MeasurementsofVolatileOrganicCompoundsintheAtmospherebyProton-Transfer-ReactionMassSpectrometry

JoostdeGouw

CooperativeInstituteforResearchinEnvironmentalSciencesUniversityofColoradoBoulder

WithsupportfromAerodyneandTofwerk

Outline:• VOCsintheatmosphere

• PTR-MSprinciplesofoperation

• Evolutionofinstrumentdesign

• Highlightsofrecentmeasurements

Joost.deGouw@colorado.edu

VOC

Oxygenated VOC

NO

NO2

OH, NO3

hνO3

OHSVOC

OHSVOC2

OHLVOC…

OH

OHVOC3

OHVOC2

Gas Phase

Aerosol

SOA+OH

SVOC+OHproducts

VOC

SVOCSOA

1. Ozone Formation2. Secondary organic aerosol

(SOA) formation3. Direct health effects

e.g. formaldehyde, benzene;

VOCs are important for Air Quality and Climate

SVOC: semi-volatile organic compoundsLVOC: low-volatile organic compounds

GC-MS

Acetate or I- CIMS

Kroll et al., Nature Chem (2011)

(NO+ CIMS)

PTR-MS

CIMS with I-, Acetate and Nitrate)

VOC measurement techniques

Mor

e ox

idiz

ed

Gas Chromatography Mass Spectrometer (GC-MS)Optical methods (e.g. absorption spectroscopy)Chemical Ionization Mass Spectrometer

Proton Transfer Reaction Mass Spectrometer (PTR-MS or H3O+ CIMS)

PTR-MSPrinciplesofOperation

Proton-Transfer-ReactionMassSpectrometry(PTR-MS)1. Ionizationoftracegasesbyprotontransfer: H3O+ +R->RH+ +H2O2. DetectionofRH+ bymassspectrometry

IonSource DriftReactor IonTransfer MassSpectrometer

WernerLindinger etal.,1998

ProtonAffinitiesofVariousAtmosphericTraceGases

Protontransferisexothermicandfastfor:

• Mostalkenes

• Aromatics

• Mostfunctionalgroups

NoRe

action

Proton

TransferOccurs

KineticsofProton-TransferReactionsintheDriftTube

H3O+ +R→RH+ +H2O

! "#$%

!&= −) * "#$%Removalofprimaryions

"#$% = "#$% +×-./ 0 1[R]constant

*"% = "#$% +× 1 − -./ 0 1Productionsformed

*"% ≈ "#$% +×) * tSmallreactiontimet

ProtonTransferReactionRateCoefficients

• Distributionofproton-transferratecoefficientsfor110VOCs

• Reactionsareefficient(collision-limited)� Highsensitivity

• Ratecoefficientshaveanarrowdistribution(1s =25%)� SimilarsensitivityformostVOCs

*"% ≈ "#$% +×) * t

UseofDriftFieldtoAvoidClusterIonFormation

• H3O+ ionsclusterefficientlywithwatertoformH3O+(H2O)n

• Clusterscomplicatemassspectraand manyhydrocarbonsdonotreactwithclusters

• Clusterformationisavoidedbyapplyingadriftfield,whichincreasesionkineticenergy

CalculationofSensitivity

*"% ≈ "#$% +×) * t

k =2.5�10-9 cm3 molecule-1 s-1

[R]=5.8�107 moleculecm-3 p=2.4mbar;1ppbv mixingratio

67 = 8×9 = 8+×1013<=>?

@×

A273D

×9

k =1270cm2 V-1 s-1 p=2.4mbar;T=298K;k0 =2.76cm2 V-1 s-1

vd =8.9�105 cms-1 E=70Vcm-1

t=110µs length=10cm

k isionmobilitydriftvelocity

~500countss-1 ppbv-1 @30�106 countss-1 H3O+

PrecisionisLimitedbyCountingStatistics

1E = F�

1ppbv ≅ 500counts 1s =22counts=4.5%

100pptv ≅ 50counts 1s =7counts=14%

10pptv ≅ 5counts 1s =2.2counts=45%

improveswhenaveraginglonger

Improvethesensitivity:• Makemoreprimaryions• Improvereactionrate:higherpressure,longer

reactiontime(butstillneedde-clustering)• Detectionsmoreefficiently

EvolutionofInstrumentDesign

EvolutionofInstrumentDesign

IonSource DriftReactor IonTransfer MassSpectrometer

EvolutionofInstrumentDesign

IonSource DriftReactor IonTransfer MassSpectrometer

1. QuadrupolemassspectrometerPTR-MS [Lindinger,1998]

2. Iontrapmassspectrometer[Warneke,2005]:tandemMS

3. Time-of-FlightmassspectrometerPTR-ToF [Jordan,2009]

Highermassresolution=separationofmanymoreVOCs

EvolutionofInstrumentDesign

IonSource DriftReactor IonTransfer MassSpectrometer

1. QuadrupolemassspectrometerPTR-MS [Lindinger,1998]

2. Iontrapmassspectrometer[Warneke,2005]

3. Time-of-FlightmassspectrometerPTR-ToF [Jordan,2009]

1. Lenses

2. RFionguidesPTR-Qi-TOF[Sulzer,2014]H3O+ CIMS[Yuan,2016]

1. Onlyaxialfield

2. Ionfunnel

3. RFfield:PTR-3,VOCUSPTR

1. Hollowcathode

2. Nodramaticimprovements

101

102

103

104

105

Cou

nts

(ppb

v-1)

ITCTX2002

ARCPAC2008

CalNex2010

UBWOS2013

UBWOS2013

SONGNEX2015

Sulzer etal., 2014

NOAA PTR-qMS PTR-ToF

methanol acetone benzene

PTR-ToF H3O+ CIMS PTR-Qi-ToFNOAAPTR-MS(2002-2013) VOCUSPTR

Yuan[AMT2016]

VOCUSPTR

SECTION A-ASCALE 4

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SECTION A-ASCALE 4

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PRODUCED BY AN AUTODESK EDUCATIONAL PRODUCT

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E"

• Lopez-Hilfiker etal.@Tofwerk

• EvaluationatNOAA-CIRESinBoulderthissummerincollaborationwithAerodyne

HighlightsofRecentMeasurements

OilandNaturalGasProduction

Photo:NationalGeographicJonahField,Wyoming

NOAASONGNEXMissioninMarch-April2015

• 18researchflights• 9differentoilandgasproductionregions• Othersources:coal,coal-bedCH4,oilstorage

SONGNEXScienceTeam

Permianbasin

NitrogenCompoundsinthePermianBasin

HighmassresolutionoftheH3O+

CIMSallowsdetectionofmorespeciesthanpreviouslypossible

Chlorophyll

ConnectionwithBiomarkersinCrudeOil?

Porphyrins

Pristane

Foundincrudeoil

Questions:

• Arethesereducednitrogencompoundsderivedfromporphyrin,orarethesecompoundsformedinoil?

• WhyaretheresofewreportsoftheseVOCsintheliterature?

• Implicationsforatmosphericchemistry?pyrrole+OH 1.45�10-10 cm3 molecule-1 s-1

pyrrole+NO3 5�10-11 cm3 molecule-1 s-1

• Whataretheproductsofpyrrole?Arewedetectingthese??

Pyrrole

Pyrroline

AgriculturalEmissions

Photo:HighCountryNews

AgriculturalEmissions

Downwindfrommajorfeedlot:• Methane• Ammonia,amines,amides• Alkanoic acids(C2-C5)• Sulfides(H2S,CH3SH,DMS)• Phenol,cresols• Ethanol,carbonyls

• Alkanoic acids,sulfidesandphenolsaremicrobialbreakdownproductsofaminoacidsinthefeed

• Doemissions(andodors)dependonfeedcomposition?

Hobbsetal.[2004]

MobileLaboratoryMeasurementsAroundaCattleFeedlot

CSDMobileLaboratory

Mobilelaboratorymeasurementsallowseparationofsources:• Ammoniafromanimalwaste• Ethanolfromstorageandhandlingoffeed(fermentation)

AtmosphericEffectsofVOCsfromFeedlots

Yuanetal.[2017]

DifferentVOCsareimportantfordifferentissues:

Mass alcohols

Odor sulfides

OH alcohols

NO3 phenols

Sourcesfromfeedandanimalwastecanbeseparated

DairycowsandbeefcattleemitdifferentVOCs(differentdiet)

BiomassBurning

Photo:U.S.ForestService

ObservationsinFreshandAgedFirePlumes

Morereactivetracers Products

GrassfireinNorthDakota

FireplumefromAsia

Highernitriles

Productioninagedplume

Removalfromagedplume

• Detectionofmanymorefiretracers

• Degreeofprocessingcanbeestimatedfromremovalofreactivetracers

• Productsgivedetailedlookatchemistry

ResidentialWoodBurninginBoulder– December2015

inlet

Broadway

Residences

PositiveMatrixFactorizationgives4factors:• Background• Chemicalformation• Vehicles:morning+eveningrushhour• Burning:early-lateevening

Acetonitrileismissingfromburningfactor?!Photo:JesseVarner

BiomassBurningVOCsandFuelNitrogenContent

• Mostnitrogeninvegetationresidesintheleaves

• Literaturedatashowdependenceofnitrogen-containingVOCsonfuelnitrogencontent

• Woodburningresultsinloweremissionsofspeciesthataffectairquality(NOx,NH3)andhealth(HNCO,HCN)

Coggonetal.[2016]

Yokelson [2013]

Gilman[2015]

Stockwell [2013]

People

Photo:NewYorkTimes

DiurnalVariationofSiloxanesinBoulder

• Diurnalvariationofsiloxanesfollowstrafficemissions

• Usedinshampoo,deodorant,lotionetc.

• Observedsiloxanesfrompeopleinsidethevehicles!

SiloxaneEmissionsinBoulder

Calculatedsiloxaneemissionsfrom:1. Benzeneemissionfactor2. Avg.commutetime&distance3. Avg.vehicleoccupancy

EmissionsdecreaseduringdayinagreementwithUCBerkeleyclassroomstudy[Tangetal.,2015]

Atmosphericimplication:(new)particleformation?Si-containingnanoparticlesweredetectedinLA[Bzdek etal.,2014]

Coggonetal.[inprep]

Conclusions

• LatestgenerationofPTR-ToF instrumentshaveledtoanewdiscoveryphaseinatmosphericVOCresearch

• Furtherimprovementsareunderway

34

Thankyou!

JessicaGilman

CarstenWarneke

BrianLerner(Now:Aerodyne)

KanakoSekimoto(Yokohama)

BinYuan(Now:PSI)AbbyKoss(PhD‘17)

MattCoggon