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TOCTN分析仪法测定水质总氮的不确定度评定.docx

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TOCTN分析仪法测定水质总氮的不确定度评定 Abstract TOCTN(TotalOxygenDemand-TotalNitrogen)analyzerisacommonlyusedmethodfordeterminingthetotalnitrogencontentinwaterqualityanalysis.TheuncertaintyevaluationofTOCTNanalyzermethodforwaterqualityiscrucialandnecessary.Thispaperwilldiscussthesourcesofuncertainty,establishmentofuncertaintymodel,andcalculationofuncertaintybudgetforTOCTNanalyzermethodbyanalyzingtheTOCTNmeasurementprocessandexperimentaldata. Keywords:TOCTNanalyzer,uncertaintyevaluation,waterquality,measurementprocess,uncertaintybudget. Introduction Waterqualitymonitoringisanimportantenvironmentalmanagementtoolusedtoevaluatethephysical,chemical,andbiologicalcharacteristicsofsurfacewaterandgroundwater.Onekeyparameterinwaterqualityanalysisistotalnitrogen,whichcanbemeasuredusingtheTOCTNanalyzermethod.TheuncertaintyevaluationfortheTOCTNanalyzermethodisimportantforassessingtheaccuracyandreliabilityofwaterqualitymeasurementresults.Inordertodeterminetheuncertaintyofwaterqualitymeasurements,itisnecessarytoidentifyandquantifythesourcesofuncertaintyassociatedwiththemeasuringinstrumentandmethodology. SourcesofUncertainty ThesourcesofuncertaintyforTOCTNanalyzermethodcanbecategorizedintotwotypes:TypeAandTypeB.TypeAuncertaintyresultsfromrandomerrorassociatedwiththemeasuringinstrument,whileTypeBuncertaintyresultsfromsystematicerrorassociatedwiththemeasuringmethodology. TypeAUncertainty TheTOCTNanalyzerinstrumenthasmeasurementuncertaintyassociatedwiththefollowingfactors: -Randomnoisegeneratedbyelectronicpartsandcircuits -Fluctuationsinambienttemperature -Vibrationorexternalelectromagneticinterference -Inherentuncertaintyassociatedwithreadingandsettingtheinstrument TypeBUncertainty TheTOCTNanalyzermethodhasuncertaintysourcesprimarilyassociatedwiththefollowingfactors: -Calibrationuncertainty-duetotheaccuracyanduncertaintyofreferencestandards,suchasliquidnitrogenandpotassiumpermanganate. -Samplinguncertainty-differencesinsamplecollectionandanalysisleadtonon-reproducibleresults. -Homogeneityuncertainty