Radiocarbon analysis on organic and elemental carbon in aerosol samples and source apportionment at an urban site in Northern Italy

This workaimsatgaininginformationontheeffectsofdifferentthermaltreatmentson radiocarbonmeasurementsoforganic(OC)andelemental(EC)carbonfractionsinthe atmosphericaerosol.Improvementstothetraditionalapproachesforthedetermination of thefractionofmoderncarbonofOCandECfm(OC) and fm(EC)- areproposed. As for fm(EC) determination,weproposetoadd aHestepathightemperaturetothe standard oxygentreatment.Ourtestsdemonstrate thattheadditionofahightemperatureHe step (finalchoice:750 1C) totheoxygentreatmentiseffectiveinremovingtherefractoryOC. As for fm(OC) determination,weproposetoquantifyitbymeasuringeitherthefractionof modern carbonofTCandECorthefraction ofmoderncarbonofwatersoluble(fm(WSOC)) andwaterinsoluble(fm(WINSOC))organiccarbontolimittheinfluenceofpossiblepyrolysis on thedirectdeterminationof fm(OC). Testsontheequivalenceoftheapproacheshaveshown good agreementbetweenthem. Our testswerecarriedoutonsamplescollectedinaheavilypollutedarea(Milan,Italy) during wintertime. fm(OC), fm(EC),and fm(TC) valuesobtainedinourtestswerealsousedto attemptapreliminarysourceapportionmentintheareausing 14C measurements. WintertimeECresultedtobemainlyfossil(84%),whereasOCwasdominatedbymodern contribution(63%). Two approachesweretestedfortheevaluation ofthewoodburningcontributiontoOC and agoodagreementwasfound.Woodburning primarycontributionaccountedforabout 18%ofOCinMilanduringwintertime. Secondary OCfrombiomassburningandthecontributionfromotherurbansources were tentativelyidentifiedfollowingliterature approaches,withtheaimofevaluatingthe biogeniccontributiontoOCinthearea,whichwasestimatedtobeabout18%.