Application of combined 81Kr and 4He chronometers to the dating of old groundwater in a tectonically active region of the North China Plain

Matsumoto, Takuya; Chen, Zongyu; Wen, Wei; Yang, Guo‐Min; Hu, Shui-Ming; Zhang, Xiangyang

doi:10.1016/j.epsl.2018.04.042

Cited by 42 publications

(26 citation statements)

References 35 publications

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“…The most recent development in this field is the introduction of an analytical method from atomic physics (Atom Trap Trace Analysis), which greatly facilitates the use of the noble gas radioisotopes 39 Ar, 81 Kr, and 85 Kr (Lu et al, 2014). This new method of groundwater dating is now increasingly being applied, making successful use of the advantageous properties of the noble gas radioisotopes (e.g., Aggarwal et al, 2015;Gerber et al, 2017;Matsumoto et al, 2018;Ritterbusch et al, 2014;Yechieli et al, 2019).…”

Section: Dating Tracersmentioning

confidence: 99%

The Demographics of Water: A Review of Water Ages in the Critical Zone

Sprenger

Stumpp

Weiler

et al. 2019

Reviews of Geophysics

246

214

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The time that water takes to travel through the terrestrial hydrological cycle and the critical zone is of great interest in Earth system sciences with broad implications for water quality and quantity. Most water age studies to date have focused on individual compartments (or subdisciplines) of the hydrological cycle such as the unsaturated or saturated zone, vegetation, atmosphere, or rivers. However, recent studies have shown that processes at the interfaces between the hydrological compartments (e.g., soil‐atmosphere or soil‐groundwater) govern the age distribution of the water fluxes between these compartments and thus can greatly affect water travel times. The broad variation from complete to nearly absent mixing of water at these interfaces affects the water ages in the compartments. This is especially the case for the highly heterogeneous critical zone between the top of the vegetation and the bottom of the groundwater storage. Here, we review a wide variety of studies about water ages in the critical zone and provide (1) an overview of new prospects and challenges in the use of hydrological tracers to study water ages, (2) a discussion of the limiting assumptions linked to our lack of process understanding and methodological transfer of water age estimations to individual disciplines or compartments, and (3) a vision for how to improve future interdisciplinary efforts to better understand the feedbacks between the atmosphere, vegetation, soil, groundwater, and surface water that control water ages in the critical zone.

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Section: Dating Tracersmentioning

confidence: 99%

The Demographics of Water: A Review of Water Ages in the Critical Zone

Sprenger

Stumpp

Weiler

et al. 2019

Reviews of Geophysics

246

214

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“…The estimated upward flow velocity is within the range modeled at the discharge zones of topography‐driven regional groundwater flow with flow path length on the order of tens to >100 km (Cao et al, 2016). However, groundwater ages derived by modeled mean age distribution and 81 Kr dating suggest that groundwater age in the deep part of the aquifer under the coastal region is on the same order as the sediment age (approaching ~1 Myr) (Cao et al, 2016; Matsumoto et al, 2018). This suggests that deep groundwater in coastal areas may be influenced by regional flow over long travel times (from the piedmont recharge region) with a degree of stagnation in the coastal zone and that the regional groundwater flow system has not yet flushed the porewater deposited in deep aquifers on this timescale.…”

Section: Resultsmentioning

confidence: 99%

“…Water supply in coastal regions—in which 20–40% of the global population live—is jeopardized by the widespread occurrence of saline groundwater (Larsen et al, 2017), and this threat is increasing (Michael et al, 2017). Groundwater residence time assessments (e.g., with isotopic tracers) have shown that groundwater evolution in large sedimentary basins in coastal regions is associated with geological evolution on timescales of millions of years (e.g., Cao et al, 2016; Gerber et al, 2017; Hanor & Mcintosh, 2007; Matsumoto et al, 2018; Yechieli et al, 2019). The primary driver influencing groundwater quality in coastal systems on these timescales is global sea level change associated with glacial and interglacial periods (Aquilina et al, 2015; Harrar et al, 2001; Kooi et al, 2000).…”

Section: Introductionmentioning

confidence: 99%

“…The hydraulic gradient cannot have been significantly enhanced during glaciation, due to the relatively low continental shelf slope (Cao et al, 2016). Groundwater residence times of 0.5 to 1 million years found in the deep coastal aquifer indicate that “fossil” groundwater may have not been fully flushed during the Last Glacial period (Cao et al, 2016; Matsumoto et al, 2018).…”

Section: Introductionmentioning

confidence: 99%

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Groundwater Salinization and Flushing During Glacial‐Interglacial Cycles: Insights From Aquitard Porewater Tracer Profiles in the North China Plain

Han

Cao

Currell

et al. 2020

Water Resources Research

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Using natural tracer profiles to study migration of porewater salinity can help determine fluid fluxes and the timescales of salinization and freshening in coastal regions. Saline groundwater associated with evaporation and transgression events is widely distributed in the North China Plain (NCP). However, the fluid flux, time scales, and importance of different salinization processes are poorly constrained, particularly in areas beyond the limit of marine influence. Chloride (Cl) and δ 18 O profiles were obtained from two boreholes: one drilled at the edge of the piedmont alluvial fan (HS borehole) and one in the coastal region (G1 borehole). Numerical simulation of Cl and δ 18 O profiles confirmed diffusion-dominated solute transport but also indicated slow upward advective flow over geological timescales. The profile modeling at HS indicated that salinization related to evaporation has occurred since the Late Pleistocene. Assessment of alternative conceptual models indicates that intensive groundwater pumping in recent decades has also caused significant downward movement of saline porewater (e.g., movement of brackish water at~0.6 m/yr), mixing modern or Holocene water with Pleistocene water. The coastal Cl profile modeling in contrast shows that porewater salinity can be primarily attributed to salt diffusion during four transgression/regression cycles since the late Middle Pleistocene. The Cl transport appears never to have reached an equilibrium state during the glacial-interglacial cycles. This suggests not only that trapped Holocene seawater is still present and leaching into adjacent sediments but also that Pleistocene water has never been entirely flushed from the deep part of the coastal sediments.

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“…Recent research has been focused in the northern part of the GAS, and new samples from deep confined wells were collected according to the multitracer approaches. Recent advances in the atom trap trace analysis technique (Lu et al, ) turned possible the use of 81 Kr for dating very old groundwater beyond the 14 C age range (Lehmann et al, ; Sturchio et al, ; Aeschbach‐Hertig, and Matsumoto et al, ). The 81 Kr is used to constrain model parameters to convert 4 He concentrations in groundwater into ages (Aggarwal et al, ).…”

Section: Evolution Of Isotope Applicationsmentioning

confidence: 99%

The use of isotopes in evolving groundwater circulation models of regional continental aquifers: The case of the Guarani Aquifer System

Kirchheim

Gastmans

Chang

et al. 2019

Hydrological Processes

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The Guarani Aquifer System (GAS) has been studied since the 1970s, a time frame that coincides with the advent of isotopic techniques in Brazil. The GAS isotope data from many studies are organized in different phases: (a) the advent of isotope techniques, (b) consolidation and new applications, (c) isotope assessments and hydrochemistry evolution, and (d) a roadmap to a new conceptual model. The reasons behind the phases, their methodological approaches, and impacts on the regional flow conceptual models are examined. Starting with local δ2H and δ18O assessments of values for water fingerprinting and estimates of recharge palaeoclimate scenarios, studies evolved to more integrated approaches based on multiple tracers. Stable isotope application techniques were consolidated during the 1980s, when new dating approaches dealing with radiogenic and heavy isotopes were introduced. Through the execution of an international transboundary project, the GAS was studied and extensively sampled for isotopes. These results have triggered wider application of isotope techniques, reflecting also world research trends. Presently, hydrochemical evolution models along flow lines from recharge to discharge areas, across large‐scale tectonic features within the entire sedimentary basin, are being combined with residence time estimates at GAS outcrop areas and deep confined units. In a complex system, it is normal that many, and even contradictory hypotheses are proposed, but isotope techniques provide a unique chance to test them. Stable isotope assessments are still needed near recharge areas, and they can be combined with groundwater classical dating procedures, complemented by newer techniques (3H‐3He, CFCs, and SF6). Recent noble gas sampling and world pioneer analytical efforts focused on the confined units in the GAS will certainly led to new findings on the overall GAS circulation. The objective of this article is to discuss how isotope information can contribute to the evolution of conceptual groundwater flow models for regional continental aquifers, such as the GAS.

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Application of combined 81Kr and 4He chronometers to the dating of old groundwater in a tectonically active region of the North China Plain

Cited by 42 publications

References 35 publications

The Demographics of Water: A Review of Water Ages in the Critical Zone

The Demographics of Water: A Review of Water Ages in the Critical Zone

Groundwater Salinization and Flushing During Glacial‐Interglacial Cycles: Insights From Aquitard Porewater Tracer Profiles in the North China Plain

The use of isotopes in evolving groundwater circulation models of regional continental aquifers: The case of the Guarani Aquifer System

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