Oxidative processing studies on - PDF document

Oxidative processing studies onbiologic
Oxidative processing studies onbiological ice nucleating particlesDepartment of Chemistry, University of Toronto, 80 St. George Street, Toronto ON M5S 3H6, CanadaE-Mail: ellen.gute@mail.utoronto.caEllen Gute, Jonathan P.D. Abbatt1 Introduction6 References4 Results: Solar Simulator and controls5 Conclusion and outlook3 Results: OH exposure studies 2 ObjectivesIcenucleatingparticles(INP)arereleventforcloudformationandthereforecontributetotheoverallimpactofcloudsontheEarth‘sclimate.However,modelsarestillmissingrelevantinformationontypesofINPs,underlyingprocessesandINPconcentrations(1-2).Todate,itisknownthatbiologicalparticles,suchaspollen,canactasINPs.Yet,onlyfewpollentypesarestudiedfortheirINbehaviour.Experimental Designaqueous phase oxidative pre-processing 1Boucheretal.,2013,CloudsandaerosolsIPCC.pp.571-6582Hoose,C.&Moehler,O.,2012,ACP,12(20),pp.9817-98543Sullivan,R.C.etal.2010.ACP,10(23),pp.11471-114874Lam,M.W.etal.,2003,Environ.Sci.Technol.,37,pp.899907WearestudyingtheeffectofOHoxidationontheicenucleationactivityofthreetypesofpollen:SilverBirch,GreyAlderandSycamoreMaple.TheicenucleationactivityunderOHexposureofthebiologicalmaterialsiscomparedtoATDasanon-biologicalmaterial.2 Method overviewNext steps are:a)Most importantly, measure the OH concentration in the sample using HPLCb)Study chemical bonds and their potential change due to theOH exposure using FTIR-ATR analysisc)Image the pollen samples before and after OH exposured)Conduct same experiments in an environmental chamberUniversity of Toronto Continuous Flow Diffusion Chamber (UT-CFDC)Icenucleationofthebiologicalparticlesisstudiedindepositionmodeat233K(-40⁰C)sizeselection (200nm)countsice� 2µmdryerH2O2+ UV (254nm) OH OPC (OpticalParticleCounter)Allpollenarenon-defattedpollenfromlandandroadsideinSouthCzechRepublic(Pharmallerga®).Shownaretheactivatedfractionsforicecrystals�2µmatatemperatureof233K.Birchpollen(0.2g)/Alderpollen(0.4g)/ATD(3g)suspendedin200mlMilliQ®water,shakenfor5minandleftfor2h(large&heavyparticlessettle).Thentheclearpartistransferredtotheatomizerbottle.Sample preparationIce nucleation inactiveMaple PollenSycamore maple (Acer pseudoplatanus):Thin beige powder. Microscopic size 30-50µm.Ice nucleation activeBirch and Alder Pollen exposed to OHSilver birch (Betula pendula):Thin gold yellow powder. Microspcopic size 20-27 µm. Grey Alder (Alnus incana): Yellow, loose pollen. Microscopic size 18-30 µm.Can ice nucleation activity of pollen be alteredby exposure to OH (chemical oxidation)? From the presented data we can conclude that-depending on the pollen type, ice nucleation activity can be observed-exposure to OH decreases the IN activity of these pollen-exposure to OH did not affect the IN activity of the non-biological materialTherefore, the change in IN activity due to OH exposureis of biological origin. Note:Asnoactivationwasobservedformaplepollen,exposuretoOHwasnottested.Comparison to a non biological material -ATDControl experimentsControlexperimentsweredoneforallsubstancesthatshowedicenucleationactivity.Noeffectcouldbeobservedforanysample,whenthetestmaterialwasexposedtoUVlight(254nm)orH2O2only,orwhenleftpurefor4hours.Inbothcases,theinitiallylightyellowcolourofthesamplewaslostduringOHexposure.NSERC Natural Sciencesand Engineering ResearchCouncil of Canadacount number of particles injectedSolarsimulatorIce saturation ratio1.010-5TOC value (birch): 128 mg/LTOC value (alder): 183 mg/L.ForOHexposure,500mMH2O2areaddedandOHisgeneratedusinga254nmHg-lamp.NO activation observedActivation decreases when exposed to OHHowever, less active than Birch pollenActivation decreases when exposed to OHNo decrease of IN activity observed due to OH exposureObserved activated fractionBirchAlderIce saturation ratioIce saturation ratioIce saturation ratio10-510-510-51001001001001.51.51.51.51.01.01.0Observed activated fractionObserved activated fraction1.5100Ice saturation ratio10-510-51001.0Observed activated fractionAcknowledgementsBirchAlderPollenwereexposedtolight(300–800nm)inasunlightsimulator(4)for4h.ThenINactivitywasmeasured.Pure pollenPure pollen4h sunlightPure Arizona Test Dust (ATD)AnotherkeyaspectwhenstudyingINPsisthepossibleinfluenceofparticleageingandchemicalprocessingontheicenucleationactivity(e.g.3).ChemicalexposuretooxidantssuchasOHandO3mayimpacttheINabilityofINPs.