木年轮及历史文献记载等历史气候研究成果的基础上,给出了我国西部全新世以来气候变化序列。主要结果如下:1.全新世气候变化的总趋势按其演变可分为三个阶段。由中全新世向晚全新世的转变可能出现在3500年以前,比我国东部大约早500年,同时发现这种转变具有某种程度的突变性。2.全新世以来,千年尺度的气候振荡经历了6个寒冷期和5个温暖期。寒冷期分别在8700～7500a.B.P,5900～5400a.B.P,4200～3800a.B.P,3000～2700a.B.P,2000～1400a.B.P,1000a.B.P至今;温暖期分别为7500～5900a.B.P,5400～4200a.B.P,3800～3000a.B.P,2700～2000a.B.P,1400～1000a.B.P。千年尺度气候振荡的周期变化在1000～3000年之间。3.近千年来,百年尺度气候振荡的温度变化出现了6个低温期和5个高温期。低温谷值分别在公元1100's(1100～1109年),1310's,1480's,1680's,1830's,1950's;高温峰值分别在公元1220's,1390's,1570's,1780's,1900's,变化周期在120～210年之间。近千年中最冷的时期出现在17世纪中到18世纪初。近500年来,公元1480～1650年是我国西部降水最少、干旱频率最高的时期,出现了三次特大旱灾。18世纪前期是降水量较多的时期。近百年来,我国西北地区东部及华北地区出现了变干的趋势。     

Centennial-to-millennial fluctuations in July temperatures in North Finland as recorded by timberline tree rings of Scots pine

A tree-ring proxy of summer temperature anomalies for northern Finland for the past 7500 yr was analyzed using Fourier spectrum and wavelet approaches. Multicentennial (250-450 yr) variability is present in the proxy record during most of the time range. This variability is suggested to reflect low-frequency variability in the North Atlantic Oscillation. Century-scale (90-130 yr) variation is another important feature of the tree-ring proxy data during the Holocene and may be attributed to Glessberg solar activity variations. In addition, an approximately 2000-yr quasi-period is found in this temperature proxy data, similar to the millennial-scale variability, present in many climate records from the North Atlantic region. The results point to the importance of multiple forcings underlying significant Holocene climatic fluctuations.     

Mid to late holocene climate evolution of the lake telmen basin, north central mongolia, based on palynological data

Palynological and sedimentological data from Lake Telmen, in north-central Mongolia, permit qualitative reconstruction of relative changes in moisture balance throughout the mid to late Holocene. The climate of the Atlantic period (7500–4500 yr ago) was relatively arid, indicating that Lake Telmen lay beyond the region of enhanced precipitation delivered by the expanded Asian monsoon. Maximum humidity is recorded between 4500 and 1600 cal yr B.P., during the Subboreal (4500–2500 yr ago) and early Subatlantic (2500 yr–present) periods. Additional humid intervals during the Medieval Warm Epoch (1000–1300 A.D. or 950–650 ago) and the Little Ice Age (1500– 1900 A.D. or 450–50 yr B.P.) demonstrate the lack of long-term correlation between temperature and moisture availability in this region. A brief aridification centered around 1410 cal yr B.P. encompasses a decade of cold temperatures and summer frost between A.D. 536 and 545 (1414–1405 yr B.P.) inferred from records of Mongolian tree-ring widths. These data suggest that steppe vegetation of the Lake Telmen region is sensitive to centennial- and decadal-scale climatic perturbations.     

Holocene offset and seismicity along the panamint valley fault zone, western basin-and-range province, California

Holocene right-slip along the central segment of the Panamint Valley totals 20 m and dip-slip is somewhat less. The most recent offset, about 2 m right-slip, probably occurred at least several hundred years ago. If a comparable amount of slip occurred during earlier earthquakes, mean seismic recurrence intervals would have been about 700–2500 years during the Holocene.     

A 10,700 years' paleotemperature record from Gotland and Pleistocene/Holocene boundary events in Sweden.

Lacustrine carbonate (Chara lime) from the Island of Gotland provides an excellent paleotemperature record for the last 10,700 years. From arctic conditions during the Younger Dryas Stadial, the temperature rapidly rose to the present level, which was reached at about 9000–9250 B.P. A Holocene climatic optimum is clearly recorded. It ended with a drastic deterioration at about 2500 B.P. at the Subboreal/Subatlantic transition. The Subatlantic temperatures are significantly lower than those of the climatic optimum. The Holocene of Sweden seems to have started with a tremendous earthquake linked to extensive faulting (explaining the inconsistencies in the sea level records and the 'drainage of the Baltic Ice Lake'), a distinct peak in the non-dipole geomagnetic field (explaining the intensity peak at this level in cores from different environments) and regional disturbancies of the sedimentation (explaining the 'drainage varve' character of varve - 1073 in the Swedish Time Scale).