Carbon isotope systematics of the Cambrian–Vendian aquifer system in the northern Baltic Basin: Implications to the age and evolution of groundwater

Raidla, Valle; Kirsimäe, Kalle; Vaikmäe, Rein; Kaup, Enn; Martma, Tõnu

doi:10.1016/j.apgeochem.2012.06.005

Cited by 23 publications

(20 citation statements)

References 34 publications

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“…However, without any support from isotope and bacteriological data, it is not possible to judge to what degree denitrification might explain the excess in N 2 . Similarly unknown is the original source of CH 4 except that the isotopic composition indicates a biogenic origin (see Raidla et al, 2012 for discussion). Based on measured redox potentials and isotope compositions of dissolved CH 4 , TIC, SO 4 2- (Raidla et al, 2012(Raidla et al, , 2014), it appears that, currently, CH 4 in the deep CAS groundwaters is being consumed by sulphate reduction rather than being produced by methanogenesis.…”

Section: Dissolved Gasesmentioning

confidence: 99%

Using 81Kr and noble gases to characterize and date groundwater and brines in the Baltic Artesian Basin on the one-million-year timescale

Gerber

Vaikmäe

Aeschbach–Hertig

et al. 2017

Geochimica et Cosmochimica Acta

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Analyses for 81 Kr and noble gases on groundwater from the deepest aquifer system of the Baltic Artesian Basin (BAB) were performed to determine groundwater ages and uncover the flow dynamics of the system on a timescale of several hundred thousand years. We find that the system is controlled by mixing of three distinct water masses: Interglacial or recent meteoric water (δ 18 O ≈ −10.4‰) with a poorly evolved chemical and noble gas signature, glacial meltwater (δ 18 O ≤ −18 ‰) with elevated noble gas concentrations, and an old, high-salinity brine component (δ 18 O ≥ −4.5‰, ≥ 90 g Cl − /L) with strongly depleted atmospheric noble gas concentrations. The 81 Kr measurements are interpreted within this mixing framework to estimate the age of the endmembers. Deconvoluted 81 Kr ages range from 300 ka to 1.3 Ma for interglacial or recent meteoric water and glacial meltwater. For the brine component, ages exceed the dating range of the ATTA-3 instrument of 1.3 Ma. The radiogenic noble gas components 4 He* and 40 Ar* are less conclusive butalso support an age of > 1 Ma for the brine. Based on the chemical and noble gas concentrations and the dating results, we conclude that the brine originates from evaporated seawater that has been modified by later water-rock interaction. As the obtained tracer ages cover several glacial cycles, we discuss the impact of the glacial cycles on flow patterns in the studied aquifer system. Virbulis et al., 2013), the latter of which estimated the hydraulic age of groundwater in the CAS to be on the order of several hundreds of ka to 1 Ma. In the light of such long residence times, it is crucial to consider the effect of repeated glacial cycles on the long-term evolution of groundwater composition and flow. Sampling the deeper parts of the CAS on a regional scale for chemistry, noble gases, and multiple dating tracers ( 81 Kr, 85 Kr, 39 Ar, 14 C, 4 He, 40 Ar) allows us to elucidate the evolution of the brine, mixing proportions of the different groundwater components, and the flow dynamics over the last 1 Ma.

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Section: Dissolved Gasesmentioning

confidence: 99%

Using 81Kr and noble gases to characterize and date groundwater and brines in the Baltic Artesian Basin on the one-million-year timescale

Gerber

Vaikmäe

Aeschbach–Hertig

et al. 2017

Geochimica et Cosmochimica Acta

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“…The information about the water in this aquifer is scarce, but available data show that it contains Na-Cl or Ca-Cl type brackish and saline groundwater with electrical conductivity from 2 to 20 mS•cm −1 [25,42]. Several studies [21,24,42] have shown that the Cm-V aquifer system and the underlying crystalline basement aquifer are hydraulically connected and the hydrochemistry in the deeper Gdov aquifer system is influenced by saline water in the crystalline basement aquifer.…”

Section: Geology and Hydrogeological Settingmentioning

confidence: 99%

“…Anoxic conditions predominate in the Cm-V aquifer system, but Raidla et al [21,48] show that oxygen-rich conditions dominated in the aquifer system in the relatively short infiltration period during the advance and maximum extent of the Scandinavian ice sheet in the Last Glacial Maximum. Vaikmäe et al [20] have shown that groundwater in the Cm-V aquifer system in North-Estonia is characterised by enormous amounts of excess air (oversaturation of Ne up to 200-400%).…”

Section: Secondary U Deposits As the Source Of 226 Ramentioning

confidence: 99%

“…The groundwater from the Cm-V aquifer system in North Estonia is typically strongly depleted in 18 O (δ 18 O= −18 to −23‰) [18] with respect to local shallow groundwater (−11 to −12.5‰) [19]. The Cm-V groundwater originates from glacial meltwater of the Scandinavian Ice Sheet that covered the territory of Estonia during the Pleistocene [20,21]. Thus, the aquifer system contains groundwater that is essentially non-renewable on a human timescale and the quality of which can be strongly altered during groundwater abstraction.…”

Section: Introductionmentioning

confidence: 99%

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Intrusion of Saline Water into a Coastal Aquifer Containing Palaeogroundwater in the Viimsi Peninsula in Estonia

et al. 2019

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The Viimsi peninsula is located north-east of Tallinn, capital of Estonia. The Cambrian-Vendian (Cm-V) aquifer system is a sole source of drinking water in the area. Historically, the groundwater exploitation has led to freshening of groundwater in the peninsula, but in recent years an increase in chloride concentrations and enrichment in δ18O values has been detected, but in recent years hydrochemical parameters indicate an increasing influence of a saline water source. The exact origin of this saline water has remained unclear. The aim of the current study is to elucidate whether the increase in Cl− concentrations is related to seawater intrusion or to the infiltration of saline water from the underlying crystalline basement. To identify the source of salinity, chemical composition of the groundwater and the isotope tracers (e.g., δ18O and radium isotopes) were studied in the Viimsi peninsula in the period from 1987 to 2018. Our results show that chemical composition of Cm-V groundwater in the peninsula is clearly controlled by three-component mixing between glacial palaeogroundwater, saline water from the underling crystalline basement and modern meteoric water. The concentrations of Ra are also significantly affected by the mixing, but the spatial variation of radium isotopes (226Ra and 228Ra) suggests the widespread occurrence of the U in the surrounding sedimentary sequence. Our hypothesis is that, in addition to U originating from the crystalline basement, some U could be associated with secondary U deposits in sedimentary rocks. The formation of these secondary U deposits could be related to glacial meltwater intrusion in the Pleistocene. Although the results suggest that the infiltration of saline groundwater from the underlying crystalline basement as the main source of salinity in the study area, the risk of seawater intrusion in the future cannot be ruled out. It needs to be highlighted that the present groundwater monitoring networks may not be precise enough to detect the potential seawater intrusion and subsequent changes in water quality of the Cm-V aquifer system in the Viimsi peninsula.

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“…The Cm-V system of the BAB has been extensively studied using isotopic and geochemical tools ( 3 H, 14 C, δ 18 O, δ 13 C, 39 Ar, 4 He, 40 Ar/, 36 Ar, atmospheric noble gases (Ne, Ar, Kr, Xe) for recharge temperature, amount, and composition of extracted gases (Vaikmäe et al, 2001;Karro et al, 2004;Raidla et al 2012). Recently, 81 Kr dating together with the noble gas and isotope analysis has been carried out in the deep brines of the BAB.…”

Section: Europementioning

confidence: 99%

Groundwater and Global Palaeoclimate Signals (G@GPS)

Haldorsen¹,

Ploeg²,

Cendón³

et al. 2016

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Groundwater sources supply fresh drinking water to almost half of the World's population and are a main source of water for irrigation across world. Characterization of groundwater resources, surfacegroundwater interactions and their link to the global water cycle and modern global change are important themes in hydrogeological research, whereas little attention has been given to the relation between groundwater and past climate variations. A groundwater system's history is vital to assess its vulnerability under future and potentially adverse climatic changes. The scientific initiative Groundwater and Global Palaeoclimate Signals (G@GPS) investigates major recharge periods of large groundwater aquifers worldwide. We describe the findings for a major basin on each permanently inhabited continent and one with coastal influences in Australia. As palaeo-signals in groundwater are inherently low-resolution records, they can only be related to considerable amounts of recharge. Long periods with substantial groundwater recharge ought to be well identifiable in terrestrial records. Correlation with regional and global climate records may give ideas of the conditions under which such large amounts of recharge were initiated.

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Carbon isotope systematics of the Cambrian–Vendian aquifer system in the northern Baltic Basin: Implications to the age and evolution of groundwater

Cited by 23 publications

References 34 publications

Using 81Kr and noble gases to characterize and date groundwater and brines in the Baltic Artesian Basin on the one-million-year timescale

Using 81Kr and noble gases to characterize and date groundwater and brines in the Baltic Artesian Basin on the one-million-year timescale

Intrusion of Saline Water into a Coastal Aquifer Containing Palaeogroundwater in the Viimsi Peninsula in Estonia

Groundwater and Global Palaeoclimate Signals (G@GPS)

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