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Estimation of groundwater residence time using radiocarbon and stable carbon isotope ratio in dissolved inorganic carbon and soil CO2 利用溶解无机碳和土壤二氧化碳中的放射性碳和稳定碳同位素比值估算地下水的停留时间
IF 8.3 3区 地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS Pub Date : 2024-04-29 DOI: 10.1017/rdc.2024.43
Rahul Kumar Agrawal, Ranjan Kumar Mohanty, Ajayeta Rathi, Shreya Mehta, M G Yadava, Sanjeev Kumar, Amzad H Laskar

Estimation of residence time of groundwater, particularly in regions with inadequate surface waters are very important for formulating sustainable groundwater management policies. We developed a technique for extracting dissolved inorganic carbon (DIC) quantitatively from water for measuring its 14C contents and presented the analytical details here. We also measured stable carbon isotope ratio (δ13C) in soil CO2 and groundwater DIC to correct the groundwater 14C ages. In addition, 14C in soil CO2 were measured for making necessary correction in the initial activity of the recharging water. The corrected 14C contents in the groundwater samples were used to estimate their residence times employing Lumped Parameter Models (LPM), a set of mathematical models to account for the processes that take place during transport from the recharge to the sampling spots. We present a case study focused on the calculation of radiocarbon ages and residence times for a groundwater sample collected from the campus of Physical Research Laboratory in Ahmedabad, Gujarat, India. The study also includes estimations of groundwater residence times using previously measured 14C ages of groundwater samples from Gujarat, India. Various factors controlling the groundwater ages in the LPM and their applicability are discussed.

估算地下水的停留时间,尤其是在地表水不足的地区,对于制定可持续的地下水管理政策非常重要。我们开发了一种从水中定量提取溶解无机碳(DIC)以测量其 14C 含量的技术,并在此介绍了分析细节。我们还测量了土壤 CO2 和地下水 DIC 中的稳定碳同位素比值(δ13C),以校正地下水 14C 年龄。此外,我们还测量了土壤 CO2 中的 14C 含量,以便对补给水的初始活性进行必要的修正。地下水样本中校正后的 14C 含量可用于采用集合参数模型(LPM)估算其停留时间,集合参数模型是一套数学模型,用于解释从补给点到采样点的传输过程。我们介绍了一项案例研究,重点是计算从印度古吉拉特邦艾哈迈达巴德物理研究实验室校园采集的地下水样本的放射性碳年龄和停留时间。该研究还包括利用之前测量的印度古吉拉特邦地下水样本的 14C 年龄估算地下水的停留时间。研究还讨论了控制 LPM 中地下水年龄的各种因素及其适用性。
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引用次数: 0
A HOMEMADE SEMIAUTOMATIC GRAPHITIZATION DEVICE FOR AMS 14C DATING AT NTUAMS LAB 自制半自动石墨化装置,用于在 Ntuams 实验室进行 ams 14c 测定
IF 8.3 3区 地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS Pub Date : 2024-04-29 DOI: 10.1017/rdc.2024.48
Tzu-Tsen Shen, Hong-Chun Li, Rick Qiu

A low-cost and computer-controlled graphitization system connected to an elemental analyzer (EA) has been designed and built at the NTUAMS Lab. This semiautomatic system equips 6-unit reactors for the graphitization of CO2 with H2 on the iron catalyst. The entire procedure takes about 7 hours for iron conditioning, sample combustion and loading, and graphitization. The system can produce good-quality graphite for samples containing 0.5–1.6 mg carbon mass, with the pressure yield of graphitization ranging from 57.7% to 87.1%. The average values of OXI and OXII agree well with the consensus value, but the result of ANU sucrose was observed to be slightly higher than the reported one. The background samples of anthracite over ten months yielded an average of 0.38±0.10 pMC (n=21) corresponding to a 14C age of 45 kyr BP. Intercomparison samples L and M of FIRI exhibit that the measured 14C ages are almost identical to the consensus values and have a small spread in these values. The system has been carrying out graphitization for total organic carbon (TOC) of peat samples, and providing a more efficient and convenient way for AMS 14C dating.

NTUAMS 实验室设计并建造了一个与元素分析仪(EA)相连的低成本计算机控制石墨化系统。这套半自动系统配备了 6 个反应器,用于在铁催化剂上将 CO2 与 H2 石墨化。整个过程大约需要 7 个小时,包括铁调节、样品燃烧和装载以及石墨化。该系统能为含碳量为 0.5-1.6 毫克的样品生产优质石墨,石墨化的压力产率为 57.7% 至 87.1%。OXI 和 OXII 的平均值与共识值吻合,但 ANU 蔗糖的结果略高于报告值。十个月的无烟煤本底样品的平均值为 0.38±0.10 pMC(n=21),对应的 14C 年龄为 45 kyr BP。FIRI 的互比样品 L 和 M 表明,测得的 14C 年龄与共识值几乎相同,而且这些值的差值较小。该系统对泥炭样本的总有机碳(TOC)进行了石墨化处理,为 AMS 14C 测年提供了更高效、更便捷的方法。
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引用次数: 0
Radiocarbon dates from the archaeological site of Sakas, Bihar, India 印度比哈尔邦萨卡斯考古遗址的放射性碳年代测定
IF 8.3 3区 地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS Pub Date : 2024-04-29 DOI: 10.1017/rdc.2024.42
J Bates, V K Singh, R N Singh, Manisha Singh, Brij Mohan, Sudarshan Chakradhari, Abhay P Singh, Matthew Conte, Yongje Oh

Dates from recently excavated Gangetic site of Sakas in Bihar, India, place it at ca.1800–1100 BC. The ceramic and lithic chronologies have been interpreted as Early Farming, Transitional and Chalcolithic/Developed Farming in date. However, depending on where in the Ganges Plains is studied, the time frame of Early, Developed and Advanced Farming periods varies widely, from 7th millennium to 2nd millennium BC and beyond, making the chronological framing of absolute dates within a regional scheme highly complex. In this paper we report the new radiocarbon results from Sakas and note how while these are critical for cementing the absolute dating of the site, until such time as a more stable periodization linked not only to relative and absolute dates but also human lifeways within the different zones of the Ganges plains is created, there remains difficulties in understanding how Sakas and other sites of similar date fit into the changing social, cultural and economic systems in this region.

最近发掘的印度比哈尔邦萨卡斯恒河遗址的年代约为公元前 1800-1100 年。陶瓷和石器年代学被解释为早期农耕、过渡时期和旧石器时代/发达农耕。然而,根据对恒河平原不同地区的研究,早期农耕、发达农耕和先进农耕时期的时间范围差异很大,从公元前 7 千年到公元前 2 千年甚至更远,这使得在一个地区方案中确定绝对日期的年代框架变得非常复杂。在本文中,我们报告了萨卡遗址的新放射性碳测定结果,并指出这些结果对于确定该遗址的绝对年代至关重要,但在建立不仅与相对年代和绝对年代相关,而且与恒河平原不同区域人类生活方式相关的更稳定的年代划分之前,要了解萨卡遗址和其他类似年代的遗址如何融入该地区不断变化的社会、文化和经济体系仍然存在困难。
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引用次数: 0
SQUEAKY CLEAN CELLULOSE: COMPARING PRETREATMENT EFFECTIVENESS ON SINGLE TREE RINGS AND WOODEN LATHS 吱吱作响的洁净纤维素:比较单个树环和木板条的预处理效果
IF 8.3 3区 地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS Pub Date : 2024-04-04 DOI: 10.1017/rdc.2024.20
Wendy Hlengiwe Khumalo, Helene Løvstrand Svarva, Damaris Zurbach, Marie-Josée Nadeau
Obtaining accurate radiocarbon (14C) results from wood samples requires the extraction of cellulose. In the past, this has been done using different combinations of methods including acidified bleaching, acid-base-acid, and strong bases. This often becomes a time-consuming task in most analyses, especially when single ring isotope chronologies are needed from wood samples. Using 14C and Fourier-transform infrared spectroscopy (FTIR), we tested four different pretreatment methods to determine their ability to produce high quality cellulose. We then adjusted the best methods to determine a method for pretreating wood laths of multiple rings. A sequence of base-acid-base-acid-bleach + strong base (BABAB+) and BABAB produced the most accurate results when compared to the Bomb20 Northern Hemisphere Zone 1 curve with an average difference in Δ14C of 1.3‰ and 5.8‰ respectively. These methods were adjusted to pretreat an entire wood lath and a comparison of the FTIR results suggest that our adjusted BABAB+ and BABAB produced high quality cellulose comparable to that of an individually pretreated ring. The possibility to pretreat wood lath samples has the potential to more than double the number of tree rings which can be pretreated in a week. This is a significant reduction in time when creating long tree ring chronologies.
从木材样本中获取准确的放射性碳(14C)结果需要提取纤维素。在过去,提取纤维素需要使用不同的方法组合,包括酸化漂白、酸-碱-酸和强碱。在大多数分析中,这往往是一项耗时的工作,尤其是需要从木材样本中提取单环同位素年代学时更是如此。利用 14C 和傅立叶变换红外光谱(FTIR),我们测试了四种不同的预处理方法,以确定它们生成高质量纤维素的能力。然后,我们对最佳方法进行了调整,确定了一种用于预处理多环木板条的方法。与 Bomb20 北半球 1 区曲线相比,碱-酸-碱-酸-漂白+强碱(BABAB+)和 BABAB 的序列产生了最准确的结果,Δ14C 的平均差异分别为 1.3‰ 和 5.8‰。对这些方法进行调整后,可对整块木板条进行预处理,傅立叶变换红外光谱(FTIR)结果比较表明,调整后的 BABAB+ 和 BABAB 所产生的高质量纤维素可与单独预处理的环相媲美。对木板条样本进行预处理有可能使一周内可预处理的树环数量增加一倍以上。这大大缩短了制作长树龄年表的时间。
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引用次数: 0
EARLY HOLOCENE OXYGEN ISOTOPE CHRONOLOGIES (11,267–6420 CAL BP) FROM ICE WEDGE AT CHARA, TRANSBAIKALIA 横贝加尔湖畔查拉冰楔的全新世早期氧同位素年代学(11267-6420 卡平方公里
IF 8.3 3区 地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS Pub Date : 2024-04-04 DOI: 10.1017/rdc.2024.34
Yurij K Vasil’chuk, Alla C Vasil’chuk, Nadine A Budantseva, Alexander P Ginzburg, Igor V Tokarev, Jessica Yu Vasil’chuk
Accelerator mass spectrometry radiocarbon (AMS 14C) dating was used for determining the age of wedge ice. It has been found that between 11,270 and 6420 cal BP, or the Greenlandian and Northgrippian stages of the Holocene, ice wedges grew syngenetically in sandy deposits with gravel in the Chara River valley. The variations of δ18O values in the ice wedges are about 8‰, from –25.5‰ to –18.8‰. Based on the stable isotope composition of ice wedges, paleotemperature reconstructions revealed that the mean January temperature was as low as –38°C during the coldest periods of the early half of the Holocene and as high as –28°C during the warmer periods.
加速器质谱放射性碳(AMS 14C)测定法用于确定楔冰的年龄。研究发现,在公元前 11,270 年至公元前 6420 年之间,即全新世的格陵兰期和北格里皮期,冰楔在查拉河流域的砂砾沉积物中合成生长。冰楔的δ18O值变化约为8‰,从-25.5‰到-18.8‰。根据冰楔的稳定同位素组成,古温度重建显示,在全新世早期最寒冷的时期,一月平均温度低至-38°C,而在较温暖的时期,一月平均温度则高达-28°C。
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引用次数: 0
RADIOCARBON AGES OF PLANT REMAINS IN MASSIVE GROUND ICE AND UNDERLYING SEDIMENTS OF THE BARROW PERMAFROST TUNNEL, ALASKA 阿拉斯加巴罗永久冻土隧道块状地表冰和底层沉积物中植物遗骸的放射性碳年龄
IF 8.3 3区 地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS Pub Date : 2024-04-04 DOI: 10.1017/rdc.2024.25
Go Iwahana, Masao Uchida, Kazuho Horiuchi, Jody Deming, Hajo Eicken, Hiroshi Ohno, Kanako Mantoku, Toshiyuki Kobayashi, Kazuyuki Saito
Massive ground ice found in the Barrow Permafrost Tunnel at 3–7 m depths from the surface has been interpreted as an ice wedge and used to reconstruct early Holocene environmental changes. To better understand the development of this ground ice, we conducted radiocarbon dating for 34 samples of plant remains from the massive ground ice and underlying sediment layer. A significantly large gap in the measured radiocarbon ages (more than 24 ka) between massive ice and the underlying sediment layer throughout the tunnel profile suggested at least two possibilities. One is that the lower and older sediment layer had thrust upwards at the boundary between intruding ice wedge and adjacent sediment, and the growing ice had pushed the sediment sideways. Another is that erosional events had removed surface materials at about 12–36 ka BP (14–41 cal ka BP) before the overlaying sediment layer with massive ground ice developed. The overall distribution of radiocarbon ages from the massive ice supported the ice-wedge hypothesis as a formation mechanism, although our results showed several age inversions and large fluctuations. Dating of densely spaced samples revealed two ground-ice regions with similar ages around 11–11.5 and 10–10.5 ka BP divided by a relatively narrow region of transitional ages along the tunnel long-axis. This distribution may be explained by a possible misalignment between the sampling direction and the ice-wedge growth line or by intermittent ice growth with repeated cracking at more random locations than the classic ice-wedge growth model suggested.
在巴罗永久冻土隧道(Barrow Permafrost Tunnel)距地表 3-7 米深处发现的大量地冰被解释为冰楔,并被用来重建全新世早期的环境变化。为了更好地了解这些地冰的发展过程,我们对大量地冰和底层沉积层中的 34 个植物遗骸样本进行了放射性碳测年。在整个隧道剖面中,大块冰和下层沉积层之间的放射性碳年代测定结果差距很大(超过 24 ka),这至少说明了两种可能性。一种可能是,下层较早的沉积层在侵入的冰楔与相邻沉积层之间的边界向上推移,不断增长的冰将沉积层推向一侧。另一种可能是,大约在公元前 12-36 ka 年(公元前 14-41 cal ka 年),侵蚀事件清除了地表物质,然后才形成了覆盖着大量地表冰的沉积层。块冰的放射性碳年龄的总体分布支持冰缘假说的形成机制,尽管我们的结果显示出一些年龄倒置和较大的波动。对间隔密集的样本进行的年代测定显示,在 11-11.5 ka BP 和 10-10.5 ka BP 附近有两个年代相近的地冰区域,而沿隧道长轴则有一个相对狭窄的年代过渡区域。这种分布的原因可能是取样方向与冰缘生长线之间可能存在错位,或者是冰的间歇性生长,在比经典的冰缘生长模型更随机的位置反复开裂。
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引用次数: 0
NEW PERSPECTIVES ON OLD MATTERS: A REVIEW OF ARCHAEOLOGICAL AND CHRONOMETRIC DATA FROM ABRIGO DO SOL (MATO GROSSO, BRAZIL) 旧问题的新视角:巴西马托格罗索州阿布里戈-多索尔的考古和年代测定数据综述
IF 8.3 3区 地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS Pub Date : 2024-04-04 DOI: 10.1017/rdc.2024.30
Simon-Pierre Gilson, Lucas Bueno

Based on the study of the primary documentation related to the excavations carried out by Eurico Miller in the 1970s at Abrigo do Sol, Mato Grosso (Brazil), we propose a new reading of the stratigraphic and chronological information obtained from this rock shelter. Despite the apparent incongruity in the chrono-stratigraphic distribution of published dates, a detailed examination of the stratigraphy and field notes allowed us to identify a chronometric sequence with regular distribution between the Middle Holocene and the Late Pleistocene periods for the Abrigo do Sol site. We present here the original documents related to radiocarbon dating and their analysis. We finally show the implications of this study for understanding this site and the discussions related to the ancient settlements of the Amazon forest.

根据对尤里科-米勒(Eurico Miller)于 20 世纪 70 年代在巴西马托格罗索州阿布里戈-多索尔(Abrigo do Sol)进行发掘的相关原始文献的研究,我们对从该岩洞获得的地层学和年代学信息提出了新的解读。尽管已公布日期的年代-地层分布明显不一致,但通过对地层和实地记录的详细研究,我们确定了 Abrigo do Sol 遗址的年代序列,其在全新世中期和更新世晚期之间的分布是有规律的。我们在此介绍与放射性碳测年有关的原始文件及其分析。最后,我们展示了这项研究对于了解该遗址以及与亚马逊森林古代定居点相关的讨论的意义。
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引用次数: 0
ADDRESSING THE INTENSITY OF CHANGES IN THE PREHISTORIC POPULATION DYNAMICS: POPULATION GROWTH RATE ESTIMATIONS IN THE CENTRAL BALKANS EARLY NEOLITHIC 研究史前人口动态变化的强度:新石器时代早期中巴尔干地区人口增长率的估算
IF 8.3 3区 地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS Pub Date : 2024-04-04 DOI: 10.1017/rdc.2024.23
Tamara Blagojević, Marko Porčić, Sofija Stefanović
The intensity of changes in the population dynamics of the Early Neolithic (ca. 6250–5300 cal BC) communities in the Central Balkans was addressed by estimating the growth rate values. The Bayesian approach (Crema and Shoda 2021) of estimating intrinsic growth rates by fitting different models of population growth was applied to radiocarbon dates from the Early Neolithic sites in Serbia. We explored two possible episodes of population growth based on the results of the population dynamics reconstruction using the summed calibrated radiocarbon probability distributions (SPD) method. The results have shown that, within the first episode of growth, the intrinsic growth rate mean values are higher than the estimated continental average (between 1% and 2%). The results indicate a sudden and fast rise in population size, possibly due to the influx of the new population settling in the region at the beginning of the Neolithic. Lower values for the second episode could indicate more gradual population growth due to the mechanisms associated with the Neolithic Demographic Transition and the rise in fertility.
通过估算增长率值,研究了巴尔干半岛中部新石器时代早期(约公元前 6250-5300 年)族群人口动态变化的强度。我们将贝叶斯方法(Crema 和 Shoda,2021 年)应用于塞尔维亚新石器时代早期遗址的放射性碳年代,通过拟合不同的人口增长模型来估算内在增长率。根据人口动态重建的结果,我们使用总和校准放射性碳概率分布法(SPD)探讨了两个可能的人口增长事件。结果表明,在第一个增长期,内在增长率的平均值高于估计的大陆平均值(1% 到 2%)。结果表明,可能是由于新石器时代初期定居在该地区的新人口的涌入,人口数量突然快速上升。第二个阶段较低的数值可能表明,由于与新石器时代人口转变和生育率上升相关的机制,人口增长更为渐进。
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引用次数: 0
IMPROVING IONPLUS MICADAS PERFORMANCE WITH RECESSED GRAPHITE 利用嵌入式石墨提高 ionplus micadas 的性能
IF 8.3 3区 地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS Pub Date : 2024-04-04 DOI: 10.1017/rdc.2024.36
Taylor A B Broek, Mark L Roberts
Cathodes with recessed sample surfaces have several benefits in cesium sputter ion sources, including higher output, more efficient use of sample material, and improved focusing of the extracted ion beam. However, the Ionplus MICADAS uses cathodes with a graphite surface that is essentially flush with the sample holder. To evaluate the performance of recessed graphite with the MICADAS and determine the optimal surface depth, we tested four different depths, including the standard (flush) pressing method, 0.5 mm, 1.0 mm, and 1.5 mm. We found that recessed depths of 1.0 and 1.5 mm resulted in 20% higher ion beam current compared to the standard method under the same source conditions. The results are consistent with the beam produced from the recessed targets being more narrowly focused with a lower emittance, resulting in better transmission through the accelerator. Small graphite samples (200 µg C) with recessed surfaces produced higher currents for longer, leading to a 2–3× increase in sample ionization efficiency. Additionally, there was some evidence that isotopic ratio measurements of recessed samples were more stable over time. Overall, samples recessed to 1 mm depth offered numerous advantages over the standard pressing method and we have subsequently started pressing all MICADAS graphite using this approach.
在铯溅射离子源中,具有凹陷样品表面的阴极有多种优点,包括更高的输出功率、更有效地利用样品材料以及改进提取离子束的聚焦。然而,Ionplus MICADAS 使用的阴极的石墨表面基本上与样品架齐平。为了评估嵌入式石墨在 MICADAS 中的性能并确定最佳表面深度,我们测试了四种不同的深度,包括标准(齐平)压制法、0.5 毫米、1.0 毫米和 1.5 毫米。我们发现,在相同的源条件下,与标准方法相比,1.0 毫米和 1.5 毫米的凹入深度可使离子束电流增加 20%。这一结果与凹靶产生的离子束聚焦范围更窄、发射率更低,从而通过加速器的传输效果更好相一致。表面凹陷的小型石墨样品(200 微克 C)能在更长的时间内产生更大的电流,从而使样品电离效率提高 2-3 倍。此外,有证据表明,凹陷样品的同位素比测量结果随着时间的推移更加稳定。总之,与标准压制方法相比,凹入 1 毫米深度的样品具有许多优势,因此我们随后开始采用这种方法压制所有 MICADAS 石墨。
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引用次数: 0
DISCUSSION: PRESENTATION OF ATMOSPHERIC 14CO2 DATA 讨论:大气 14co2 数据的介绍
IF 8.3 3区 地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS Pub Date : 2024-03-27 DOI: 10.1017/rdc.2024.27
Stephen E Schwartz, Quan Hua, David E Andrews, Ralph F Keeling, Scott J Lehman, Jocelyn C Turnbull, Paula J Reimer, John B Miller, Harro A J Meijer

Observations of radiocarbon (14C) in Earth’s atmosphere and other carbon reservoirs are important to quantify exchanges of CO2 between reservoirs. The amount of 14C is commonly reported in the so-called Delta notation, i.e., Δ14C, the decay- and fractionation-corrected departure of the ratio of 14C to total C from that ratio in an absolute international standard; this Delta notation permits direct comparison of 14C/C ratios in the several reservoirs. However, as Δ14C of atmospheric CO2, Δ14CO2 is based on the ratio of 14CO2 to total atmospheric CO2, its value can and does change not just because of change in the amount of atmospheric14CO2 but also because of change in the amount of total atmospheric CO2, complicating ascription of change in Δ14CO2 to change in one or the other quantity. Here we suggest that presentation of atmospheric 14CO2 amount as mole fraction relative to dry air (moles of 14CO2 per moles of dry air in Earth’s atmosphere), or as moles or molecules of 14CO2 in Earth’s atmosphere, all readily calculated from Δ14CO2 and the amount of atmospheric CO2 (with slight dependence on δ13CO2), complements presentation only as Δ14CO2, and can provide valuable insight into the evolving budget and distribution of atmospheric 14CO2.

对地球大气层和其他碳库中放射性碳(14C)的观测对于量化碳库之间的二氧化碳交换非常重要。14C 的数量通常用所谓的 Delta 符号来报告,即 Δ14C,即经过衰变和分馏校正的 14C 与总 C 之比偏离绝对国际标准的比率;这种 Delta 符号允许直接比较几个储层中的 14C/C 比率。然而,由于大气中 CO2 的 Δ14C (Δ14CO2)是基于 14CO2 与大气中 CO2 总量之比,因此其值不仅会因为大气中 14CO2 量的变化而变化,而且也会因为大气中 CO2 总量的变化而变化,这就使得将 Δ14CO2 的变化归因于其中一个或另一个量的变化变得更加复杂。在此,我们建议将大气中的 14CO2 量表述为相对于干燥空气的摩尔分数(地球大气中每摩尔干燥空气中 14CO2 的摩尔数),或表述为地球大气中 14CO2 的摩尔数或分子数,所有这些都很容易从 Δ14CO2 和大气中 CO2 的数量(与 δ13CO2 稍有关系)计算出来,这是对仅表述为 Δ14CO2 的表述的补充,可以为了解大气中 14CO2 不断变化的预算和分布提供有价值的信息。
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