Generang Quality Metals Data at Sites using Field-Portable XRF
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Genera&ng Quality Metals Data at Sites using Field-Portable XRF
Transcript of Generang Quality Metals Data at Sites using Field-Portable XRF
Genera&ngQualityMetalsDataatSitesusingField-PortableXRF
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WhatisQualityData?
o Qualitydataisofknownanddocumentedqualityappropriateforitsintendeduse.
o Qualitydatacanthusincludebothscreeninganddefini&vedata,dependingontheenduseofthedata.
o Field-portableXRFcangeneratebothscreeninganddefini&vedata,dependingontheinstrumenta&onused;andthesamplecollec&on,prepara&onandanaly&calproceduresemployed.
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HowDoWeDocumenttheQualityoftheData?o Accuracy:Thedegreeofagreementofameasurementtoan
acceptedreferenceortruevalue.ü AccuracyisdemonstratedbyuseofNIST-traceablecalibra8onchecks
andsplitswithoff-sitelaboratories,whereappropriate
o Precision:Themeasureofvariabilitybetweenindividualsamplemeasurementsunderprescribedcondi&ons.ü Precisionisdemonstratedbymeasuringaminimumof3replicate
samples,withagoalof%RSDsoflessthan20%ü ThisisthesamecriteriausedinEPAMethods6010and6020
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HowDoWeDocumenttheQualityoftheData?o Representa&veness:Thedegreetowhichdataaccurately
andpreciselyexpressacharacteris&cofapopula&on,parametervaria&onsatasamplingpoint,oranenvironmentalcondi&on.ü Therobustsampleprepara8onstepsand“flipping”thesample
betweenreplicatesensuresthemethodprovidesdatathatisrepresenta8ve.
ü Formalizedprepara8onandanaly8calrequirementsinwriQenSOPsalsoensuresrepresenta8vedata.
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KeyElementsofMethodology?
o BasedonEPAMethod6200
o ComprehensiveSOPscoveringbothsampleprepara&onandanalysis
o Keyelementsofthemethodologyinclude:
ü Prepara8onofthesamples
ü Useofmul8pleNIST-traceablestandards
ü Replicateanalysesofallsamples
ü Monitoringof%RSDofkeyelements
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Innov-XAlpha4000HandheldXRFConvenienthandhelddetectorwithlimitsofdetec&on(LOD)wellbelowEPAMethod6200guidelines-----
10-40kV,10-50µAX-raytubeSiliconPINdiodedetector(<230eVresolu&on)
OlympusX-5000BenchtopXRFLowerLODandshorteranalysis&mesthantypicalhandhelddetector,duetoamorepowerfulx-raytubeandmoresensi&vedetector-----
50kV,200µAx-raytubeLarge-areasilicondri`detector(<165eVresolu&on)
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SampleCollec&onandProcessing
o Collectrepresenta&vesamplesofthegeologicmaterials
o Describethesamplesonthesamplecollec&onlogs
o Forgranularsamples:
ü Removevisibledebrisandnotedescrip&onofdebrisonthesamplecollec&onlogs
ü Ifthesamplesarewet(>20%moisture),thendryinanonsiteovenü Sievethesamplesusinga#10mesh(2mm)sievetoremoveorganic
materialsandsmallerdebrisü Op&onally,furtherhomogenizethesamplesbycrushingandpassing
througha#100sieve(sameasrocksamplesonnextpage)
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SampleCollec&onandProcessing
o Forsolidsamples,crushthesamplesusingaPlaenerMortar
o Sievetopassa#100meshsievetohomogenizethesamples
o Placethesamplesinsmallplas&cbagsforanalysis
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InstrumentStartupandCalibra&on
o Powerontheunitandallowittowarmup
o Standardizetheunitusinga“coin”ofknownmetalliccontent
o Performanini&alcalibra&onverifica&on(ICV),consis&ngofreplicateanalysesof:
ü Ablanksample(synthe8cquartz)
ü Aminimumof2NISTtraceablestandardsofdifferenttargetanalyteconcentra8ons
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Con&nuingandEndingCalibra&on
o Con&nuingcalibra&onverifica&ons(CCVs)areperformedduringtheday(typicallyat4-hourintervals)
o AclosingCCVisperformedattheendofeachday
o IfaCCVfails,samplesanalyzeda`erthelastsuccessfulCCVandpriortotheunsuccessfulCCVarereanalyzed
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SampleAnalysis
o PlacethesampleontheXRFanalyzerandini&ateanalysis
o 3consecu&vemeasurementsareperformedforeachsample,flippingorrota&ngthesamplebagbetweeneachmeasurement
o The%RSDforthe3replicatemeasurementsiscalculatedforeachtargetanalyte
o Ifthe%RSDis>20%,anaddi&onal3replicatemeasurementsareperformed
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SampleAnalysis
o Thereadingsforthe3measurementsisaveraged,andtheaveragedresultisusedasthereportedconcentra&onforthesample.
o Forsampleswith2setsof3measurements,theaverageofthesetof3measurementswiththelowest%RSDforthetargetanalytesisselected
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ExampleDailyAnaly&calLogbook
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ExampleDailyAnaly&calSpreadsheet
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Representa&vePrecisionandAccuracyStudy
o Mul&ple(9ormore)readingsofNISTstandard2710aweretakenusing3differentXRFinstruments:
ü 2Innov-XAlphahandheldunits(SN#6009and9767)
ü 1OlympusX-5000benchtopunit
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WhereHasXRFBeenUsed?
o Gilbanehasemployedfield-portableXRFtocharacterizemetalsandmetalloidsingeologicmaterialsatmanysitesthroughouttheU.S.,including:
1) leadinsoilsandsedimentatmuni8onsresponseareas(MRAs)
2) arsenicandheavymetalsinrock,soilandsedimentataformernavalfacilityinmountainsofSouthernCalifornia
o FortheSouthernCaliforniasite,field-portableXRFwassubjectedto3rdpartyvalida&onandyieldeddefini&vedataacceptedbystateregulatorstosupportsiteclosure.
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Example1–LeadinSoilatMRAs
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Representa&veResultsforLeadinSoil
Correlation Coefficient = 0.98
Theoretical 1:1 Line
XRF
Res
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(ppm
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Laboratory Results (ppm)0 200 400 600
Joint Base Lewis-McChord, Washington
Correlation Coefficient = 0.96
Theoretical 1:1 Line
XRF
Res
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(ppm
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200
400
600
Laboratory Results (ppm)0 200 400 600
Davis-Monthan AFB, Arizona
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Representa&veResultsforLeadinSoilo Over2,780samplesanalyzedatmorethanadozenac&ve
militaryfacili&esthroughouttheU.S.,withanaveragecorrela&oncoefficientof0.945
o Siteswithsamplescontainingleadupto600ppm(1.5xtheRSL)exhibitedveryhighcorrela&on(0.9-1.0),andlow%RSD(<10%)
o Siteswithsamplescontainingleadabove600ppms&llexhibitedhighcorrela&on(0.7-0.9),butwithmoderatetohigh%RSD(o`en>20%)
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Example2–ArsenicinGeologicMaterialsinCalifornia
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Representa&veResultsforArsenicinSoilandSedimento ThreeroundsofonsiteXRFanalyses:
ü ‘Screening’analysisduringremovalof10,000CYofcrushedrockbackfillimpactedwithorganicandinorganiccontaminants
ü ‘Defini8ve’analysisduringgeochemicalstudyofbedrockfollowingcomple8onofNTCRA
ü ‘Defini8ve’analysisduringgeochemicalstudyofsedimentsinadjacentreservoir
o Limited‘confirma&on’analysesperformedduringgeochemicalstudies,duetoAsbeingpresentinresistantmineralphasesfromregionalhydrothermalmineraliza&on
o EPAdiges&onmethodsonlyyield‘environmentallyavailable’metalsandmetalloids
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o ‘Screening’performedusinghandheldXRF(Alpha)
o Analysesperformedoncoa&ngspresentonrocksinfracturedbedrock
o 19samplesanalyzedforAsbyXRFandEPA6010,withacorrela&oncoefficientof0.97,with
o Goodmatchwith1:1line
Correlation Coefficent = 0.97
Theoretical 1:1 Line
XRF
Res
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Laboratory Results (ppm)0 20 40 60
Arsenic in Mineral Coatings, Morris Dam, Southern California
Representa&veResultsforArsenicinMineralCoa&ngs
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o ‘Defini&ve’analysisperformedusingbenchtopXRF(X-5000)
o Analysesperformedoncoarse-grainedsediments
o 20samplesanalyzedforAsbyXRFandEPA6020,withü poorcorrela8onü Poormatchwith1:1line
o However,poorcorrela&onwasexpectedbasedonothergeochemicalanalyses
Representa&veResultsforArsenicinSediment
Theoretical 1:1 Line
XRF
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Laboratory Results (ppm)0 20 40 60
Arsenic in Sediment Samples, Morris Dam, Southern California
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Representa&veResultsforArsenicinSoilandSedimento XRFanalysisofmineralcoa&ngsshowedveryhighcorrela&on
withEPAmethods
ü Dueinlargeparttotheweatheredstateofthemineralcoa8ngs(hydrothermalmineralsarenolongerthedominantAs-bearingphase)
o XRFanalysesperformedonsedimentsshowedpoorcorrela&on
ü DuetothepresenceofhydrothermalmineralsasthedominantAs-bearingphase
o PresenceofAsinhydrothermalmineraliza&onwasconfirmedbyop&calpetrography,x-raydiffrac&on,andelectronmicroprobe
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Conclusionso FieldportableXRFisavaluabletoolforcharacterizingmetalsinavarietyofgeologicalmaterials
o Systema&ctes&ngmethodologycanproducedataofknownanddocumentedqualityappropriateforavarietyofuses,includingevalua&onofhumanandecologicalrisk
Genera&ngQualityMetalsDatausingXRF
