Mecsek Hills, Hungary precipitation from 2004 to 2017 in the ( δ O, δ H) and tritium activity in Monthly data of stable isotopic composition

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Data in Brief

journalhomepage:www.elsevier.com/locate/dib

Data Article

Monthly data of stable isotopic composition ( δ ^{18 O,} δ ^{2 H) and tritium activity in}

precipitation from 2004 to 2017 in the Mecsek Hills, Hungary

István Fórizs

^a,∗

, Zoltán Kern

^a,∗

, József Csicsák

^b

, Gergely Csurgó

^b

, Gábor Földing

^b

, Zoltán Máthé

^b

, János Ország

^c

, Géza Szreda

^b

, Roland Vendégh

^b

aInstitute for Geological and Geochemical Research, Research Centre for Astronomy and Earth Sciences

bMECSEKÉRC Zrt. Esztergár Lajos u. 19. H-7633 Pécs, Hungary

cPublic Limited Company for Radioactive Waste Management (PURAM), H-7031 Pf. 12. Paks, Hungary

a rt i c l e i n f o

Article history:

Received 5 June 2020 Revised 14 August 2020 Accepted 18 August 2020 Available online 21 August 2020 Keywords:

Precipitation isotope monitoring

3H

Oxygen isotopes Hydrogen isotopes D-excess Isotope hydrology Hungary

a b s t r a c t

The stableisotopiccomposition(δ^18O, δ^{²H)and tritium ac-} tivityofmonthlyaggregatedprecipitationsampleswerecol- lectedbetween April 2004and December2017 atsix sites representingthefirstpublishedprecipitationisotopedataset fromthe MecsekHills (Hungary). Thedataset includes 697 stableisotopicand653tritiumactivityconcentrationdataof monthly precipitationsamples collectedacross the Mecsek Hills.Atthebeginningofthemonitoringperiod,theisotopic compositionvaluessuggestaninsufficientprotectionagainst evaporationandthisissuehasoccasionallyreappearedlater onlyinlimitedperiods.Thesedataarepresentedinbrackets intheSupplementaryTableandshouldbedisregardedfrom furtheranalysisuntiladditionalverification.Thisdatasetpro- vides isotope hydrological benchmark in comparison with otherlocaland regionaldatasetsofstableisotopesand tri- tiumactivitiesinsurfacewaterandgroundwaternotonlyin the Mecsek Hills butalso inthe surroundings. It can sup- portwaterresourcemanagement,andpaleoclimatologicalre- search.Isotopehydrologicalevaluationandfurtherdiscussion

∗ Corresponding author.

E-mail addresses: forizs@geochem.hu (I. Fórizs), zoltan.kern@gmail.com (Z. Kern).

https://doi.org/10.1016/j.dib.2020.106206

2352-3409/© 2020 The Author(s). Published by Elsevier Inc. This is an open access article under the CC BY-NC-ND license ( http://creativecommons.org/licenses/by-nc-nd/4.0/ )

onthe seasonaltrendsinthe precipitationisotopiccharac- teristics areinprogress and thetritium datawereused in the derivationofagridded database(1×1km)ofamount- weighted annualmeanprecipitationtritiumactivityforthe Adriatic-PannonianRegion(AP³H_v1,[1]).

© 2020TheAuthor(s).PublishedbyElsevierInc.

ThisisanopenaccessarticleundertheCCBY-NC-ND license(http://creativecommons.org/licenses/by-nc-nd/4.0/)

SpecificationsTable

Subject Earth and Planetary Sciences

Specific subject area

isotope hydrology

Type of data Table

Figure How data were

acquired

Aggregated monthly precipitation samples were collected. Stable oxygen and hydrogen isotope composition of monthly precipitation samples were measured by isotope ratio mass spectrometry from 2004 to 2010, and by laser spectrometry (with cavity enhanced absorption technique) from 2011 to 2017.

Tritium activities have been analyzed by low-level liquid scintillation counting following electrolytic enrichment.

Data format Raw data are provided in Excel files as supplementary material.

Parameters for data collection

No pretreatment was required before the stable isotope analysis. Electrolytic enrichment was applied before the analysis of the tritium activities.

Description of data collection

Stable oxygen and hydrogen isotopic compositions were measured by isotope ratio mass spectrometry using a dual inlet Finnigan MAT Delta S, and Finnigan Delta ^plusXP mass spectrometer in continuous-flow mode until the end of 2010, and by laser spectrometry using a Liquid Water Isotope Analyser (LWIA-24d, Los Gatos Research) thereafter. Tritium activities have been analyzed by low-level liquid scintillation counting following electrolytic enrichment.

Data source location

Six sites in the Mecsek Hills, Hungary Z 46.03744 °N 18.12443 °E 117 m a.s.l.

B 46.06854 °N 18.11269 °E 172 m a.s.l.

V 46.12153 °N 18.09230 °E 330 m a.s.l.

II 46.09927 °N 18.09149 °E 332 m a.s.l.

Boda 46.08668 °N 18.04671 °E 233 m a.s.l.

Het 46.12524 °N 18.04776 °E 165 m a.s.l.

Data accessibility With the article

ValueoftheData

• Thedatasetprovidesbenchmarkdataforisotopehydrologicalevaluationofthesurfacewater andgroundwaterintheMecsekregion(e.g.estimatingthemeanresidencetimeofstreamwa- terandkarsticreservoirs).

• Thedataareespeciallyimportantbecausethey providenecessarybasicisotopehydrological background datafortheenvironmentalmonitoring oftheplanned highactivityradioactive wasterepository.

• Regionalpaleoclimatologicalresearchcouldalsobenefitfromthesedatabecausetheisotopic

‘temperature’effectinmodernprecipitationintheMecsekregioncanbeinferred,whichcan beacrucialparameterinpaleoclimatologicalapplications.

• Thedatasetprovidesreferencedatafor(i)authenticityandtraceability ofagriculturalprod- ucts from this region e.g. forlocal wines, and (ii) archaeological research of migration of peoples,animalsandobjectsmadeoforganicmaterial.

1. DataDescription

Thestudyoftheisotopiccompositionofsurfaceandgroundwaterstartedin2004(Fig.1)in theMecsek region(South Hungary)inordertoprovidefield datatohydrogeological modeling forthegeologicalresearchprogrammeofBodaClaystoneFormation(BCF)withinthesiteselec- tion ofa planned highactivityradioactivewaste repository.The research programmeis man- agedbythePublicLimitedCompanyforRadioactive WasteManagement.Precipitationsamples werecollectedbytheMECSEKÉRCZrt,stableisotopeanalysiswasperformedbytheInstitutefor

Fig. 1. Isotopic characteristics of monthly precipitation collected in the Mecsek Hills (Hungary) between April 2004 and November 2017. Stable oxygen isotopic composition (A), d-excess (B), and tritium activity concentration (C).

Fig. 2. Distribution of monthly averaged δ^2H–δ¹⁸O for precipitation in the Mecsek Hills between 2004 and 2017. The dashed black line shows the Global Meteoric Waterline [3] . Data obtained from samples before May 2005 are marked by open circles and the extreme outliers in the dataset of station B (from July 2012 to August 2014 and also in March 2015) are marked by crosses.

Geological andGeochemical Research,Research Centre for Astronomy andEarth Sciences and itspredecessor(Institute forGeological andGeochemicalResearch,HungarianAcademyofSci- ences),andtritiumactivityofthewatersampleswereanalyzedbytheHYDROSYSLaborLtd.

AuniquemonthinthedatasetisApril2007whentherewasnoprecipitationatanystation ofthenetwork,howeverNovember2011,December2013,andDecember2016werealsorather drymonthswhensomeofthestationsdidnotrecordprecipitation.Inaddition,inmonthswith lowprecipitationamountitwasaquite frequentsituationthatthecollectedprecipitationwas sufficientonlyforstableisotopeanalysisandtherewasnotenoughmaterialfortritiumactivity measurements.Inonecase, October2010thesamplesubmittedforstableisotopeanalysishas beenlost.Altogether,stableoxygen andhydrogenisotopiccompositionsare presentedfor697 samplesandTritiumactivityisavailablefor653samples(SupplementaryTable).

The time series of the primary isotopic parameters of monthly precipitation data show a highdegreeofcoherency(Fig.1).Therearetworemarkableperiodswhenthecoherencyinthe stableisotope data is weaker. Especially d-excess [2] indicates the problematic data in these periods becaused-excess values obviouslystand out fromthe typical rangeof distribution of thisparameter.ThefirstperiodisfromthebeginningoftherecordtoMay2005andthesecond oneisbetweenJuly2012andMarch2015.Inthefirstperiodunusuallylowd-excessvalueswere observedatstationsZandVsuggestingevaporationeffectuntilthecollectorvesselwasburied.

FailureinevaporationprotectioncanbeassumedforsamplescollectedinFebruaryandJulyof 2007atstationZ.There isno deviationinthemetadata ofstationB whichcould explain the extremelyanomalousvaluesseenintherecordfromJuly2012toAugust2014andalsoinMarch 2015.

For the sake of completeness these potentially problematic data are also reported in the dataset,howeverpresentedinbracketsanditisrecommendeddisregardingtheseisotopicdata inisotopehydrologicalcharacterizationofthemodernprecipitationintheMecsekHills.Tritium activitydata donot seem to reflectthesedisturbances (Fig.1c). The point cloud inthe dual- isotopespacedefinedbythevastmajorityofthedata(Fig.2)fitsnicelytotheGlobalMeteoric WaterLine,describingtheglobalrelationoftheseparameters[3].Hencethesedatawillbesuit- ableinputdataforfurtherisotopehydrologicalmodellingandprovidearobustmodernreference forpaleoclimatestudies.Wepointoutagainthatproblematicdata,presentedinbracketsinthe SupplementaryTable,shouldnotbeconsidereduntiladditionalverification.

2. ExperimentalDesign,MaterialsandMethods 2.1. Samplecollection

The collectionof precipitationsamples forisotope hydrological monitoringstartedin April 2004attwostations(Z andV)andfora shortperiod(fromNov2004toNov2005) atstation B. Dailyprecipitation sampleswere collectedineach morning andaggregatedina 5Lplastic (HDPE) container on a monthlybasis. Winter precipitationwas collectedby the same instru- mentation as(sono heatedfunnelwasused) ifsnow hadaccumulatedin thecollectorwhen thesamplewasharvested,itwasaddedtothecollectionvesselbymelting.Specialprecautions forevaporationpreventionwasnotappliedwhenmeltingthesnow.Thenetworkwasexpanded withtwoadditionalstationsfromMay2005.Fromthenon,thesamplecollectingvessels were placed ingroundcavity,primarily toprevent summerevaporationandwinterfreezing. Thisis an approvedoptionforcollectorconfigurationforprecipitationisotopeanalysis(‘Buriedcollec- tor’:[4]).MonitoringceasedatstationVbyMayof2010andthecollectionplacewasmovedto

∼4kmsouthward(stationII)by June2011.Thesamplecollectorswere installedintherecom- mendedsafetydistancefrompotentialphysicalbarriers[4].Thewatersamplesweretransferred toleak-proofplasticbottleandshippedtolaboratories. Sampleswere keptinglassvialsclosed withplasticcapswithconicalinteriorinrefrigerator.

2.2. Analyticalmethods

Stableisotoperatiosinwaterwereanalyzedinthedifferentperiodsoftimebythefollowing methodsandanalyticalinstruments:

2.2.1. From2004to2005

- the

δ

^{18Ovalueofwaterwasdeterminedby FinniganMAT deltaS mass}spectrometerusing CO₂ gasequilibratedwithH₂Oat20°Ctemperatureduringovernight,wheresamplecontain- ingvesselswereshaken.ThedetailsofthesamplepreparationsetupisdescribedbyRoether [5],theoriginalprincipleistheonedescribedbyEpstein&Mayeda[6].

- the

δ

^{2Hvalue ofwater wasdetermined by Finnigan MAT deltaSmass} spectrometerusing H₂ gasliberatedfrom3

μ

^{Lwaterbyreactingwith100mgspecialzincalloy[7]inasealed}

vacuumglasstubeat500°Cduring30min[8,9].

The applied laboratory standard was the BTW (Budapest Tap Water) calibrated against SMOW andSLAP. The normalizationfactors [10] for both H and O, which were found to be rather stable, were determined circa monthly by applying reference materials W-63333 as- signed

δ

^2HVSMOW-SLAPand

δ

^18OVSMOW-SLAPvaluesof-399.8and–52.28‰,andW-39500assigned

δ

^2HVSMOW-SLAP and

δ

^18OVSMOW-SLAP valuesof-1.5and-1.52‰,respectively[11,12,13].Theseref- erencematerialswerekindlyprovidedbyTylerB.Coplen,theRestonStable IsotopeLaboratory (RSIL),ofU.S.GeologicalSurvey(USGS).

Thereproducibilitywasaround±0.06–0.07‰foroxygen.Whenthedifferencebetweenthe duplicates exceeded 0.2‰(foroxygen)then we dida thirdanalysis(or a fourthoneifit was recommended)forthesakeofkeepingthereproducibilitybelow±0.1‰.Occasionallywerean- alyzedsomesamplesafterseveralmonthsandtheremeasureddeltavalueswerealwayswithin the±0.1‰rangetotheoriginallydeterminedone.Thereforewestatethattheoverallestimated (sample storage+sample preparation+analysis) uncertainty was±0.1‰ foroxygen and ±1‰ forhydrogen.

2.2.2. From2006to2010

- the

δ

^{18O value of water was determined by Finnigan DeltaplusXP mass} spectrometer in continuous-flowmode. The sample preparingprocess before themass spectrometric mea- surementwas the following: 1 mL waterfrom each sample (unknown andstandard) was

pipetted intoa 10mLvialclosedbyseptum+cap.EachvialwasflushedbyHegascontain- ing 0.3v/v%CO₂ during6minutes,andthewhole setwaskeptina heatingblock at32°C forminimum18hoursforgettingtheisotopicequilibriumintheCO₂-H₂Osystem.

- the

δ

^{2H value of water was determined by Finnigan DeltaplusXP mass} spectrometer in continuous-flow mode. The samplepreparing process before the mass spectrometric mea- surement wasthe following: platinized catalyzer wasinserted and 1mL water fromeach sample(unknownandstandard)waspipettedintoa10mLvialclosedbyseptum+cap.Each vialwasflushedbyHegascontaining2.1v/v%H₂ during6min,andthewholesetwaskept ina heatingblock at32°C forminimum40minforgettingtheisotopic equilibriuminthe H₂-H₂Osystem[14].

The applied laboratory standard was the BTW (Budapest Tap Water) calibrated against SMOW and SLAP. The normalization factors [10] for both H andO, which were found to be veryclose to1.0, were determined circa weekly by applyingreferencematerials W-63333 as- signed

δ

^2HVSMOW-SLAPand

δ

^18OVSMOW-SLAPvaluesof-399.8and–52.28‰,andW-39500assigned

δ

^2HVSMOW-SLAP and

δ

^18OVSMOW-SLAP valuesof-1.5and-1.52‰,respectively[11,12,13].Theoverall estimated(sample storage+sample preparation+analysis) uncertainty was±0.2‰ foroxygen and±2‰forhydrogen.

2.2.3. Since2011

Both

δ

^{2H and}

δ

^{18O values of water were determined by a Liquid Water Isotope Analyser}

(LWIA-24d,Los GatosResearch). Thesamplepreparing andmeasurementprocess wasthefol- lowing:1mLwaterwaspipettedintoeach 2mLvialclosedwithseptum+cap.Thevialswere arrangedonthetrayinthefollowingway:3labstandards– 5unknownsamples– 3labstan- dards,etc.inthesaketopreventtheeffectofambienttemperaturevariation[15].Anautosam- pler(CTCAnalyticsGCPAL)usingaHamiltonsyringetook 1

μ

^{Lwaterfromthe2mLvialand}

injecteditthroughapreformedseptumintothevaporizerofthelaseranalyzerwherethewater wasevaporated at80°Cinlow vacuuminto thecavityoftheanalyzer.From eachvial6injec- tions were carried out,but becauseof memoryeffect only thedata of thelatest 4 injections weretakenintoaccount.Theoverallestimateduncertaintywas±0.2‰foroxygenand±1‰for hydrogen.Theappliedlaboratorystandardswerethefollowingoneswiththeassigned

δ

^2Hand

δ

^{18Ovaluesinbrackets:BWS1(-9.0;-0.53),BWS2(-74.9;-10.41),BWS3(-147.7;-19.95)[16].}

Eachsampleduringboth themassspectrometric andlaser instrumentalanalysiswasmea- suredin duplicate and the meanvalues are here presented. All stableisotope measurements werecarriedout intheInstituteforGeologicalandGeochemicalResearch,ResearchCentrefor AstronomyandEarthSciences(Budapest,Hungary)anditspredecessors.

Theresultsare expressedinthestandard

δ

^{-notation[17] relativeto ViennaStandard Mean}

OceanWater:

δ

(‰)=(^R−R_std)/R_std∗1000[‰]_VSMOW,

whereRandR_stdare¹⁸O/¹⁶Oor²H/¹Hratiosinthesampleandinthestandard(ViennaStandard MeanOceanWater-VSMOW),respectively[18].

Duringthetransitionfrommassspectrometrictolaserspectroscopicanalysesseveralsetsof sampleswere measuredby both techniques,anditwasfound that themeasured deltavalues werethesamewithintheanalyticaluncertainties.Thelaboratory– usingbothmassspectrom- eters(FinniganMATDeltaS,andFinniganDelta^plusXP)andtheLiquidWaterIsotopeAnalyser– hassuccessfullyparticipatedinthewaterisotopelaboratoryproficiencytests[19].

A secondary isotopic parameter of natural waters, d-excess [2], has been calculated as d=

δ

^2H-8×

δ

^18O.

Tritiumactivitieshavebeenanalyzedbylowlevelliquidscintillationcountingfollowingelec- trolyticenrichmentatHYDROSYS LaborLtd, Budapest.Tritiated water,SRM4361C H-3 (NIST), wasused asstandard referencematerial.Activityconcentration ofthesamplesis expressedin Bq/L.

DeclarationofCompetingInterest

Theauthorsdeclarethattheyhavenoknowncompetingfinancialinterestsorpersonalrela- tionshipswhichhave,orcouldbeperceivedtohave,influencedtheworkreportedinthisarticle.

Acknowledgments

TheauthorsacknowledgetheconsentofPublicLimitedCompanyforRadioactiveWasteMan- agement andMECSEKÉRCZrt.to publishtheir data. Thiswork wassupported by the National Research,DevelopmentandInnovationOffice,Hungary[SNN118205].

Supplementarymaterials

Supplementary material associatedwiththisarticle canbe found, inthe onlineversion, at doi:10.1016/j.dib.2020.106206.

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