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2.5 % of those observed. Together, these results ± 14 pmol per minute per µg of SOA material. Mea- cient was calculated to be (7.0 ± Climate ffi Sciences Sciences Dynamics Chemistry of the Past Solid Earth Techniques Geoscientific Methods and and Physics Advances in Advances Atmospheric Atmospheric Atmospheric C. This value suggests that under typical warm conditions, Data Systems Geoscientific Geosciences Earth System Earth System ◦ Measurement Instrumentation Hydrology and Ocean Science Biogeosciences The Cryosphere Natural Hazards Hazards Natural EGU Journal Logos (RGB) EGU Journal and Earth System System Earth and Model Development This discussion paper is/has beenand under Physics review (ACP). for Please the refer journal to Atmospheric the Chemistry corresponding final paper in ACP if available. Exposure to particulate matteridative (PM) stress is induction known is to believed be to a be concern a to major human toxicological health. mechanism Ox- of inhaled particles, although further work isditions needed such to as determine the low potential temperaturesAs impact where well, under partitioning higher con- to order the oxidationthe particle products redox that is cycling more likely capability account favourable. strongly of for to the a the naphthalene substantial particle SOA fraction phase. are of likely to partition much more 1 Introduction suggest that there arethe substantial small unidentified quinones redox-active that SOA mayto-SOA constituents particle be partitioning beyond important coe toxic components1,4-naphthoquinone of at these 25 particles. A1,4-naphthoquinone gas- is unlikely to contribute strongly to redox behaviour of ambient sured particle-phase masses of1,2- the and major 1,4-naphthoquinone, previously accounted identifiedcling for redox activity. active only The products, redox-active 21 5-hydroxy-1,4-naphthoquinoneminor was identified product as of apredictions naphthalene new increased oxidation, the and predicted DTTattempts including reactivity to this to predict 30 redox species behaviourmeasuring in of 1,2-naphthoquinone, oxidised redox two-stroke 1,4-naphthoquinone activity engine and exhaustpredicted particles 9,10-phenanthrenequinone DTT by decay rates only 4.9 Chamber secondary organic aerosollene (SOA) by from hydroxyl radical low-NO was examinedthe with respect dithiothreitol to (DTT) its assay. redoxDTT Naphthalene cycling behaviour SOA at using was an highly average redox rate active, of consuming 118 Abstract Redox activity of naphthalene secondary organic aerosol R. D. McWhinney, S. Zhou, and J. P.Department D. of Abbatt Chemistry, University of Toronto, Toronto ON, Canada Received: 20 March 2013 – Accepted: 25Correspondence March to: 2013 J. – P. D. Published: Abbatt 5 ([email protected]) AprilPublished 2013 by Copernicus Publications on behalf of the European Geosciences Union. Atmos. Chem. Phys. Discuss., 13, 9107–9149,www.atmos-chem-phys-discuss.net/13/9107/2013/ 2013 doi:10.5194/acpd-13-9107-2013 © Author(s) 2013. CC Attribution 3.0 License. 5 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ; , ; ). ), ; the ). 2004 2009 1 ), and 2008 2002 , , , , ). A gen- 2009 ), and an- , 2012 , Charrier and 2001 ; Li et al. 2007 , , Cho et al. 1996 , Lee and Lane ). The source of these Gurgueira et al. ; Verma et al. Verma et al. Tsapakis and Stephanou ; ; ) and contribute to particle- 2006 Wang et al. 2010 , ; , Squadrito et al. 2011 2006 ). Constituents of PM that have 2009 , , , 2010 , 2006 ered aqueous extract of a PM sample , ff ). They may also be produced as sec- cient redox cycling catalysts can accept Netto and Stadtman ffi ). It has also been observed that particles Lin and Yu ). 2007 9109 9110 Kautzman et al. Valavanidis et al. Ahmed et al. , ; ; ; ) and other respiratory diseases ( 2008b Valavanidis et al. Lee and Lane 1988 , ; , 2004 2009 ) all generate their corresponding quinone species , , 2008a 2003a ). , ects, their sources and ambient concentrations are im- , 2006 ff , 2006 ). In the assay, a bu , Koike and Kobayashi 2002 Jakober et al. ; , Gant et al. ), transition metals ( ; Li et al. Pan et al. 2002 ; ; , Chan et al. ; 2009 2006 ), phenanthrene ( 2003b , Chung et al. , , 2002 2001 ), humic-like substances ( ; , , 1997 1997 , , 2012 2004 Eiguren-Fernandez et al. Kumagai et al. Kwamena et al. , , Li et al. Kumagai et al. Eiguren-Fernandez et al. ; Evidence of secondary organic aerosol contribution to redox activity has also been Quinones are a class of organic molecules derived from aromatic species, containing Quinones are minor PM constituents, but due to their aforementioned potential to Inducing oxidative stress can involve either producing an excess of oxidants or de- Dellinger et al. Bunce et al. Shinyashiki et al. Cho et al. Gurgueira et al. particles formed from aging diesel exhaust particles with ozone in an outdoor chamber eral redox cycle withability a of quinone quinones to species act (1,2-naphthoquinone)that as is redox is cycling shown formed agents in in lies the Fig. in process. the Quinones stable and semi-quinone radical their biochemistry have been well-studied collected in the afternooncarbon, in organic Los acids Angeles andformation tend may redox contribute to activity, to be suggesting redox higher activity that of in secondary ambient water particles organic soluble ( found aerosol from organic controlled oxidation studies. The redox activity of the water-soluble extract of thracene ( two carbonyl functionalities on agested larger that redox conjugated cycling hydrocarbon by ring.idant quinone It generation species has once within particles been particles deposit sug- can within lead the to body sustained ( ox- bound stable radical( species, asspecies measured may be by primary1,2-naphthoquinone, electron 1,4-naphthoquinone, or and secondary. paramagnetic 9,10-phenanthrenequinone, have Specificmeasured been resonance quinones, as including products theValavanidis redox-active in et diesel al. and gasoline exhaust particles ( sphere could increaseaging the in redox locations activity with9,10-phenanthrenequinone of PAH has ambient emission been particles sources. observedles Indeed, during as basin photochemical ( air photochemical production masses of age in the Los Ange- ( (naphthoquinone, phenanthrenequinone, and anthraquinone, respectively) viawith reaction gas-phase oxidants. Formation of these species from PAH precursors in the atmo- Anastasio quinones ( ondary products of polycyclic aromatic hydrocarbon (PAH) oxidation. Naphthalene been shown as active redox cycling( catalysts include black carbon from diesel particles Sasaki et al. 2007 of DTT to transfer thesethe electrons DTT to rate molecular of oxygen decay, which cansystems has be ( been observed correlated by to measuring oxidative stress markers in cellular jugate with thiol groups ( contribute to adverse health e portant to understand. Quinones( have been shown to be present in ambient particles is mixed with DTT, which contains two electron-rich thiol groups. The catalytic capacity and are known to be cytotoxic by both redox cycling reactions and their ability to con- is through redox cyclingelectrons reactions, from where e electron-richferred reducing to agents; molecular subsequently, oxygen theprocess to has electrons generate the superoxide, are potential allowing trans- reactive to the oxygen both cycle species, contributing deplete to to antioxidant repeat. inductionpacity species of This can in oxidative be stress. the Redox measured cell cycling using ca- assay and an ( generate acellular technique known as the dithiothreitol (DTT) pleting antioxidants within a cell. One chemical mechanism for inducing oxidative stress the lungs and hearts of ratsand after inhalation oxidative of ambient stress particles ( mechanisms( have been implicated in playing a role in asthma particles. For example, reactive oxygen species have been observed to quickly rise in 5 5 25 25 10 20 20 15 15 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 3 ). ) to Lee 2009 , 2011 , Li et al. ). Previous experiments McWhinney et al. 2011 , ). cient to explore the likely contribution of ) 129 and 159, respectively, as the singly ). Another study, which assigned the DTT 2011 ffi , m/z 9111 9112 2006 ). , Rattanavaraha et al. 2012 , of zero air. 1 − Chung et al. McWhinney et al. min ) for one hour. Naphthalene was introduced to the chamber by 3 1 − min ), this provided a relatively simple system of redox-active aerosol gen- 3 2009 , Charrier and Anastasio cient redox-cycling agents, very few studies so far have tried to extend this into ffi The aim of the current study was to examine to what extent redox behaviour Naphthalene concentrations in the chamber were monitored with an Ionicon Proton While we know that PAH oxidation can generate quinone species and that quinones loss rate to individual particulatedict species DTT again decay from as thespecies arising Fresno ( area, 80 % was able from to transition pre- metal species and 20 % from quinone spectrometry. During the chamber experiments, we used online measurements taken spectrometer. Naphthalene and naphthoquinone concentrationssuring were the tracked by signal mea- at mass-to-charge ratio ( can be predictednaphthoquinone, based and 9,10-phenanthrenequinone, on i.e. the particulateare small, commonly mass soluble associated quinones loadings with that ondary redox of cycling. organic 1,2-naphthoquinone, We aerosol have 1,4- focussed (SOA)action on chamber. generated naphthalene Known by to sec- hydroxyl produceand radical both Lane 1,2 oxidation and in 1,4 a isomers photore- of naphthoquinone ( and the extent toredox which cycling these was two examined naphthoquinone based isomers contributed on to quantification observed by gas chromatography-mass AADCO 737 Pure Air Generator. Forwas the added hydroxyl radical to precursor, hydrogen theperoxide peroxide solution chamber (Sigma Aldrich) by at bubblingper a flow zero minute rate (cm air of approximately through 400vapourising cubic a a centimetres 30 known % massapproximately aqueous 400 of cm hydrogen solid naphthalene (99 %, Acros Organics)Transfer Reaction in Mass a flow Spectrometer of (PTR-MS) equipped with a quadrupole mass erated through laboratory oxidation. The redox-activity of the particles was confirmed, 2.1 Naphthalene SOA generation and collection Chamber aerosol was generated by hydroxylTeflon radical (fluorinated oxidation ethylene of propylene naphthalene in [FEP])generation, a photoreaction the 1 chamber chamber. m was Prior flushed to with several particle chamber volumes of zero air from an work, we hope to gainganic redox a cycling more catalysis on thorough a understandinginventory molecular of of basis and how redox-active determine well organic how weprocesses well products. we understand that As know or- generate the we redox furtherinfluences activity examine of in the aerosol particles, photochemical aging we on can particle toxicity. better predict the possible 2 Experimental and 1,4-naphthoquinone ( to determine a gas-particlenaphthoquinone partitioning species to coe ambient particleited redox earlier cycling work behaviour. with Finally, we oxidiseddetermine revis- two-stroke our engine particles ability ( tonaphthoquinone, predict 1,4-naphthoquinone, the and behaviour 9,10-phenanthrenequinone. observed Through based this on generation of 1,2- are e examining our ability toredox activity. predict One and such study quantifyassay found performed the that on contribution hydrogen particles peroxide of fromsuring generation Fresno, quinones the from California, aerosol the to could mass DTT be particle loadings accounted of for 9,10-phenanthrenequinone, by 1,2-naphthoquinone, mea- with an aerosol mass spectrometer and a proton transfer reaction mass spectrometer organic aerosol that is moreprimary than engine ten particles times ( more active per unit mass than the original Additionally, modifying the VOC mix within thewater-soluble chamber redox could activity alter increased, the regardless amount of byexhaust which the particles presence or in absence the ofwe chamber have diesel performed ( found that when two-strokeozone, gasoline the engine exhaust redox is oxidised activity with that results can be modelled with a redox-active secondary was about a factor of two higher than particles not exposed to ozone ( 5 5 15 20 25 20 25 15 10 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | , 1 ). C ◦ − 20 2011 − , Cho et al. of chamber erential mo- 1 ff − er due to lower ff McWhinney et al. to stop the oxidation ff McWhinney et al. er (0.1 M, pH 7.4). In the case ff 9114 9113 ). Briefly, exhaust from a two-stroke gasoline engine or as a particle mass normalised DTT decay rate in 1 ). To prevent the chamber from collapsing, a 20 L m − 2011 -dithiobis-(2-nitrobenzoic acid) (DTNB, Alfa Aesar). DTT 1 0 , − FEP chamber. The gas- and particle-phases of the exhaust 3 C until further analysis. ◦ . DTT analysis was carried out on the filter extract without filtration of 20 1 − − McWhinney et al. µg 1 − ), and was slightly modified from our previous work ( ). C. ◦ When the AMS exhibited maximum particle loading, which was typically 90–120 min 2005 redox activity was found in2013 the water-soluble fraction of the extract ( intervals over the course of oneadding hour 1 by mL taking of 0.25 mL 0.25was aliquots of mM quantified the 5,5 by DTT mixture measuringa and the UV-Vis spectrophotometer. absorbance Redox activity of isDTT the expressed concentrations resulting as the in product time M at rate-of-changepmolmin of 412 min nm with insoluble matter, as assay results fromfilter extracts showed passed that through a 96 % 0.2 µm of PTFE the syringe naphthalene SOA redox activity and 91 % of the engine was extracted by stirringof with engine 10 mL filters, one of halflevels phosphate of of bu the redox filter activity. DTT wasous extracted (Sigma filter into Aldrich) extracts phosphate was bu to addedmM. The give to redox 1 a mL reaction final aliquots was performed of volume at the of room aque- 1.25 temperature mL and and quenched a at 15 DTT min concentration of 0.1 either oxygen, nitrogen andand ozone fresh or (i.e. a control) controluntil particles flow further were of analysis. collected oxygen and on nitrogen. Zefluor Oxidised filters and2.3 stored at DTT assay The DTT analysis used was adaptedNaphthalene from SOA particle the filter procedure samples described were by divided into quarters and one quarter Two-stroke engine particles were oxidised andpreviously collected ( in the same manner described was collected in awere 0.5 m pulled through two vertically mounted glass flow tubes, to which were added 2.2 Two-stroke engine particle oxidation and collection ( zero air make-up flowconstituents were was collected added during this toair time the through by pulling a chamber. an PTFE In additional filter20 1 some to Lm cartridge remove (Sigma-Aldrich) experiments, particles containing gas-phase two and XAD-2average, then polystyrene more through resin an than beds in ORBO 98 series. % 43 On indicating of Supelpak- that 1,4-naphthoquinone analyte was breakthrough collectedSOA was on filter not samples the and a front gas-phase concern. XAD XADand cartridge bed, Together, stored samples these were at naphthalene collected for 60–90 min after the beginning ofreaction. the Particles experiment, were the subsequently lamps collectedfilters were by (Pall, turned pulling polytetrafluoroethylene, chamber o 47 mm air diameterof through and Zefluor 20 2 µm litres pore per size) at minute a (Lm flow rate cles were formed by thecles. nucleation The of resultant SOA oxidised was organics characterised without(AMS) by addition an equipped Aerodyne of with aerosol seed a mass parti- spectrometer instances, high-resolution time-of-flight a mass scanning spectrometer mobilitybility and, analyser particle in some (model sizer 3081) (SMPS)Shoreview and MN consisting USA). a Temperature of was condensation not awas particle controlled typically di or counter slightly monitored above (model in room 3025)25 the temperature due chamber (TSI, to but heat from the UV lamps, at about chamber, indicating that mixingthe was chamber complete, with oxidationNaphthalene ultraviolet was concentrations initiated lamps were by with measured illuminating ato based the peak on known emission the mass PTR-MScentrations at of signal are 310 naphthalene nm calibrated reported added (F40T12 based to UVB). on the observed chamber, and first hydroxyl order radical decay con- of naphthalene. Parti- protonated molecular ion. Once the PTR-MS naphthalene signal had stabilised in the 5 5 25 15 20 10 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | m/z 0.9 for are the = g 2 c r ciency of 0.5 ffi and p c ) where 2000 , er extract with dichloromethane. ff er and carried through the extrac- ff ). The derivatisation was performed 2 ). Since the DTT analysis is performed 2004 ( 9116 9115 cient calculation ffi cient of 1,4-naphthoquinone was determined using ffi er extracts of naphthalene SOA filters yielded very low Cho et al. 0.6 for AMS calibration). The particulate mass loading ff Finlayson-Pitts and Pitts = )( g ). The PTR-MS response was calibrated by comparison with 2 c r + er extract of the filter samples, we first attempted to quantify p ff C and mixed every five minutes. After 15 min, the reaction was M ◦ ( / p 158 (M c = p m/z is the mass loading of the particles in the chamber. The concentration of ), and the concentration in the particle phase was determined from the K + p M H] er to an organic solvent for compatibility with the derivatisation technique. ff + . Calibration standards of 1,2-naphthoquinone, 1,4-naphthoquinone, 5-hydroxy- 1 The quinone species were derivatised using reductive acetylation, wherein the While quinone standard solutions provided satisfactory calibrations using both the were compared to mass loadings calculated from SMPS-measured particle volumes 159 ([M AMS signal at the quantified 1,4-naphthoquinone from thewere XAD calibrated cartridge with samples the while quantified AMS 1,4-naphthoquinonePTR-MS signals from calibration filter samples and ( was taken as thedue total to organics the measured low by relativewas humidities the used used AMS. in for To the correct all experiments, AMS for a particle data. collection To bounce e verify the suitability of this choice, AMS mass loadings The gas-particle partitioning coe the equation concentrations of 1,4-naphthoquinone in the particletively, and phase and the gas phase,1,4-naphthoquinone respec- in the gas phase was calculated from the PTR-MS signal at dried under aThe stream dichloromethane of mixture nitrogen, wasble analysed and by reconstituted GC-MS1,4-naphthoquinone in using and 100 the µL phenanthrenequinone (Sigma parameters ofthe Aldrich) in same dichloromethane. were Ta- procedure. prepared Thedeacetylated using calibration fragment was ion. performed in each case2.5 based on the Gas-particle fully partitioning coe ture was heated to 80 cooled, an additional 100 mgother 15 of min. zinc After cooling, wasdeionized the added, remaining water and acetic and the anhydride the was mixtureAfter quenched diacetylated was with shaking, quinones heated 1 the mL were for of extracted mixture an- with was 3 centrifuged mL of and pentane. the top organic layer was removed, powdered zinc (Sigma Aldrich) to the dichloromethane or acetonitrile extract. The mix- Quinones were quantified by gasthe chromatography-mass derivatisation spectrometry method (GC-MS) from using by adding 0.5 mL of acetic anhydride (ACP Chemicals) and approximately 100 mg of 2.4 Quinone analysis water-extractable quinones from the naphthalene SOAa filters one-quarter was not portion achieved. of Rather, themately filter 0.5 was mL) extracted by directly sonication with forspike dichloromethane 15 and min (approxi- in recovery a measurements glasseries, using centrifuge and the tube. For thus SPE engine the method samples, quinone yielded SPE concentrations. satisfactory method recov- was used to directly measurequinone is the reduced water-extractable to theified hydroquinone in functionality the in presence the of presence acetic of anhydride zinc (see and Fig. ester- SPE and liquid-liquidformed with extraction the methods, phosphate bu recoveries spike for and both recoveryobserved 1,2- measurements for and both per- 1,4-naphthoquinone the (1–3 %). SPE The and low liquid-liquid recoveries extractions. were Thus, the measurement of phate bu Two techniques were attempted:ENVI-18 in solid the phase first, extraction thephase (SPE) (Supelco) extracts and cartridges passed removed through with with acetonitrile;traction Supelclean a in was bonded the performed second, by octadecyl a shakingStandard stationary simple the liquid-liquid solutions phosphate ex- were bu prepared intion phosphate methods. Menadione bu (2-methyl-1,4-naphthoquinone, Sigma Aldrich)each was extract added as to an internal standard. using the phosphate bu quinones in this extract. This required extracting the quinones from aqueous phos- 5 5 25 15 20 10 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | . , , 1 4 er − ff µg 1 − er to de- ) – which ff 3 % of the ). The par- ± 10; individual 2009 DeCarlo et al. = 2009 , , n ( 1 2.0 pmolmin − ± ciency. µg ffi Charrier and Anastasio 1 ; − Chan et al. ); good agreement between Lee and Lane 2006 , 2009 , 14 pmolmin ). As a comparison, we previously esti- conditions ( ± 3 x Chung et al. ). Each run of the DTT assay included pos- 9118 9117 Chan et al. 3 ( 3 − . There was an unexpected small fraction of the particle 3 , as obtained using established methods ( ciency of quinone extraction was equal for phosphate bu 2 ffi ). N type fragments potentially as a result of amine contamina- ), and the average AMS mass spectrum from two representative y H x 8 %, respectively), predicted values accounted for 21 2011 2007 , ± , Aiken et al. 0.87). However, predicted DTT decay rates fell considerably below those ob- ). As mentioned in the Experimental section, the quinones were extracted directly ; 10 % and 87 = ± Based on the measured loadings of the two naphthoquinone isomers on the filters, Both 1,2- and 1,4-naphthoquinone were detected in the particle phase at mass load- SOA generated from naphthalene oxidation was expected to exhibit high redox activ- For prediction of the SOA activity, we focussed on the 1,2- and 1,4- 2 r McWhinney et al. the aqueous extraction method. Considering the high solubility of naphthoquinone in There is a strong( correlation between theserved. predicted After and correction observed for83 DTT recovery decay (measured rates formeasured 1,2- values. and 1,4-naphthoquinone as we are considerably underestimatingter the extracts. observed One redox possibleof activity explanation the of for quinone the this species aqueous discrepancy fil- using could the be poor dichloromethane extraction extraction method compared to termine the mass-dependent DTTassay decay runs. rates The activities for ofDTT these the decay species positive of for controls each any were SOAdichloromethane given used filter extract. to set extract The based predicted calculate of values on theparticulate based the expected on measured concentrations 1,2- naphthoquinones are and in 1,4-naphthoquinone plotted the against the measured redox activity in Fig. 2012 from the filter using dichloromethaneso rather it than is measuring assumed the that the water-solubleand e species, dichloromethane. ings of a similaritive magnitude controls (see containing Table only 1,2- or 1,4-naphthoquinone in phosphate bu the reproducible composition, DTT decay ratesage were DTT reasonably decay invariant per with unit an mass aver- of particle of 118 tion in the chamber, which wasThese previously peaks used make for up the approximately photooxidationoverall of only N ethanolamine. 3 : % C of ratio the ofwould organic approximately be mass, 0.03. contributing on these It average, fragments is for to currently an the unknown overall what mass types spectrum. ity, based of on species knowledge that bothin 1,2- the and particle 1,4-naphthoquinone phase isomers as could naphthalene beticles oxidation found generated products ( from naphthalene oxidation were highly redox active, and reflective of experimental results are summarised in Table naphthoquinone isomers, whichphenanthrenequinone, as are mentioned commonly in believedble the to quinone electron be Introduction, transfer the agents along (e.g. most with important 9,10- water solu- mostly of hydrocarbon and oxidised hydrocarbonformation fragments. is Elemental composition given in- in2006 Table mass made up of C mated the activity of the two-stroke( engine exhaust SOA to be 8.6 3.1 Redox activity prediction for naphthaleneWe SOA are interested inondary organic determining aerosol how particles using wellloadings molecular-level we information of on can the known activities predict quinones.only and the one To redox start SOA precursor, activity with naphthaleneatively of as was high sec- chosen simple yield for – a itswas particularly system ability advantageous for under to as the low form small possible NO aerosol sizethe by of in SOA our using generated rel- photoreaction in chamber. the The composition chamber of was fairly invariable from day-to-day and consisted experiments is shown in Fig. the two values was obtained using 0.5 as the AMS collection e 3 Results and discussion using a particle density of 1.55 gcm 5 5 25 15 20 10 25 20 15 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | , 158 89 mV, for 1,4- m/z − 1 Roginsky − ). Including 7 ng 1 − ). We compared 2013 140 mV and , − ) – were examined due to the NIST Mass Spec Data Centre erent recoveries, 5-hydroxy-1,4- , are supportive of the production ff 6 1989 , ) and fragmentation pattern. To the best 5 ) fragment ( + 9120 9119 Wardman O 7 H compared to 2.1 and 5.7 pmolmin 9 174 signal for the molecular ion of 5-hydroxy-1,4- 1 12 % from spike and recovery measurements. While (C − NIST Mass Spec Data Centre ± + m/z ng 3 % for the 3 and 4 August filter samples using only 1,2- ), we have looked for plausible products of the reaction 1 ± − ) from high-resolution data (i.e. excluding other ions at each CHO] + 3 1989 − O , 6 H 10 (versus 20 110 mV, respectively ( 131 [M − 4 Wardman m/z ). Therefore, quinones with low one-electron reduction potentials are likely to ), and the expected + 2 O 6 1999 ), the second generation product 1,4-naphthoquinone molecular ion at , 5 % in Fig. H 93 mV and ± − 10 The recovery of 5-hydroxy-1,4-naphthoquinone was low and variable compared to As is anticipated from a probable third generation oxidation product of naphthalene, The 5-hydroxy-1,4-naphthoquinone product (but not 5,8-dihydroxy-1,4- naphthoquinone is still expected to account for about 19 % of the predicted redox 30 and 1,4-naphthoquinone to predict redox activity). 1,2- and 1,4-naphthoquinone; ittimation is in possible particulate that this masscontribution may of loadings have the for resulted molecule thisbers in to species an the reported (and overes- measured to subsequently redoxless, this cycling the this rates). species relative product As above such, isof may the significant the be num- particles in considered is terms as calculated of without an overall correcting upper redox for limit. di cycling. Regard- If the redox activity dox activity of 5-hydroxy-1,4-naphthoquinone isspecies higher than (about that 7.8 the pmolmin otherand two 1,2-naphthoquinone, quinone respectively). Thefor, on 5-hydroxy-1,4-naphthoquinone average, accounts 33 %5-hydroxy-1,4-naphthoquinone of in the the predicted predicted redox DTT activity decay in rates, the closure particles improves (Fig. to rising and falling in concentration progressively later in the experiment. the yield of 5-hydroxy-1,4-naphthoquinoneond is generation 1,2- somewhat and lower 1,4-naphthoquinones.phase compared The XAD to molecule samples was the from notabout the sec- detected 41 chamber % in and gas of particleusing 1,4-naphthoquinone phase an average loadings and recovery were 55 of % on 40 5-hydroxy-1,4-naphthoquinone is of average a 1,2-naphthoquinone minor after contributor in correction terms of aerosol mass, the re- (C naphthoquinone (C nominal mass). The temporal trends,of shown in first Fig. generationand 2-formylcinnamaldehyde, second third generation generation 5-hydroxy-1,4-naphthoquinone 1,4-naphthoquinone, in the particle phase, with each 2013 naphthalene. naphthoquinone) was identifiedby GC-MS, and confirmed by quantified retention time in (Fig. the naphthalene SOA particles plausibility of these compounds as third and fourth generation oxidation products of The rate of quinonepotential redox of cycling the is variouslogarithm determined species. of the primarily For rate example, constant by ofa it the the given has reaction one-electron quinone between species been redox a is reducing previously linearlyconversion agent, related shown of ascorbate, to and that the the one-electron the quinone reductionet to al. potential of its the corresponding semiquinone radical anion ( of our knowledge, thisorganic is aerosol produced the from first the5-hydroxyl-1,4-naphthoquinone oxidation time of has this naphthalene. a Like product 1,4-naphthoquinone, considerable hadelectron signal impact been at mass identified the spectrum in molecular ( secondary ion in the is not believed to beother the species cause in of the the naphthalene discrepancy. SOA Rather, exhibiting we redox postulate activity. 3.2 that there are Redox activity of naphthoquinone analogues respectively ( of naphthalene andbeen hydroxyl previously radical identified with in a1,4-naphthoquinone product and similar studies. 5,8-dihydroxy-1,4-naphthoquinone – reduction Specifically, with the reduction potentialof potentials presence that of have 5-hydroxy- not the AMS timethrough series the data for the first generation product 2-formylcinnamaldehyde dichloromethane and the aforementioned reasonable recoveries from spiked filters, this exhibit slower redox cycling ratesnaphthoquinones than having those with one-electron higher reduction potentials. potentials With of 1,4- and 1,2- 5 5 25 15 20 10 20 25 15 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Lee ). A sig- + 2 O cient for 1,4- 18 molecular ion, ffi H 9 + 2 O 158 was assumed 6 158 came from the ). We aim to verify H 10 m/z m/z to be used with an error 2007 , m/z ). The authors attributed the ther- 2012 , Jakober et al. 9122 9121 cients allow some estimation of how important ffi C, 1,2-naphthoquinone begins decomposing at ◦ C temperature of the AMS vapouriser, 1,2- Sousa et al. ◦ C, and the thermal instability was verified by very poor ◦ 158 from BES without quinone and with the 1,4 and 1,2 . As hypothesised, the BES with 1,4-naphthoquinone ex- ion, which is the molecular ion of naphthoquinone. As the 8 + 2 O m/z 6 H 10 ) due to the tendency of the 1,2 isomer to degrade under the GC-MS ciency calibration was more reliable for the lower-resolution V-mode data ffi 2009 ion, allowing the unit-mass resolution data from , + 2 O 6 H With the approximately 600 The second assumption was that the AMS was sensitive to the 1,4 isomer but not The gas- and particle-phase concentrations of 1,4-naphthoquinone were obtained 10 nal for this ion was not observed for 1,2-naphthoquinone. Based on these results, we conditions normally used toinjector separate temperatures. and As measure such, quinone weMS are species, when only particularly using able high the to reductive detect acetylation 1,2-naphthoquinone derivatisation by technique. GC- naphthoquinone is notof expected the to naphthoquinone be isomersoil, observable were bis(2-ethylhexyl) by separately sebacate the mixed (BES).nucleate AMS. with particles, The To a which verify mixtures high were this, subsequentlyof were molecular sampled each the heated weight under AMS. to the Signals high-resolutionisomers homogeneously at mode are shown inhibited Fig. signal at a nominalwhich mass is of partially 158 obscured corresponding by to signal the from C BES (from a fragment of C and Lane tulate that 1,2-naphthoquinone was only recently identified in naphthalene SOA ( mal instability to theeach other, carbonyl as groups 9,10-phenanthrenequinone of also the exhibited quinones thermal being instability. in We pos- the ortho position to the 1,2 isomernaphthoquinone. of Thermal naphthoquinone. analysis This ofexhibits quinones is thermal found based stability that ontemperatures while up higher the 1,4-naphthoquinone to than thermal 100 600 reproducibility instability in GC-MS of analysis 1,2- ( used to calculate theHigher total resolution W-mode masses data offlight from naphthoquinone region) the confirmed and AMS that total (usingC on SOA a average, longer mass 90 % W-shaped loading. of ionof the approximately time-of- signal 10 %. at from the AMS (using a shorter V-shaped ion time-of-flight region), these data were to come from theionisation C e Only one study hasnaphthoquinone, previously in reported diesel a exhaustthe gas-particle partitioning particles partitioning behaviour ( coe of 1,4-naphthoquinoneaerosol in and a without system potential with interferencediesel only from particles. organic adsorption carbon to the black carbon found in from the PTR-MS andof AMS measurements, assumptions respectively. needed In to order to be do made. so, First, a all number AMS signal at on the order ofnot several 1,2- hundreds or ofquantities micrograms 1,4-naphthoquinone to per partition be cubic to of metre,question. concern the and Gas-particle to particle partitioning so health coe whether phase undernaphthoquinone or typical in photooxidation ambient significant conditions is enough isularly to an in the important urban health areas impact where of anthropogenic particulate emissions matter, of partic- naphthalene are important. 3.3 Air-particle partitioning of 1,4-naphthoquinone The degree to whichof the particles redox-active depends naphthoquinone products onof influence the chamber the partitioning photooxidation toxicity behaviour studiestimes of higher is than the that those compounds. observed particletitioning The under to ambient mass drawback conditions, the loadings which particle tends are phase. to In typically favour par- the many current experiments, particle mass loadings were species contribute small amountsyond the to scope the of the unaccountednote current redox project that cycling to there identify activity. remaining are Itthat redox-active very species, could is but contribute likely be- we to as-of-yet redoxquinone unidentified cycling species in redox-active that particulate organic have matter been compounds in the addition subject to of the previous three focus. small cycling on average. It is not implausible that other functionalised naphthoquinone 5 5 25 15 20 10 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | , 0.010 for 1,4- ± Jakober usion of Eiguren- 1 0.010 (as ff . An aver- 158 signal − ± ff µg 3 Jakober et al. m/z in the chamber, m cient of approxi- 4 while the octanol- ffi ff − 1 torr for 1,2 and 1,4 − 10 ). However, this value 4 − × µg ) and ambient ( 3 ), the 1,2 isomer of naph- ). As such, the conditions 10 0.90). m 2013 × usion coe , 5 = ff − 2009 was obtained; the uncertainty 2 2011 , 2008a r , 10 1 , − × 0.6) was obtained. µg US EPA cient were not constant, but tended 3 ( = ffi 2 1 m r − 4 ), partitioning trends are consistent with − torr and 1.69 cient for a single experiment by averaging µg 3 ffi 4 10 Lee and Lane − m 2013 Shiraiwa et al. 9124 9123 × 4 , 10 − × 2.5) 10 ), the ratio of 1,2- to 1,4-naphthoquinone tends to ± × 0.27, respectively, indicating that 1,2-naphthoquinone ), although based on the Modified Grain method struc- ), which suggests that the yield of 1,2-naphthoquinone ± US EPA 2009 Eiguren-Fernandez et al. ( ; 2009 2009 , ( C are 1.08 of 1,4-naphthoquinone in the SOA particle, which is within the ◦ ) particles. This observation held true with our chamber exper- 1 2009 − , cient of (7.0 s ffi 2 . This is a larger value than those estimated from the EPI Suite . The stable value indicated that the system likely reached equi- 4 9 2008a cm , usion in the bulk. Indeed, during the course of an experiment, the cal- ff 15 Lee and Lane cient assuming partitioning into a bulk phase. The low relative humidity − ), a time scale of 90 min corresponds to a di cient is that we cannot use a similar technique to calculate a partitioning Lee and Lane ffi Lee and Lane ; ffi 10 πD × Lee and Lane (4 / 2007 2 cient for 1,2-naphthoquinone. This is unfortunate as we have found, like earlier ). , d ffi We obtained an average partitioning coe Finally, some evidence of equilibrium must be exhibited to properly calculate a par- The third assumption made was that the PTR-MS signal primarily arises from gas- = vapour pressure. The ratios themselves aremarised on in the lower than the range of values sum- tural activity relationship fromvapour the pressures EPI at Suitenaphthoquinone, 25 software respectively package, ( where the calculated mers we have measured in thementioned gas previously) phase and and 0.58 in theis particle much phase is more 0.015 abundantthe in the vapour particulate pressure phase. ofet This the al. is 1,2 despite isomer previous is reports higher that than that of the 1,4 isomer ( thoquinone partitions to thediscussed particle by phase to abe greater higher extent than in the the 1,4 particle isomer. phase As than in the gas phase. The ratio of the 1,2 to 1,4 iso- tioning coe coe studies ( air model predicts a valueis of in 1.56 good agreementnaphthoquinone with organic matter the partitioning previously2007 in reported diesel value exhaust particles of ( 4 3.4 Air-particle partitioning of 1,2-naphthoquinone A corollary to the assumptions we made to calculate the 1,4-naphthoquinone parti- the values taken overage a partitioning coe 10 minis period based prior on to themarised the standard in lamps deviation of Table being allsoftware; turned experiments, the o for McKay which model predicts the a results value are of sum- 1.24 to assume equilibrium partitioning in the bulk phase appear to be met. fast enough di culated values for thetowards gas-particle a partition stable coe valueillustrated near in the Fig. timelibrium when by the the lights endτ are of turned a o typicalmately 90 2 min experiment. Usingrange expected a for a time semi-solid scale particle of ( di the 1,4-naphthoquinone extracted from the XAD resin ( titioning coe in the chamber isestablished likely over to appreciable result periods in of particles time if that the are particles not are liquid, at but least equilibrium semi-solid with can be amounts of 1,2-naphthoquinone andstudies 1,4-naphthoquinone have in found the that gasthan in for phase. the the Previous gas-phase, 1,4 concentrations isomerFernandez of et in the al. both 1,2 chamber isomer ( iments, are with lower the ratioin of the the gas 1,2naphthoquinone phase. to is Based 1,4 a on naphthoquinone reasonablecollected this isomers assumption. XAD observation, being Calibration cartridges attributing 0.015 using yielded the five a experiments PTR-MS strong with correlation signal between to the 1,4- PTR-MS data and the AMS vapouriser and thatattributed the to signal from the the 1,4 naphthoquinone isomer.with molecular Reasonable 1,4-naphthoquinone ion correlation filter can between measurements be the ( AMS phase 1,4-naphthoquinone. The reliability of this assumption depends on the relative believe 1,2-naphthoquinone is likely to thermally decompose upon making contact with 5 5 25 15 20 10 25 20 10 15 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ) ) 1 − µg 2009 3 ( 2008a ( m 3 − cient for 1,2- 10 % for 1,4- 10 ; this calcula- ffi ± 1 × cient increases − ffi µg 2.2) 3 ± chamber studies, this Lee and Lane m x 2 − 10 cients, we consider the cal- ffi × ) using the same techniques. ) values are taken from ambi- ) and (3.6 2.7) Eiguren-Fernandez et al. er extract using SPE extraction to 2011 ± ff , 2009 2008a ( , cient expressions for the two species to give ) and the 9126 9125 ffi are the ratio of the 1,2 to the 1,4 isomer of naph- 2009 ( g conditions used in this study. Regardless, our find- usion of 1,4-naphthoquinone out of the particle that r Lee and Lane ). ( ff x McWhinney et al. 1 − and p µg is estimated to be (3.8 r 2008a 3 , p m K 3 22 % for 9,10-phenanthrenequinone, and a somewhat lower re- Eiguren-Fernandez et al. − cient for 1,2-naphthoquinone, as during the filter collection period, ± Lee and Lane 2.5 % of the observed DTT decay rate. Perhaps not surprisingly, 10 ffi ), where ± × g /r 15 % for 1,2-naphthoquinone. Of the three redox active quinone species 0.75). With spike and recovery correction, the average predicted DTT p 4.6) r ± ( = ± 2 r p1,4 ; K 10 cient by combining partitioning coe = ffi It is somewhat unsatisfactory to use the filter and XAD cartridge data to estimate We note that the estimate based on our data is approximately an order of magnitude p1,2 Eiguren-Fernandez et al. as such the generationHowever, due of to quinone high SOA species mass is yields, naphthalene not itself a has a concern potential to to contribute SOA mass loadings. than the simpler system ofredox-active naphthalene SOA SOA. This species again suggests beingexamining that typical produced there redox are active that other quinone are species. currently unaccounted for when 4 Atmospheric implications Naphthoquinones are already known to be minor contributors to particle mass, and compared to levels measured inbased fresh on particles. 1,2-naphthoquinone When concentrationsa the in function predicted of the DTT observed particle decay DTT rates (Fig. extracts decay rates, were a plotted moderate positive as decay correlation was rate observed is 4.9 the prediction of redox activity based on known quinone species is less satisfactory Quinones were measured fromobtain the the phosphate analytes. Aqueous bu extractsthe of same low the recoveries engine using particlenaphthoquinone, the filters SPE 87 technique, were with not recoveries subjectcovery of to of 92 21 measured, only 1,2-naphthoquinone was observed to increase by a significant amount plex chemical systems,particles we examined revisited previously the ( ozone-exposed two-stroke engine exhaust naphthoquinone. 3.5 Redox activity prediction for oxidizedTo two-stroke engine determine particles the extent to which redox closure could be obtained for more com- values to be a more reliable estimate of the gas-particle partitioning coe particle-phase measurements. Using ratios obtainedues in of other (5.3 studies, we obtained val- coe K thoquinone in the particulatechamber, and the gaseous value phases, for respectively.tion Using was data performed using from only our experimental data that included simultaneous gas- and phase than 1,4-naphthoquinone. the partitioning coe the system deviates from equilibrium.as The the calculated chamber partitioning is coe pumped,on presumably a due faster to time dilution scaleis rates than required of the to the di particles re-establishratio occurring equilibrium. of In the absence 1,2 of to appropriate 1,4 measurements, isomers the can be used to obtain an estimate of the partitioning values are taken from enginemay samples, urban be PM, attributed and to high-NO ings the agree low-NO that theof vapour 1,4-naphthoquinone based pressure on of thecle 1,2-naphthoquinone partitioning phases, behaviour is and between in the thus gas fact 1,2-naphthoquinone and lower is parti- potentially than of that more interest in the particle relative to 1,4-naphthoquinone in our system is lower than in other studies. As those ( higher than when wevalues use are the obtained from values a from largersampling, other chamber and studies. that does as As not the the require dilution during particle culations using the ent particles, these valuesGiven the are close more agreement between likely these to estimated coe be taken under equilibrium conditions. 5 5 25 15 20 10 20 10 15 25 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | , 1 ), − p and µg cient /M 1 1 ffi p − − cient of K Eiguren- ffi pg + of SOA in 1 − 1 (1 − / T ). With a signif- c ) Valavanidis et al. p ; . DTT activity was 2009 pmolmin /M from mobile sources, , 11 is the ratio of the par- p 3 1 p − K − ( 2008a based on modelled naph- 10 /M , = based on the average of p erent mass loadings of or- 3 × p ff − 1 K ). These values are similar in c − Chan et al. µg for 1,4-naphthoquinone. As PM 3 2005 1 ) and , m − g 3 c µg − + 1 p − 10 are shown in Fig. ), both quinones seem to be unlikely con- c × 3 Lu et al. − 9128 9127 , which is higher than the range we have es- 2007 3 and up to 2.5 ngm , − 3 , the particulate mass loading was calculated for − 3 ). For diesel exhaust, it was estimated that of SOA Eiguren-Fernandez et al. − ; 2010 ciently high. This treatment is beyond the scope of this , 2004 ffi n , for 1,4- and 1,2-naphthoquinone, respectively. for 1,4-naphthoquinone. For 1,2-naphthoquinone, the par- ffi 1 1 − ). We have used the modelled as well as the observed quinone − equation was rearranged to yield pg µg 1 p Ntziachristos et al. 3 ( − based on the upper and lower standard deviations of those esti- K 1 Cho et al. m 2008a 1 − − , 4 − cient was estimated as 4.4 µg µg 1 ffi 10 3 − pmolmin m × Shakya and Gri is the total quinone mass loading ( 3 4 T − − c 2.5) 10 10 ) are often in excess of 100 pgm ± × C based on the experimentally determined gas-particle partitioning coe × ◦ Unsurprisingly, the particulate mass loading of each quinone rises substantially as This is a simplistic analysis of the partitioning behaviour, assuming equilibrium To predict particulate quinone mass loadings under di There are few studies that have attempted to model the atmospheric burden of 1,4- normalised DTT decay rates arefor anticipated to 1,2-naphthoquinone be and on thein 0.0015 order pmolmin of Los 0.02 pmolmin Angeles20 pmolmin has been measured to decay dithiothreitol at rates greater than ranging from approximately 0.1–100calculated µgm based on5.7 an average DTT decay rate ofmore 2.1 organic particles areunit volume present of for air, partitioning.with which particle As is mass a loading. an result, Themains important DTT relatively the unchanged activity metric DTT and normalized for actually to activityas exposure falls particle per somewhat the to mass, at however, toxic high additional re- particle particles, mass mass rises loadings partitioning to particles begins to diminish. Expected mass- conditions withnaphthoquinone bulk ( partitioning. Measured ambient particulate loadings of 1,4- (7.0 titioning coe the two estimates9.9) discussed previously, withmates. the The uncertainty results of in the the calculations range for of a range (1.4– of organic particle mass loadings tributors to redox activity of ambient particles in that locale. partitioning, namely low temperatures, providedist significant and naphthalene photoreactivity emissions ex- is su 2006 timated based on equilibriumor partitioning, perhaps partitioning due to tonot non-organic non-equilibrium explored partitioning aerosol how species ambientsis. such temperature Naphthoquinone species might as may change become black more the carbon. important outcome under We of conditions that have such favour also an analy- has been estimated thatand naphthalene, acenaphthylene 1- from and mobileHouston, 2-methylnaphthalene, Texas, sources compared acenaphthalene to could a contributewith total a SOA 37–162 kgd estimate substantial of fraction 268 (36–48oxidation kgd %) ( of the PAH SOA mass coming from naphthalene a quinone concentration of25 1 ngm considerably to particulate mass in areas with strong PAH emissions. For example, it production from oxidation of light aromatics,aerosol PAHs, produced and arises long-chain from alkanes, 58 PAH precursor % species of ( the Fernandez et al. concentrations to make an estimate asticle to phase how abundant and quinones what shouldrange be their of in contribution particle the par- to mass loadings. redox cycling activity wouldganic be aerosol, over the a wide where ticulate phase mass loading and the gas phase mass loading of the quinone. Using of naphthalene and 1-naphtholCalifornia, and and much the of central photolysis Losconcentrations of Angeles in was 1-nitronaphthalene excess predicted to in of have 0.5 Southern 1,4-naphthoquinone thalene ngm emissions for a weekmagnitude in to July those 1998 that ( were subsequently measured in Southern California ( icant amount of naphthoquinone productionorganic from aerosol naphthalene mass oxidation loading andmay available su have for a gas-particle significant partitioning, impactparticles. naphthoquinones in terms of the redox behaviour andnaphthoquinone. toxicity One of study ambient modelled the atmospheric burden resulting from oxidation 5 5 15 10 20 25 25 20 10 15 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ). erent ff 2012 , ), which 9110 9129 , , Aerosol Sci. 2010 , 2.5 9118 , Eiguren-Fernandez 9129 9111 , , 9114 9118 9109 Lee and Lane , ; Charrier and Anastasio ; 9127 9111 , , , 2012. 2007 , 2006 9110 9117 , 9110 , 9110 9135 , 9130 9129 Wang et al. 9128 Chung et al. , 2009. , ). In terms of importance, oxidation of phenanthrene 9115 , 2013 10.5194/acp-12-9321-2012 , 9110 9117 The authors would like to extend thanks to the Mabury group, and in par- US EPA ). Certainly, previous apportioning of DTT activity to chemical species have 10.5194/acp-9-3049-2009 2008b , ¨ urten, A., Wennberg, P. O., Flagan, R. C., and Seinfeld, J. H.: Secondary organic aerosol Aerosol-borne quinones and reactivetracts, Environ. oxygen Sci. species Tech., 40, generation 4880–4886, by 2006. particulate matternin, ex- M., Fuhrer,Field-deployable, high-resolution, K., time-of-flight aerosol Horvath, mass spectrometer,8281–8289, Anal. T., 2006. Chem., Docherty, 78, K. S., Worsnop, D. R., and Jimenez, J. L.: Fernandez, A., and Froines,sites J. in R.: the Redox Los Angeles activity Basin, of Environ. airborne Res., 99, particulate 40–47, matter 2005. at di A. H., Eiguren-Fernandez, A.,four Kobayashi, quinones T., in Avol, diesel E., exhaustTech., and 38, particles, 68–81, Froines, SRM 2004. J. 1649a, R.: and atmospheric Determination PM of electron ionization high-resolution mass9117 spectrometry, Anal. Chem., 79, 8350–8358, 2007. hydroxyl radicals in the gas phase, Environ. Sci. Technol., 31, 2252–2259, 1997. 3060, doi: for ambient particles: evidence for thePhys., importance 12, of 9321–9333, soluble doi: transition metals, Atmos. Chem. N.: An ultrasensitiveperformance and liquid chromatography highlycence, with J. selective Chromatogr. photochemically A, determination 1216, initiated 3977–3984, method 2009. luminol for chemilumines- quinones by high- K formation from photooxidation of naphthalenetion and of alkylnaphthalenes: implications intermediate for volatility oxida- organic compounds (IVOCs), Atmos. Chem. Phys., 9, 3049– Furthermore, there is currently little information on the production rates of the more Chung, M. Y., Lazaro, R. A., Lim, D., Jackson, J., Lyon, J., Rendulic, D., and Hasson, A. S.: DeCarlo, P. F., Kimmel, J. R., Trimborn, A., Northway, M. J., Jayne, J. T., Aiken, A. C., Go- Cho, A. K., Sioutas, C., Miguel, A. H., Kumagai, Y., Schmitz, D. A., Singh, M., Eiguren- Cho, A. K., Di Stefano, E., You, Y., Rodriguez, C. E., Schmitz, D. A., Kumagai, Y., Miguel, in the design and buildingCanada of Foundation the for oxidation Innovation. chamber. Funding was provided by NSERC and the The influence of naphthalenetive oxidation species on such redox activity ashumic-like in 9,10-phenanthrenequinone, substances relation transition – to metals, particularly other blackgas in carbon, redox phase ac- warmer and for climates small whenunknown naphthoquinones partitioning redox-active – species favours may generated the ultimately through depend its photooxidation. on theAcknowledgements. volatility of the ticular Derek Jackson, for thequinone use analysis. of Thanks their to GC-MS the and University assistance of and advice Toronto Department in of performing Chemistry the for assistance Aiken, A. C., DeCarlo, P. F., and Jimenez, J. L.: ElementalBunce, N. analysis J., of Liu, L., organic Zhu, species J., and with Lane, D. A.: Reaction of naphthalene and its derivatives with Charrier, J. G. and Anastasio, C.: On dithiothreitol (DTT) as a measure of oxidative potential Ahmed, S., Kishikawa, N., Ohyama, K., Maki, T., Kurosaki, H., Nakashima, K., and Kuroda, Chan, A. W. H., Kautzman, K. E., Chhabra, P. S., Surratt, J. D., Chan, M. N., Crounse, J. D., References redox-active, may be aand greater source has of been particle-phase shownet redox-active al. to organic be species anfound atmospherically phenanthrenequinone to relevant be species a much ( than more 1,2- substantial and contributor 1,4-naphthoquinone to ( redox activity is of much lower volatility than either 1,2- or 1,4-naphthoquinone and is more highly not account foring based activity on could thelow arise three from vapour naphthoquinone highly pressures speciescle functionalised and measured. loading; products, structural The could which activity1,4-naphthoquinone miss- are contribute relationships likely predict to to to the redox benaphthoquinone have vapour pressure ( cycling about of under 5-hydroxy- anto ambient produce order phenanthrenequinone parti- (e.g. of magnitude lower than that of 1,4- tribute to the toxicity of particles. redox-active and less volatile 1,2-naphthoquinoneproducts and for 5-hydroxy-1,4-naphthoquinone the purposeabout of 70 % atmospheric of modelling, and the there redox remains, activity at with minimum, unknown partitioning behaviour that we could project but may be important for determining how atmospheric processes may con- 5 5 25 30 20 25 20 15 10 15 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | , 9124 9125 9109 , , 9114 9123 9124 , , ects of ozone ects, Clin. Im- ff ff , 2013. 9110 9123 , 9109 ´ alez-Flecha, B.: Rapid 9122 9129 , , ects of carbon black nanopar- ff 9127 9117 9110 , 10.1021/es304676x 9111 9111 9119 , 9109 9109 9126 9110 9109 , , 2013. 9110 9109 9124 9131 9132 9118 , , 9121 9114 , 9116 , 9109 9109 9110 9112 , 9110 9111 http://webbook.nist.gov 9110 9110 9128 , 9129 9127 , , lung diseases and itsBio. implications Med., in 44, 1689–1699, the 2008. toxicity of engineered nanoparticles,diesel Free exhaust, Radical Atmos. Environ., 43, 1037–1042, 2009. study of the heterogeneousA, gas-surface 110, reaction 3638–3646, of 2006. anthracene and ozone, J. Phys. Chem. and Nel, A.: Ultrafineage, particulate Environ. pollutants Health Persp., induce 111, oxidative 455–460, stress 2003b. and mitochondrial dam- in atmospheric aerosols, Environ. Sci. Tech., 45, 10362–10368, 2011. Kleeman, M. J.: QuinoneTech., emissions 41, 4548–4554, from 2007. gasoline and diesel motor vehicles,Dalleska, Environ. N. Sci. F., Wennberg, P. O., Flagan,gas- R. and C., aerosol-phase and products Seinfeld, from114, J. the H.: 913–934, photooxidation Chemical 2010. of composition naphthalene, of J. Phys. Chem. A, ticles, Chemosphere, 65, 946–951, 2006. dation of proximal protein sulfhydrylsparticles, by Chem. phenanthraquinone, Res. a Toxicol., component 15, of 483–489, diesel 2002. exhaust A paradigm for themunol., role 109, 250–265, of 2003a. oxidative stress in PM-induced adverse health e Miguel, A. H., andin Eiguren-Fernandez, Southern A.: California, Atmos. Naphthalene Environ., distributions 39, and 489–507, human 2005. exposure 9110 their relative importance inChem.-Biol. the Interact., mechanism 65, of 157–173, quinone 1988. cytotoxicity to isolated hepatocytes., increases in the steady-state concentration ofafter reactive particulate oxygen air species pollution in the inhalation, lungs Environ. and Health heart Persp., 110, 749–755, 2002. radical, Atmos. Environ., 43, 4886–4893, 2009. threne with the OH radical in a reaction chamber, Atmos. Environ., 44, 2469–2477, 2010. oxidation on redox-cycling activity of two-stroke45, engine 2131–2136, exhaust particles, 2011. Environ. Sci. Tech., constituents, Environ. Sci. Technol., 47, 3362–3369, doi: process: hydrogen peroxide isArch. involved Biochem. in Biophys., 333, the 233–242, initiation 1996. of a freeReference radical Database chain Number of 69, Nationalburg reactions, MD, Institute available of at: Standards and Technology, Gaithers- cling activity: a comparison between diesel exhaust particles and secondary organic aerosol Cho, A. K., andAngeles air Froines, basin, J.: Atmos. Atmospheric Environ., 42, formation 2312–2319, of 2008b. 9,10-phenanthraquinonePress, in San Diego the CA Los USA, 2000. 9125 of free radicals in1371–1377, 2001. the toxicity of airborne fine particulatenam, matter, S., Avol, Chem. E. Res. L.,quinones Toxicol., in and 14, Southern Froines, California, J. Aerosol R.: Sci. Atmospheric Tech., 42, distribution 854–861, of 2008a. gas- and particle-phase Li, Q., Wyatt, A., and Kamens, R. M.: Oxidant generation and toxicity enhancement of aged- Li, N., Sioutas, C., Cho, A., Schmitz, D., Misra, C., Sempf, J., Wang, M., Oberley, T., Froines,Li, J., N., Xia, T., and Nel, A. E.: The role of oxidative stress in ambient particulate matter-induced Lin, P. and Yu, J. Z.: Generation of reactive oxygen species mediated by humic-like substances Kwamena, N.-O. A., Earp, M. E., Young, C. J., and Abbatt, J. P. D.: Kinetic and product yield Jakober, C. A., Riddle, S. G., Robert, M. A., Destaillats, H., Charles, M. J., Green, P. G., and Kumagai, Y., Koide, S., Taguchi, K., Endo, A., Nakai, Y., Yoshikawa, T., and Shimojo, N.: Oxi- Lu, R., Wu, J., Turco, R. P., Winer, A. M., Atkinson, R., Arey, J., Paulson, S. E., Lurmann, F. W., Koike, E. and Kobayashi, T.: Chemical and biological oxidative e Kautzman, K. E., Surratt, J. D., Chan, M. N., Chan, A. W. H., Hersey, S. P., Chhabra, P. S., Li, N., Hao, M., Phalen, R. F., Hinds, W. C., and Nel, A. E.: Particulate air pollutants and asthma. Lee, J. Y. and Lane, D. A.: Formation of oxidized products from the reaction of gaseous phenan- Netto, L. E. S. and Stadtman, E. R.: The iron-catalyzed oxidation of dithiothreitol is a biphasic Gurgueira, S. A., Lawrence, J., Coull, B., Murthy, G. G. K., and Gonz Lee, J. Y. and Lane, D. A.: Unique products from the reaction of naphthalene with the hydroxyl NIST Mass Spec Data Centre: “Mass Spectra” in NIST Chemistry WebBook, NIST Standard Gant, T. W., Rao, D. N., Mason, R. P.,and Cohen, G. M.: Redox cycling and sulphydryl arylation, McWhinney, R. D., Gao, S. S., Zhou, S., and Abbatt, J. P. D.: Evaluation ofMcWhinney, the R. e D., Badali, K., Liggio, J., Li, S.-M., and Abbatt, J. P. D.: Filterable redox cy- Finlayson-Pitts, B. J. and Pitts, J. N.: Chemistry of the Upper and Lower Atmosphere, Academic Eiguren-Fernandez, A., Miguel, A. H., Lu, R., Purvis, K., Grant, B., Mayo, P., Di Stefano, E., Eiguren-Fernandez, A., Miguel, A. H., Di Stefano, E., Schmitz, D. A., Cho, A. K., Thurairat- Dellinger, B., Pryor, W. A., Cueto, R., Squadrito, G. L., Hegde, V., and Deutsch, W. A.: Role 5 5 15 10 30 20 20 25 15 30 25 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 9123 9129 , 9110 9127 9129 , 9128 Windows, v 4.11., United States , 9119 ® 9124 9110 9110 9109 for Microsoft ™ 9134 9133 9111 9109 9109 9122 erent types of aged atmospheric particles: an outdoor chamber study, n, R. J.: Secondary organic aerosol from photooxidation of polycyclic ff ffi radical-initiated reactions of naphthalene, Environ. Sci. Tech., 31, 3173– 9110 9138 3 , 9119 9110 9110 9128 gas-phase reactions of phenanthrene, Atmos. Environ., 41, 2025–2035, 2007. solution, J. Phys. Chem. Ref. Data, 18, 1637–1755, 1989. bution of water-soluble and insolubletions components and to their the hydrophobic/hydrophilic reactive subfrac- Sci. oxygen Tech., species-generating 46, potential 11384–11392, of 2012. fine ambient aerosols, Environ. of urban quasi-ultrafine particles from6360–6368, primary 2009. and secondary sources, Atmos. Environ., 43, tion of selective quinonesexhaust and particles, quinoid Environ. Chem., radicals 3, in 118–123, airborne 2006. particulate matter and vehicular oxidant potential of di Atmos. Environ., 45, 3848–3855, 2011. 2007. Environmental Protection Agency, Washington DC, 2013. and chemical speciation2007. of size-fractionated particulate matter, Part. Fibreerties Toxicol., of 4, diesel exhaust 5, biological particles: reductants, catalysis Toxicol. Sci., of 81, the 225–232, generation 2004. of reactive oxygen species by aromatic hydrocarbons, Environ. Sci. Tech., 44, 8134–8139, 2010. nism for sustained free radical generationBio. by inhaled Med., airborne 31, particulate 1132–1138, matter, Free 2001. Radical high oxidation capacity marine background atmosphere, Environ. Sci. Tech., 41, 8011–8017, phase OH and NO 3179, 1997. drade, J. B.: Evaluation of thermalmochim. stability Acta, of 529, quinones 1–5, by thermal 2012. analysis techniques, Ther- substituted quinones and177–197, ascorbate 1999. under aerobic conditions, Chem.-Biol. Interact., 121, S.-H., Froines, J. R.,particles, and Environ. Res., Cho, 109, A. 239–244, 2009. K.: Electrophilic and redox properties of diesel exhaust semisolid organic aerosol particles, P. Natl. Acad. Sci. USA, 108, 11003–11008, 2011. Wardman, P.: Reduction potentials of one-electron couples involving free-radicals in aqueous- Wang, L., Atkinson, R., and Arey, J.: Formation of 9,10-phenanthrenequinone by atmospheric Verma, V., Rico-Martinez, R., Kotra, N., King, L., Liu, J., Snell, T. W., and Weber, R. J.: Contri- Verma, V., Ning, Z., Cho, A. K., Schauer, J. J., Shafer, M. M., and Sioutas, C.: Redox activity Valavanidis, A., Fiotakis, K., Vlahogianni, T., Papadimitriou, V., and Pantikaki, V.: Determina- US EPA: Estimations Programs Interface Suite Rattanavaraha, W., Rosen, E., Zhang, H., Li, Q., Pantong, K., and Kamens, R. M.: The reactive Pan, C.-J. G., Schmitz, D. A., Cho, A. K., Froines, J., and Fukuto, J. M.: Inherent redox prop- Squadrito, G. L., Cueto, R., Dellinger, B., and Pryor, W. A.: Quinoid redox cyclingTsapakis, as M. a mecha- and Stephanou, E. G.: Diurnal cycle of PAHs, nitro-PAHs, and oxy-PAHs in a Ntziachristos, L., Froines, J. R., Cho, A. K., and Sioutas, C.: Relationship between redox activity Shakya, K. M. and Gri Sasaki, J., Aschmann, S. M., Kwok, E. S. C., Atkinson, R., and Arey, J.: Products of the gas- Sousa, E. T., da Silva, M. M., de Andrade, S. J., Cardoso, M. P., Silva, L. A., and de An- Roginsky, V. A., Barsukova, T. K., and Stegmann, H. B.: Kinetics of redox interaction between Shinyashiki, M., Eiguren-Fernandez, A., Schmitz, D. A., Di Stefano, E., Li, N., Linak, W. P., Cho, Shiraiwa, M., Ammann, M., Koop, T., and Poschl, U.: Gas uptake and chemical aging of 5 5 10 30 15 25 10 20 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ) + ), 302 ([M] + CO] 2 ). CH ) ) − + + 2004 ( 0.09) % 0.08 0.02 0.01 0.3) % 1) % 1) % 1) % ± flow rate ± ± ± 2) % 2) % ± 1 ), 260 ([M ± ± ± − + ), 244 ([M] ), 258 ([M] ± ± + + Cho et al. C CO] ◦ 2 CO] CO] 2 2 CH CH 2CH to 280 − − − 1 9136 9135 − C, 10.5 psi C, hold 4 min ◦ ◦ C min ◦ ), 202 ([M ), 216 ([M ), 218 ([M + + + ) Agilent 7683 Series autosampler 5 mass contribution (18 N mass contribution (0.36 mass contribution (23 m/z CO] CO] CO] 1 1 N mass contribution (1.2 2 2 2 1 > 1 > mass contribution (31 O O N mass contribution (3 O O y y y y y y H H H H H H 2CH 2CH 3CH x x x x x x − − − H : C ratioC C C 0.97 O : C ratioN : C ratioC C 0.31 0.03 C HO mass contribution (5 GC-MS method parameters as adapted from Average elemental composition of particles at the end of the photooxidation portion of Time22–25.5 min 160 ([M Selected ions ( Gas chromatograph Agilent 7890A 25.5–30 min30–34 174 min ([M 176 ([M Inlet temperature and pressure 260 InjectionCarrier gas 1 µL, He, pulsed 10.5 splitless psi, injection 1 at mL 25 min psi for 0.5 min Run timeTemperature program 100 40 min Mass spectrometerIonisation mode Agilent 5975C Electron impact the experiment. Table 2. Table 1. Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 1 / − d µg 1.7 1.8 1.7 0.3 0.2 1.1 0.5 0.4 0.4 0.4 0.5 2.5 1.7 0.7 0.7 0.7 1.5 0.5 / 3 d ± ± ± p ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± m K PM mass mg 4 − 10 c,d 0.20.2 0.54 0.2 0.37 0.2 0.31 0.59 ± ± ± ± 5-OH-1,4- NQ/µg 3 ); relative standard 895665 2.7 83 3.7 77 5.0 4.9 4.8 73 7.6 63 9.3 69 10.4 8367 6.9 8.4 56 10.1 91 5.6 93 10.7 64 8.4 46 9.7 93 7.5 − 103 4.0 103 6.2 c,f p ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± 0.20.1 0.7 0.1 0.8 0.2 0.6 0.5 0.30.2 – – 0.68 0.42 0.30.1 –0.3 – – 0.65 0.39 0.45 0.1 – 0.44 M 1997 ± ± ± ± ± ± ± ± ± ± , µgm 1,2-NQ/ µg 0.20.1 2.0 0.1 1.1 0.2 0.8 1.7 0.30.4 2.6 1.3 0.60.3 2.2 0.3 0.9 2.3 0.4 1.2 . c,e p,f ± ± ± ± ± ± ± ± ± ± ff 3 − 0.90.6 443 0.7 281 323 0.80.7 417 1.0 383 516 0.71.0 367 514 0.6 315 0.8 344 0.90.8 417 333 0.5 281 1.0 455 1.1 463 0.6 318 0.4 231 0.9 467 4.3 1,4-NQ/ µg Sasaki et al. ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± , 3 − µgm 1 cm − 1 − / [1,4-NQ] Mmin 7 with 5-OH- − c,d g,f 3 b 2.31.8 3.8 3.2 2.5 2.2 2.8 2.3 3.3 1.3 3.0 4.0 1.4 4.0 0.9 3.5 1.7 3.2 2.1 4.2 0.8 3.8 molec − 0.8 2.7 1.2 2.3 1.7 3.2 0.9 2.1 2.1 4.3 1.1 2.5 0.8 1.8 ± ± ± ± ± ± ± ± ± ± ± 11 0.30.20.3 1.5 1.2 1.8 0.4 2.3 ± ± ± ± ± ± ± − ± ± ± ± e 10 Predicted 1,4-NQ/10 × 9138 9137 time. 2.2 1 ff / − / [1,4-NQ] b = b i OH 0.20.10.3 1.2 0.9 1.4 0.30.3 – 1.7 4.8 0.3 – 3.2 0.20.3 – – 3.7 3.7 0.20.3 – – 6.6 Mmin k 7 ± ± ± ± ± ± ± ± ± ± − 502926 29.7 23 23.5 25 18.7 29 14.7 16.5 18.9 19 9.2 28 12.3 14 6.6 27 7.8 24 11.6 2616 10.6 6.5 37 14.5 31 7.1 25 8.5 18 7.2 33 10.4 Predicted 10 ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ppb µgm DTT decay rates Particulate quinone masses 1 − 1 %. µg 1 ± [Naphthalene] − 434725 0.7 0.5 1.0 1825 1.5 1.3 2019 1.1 1.5 1612 1.4 2.2 8 1.5 ± ± ± ± ± ± ± ± ± 3 ± 7 − Mass normalised/ pmolmin 20 %. /10 25 % relative standard deviation of the calibration slope for calculation of 1,4-naphthoquinone from a ± ± 10 % relative standard deviation of PTR-MS calibration for naphthalene. 1 / − ± a [OH] 1.31.21.2 113 125 125 0.91.1 140 121 0.91.01.0 122 130 87 0.80.9 116 104 Mmin 7 ± ± ± ± ± ± ± ± ± ± − 10 Summary of DTT and quinone analysis for naphthalene oxidation experiments. Summary of AMS and PTR-MS measurements for naphthalene oxidation experiments. 158. m/z 27 May 6.1 Experiment Measured 3 Aug B4 Aug A4 Aug B 3.3 3.1 5.9 3 Jun3 Aug A 7.0 5.2 1 Jun2 Jun A2 Jun B 5.7 7.0 7.1 31 May 8.1 Measured is based on dilutionPredicted of values the match extract used dilution in factors used the in assay for the a measured particular assay. sample and will notMass scale reported directly is with for reported whole5-hydroxy-1,4-naphthoquinone quinone filter. not or measured. PM masses. Quinone masses for 1,4-naphthoquinone (1,4-NQ), 1,2-naphthoquinone (1,2-NQ) and 5-hydroxy-1,4-naphthoquinone (5-OH-1,4-NQ) are corrected using spike 17 Apr 1.1 480 Experiment moleccm 14 May27 May28 May A28 May B29 May 1.2 A 1.1 1.6 1.6 1.7 279 251 225 237 282 29 May B 1.9 181 31 May 1.6 267 1 June 1.9 136 24 Jun A 1.0 257 24 Jun B 1.4 233 24 Jul25 Jul A 1.2 1.9 251 157 25 Jul B 1.0 361 3 Aug A 1.0 302 3 Aug B 1.6 244 4 Aug A 1.5 169 4 Aug B 1.3 315 a b c and recovery measurements. d e Uncertainty based on standard deviationUncertainty of based averaged on values a 10 min prior to lamp shuto Uncertainty based on Calculated from first-order decay of naphthalene ( Values averaged from 10 min of data prior to lamp shuto Uncertainty estimated at d e AMS f b c deviation of fit was typically less than a Table 4. Table 3. Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 2 2 O O c OA OAc OAc OAc OAc OAc O O OAc O O 9140 9139 O O O O O O OH Red Red 1,2-naphthoquinone (top left), 1,4-naphthoquinone (middle left), and 5-hydroxy-1,4- A general redox cycle for 1,2-napththoquinone. A generic reducing agent (red) transfers Fig. 2. naphthoquinone (bottom left) and their respective acetylated derivatives (right). Fig. 1. a single election toregenerated 1,2-naphthoquinone when to the electron generate is the transferred semiquinone to oxygen, radical. generating The superoxide. quinone is Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 160 N 10.0 >1 >1 O O N ON O y y y y y y -1 H H H H H H x x x x x x C C C C C C HO 140 8.0 M min -7 120 With 5-OH-1,4-NQ 1:5 line 6.0 100 m/z 4.0 9142 9141 80 1:1 line 2.0 60 No 5-OH-1,4-NQ Measured DTT decay rate / 10 0.0 40

2.5 2.0 1.5 1.0 0.5 0.0 3.0

M min M Predicted DTT decay rate / 10 / rate decay DTT Predicted

-1 20 -7 Predicted DTT decay rates of naphthalene SOA filter extracts plotted against the mea- Average mass spectrum of naphthalene SOA coloured by fragment family. Fig. 4. sured DTT decay rates.and Open 1,4-naphthoquinone triangles on represent thenaphthoquinone predicted (5-OH-1,4-NQ) particle in values filters, the prediction. based while Aif on filled 1 predicted : measured 1 circles DTT line decay 1,2- also indicates rates the include equal expected those 5-hydroxy-1,4- relationship observed. Fig. 3. Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | m/z ). Sig- + + + 31.2 min) for the 32.5 = (2-formylcinnamaldeyde R t + 3:00 PM + O 7 H 9 32.0 (hydroxynaphthoquinone [M] + 3 O Standard (0.25 µg) Standard (0.25 Sample, August 3a 6 H 2-formylcinnamaldehyde [M-CHO] naphthoquinone [M] hydroxynaphthoquinone [M] 2:00 PM 10 31.5 Lamps off/pumps on 9144 9143 ), and C Retention time / min + 31.0 1:00 PM 30.5 0 (naphthoquinone M Lamps on + 2 2000 1000 6000 5000 4000 3000

O 8/4/12

6 Signal 12:00 PM H 10 ,C + Time series of high-resolution AMS data for C Sample chromatogram for 5-hydroxy-1,4-naphthoquinone ( CHO] − [M nals have been scaled to appear the same magnitude. Fig. 6. Fig. 5. 176 fragment (loss of three acetyl groups from molecular ion). Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Q 158.3 Aug 4B 5-OH-1,4-N 158.2 molecular ion of 1,4-naphthoquinone (ac- Aug 4A + 2 O 8 H m/z 1,4-NQ 10 9146 9145 158.1 Aug 3B 158 for homogeneously nucleated BES without naphtho- 158.0 BES BES + 1,4 BES + 1,2 m/z Aug 3A fragment from BES (actual mass 158.131 amu), while the small + 2 1,2-NQ O 18

H

0.5 0.0 2.0 1.5 1.0 9 157.9

M min M Predicted DTT decay rate / 10 / rate decay DTT Predicted

-1 -7 Raw mass spectra at Predicted DTT decay rates by constituent for four experiments (labelled A–D) where 1,2-, quinone and with 1,4-naphthoquinone andsity 1,2-naphthoquinone. arises The peak from of a the highest C inten- Fig. 8. peak seen in the redtual mass trace 158.037 arises amu). from the C 1,4-, and 5-hydroxy-1,4-naphthoquinonewere (1,2-NQ, quantified in 1,4-NQ, the particle and phase. 5-OH-1,4-NQ, respectively) Fig. 7. Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper |

-3 PTR-MS normalised m/z 159 / 10 (outer) -3 3 -1 Calculated Kp / 10 m µg (inner)

1.0

x10

0.25 0.00 1.75 1.50 1.25 1.00 0.75 0.50 -3 ciency of 0.5. The PTR- -1 ffi 3 2 1 1:1 1:10 1:20 0.8 M min 10:00 PM -6 0.6 (black triangles) was calculated for each p 159 (blue) was normalized to the reagent Lamps off/pump on K 9:00 PM m/z 9148 9147 cient 0.4 ffi 8:00 PM 0.2 Observed DTT decay rate / 10 Lamps on 158 (orange) were corrected for a collection e 0.2 0.8 0.6 0.4 0.0 0 5 4 3 2 1 6

8/4/12

m/z 7:00 PM

M min M 0 10 / rate decay DTT Predicted

-1

500 400 300 200 100 -8

AMS m/z 158 / µg m µg / 158 m/z AMS (inner)

-3

AMS organics / µg m µg / organics AMS (outer) -3 Predicted DTT decay rates for oxidized engine exhaust particle extracts plotted as Representative experimental data for a naphthalene generation experiment. AMS or- time point using AMSnaphthoquinone, respectively. and PTR-MS data calibrated to filter and XAD measurements of 1,4- Fig. 10. a function of observedare DTT shown decay as rates. visualization aids. Guiding lines for 1 : 1, 1 : 10, and 1 : 20 relationships ion count. The gas-particle portioning coe Fig. 9. ganics (green) and MS signal for protonated naphthoquinone at Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | -3 4 2 10 4 2 1 1,2-naphthoquinone 1,4-naphthoquinone 4 2 Particle mass loading / µg m 0.1 0 -1 -2 -3 -4

10 10 10 10 10

m / pmol min pmol /

-3 -1 Air volume normalised DTT decay decay DTT normalised volume Air -3 4 2 10 4 2 1 9149 4 2 Particle mass loading / µg m 0.1 of quinone. Shaded areas represent the uncertainties 6 4 2 8 6 4 8 6 4 2 8 3 0.1

0.01 −

0.001

µg / pmol min pmol /

-1 -1 Particle mass normalised DTT decay decay DTT normalised mass Particle -3 4 2 10 4 2 1 4 2 Particle mass loading / µg m 0.1 Calculated quinone particulate mass loadings and mass- and volume-normalised DTT 1

10

0.1 100

Particlulate quinone mass loading / pg m pg / loading mass quinone Particlulate -3 as discussed in the text. Fig. 11. decay rates as aa function total of mass organic particle concentration of mass 1 loading. ngm Calculations are performed using