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Teledyne Advanced Pollution Instrumentation Model 633 Aethalometer
®
Black Carbon Monitor User Manual
07645A DCN6170 9
Itisclearthattheeffect,whenpresent,islinearwithloading(‘ATN’).Thiscanberepresented
as:
BC(reported)=BC(zeroloading)*{1‐k•ATN}
where BC (zero loading) is the desired ambient BC value that would be obtained in the
absenceofanyloadingeffect;andkisthe‘loadingcompensation parameter’ (similar to
Virkkula,2007).
Theanalysisof alarge numberof datasetsfromawide varietyoflocationsshowsthatthis
relationshipislinearinallcasesstudied;butwithdifferentvaluesofk.Itisthereforepossible
toeliminatethe‘loadingeffect’ofkbymakingtwosimultaneousidenticalmeasurementsBC1
andBC2atdifferentdegreesofloadingATN1andATN2.
BC1=BC*{1‐k•ATN1}
BC2=BC*{1‐k•ATN2}
Fromthesetwolinearequationswemaycalculatethe‘loadingcompensationparameter’k;
andthedesiredvalueofBCcompensatedbacktozeroloading.
The Model 633 Aethalometer analyzes the Black Carbon component of aerosols on two
parallel spots drawn from the same input stream, but collected at different rates of
accumulation,i.e.atdifferentvaluesofATN.Bycombiningthedataaccordingtotheabove
equations,theModel633yieldsthevalueofBCextrapolatedbackto‘zeroloading’;aswellasa
real‐timeoutputofthe‘loadingcompensationparameter’kwhichprovidesinsightsintothe
aerosolnatureandcomposition.Thisprocessisperformedinrealtimeforallwavelengths:
examinationofthe‘k’valuesasafunctionofwavelengthprovidesfurtherinformationabout
the aerosol composition. An example of this is shown for extreme concentrations of black
carbon(Figure3).