Modeling Nitrous Acid and Its Impact on Ozone and Hydroxyl Radical

Home , Nitrous acid

Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ∗ 2 ected ff into HONO Chemistry 2 , and * and Physics Discussions erential Optical Atmospheric ff only slightly a 2 , F. Ngan 1,2,† erent altitudes. Several HONO ff , D. W. Byun 1 5852 5851 into HONO on surfaces covered with organic 2 , P. Percell 1 ) hydrolysis, photo-induced formation from excited NO ¨ uck ∗ 2 ) concentrations. Photo-induced conversion of NO 3 , B. Rappengl 1 liation: Air Resources Laboratory,NOAA, Silver Spring, MD20910, USA ffi ** now at: Ajou University, Suwon, South Korea 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. University of Houston, Department of Earth and Atmospheric Sciences,Resources 4800 Laboratory, Calhoun NOAA, Rd, Silver Spring, MD20910, USA author deceased present a HONO and ozone (O on surfaces covered with organic materialsHONO. turned Since out HONO to be immediatelying a photo-dissociates strong ratios source during were of only daytime daytime hydroxyl marginally its radical altered ambient (OH) (up mix- and to ozoneneous 0.5 concentration ppbv), HONO was but formation obtained. that significant mainly In increasephoto-induced accelerated contrast in surface morning to chemistry the ozone heteroge- influenced formation, ozone inclusion throughout of the day. while measured HONO concentrationsHONO decrease concentration with with height. altitudetrations when was A heterogeneous well trend chemistry capturedinto of and with account. decreasing photolytic CMAQ sources Heterogeneous predicted offormation, albeit HONO HONO concen- slightly. were production Also taken HONO mainly formation accelerated from morning excited NO ozone Absorption Spectroscopy) measurements atsources three were di accounted for insions, simulations, nitrogen such dioxide as gas (NO and phase photo-induced formation, conversion direct emis- ofmaterials. NO Compared to thecrease gas-phase in HONO HONO formation mixing ratios there whenwhich was additional about HONO improved sources a the were tenfold taken correlation in- intotions between account, of modeled HONO and simulated measured with values. only gas Concentra- phase chemistry did not change with altitude, Nitrous acid (HONO) mixingwith ratios the for the Community Houston MultiscaleTexas Air metropolitan Air area Quality Quality were Study (CMAQ) simulated situ (TexAQS) model MC/IC II (mist-chamber/ion for in chromatograph) and an August/September long 2006 episode path DOAS and during (Di compared the to in- Abstract S. Kim 1 TX 77204-5007, Houston,2 USA * ** † Received: 14 January 2012 – Accepted:Correspondence 7 to: February 2012 B. – H. Published: Czader ([email protected]) 23 FebruaryPublished by 2012 Copernicus Publications on behalf of the European Geosciences Union. Modeling nitrous acid and itsozone impact and on hydroxyl radical duringTexas the Air Quality Study 2006 B. H. Czader Atmos. Chem. Phys. Discuss., 12,www.atmos-chem-phys-discuss.net/12/5851/2012/ 5851–5880, 2012 doi:10.5194/acpd-12-5851-2012 © Author(s) 2012. 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 | O 2 and H 2 ect simulated erent sources ff ff ) as a source of 3 and formation from 2 mann et al., 2005). OH ff mann et al., 1998; Finlayson- ff mixing ratios are analyzed. The er in an explanation of the exact ects of deposition, transport and x ff ff ) in Mexico City leading to a midday 2 HO ) and nitric acid (HNO + and HO − 3 3 OH 5854 5853 ) hydrolysis (Kle = 2 x erent HONO sources during day and nighttimes to HONO on surfaces covered with humic acid and ff ; however, they di 2 2 (HO on surfaces covered with organic materials. Of par- x 2 erent physical and chemical processes a mann, 2005, 2007; Su et al., 2008). Zhou et al. (2002, adsorbed on surfaces were accounted for. This approach ff ff erent altitudes obtained in Houston, Texas. 3 ff ect HO ff of about 6 ppb. Sarwar et al. (2008) performed CMAQ modeling 3 formation. HONO is simulated with a three dimensional Commu- x The Houston-Galveston-Brazoria (HGB) area has one of the highest ozone concen- A number of studies reported modeling of HONO formation from di The occurrence of HONO in the lower atmosphere can be attributed to either direct plemented, which arephoto-induced formation reaction from of electronically NO excitedticular NO interest is theand analysis their impact of on di vides atmospheric information chemistry. on The howconcentrations process di was analysis utilized (PA) for toolchemical that that reactions purpose. on pro- HONO The assimulated e concentrations well of as HONO O aremeasurements compared at with three in-situ di as well as with long-path and 2010 (unpublished), itthis is region. important to The evaluate presenton the study ozone impact assesses and of sources HO HONO andnity losses on Multiscale of ozone Air HONO for Quality and (CMAQ)heterogeneous model its chemistry, which impact includes and HONO emissions, gas-phase chemistry, as well as two new sources that we im- duction on the surface ispathway. the This major study source concentrated of on HONOmodel nighttime and that HONO deposition simplifies and the transport was major processes. limited removal to a use oftrations 1-D in the US often(Berkowitz exceeding the et National al., Ambient Air 2004;concentrations Quality Daum Standard were et for measured ozone al., inin 2004; Houston 2006 Wilczak during (Stutz et several air al., et quality 2009). al., campaigns, 2010; Since e.g. high Ziemba HONO et al., 2010) and thereafter repeatedly in 2009 of HONO for thechemistry, north-eastern HONO emissions, area heterogeneous of HONO theand formation US the involving NO photolysis in of which, HNO improved in surface addition to HONO the predictions1.4 ppbv. gas and The phase recent resulted study in of Wong an et average al. (2011) ozone for increase Houston showed of that HONO pro- average increase in O chemistry significantly a a photo-induced conversion of NO other similar organic compounds. Severalby studies the pointed electronic to excitation HONO ofmechanism formation of initiated NO this process, and correspondingly, theand yield Carl, of 1997; HONO formation Li (Crowley et al., 2008, 2009; Carrand et its al., 2009; impact Amedro on et ozonetions al., concentrations. with 2011). the Li et WRF-CHEMHONO al. model sources. (2010) for They performed Mexico concluded 3-D City that model in addition simula- of which HONO they sources accounted other for than several gas-phase that HONO can alsonot be formed yet in been photolytic identified2003) processes (Kle point but the to exact theHONO mechanism photolysis while has the of chamber nitrateas study (NO a of HONO precursor. Rohrer George et et al. al. (2005) (2005) and excluded Stemmler photolysis et al. of (2006, nitrate 2007) observed the formation of ozone, ininstance particular Mao et in al., urban 2010). areas with high burden ofemissions VOCs (Kirchstetter (see for et al.,Among known 1996; chemical sources Kurtenbach of HONO etbetween is OH al., the and gas-phase nitric 2001) formation oxide from (NO) or the (Pagsbergon et chemical reaction surfaces al., from formation. 1997) and nitrogen heterogeneous dioxide formation Pitts (NO et al., 2003). Results from laboratory experiments and field campaigns suggest The importance offrom nitrous its acid photo-dissociation that (HONO) serves(Lammel in as and a the significant Cape, chemistry sourceplays 1996; of of a hydroxyl Alicke crucial the radical et (OH) role atmosphere in al., stems the 2002, oxidation 2003; of volatile Kle organic compounds (VOCs) leading to 1 Introduction 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 | ] 5 1 − − 10 ) [s × S/V ( × 5 cient for reac- − ffi cient of 2 10 ffi × 5 = cient scaled by (light in- k ffi cient is the ratio of a surface area to . We adopted this approach for ffi 2 − S/V and an uptake coe 5856 5855 2 − ftp://ftp.tceq.state.tx.us/pub/OEPAA/TAD/Modeling/ on surfaces covered with humic acid and similar organic ma- 2 aq). Integrated process rate (IPR) analysis was carried out to track con- ). For SMOKE processing the Texas emission inventory was converted ae5 Stemmler et al. (2006, 2007) showed that HONO can be formed from the photo- Meteorological data were simulated with the Mesoscale Model, version 5 (MM5) Gridded emissions were derived with the Sparse Matrix Operator Kernel Emis- CMAQ simulations for Houston, but obtained unrealisticallyTherefore, high contrary HONO concentrations. to Li et al. (2010) our approach do not employ a threshold value terials. George et al. (2005)organic also observed compounds. photo-enhanced HONO production Thesetion on with solid studies organics suggested isdepends that much on larger the solar than uptake radiation. thereported coe one by Enhanced Ndour for photochemical et heterogeneous production al.al. reaction of (2008) (2010) and HONO and implemented that Monge was a et it daytime also for al. HONO light (2010). source intensities with Based an less ontensity)/400 uptake these than coe for studies 400 W Li solar m et radiation larger than 400 W m surfaces (Foley et al.,as 2009) measured with by a Kurtenbach reactionvolume et of rate al. air. coe (2001), where Forsources this into study CMAQ we as described implemented below. two additional photo-dependent HONO induced reaction of NO mat were convertedSMOKE. into The latitude-longitude National (LL) Emissionnot coordinates covered Inventory by for the v. Texas spatial 2002 inventory. allocation (NEI2002) was in 2.1 utilized for areas HONO sources In addition to theaccounts gas-phase for HONO the chemistry, heterogeneous the CMAQ formation version of used HONO in on this urban, study leaves, and particle bile emissions derivedSystem (HPMS) from data (available “linked at: HGB8H2/ei06 based” and thefrom the High AIRS Performance FacilityLocations Subsystem Monitoring of (AFS) point to sources the in Inventory the Data Lambert Analyzer Conformal (IDA) Conic format. (LCC) map projection for- the Base5b 2007 area and non-road emissions, 2006 biogenic emissions, and mo- hourly-specific Texas Point-source Special Inventory (TPSI2006) for the year 2006, (Grell et al., 1994).and An Byun updated (2008) land was usecal and utilized variables land a in cover multi-nest those(FDDA) data grid-nudging with simulations. as based the described Texas on CAMS To in and Four-Dimensionaltem further NOAA Cheng Data (MADIS) Meteorological was improve Assimilation Assimilation performed meteorologi- Data (Ngan et Ingestto al., Sys- CMAQ 2011). inputs Conversion was of the performed meteorological(MCIP) with data the (Byun Meteorological and Chemistry Schere, Interface 2006). Processor sions (SMOKE) system (Houyoux et al., 2000) using the Texas inventory, including and losses for HONO as wellwere as performed its for impact the on 25 radicalthe August–21 and Texas September, ozone Air 2006 formation. Quality time Study Simulations period II.conditions. that Two coincides days with spin-up time was used to obtain realistic initial and with 12 kmthe grid simulations resolution performed for witharea. 4 the km The Texas grid atmosphere domain. resolution wasmbar for divided Current (around the into 23 20 domain analysis km vertical covering is height).chemical layers the between based mechanism HGB Chemical the (Carter, on reactions surface 1990, were and(saprc99 50 2000) simulated with that the included SAPRC-99 tributions aerosol and of aqua chemical chemistry andintegrated reaction transport rate processes (IRR) analysis to was HONO employed mixing to investigate ratios. chemical sources In addition, Simulations for thisleased study by were the performed USFor with Environmental the purpose Protection the of Agency deriving CMAQ reliable (EPA)resolution model boundary (Byun for conditions version and CMAQ the was Schere, 4.7.1, domain run 2006). with covering re- 36 Continental km grid US, North Mexico, and South Canada 2 Model configuration 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 of (1) − s g r 3 cm 13 cient − ffi 10 . According to 2 ] scaled to (light × 1 − − ) reacts with water ∗ 2 ) [s scaled by (light inten- 5 based on the same data − S/V ( 2 10 cient that the one reported × cient of 1.7 is the surface to volume ra- chemistry causes significant 3 × ffi ffi − 2 10 S/V was confirmed by several studies. × , 2 hoto-induced HONO production. 2 p (indicated as NO cient: of 1 cient of 2 erent HONO sources and are indicated ffi 2 ff k ffi missions, e cient, the reaction uptake coe 5858 5857 ffi cient ffi concentrations as discussed further below. Fig- 2 can also be released upon collision with nitrogen, emissions occurring in 2005 were simulated. 2 x -road sources, such as emissions from ships, loco- ff . 3 − molecules, and consequently, less e eterogeneous formation; 10 overprediction. ∗ 2 h g 2 × r 8 as phase chemistry, HONO emissions were observed, Ensberg et al. (2010) obtained much smaller g is the mean molecular speed of NO x is the reactive uptake coe = V S as-phase HONO chemistry; x 2 g g r 2 resulted in a reaction rate coe NO 5 v NO − v GEH – and HONO G– GEHP – same as GEH, but with addition of 1 8 10 Three simulations were performed using di HONO emissions from mobile sources, non-road sources, such as construction and Formation of HONO initiated by excitation of NO 1. 2. 3. = × attributed to NO chemistry (case G) persistentlytrations. show significant HONO under mixingobserved prediction values ratios (e.g. of from 31 HONObetween August, GEH observed concen- 12 and and and simulated GEHP 20 HONOis values September). cases occurs mostly (e.g. are In related 1 some to much and casesure 6 mismatch closer a September). 2 in to mismatch This shows NO an the averageset diurnal (25 variation of August–21 HONOseen September and that 2006) NO higher for daytimephotolytic observed values HONO were and formation. obtained simulated from Nighttime cases. the and GEHP morning case, It overprediction which can of includes be HONO can be mist-chamber/ion chromatograph (MC/IC) systemthe University at of the Houston top (UH)ulation campus of cases (Stutz G, the et GEH, Moody al., andmeasured 2010) Tower GEHP. The during on as highest shown nighttimes HONO in and mixingare Fig. ratios in 1 much up the for to lower, sim- early 2 but ppbv mornings were still while appreciable. daytime concentrations HONO values simulated with only gas-phase 3 Results and discussion 3.1 Evaluation of HONO modeling Simulated HONO concentrations were compared with values measured in-situ by a as follow: HONO/NO k oxygen, or water;The therefore, impact these of reactions thisof were reaction Wennberg was also and subject accounted Dabdub ofozone for (2008) several increase studies. in show in California that the While (up exitedstill to model. the high NO 55 modeling ppb) NO study when modeledimpact for on past ozone period when (1987) lower when NO lawn equipment, asmotives, well and as aircraft o were estimated based on the Kurtenbach et al. (2001) formula for solar radiation assity)/900, we used where an light uptake intensitythe coe at following equation local for noon the reaches reaction rate about coe 900 W m Carr et al. (2009)involving and two Amedro et NO al.by (2011) Li suggested et that al. thisresults (2008). is provide an a In upper two bound our step ofThe study the process excess impact we energy of adopted this of reaction Li excited on at NO atmospheric chemistry. al. (2008) approach; therefore, our where tio, and 2 intensity/900). Li et al. (2008)to reported produce that HONO the and excited determined NO a reaction rate coe 5 5 20 15 10 20 25 15 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | NO cient + ffi concen- OH 2 erent paths → ff hv + mismatches, such 2 on OH formation additional ∗ 2 prediction were ignored and only erential Optical Absorption Spec- 2 ff contributed only about 30 % to that erent altitudes in the urban bound- ∗ 2 ff . Figure 4 shows a time series comparison 2 5860 5859 under prediction on 2, 7, and 8 September leads to and ozone formation x 2 HONO that can be interpreted as the amount of OH produced ects the concentration of pollutants. The correlation coe ff + OH with the values simulated with the GEH case. Too high NO 2 → O 2 is a direct precursor of HONO, a mismatch between modeled and simulated H 2 + reaction at the surface, changes in HONO mixing ratios at higher altitudes can ∗ 2 2 cient for HONO increased to 0.82. values simulated within 70 % of measured value were considered the correlation ffi 2 There are cases when simulated HONO time series do not match the measured In order to evaluate HONO modeling for di was 2–3 times higher thanmation production from (the the GEH case case). without photochemical Reactions HONO involving for- NO was employed in whichwith data were the averaged middle in cellgraph a corresponding in box consisting to Fig. of the 5and 25 NO location shows horizontal of IRR cells the resultsfrom Moody these for Tower. two the The reactions. sumsimulation bottom was of To performed reactions assess in HONO theered which with impact photochemical organic of HONO materials NO formationas was on “GEHP not surfaces (no included, cov- surf this phot)”. simulation is During indicated morning in hours the OH production graph from the GEHP case The top graph in Fig.31 5 August shows 2006. a comparisonOxides OH of Sensor was observed (GTHOS) measured and from witheled modeled the the OH concentration top Ground-based radical of of for Tropospheric OHtwice the Hydrogen from Moody as the Tower much GEH (Mao OHhours case et from and is al., about the similar 2010). 7 GEHP % to Mod- more case the OH as G around compared case, noon. to while To GEH assess there OH is case sources during the morning IRR analysis which in turn directly a between HONO values measured atis the 0.68. low path However, when and dataNO those points simulated with with wrong GEH NO case coe 3.2 Impact of HONO on HO as uncertainties in emission inventorymatches or can mixing layer be height, related in tothe some predictions night cases of these of mis- 1 meteorological September parameters.predicts the strong For measurements southerly example, indicate on winds, calm causingof conditions, lower while measurements. modeled the concentrations model On at the 6 location September the model fails to predict precipitation correctly under predictions of HONO. There may be several reasons for NO those times. In contrast, NO be explained by upwardgraph transport in of Fig. 9). HONO (see discussion in Sect.data. 3.2 For and example, bottom HONOunder is predicted over during predicted the by night theSince of model NO 5–6 September on and 1 morning andHONO of 4 can 7 be September, and linked and 8 to September. theof mismatch measured of NO NO trations on 1 and 4 September resulted in over prediction of HONO concentrations at titudes. Addition of100 photolytic ppt HONO higher sources daytime in HONOthe the GEH concentrations case at GEHP and the case anper low average resulted daytime DOAS DOAS in increase levels, level of average respectively. as 50by and Since compared NO 30 most to ppt of at the the middle photolytic and HONO up- production occurs responding to the second and thirdwhich layer, falls and into the upper model light-path layersand between three simulated 130–300 m, HONO to values. five. Whilewith Figure daytime 3 altitude, measurements shows HONO do a not mixingwith comparison show ratios maxima dependence of at measured reaching night aboutContrary and 2 to ppbv early the at morning measured thevariation decrease values, with low with height HONO while level altitude, mixing HONO and values ratioscapture obtained 0.5 from the from ppbv GEH trend the at and towards GEHP G the lower cases nighttime case correctly upper and do level. early not morning show mixing ratios at higher al- ary layer observational HONOtroscopy data (DOAS) detected were utilized. by These Di between measurements the were Moody taken Tower along super di low site and light-path Downtown detected Houston (Stutz mixingthe et first ratios al., and 2010). between second The 20–70 CMAQ m model height layer, the which middle corresponds light-path to between 70–130 m cor- 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 | x x HONO), about , HCHO, HONO 3 LOSS formation in GEHP case 3 erences in ozone between contributes 7 % by directly ff erences for the GEHP case ∗ 2 budget. The results from the ff analysis is performed for that formation rates in the morning x x x HONO) that contributes 77 % to nighttime 5862 5861 formation and NO x , and alkenes to the HO ∗ 2 ) both radicals were considered in the analysis as HO 2 HONO) contributes the most to an increase in HONO mixing erences in ozone concentration among the simulated cases the ff in the morning. In our model analysis the morning contribution of ). Since the simulated HONO values for 31 August are well corre- x PROD 2 formation rates in Houston became dominant (81 %) when HONO emis- x HO + OH HONO) during nighttime and early morning. The accumulation of HONO formed = x Even though about a tenfold increase in HONO concentration related to its hetero- Figure 7 shows comparison of observed and simulated ozone concentrations at the IRR analysis was also employed to assess HONO contribution to radical produc- layer is through upward transport (VTRAN 20 % is depositedGEH to case, the 71 % ground, of(HET and HONO 20 production % is removed causedby by by heterogeneous transport heterogeneous chemistry surface processes. chemistry andconcentration that In emitted occurs the during around 06:00 nighttimeto a.m. CST leads the (which G to is case). 3–4 the hcontribution earlier At from peak in emissions that HONO comparison increases time to 50 directcontributes %, 31 HONO while % heterogeneous emissions and and contribute 19 gas %, 27 formation %. respectively. The During main daytime removal of HONO from the surface most of the HONOmodel sources layer occur (0–34 m on a.g.l.); horizontallycell the data corresponding surface was to this averaged the analysis inchemistry location is 25 (GAS of cells confined the with to Moody the the middle Tower. first In the G case, the gas-phase geneous formation and emissions was3) simulated as with compared the to GEHsights the case into G (see sources case, Figs. and 1 theresults losses and impact of of of HONO the it theFig. process on process analysis ozone 9. analysis was for (PA) small. was theted Processes utilized. with G, To that get positive The GEH, more contribute values, andare in- and to shown GEHP those with an cases contributing negative increasesents are to values. change presented in a Note in decrease in HONO that HONO in mixing the mixing HONO ratio rate ratios mixing between of are ratio that change hour plot- at and a the given previous hour hour. repre- Since tion with OH during daytime (indicated in the graph as CHEM HONO concentrations, while atare the around 8 same ppbv. time In theand ozone afternoon di are ozone changes confined in to the11 ppbv GEH a in case smaller comparison reach to only area, the 2 ppbv while G case. in the GEHP case ozone increased up to ratio; about 60 % of produced HONO is consumed by means of photolysis and reac- case reached 3 ppbv at 09:00 a.m. CST on 31 August 2006, a day with very high at 09:00 a.m. CST (top) and 01:00 p.m. CST (bottom). Ozone increase from the GEH three DOAS levels for simulated timehard period to of distinguish 25 di August–21insert September in 2006. Fig. As 7 shows it details is to for the simulations DOAS with low path gas level phase ononly 31 HONO slightly August chemistry 2006. increases ozone Compared in concentrationmorning the in morning, ozone the but GEH formation increases case accounted for by for about about in 7 the 1–2 ppbv h GEHP andthe case. when accelerates GEH Figure and photo-induced 8 G shows HONO spatial cases di production (left) and is for the GEHP and G case (right) for 31 August 2006, sions and heterogeneous chemistrycase is HONO taken contributes into 83 accountforming % (GEH OH to radical. case). HO The Inthe day, GEHP especially the between case GEHP 09:00 also a.m.is and resulted noon 52 in % CST higher when (20 % HONO contributions contribution higher throughout to than HO contribution from GEH case at that time). lated with measured dataday. (see Figs. Figure 1 6 and(from illustrates 3), photolysis the the reaction), diurnal HO NO variationsG case of show contributions that of the(06:00–09:00 contribution O a.m. of CST) HONO is toample, 45 the %, Mao HO which et is al. lowcontributor in (2010) to comparison demonstrated HO to that other inHONO studies. to the HO For Houston ex- area HONO is the major (see Figs. 7 and 8) but also is reflected intion higher relative OH mixing to ratios. the other hydroperoxyl radical radical (HO sources.(HO Due to the fast chemistry between OH and increase. The additional OH reacted leading to additional O 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 | 2 2 2 HONO). Al- ∗ 2 NO (hv 2 modeling directly influence HONO HONO) immediately after sunrise is 2 LOSS cient for HONO formation from excited NO ffi 5864 5863 were examined. Accounting for additional HONO 3 and O x ects the HONO morning peak concentration but only slightly HONO) and formation from excited NO ff ecting its peak concentration. ff SF cient, this paper demonstrates that photochemical HONO formation can ffi erent sources on HO mixing ratios in the GEHP case (see Figs. 5, 7, and 8). ff 3 hydrolysis greatly a (up to 3 ppbv ozone increase). The implementation of additional photo-dependent 2 Although daytime HONO formation mechanisms may not be understood in all de- Heterogeneous HONO production is a major source of HONO during nighttime lead- 3 tails and the implementationsimplifications, for of example it the touptake estimation coe the of reactive model surfaces isbe or a based uncertainties strong on in source of the manyozone concentrations daytime assumptions while HONO nighttime and and that early directlyNO morning impacts HONO production OH by mixing means ratios of increases and hydroxyl peak radical and ozone concentrations. shows that actually muchresulted more in HONO doubled was morningup produced production to but of 11 ppbv. quickly hydroxyl radical In dissociated,morning contrast and ozone which formation, to an inclusion heterogeneous ozone of HONOthroughout HONO increase formation photochemical the of sources day, that a influences mainly ozone accelerates ing to HONO accumulation and earlyHONO morning dissociation peak concentration at of that up time toheterogeneous is 2 less ppbv. HONO Since important than production depositionO and only vertical slightly transport, increasesHONO concentrations sources, in of particular OH HONOon formation and surfaces from the covered photo-induced with reactionan of humic increase NO acid in and HONO similar mixing ratios organic of materials, at only most resulted 0.5 in ppbv. However, process analysis 3-D chemistry transport model suchvertically as resolved CMAQ HONO could be measurementscapture successfully during correctly validated against a day trend andis of nighttime, decreasing a and HONO precursor was concentration of withpredictions. able altitude. to HONO Since the NO mismatches in NO improved correlation between modeled and measured values. Also, for the first time a production (e.g. heterogeneous HONOtion formation) resulted in as about compared a to tenfold gas-phase increase forma- in the morning HONO concentrations causing and O 4 Conclusions CMAQ simulations of HONOand that compared included with several MC/IC sources measured ofments values at HONO at three were the altitudes. performed Moody In Towerof addition, and its source DOAS di and measure- losses for HONO as well as the impact vertical transport and chemicalmixing reactions ratios. leading HONO to chemical a lossmore net (CHEM significant decrease in in daytime thephoto-dissociates HONO GEHP in case than the the GEHPpared GEH to case case. the producing GEH About twice case. twice As as as previously much shown, much OH this HONO additional and OH NO resulted in as higher com- OH concentration. There aretion two in additional the pathways GEHPorganic of case, material these photochemical (hv are HONOthough photochemical produc- we formation used on the surfaces largestit covered resulted reaction with in coe small amountthat of from HONO gas produced phase by chemistry, this beingmechanisms. pathway, negligible which compared is The with even other photochemical less HONO than formationof production on 61 % the to surfaces HONO has production a during major daytime. contribution This production is overtaken mainly by and 12 % of HONO duringreacts nighttime to and form daytime, OH. respectively. Although 24 dryremoval % processes deposition of during and daytime nighttime, vertical HONO the transportincrease production are of significant of HONO HONO HONO is higher concentrationtochemical leading that to reactions a result add net in to the the morning removal peak. of HONO After resulting sunrise in pho- a decrease of HONO and 65 % to daytime reduction in HONO concentration. Dry deposition removes 23 % 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 | , , 2000. ¨ STR, 122 pp., afer, J., Stutz, + O, Chem. Phys. beyond the Dis- , 2010. 2 2 , 2002. , 2003. formation in the Hous- 3 , 2007. ¨ doi:10.1029/2005GL022524 atz, H. W., Sch in Houston, Texas, J. Geophys. 3 simcarter/bycarter.htm \ in the presence of H 2 , 2011. , 2004. doi:10.5194/gmd-3-205-2010 , 1994. doi:10.1029/2000JD000075 , 2010. doi:10.1029/2001JD000579 5866 5865 O”, Science, 324, 336, 2009. , 2003. 2 doi:10.1002/cphc.200700016 er, D. R.: A description of the Fifth-Generation Penn ff mann, J., Stemmler, K., and Ammann, M.: Photoenhanced http://pah.cert.ucr.edu/ and H ff 2 in laboratory systems and in outdoor and indoor atmospheres: 2 , 2000. on solid organic compounds: a photochemical source of HONO?, 2 doi:10.1029/2003JD004141 The authors would like to thank the Houston Advanced Research Center doi:10.1016/j.cplett.2011.07.062 http://www.mmm.ucar.edu/mm5/ doi:10.5194/acp-10-1171-2010 doi:10.1029/2003JD003552 on air pollution in the South Coast Air Basin of California, Atmos. Chem. Phys., 10, 2 mann, J.: Daytime Sources of Nitrous Acid (HONO)mann, in the J., Atmospheric Gavriloaiei, Boundary Layer, T., Hofzumahaus, A., Holland, F., Koppmann, R., Rupp, L., ff ff vehicle exhaust, Environ. Sci. Technol., 30, 2843–2849, 1996. Chem. Phys. Chem., 8, 1137–1144, Schlosser, E., Siese, M., andof Wahner, A.: OH Daytime radicals formation of in nitrous a acid: forest, A major Geophys. source Res. Lett., 32, L05818, System: SMOKE User Manual, MCNC-Northhttp://www.cmascenter.org/ Carolina Supercomputing Center, available at: uptake of gaseous NO Faraday Discuss., 130, 195–210, 2005. State/NCAR Mesoscale Model (MM5), NCARavailable Technical Note, at: NCAR/TN-398 NO 1171–1181, Sarwar, G., Young, J. O.,J. Gilliam, O.: R. Incremental C., testing of Nolte,version the C. 4.7, Community G., Geosci. Multiscale Model Kelly, Air J. Dev., Quality 3, T., (CMAQ) 205–226, Gilliland, modeling A. system B., and Bash, erogeneous hydrolysis of NO and integrated mechanism, Phys. Chem. Chem. Phys., 5, 223–242, 2003. assessment, Final Report to308, Riverside, the CA, California available Air at: Resources Board, Contracts 92-32 and 95- Lloyd, J., Zheng, J., andton Berkowitz, urban C. M.: and industrial A108, plumes comparative study 4715, during of the O 2000 Texas Air Quality Study, J. Geophys. Res., from Electronically Excited NO Compounds, Atmos. Environ., 24, 481–518, 1990. atmospheric modeling in the Houston-Galvestonsimulation metropolitan results, Atmos. area Environ., – 42, Part 7795–7811, 1: 2008. Meteorological sociation Threshold in the1997. Presence of Water Vapor, J. Phys. Chem. A, 101, 4178–4184, rological characteristic associated with rapidRes., increases 109, of D10307, O and Other Components of theSystem, Models-3 Appl. Community Multiscale Mech. Air Rev., 59, Quality 51–77, (CMAQ) Modeling 2006. cal budget during thestudy limitation I of Milan, oxidant J. production/Pianura Geophys. Padana Res., Produzione 107, di 8196, Ozono J., Volz-Thomas, A., and Platt,experiment, J. U.: Geophys. OH Res., 108, formation 8247, by HONO photolysis duringradicals the after BERLIOZ 565 nmLett., multi-photon 513, excitation 12–16, of NO Kle Kle Kirchstetter, T. W., Harley, R. A., and Littlejohn, D.: Measurements of nitrous acid in motor Houyoux, M., Vukovich, J., and Brandmeyer, J.: Sparse Matrix Kernel Emissions Modeling Grell, G. A., Dudhia, J., and Stau George, C., Sterkowski, R. S., Kle Ensberg, J. J., Carreras-Sospedra, M., and Dabdub, D.: Impacts of electronically photo-excited Foley, K. M., Roselle, S. J., Appel, K. W., Bhave, P. V., Pleim, J. E., Otte, T. L., Mathur, R., Finlayson-Pitts, B. J., Wingen, L. M., Sumner, A. L., Syomin, D., and Ramazan, K. A.: The het- Carter, W. P. L.: Documentation of the SAPRC-99 chemical mechanism for VOC reactivity Daum, P. H., Kleinman, L. I., Springston, S. R., Nunnermacker, L. J., Lee, Y.-N., Weinstein- Carter, W. P. L.: A Detailed Mechanism for the Gas-Phase Atmospheric Reactions of Organic Carr, S., Heard, D. E., and Blitz, M. A.: Comment on “Atmospheric Hydroxyl Radical Production Cheng, F.-Y. and Byun, D. W.: Application of high resolution land use and land cover data for Crowley, J. N. and Carl, S. A.: OH Formation in the Photoexcitation of NO Berkowitz, C. M., Jobson, T., Jiang, G., Spicer, C. W., and Doskey, P. V.: Chemical and meteo- Byun, D. and Schere, K. L.: Review of the Governing Equations, Computational Algorithms, Alicke, B., Platt, U., and Stutz, J.: Impact of nitrous acid photolysis on the total hydroxyl radi- (HARC) for support.data Observational provided DOAS by data Jack Dibb, provided UNH. by OH data Jochen provided Stutz, by UCLA Bill Brune, and Penn MC/IC StateReferences University. Alicke, B., Geyer, A., Hofzumahaus, A., Holland, F., Konrad, S., P Amedro, D., Parker, A. E., Schoemaecker, C., and Fittschen, C.: Direct observation of OH Acknowledgements. 5 5 30 25 20 15 10 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | mann, ff , 2007. , 2008. , 2010. ¨ uck, B., and , 2005. , 2010. , 2010. , 2009. conversion processes on O”, Science, 324, 336, 2 2 , 2003. mann, J., Stemmler, K., and ff ¨ orzer, J. C., Spittler, M., Wiesen, , in press, 2012. and H 2 doi:10.5194/acp-7-4237-2007 doi:10.1029/2007GL032006 doi:10.5194/acp-10-6551-2010 mann, J., L ff doi:10.5194/acp-5-2189-2005 on mineral dust: Laboratory experiments and mann, J., and George, C.: Photosensitizied ff 2 ¨ uck, B., and Stutz, J.: Vertical profiles of nitrous mann, J., D’Anna, B., George, C., Bohn, B., and ff 5868 5867 doi:10.1029/2007JD009060 environments: significant atmospheric implications, x , 2002. doi:10.1016/j.atmosenv.2009.02.003 , 2011. ¨ uning, D., Johnen, F.-J., Wahner, A., and Kle doi:10.1029/2003GL018620 c tunnel, Atmos. Environ., 35, 3385–3394, 2001. doi:10.1016/j.atmosenv.2009.01.013 ffi , 2009. , 2008. M) and the determination of the UV absorption cross section of O, Science, 319, 1657–1660, 2008. + 2 doi:10.1016/j.atmosenv.2012.01.035 and H HONO( 2 → M) doi:10.1029/2002GL015080 + doi:10.5194/acp-11-3595-2011 ¨ NO( uck, B., Flynn, J., and Leuchner, M.: Atmospheric Oxidation Capacity in the Summer + mann, J., Becker, K. H., and Wiesen, P.: Heterogeneous NO ff chemical production of nitrous acid29, on 1681, glass sample manifold surfaces, Geophys. Res. Lett., acid photolysis on surfacesGeophys. in Res. low-NO Lett., 30, 23, 2217, R., McQueen, J., and Lee, P.:TexAQS Analysis II of field regional meteorology program andmodels, and surface J. ozone an Geophys. during evaluation Res., the 114, of D00F14, the NMM-CMAQ andacid WRF-Chem air in quality the nocturnal3609, urban atmosphere of Houston, TX, Atmos. Chem. Phys., 11, 3595– 2008. Lefer, B.: Simultaneous DOASTX, and Atmos. Mist-Chamber Environ., IC 44, 4090–4098, measurements of HONO in Houston, doi:10.1029/2007JD009060 Y. H., andWiedensohler,site A.: during the Nitrous 2004 acid PRIDE-PRD experiment (HONO) in and China, its J. daytime Geophys. Res., sources 113, at D14312, a rural reduction of nitrogen dioxide198, on 2006. humic acid as a source ofAmmann, nitrous M.: acid, Light induced Nature, conversion 440,mic of nitrogen acid 195– dioxide aerosol, into Atmos. nitrous Chem. acid Phys., on 7, submicron 4237–4248, hu- Ammann, M.: Photoenhanced uptakemodel of simulations, NO Geophys. Res. Lett., 35, L05812, CMAQ HONO predictions with observationsAtmos. from Environ., 42, the 5760–5770, Northeast 2008. Oxidant and Particle Study, cally Excited NO Radical Productiondoi:10.1126/science.1166877 from Electronically Excited NO pengl of Houston 2006: ComparisonAtmos. with Environ., 44, Summer 4107–4115, Measurements in Other Metropolitan Studies, George, C.: Light changes the6609, atmospheric 2010. reactivity of soot, P. Natl. Acad. Sci., 107, 6605– ment of Retrospective Meteorological Inputs2006, for Atmos. Environ., Use in Air Quality Modeling during TexAQS OH HONO, Chem. Phys. Lett., 272, 383–390, 1997. J.: Characterisation of theSAPHIR, photolytic Atmos. Chem. HONO-source Phys., in 5, the 2189–2201, atmosphere simulation chamber 361–39, 1996. of HONO sources onCampaign, Atmos. the Chem. photochemistry Phys., 10, in 6551–6567, Mexico City during the MCMA-2006/MILAGO P., Ackermann, R., Geyer, A.,formation and of Platt, HONO U.: in Investigations a of road emissions tra and heterogeneous 2005. acid surfaces: possible atmospheric implications, Atmos. Environ., 32, 2721–2729, 1998. Zhou, X. L., He, Y., Huang, G., Thornberry, T. D., Carroll, M. A., and Bertman, S. B.: Photo- Zhou, X. L., Gao, H. L., He, Y., Huang, G., Bertman, S. B., Civerolo, K., and Schwab, J.: Nitric Wong, K. W., Oh, H.-J., Lefer, B. L., Rappengl Wilczak, J. M., Djalalova, I., McKeen, S., Bianco, L., Bao, J.-W., Grell, G., Peckham, S., Mathur, Wennberg, P. O. and Dabdub, D.: Rethinking Ozone Production, Science, 319, 1624–1625, Stutz, J., Oh, H.-J., Whitlow, S. I., Anderson, C. H., Dibb, J. E., Flynn, J., Rappengl Su, H., Cheng, Y. F., Shao, M., Gao, D. F., Yu, Z. Y., Zeng, L. M., Slanina, J., Zhang, Stemmler, K., Ndour, M., Elshorbany, Y., Kle Stemmler, K., Ammann, M., Donders, C., Kle Ndour, M., D’Anna, B., George, C., Ka, O., Balkanski, Y., Kle Rohrer, F., Bohn, B., Brauers, T., Br Sarwar, G., Roselle, S. J., Mathur, R., Appel, W., Dennis, R. L., and Vogel, B.: A comparison of Mao, J., Ren, X., Chen, S., Brune, W. H., Chen, Z., Martinez, M., Harder, H., Lefer, B., Rap- Ngan, F., Byun, D. W., Kim, H. C., Rappenglueck, B., and Pour-Biazar, A.: Performance Assess- Li, S., Matthews, J., and Sinha, A.: Response to Comment on “Atmospheric Hydroxyl Monge, M. E., D’Anna, B., Mazri, L., Giroir-Fendler, A., Ammann, M., Donaldson, D. J., and Pagsberg, P.,Bjergbakke, E., Ratajczak, E., and Sillesen, A.: Kinetics of the gas phase reaction Li, S., Matthews, J., and Sinha, A.: Atmospheric Hydroxyl Radical Production from Electroni- Li, G., Lei, W., Zavala, M., Volkamer, R., Dusanter, S., Stevens, P., and Molina, L. T.: Impacts Lammel, G. and Cape, J. N.: Nitrous acid and nitrate in the atmosphere, Chem. Soc. Rev., 25, Kurtenbach, R., Becker, K. H., Gomes, J. A. G., Kle Kle 5 5 30 25 20 15 10 25 15 30 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper |

5870 5869 , 2010. n, R. J., Anderson, C. H., Whitlow, S. I., Lefer, B. L., ﬃ ¨ uck, B., and Flynn, J.: Heterogeneous conversion of nitric acid to nitrous acid Comparison of measured vs. simulated HONO time series at the UH Moody Tower for doi:10.1016/j.atmosenv.2008.12.024 Rappengl on the surface of primary organic aerosol in an urban atmosphere, Atmos. Environ., Fig. 1. the time period 25situ August–21 September by a 2006. MC/IC Dots system,and represent the GEHP measured solid cases values lines (explanation obtained represent see CMAQ in- text). predicted Dashed concentration vertical from lines G, indicate GEH, midnight times. Ziemba, L. D., Dibb, J. E., Gri Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper |

9/20 9/20 9/20 9/19 9/19 9/19 9/18 9/18 9/18 9/17 9/17 9/17 9/16 9/16 9/16

9/15 9/15 9/15 9/14 9/14 9/14 9/13 9/13 9/13 9/12 9/12 9/12 9/11 9/11 9/11 9/10 9/10 9/10 (bottom) based on data for 25 August– 9/9 9/9 9/9 2 9/8 9/8 9/8 CST CST CST 9/7 9/7 9/7 9/6 9/6 9/6 5872 5871 9/5 9/5 9/5 9/4 9/4 9/4 9/3 9/3 9/3 9/2 9/2 9/2 9/1 9/1 9/1 8/31 8/31 8/31 8/30 8/30 8/30 8/29 8/29 8/29 path (70-130m) path (130-300m) 8/28 8/28 8/28 path (20-70m) upper middle low 8/27 8/27 8/27 GEHP DOAS G GEH DOAS G GEH GEHP 8/26 8/26 8/26 DOAS G GEH GEHP Time series comparison of HONO measured from the Moody Tower by DOAS low 8/25 8/25 8/25 Average diurnal variation of HONO (top) and NO

0.5 0.0 2.0 1.5 1.0 0.5 0.0 2.0 1.5 1.0 2.0 1.5 1.0 0.5 0.0

HONO [ppbv] HONO HONO [ppbv] HONO [ppbv] HONO Fig. 3. light-path (top graph), middlesimulated mixing light ratios path for 25 (middle August–20 graph), September 2006. and upper path (bottom graph) with 21 September 2006. Fig. 2. Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper |

9/20 9/20 9/20 9/19 9/19 9/19

9/18 9/18 9/18

9/17 9/17 9/17

9/16 9/16 9/16 8:00 PM 9/15 9/15 9/15 8:00 PM 9/14 9/14 9/14 HONO. 6:00 PM + 9/13 9/13 9/13 6:00 PM 9/12 9/12 9/12 OH → 9/11 9/11 9/11 4:00 PM O 4:00 PM 2 9/10 9/10 9/10 H 9/9 9/9 9/9 + ∗ 2 9/8 9/8 9/8 2:00 PM 2:00 PM CST CST CST 9/7 9/7 9/7 CST CST

9/6 9/6 9/6 5874 5873 12:00 PM 9/5 9/5 9/5 12:00 PM NO and NO measured from the Moody Tower by DOAS low light- 2 9/4 9/4 9/4 + 9/3 9/3 9/3 OH 10:00 AM 10:00 AM 9/2 9/2 9/2 → 9/1 9/1 9/1 hv 8:00 AM observed G GEH GEHP + 8/31 8/31 8/31 8:00 AM observed G GEH GEHP 8/30 8/30 8/30 6:00 AM 8/31/2006 8/29 8/29 8/29 path (130-300m) 1.0 0.8 0.6 0.4 0.2 0.0 path (70-130m)

path (20-70m) OH [pptv] OH 6:00 AM 8/28 8/28 8/28 8/31/2006 upper low 0.8 0.6 0.4 0.2 0.0 1.0 middle

8/27 8/27 8/27 OH [pptv] OH DOAS GEHP DOAS GEHP DOAS GEHP 8/26 8/26 8/26 Time series comparison of NO Top: time series of observed and simulated OH mixing ratios. Bottom: OH production 8/25 8/25 8/25 0 0 0

20 10 70 60 50 40 30 20 10 70 60 50 40 30 70 60 50 40 30 20 10

2 2 2 [ppbv] NO [ppbv] NO [ppbv] NO from the reaction of HONO Fig. 5. Fig. 4. path (top graph), middle light pathmixing (middle ratios graph), and for upper 25 path August– (bottom 20 graph) September with simulated 2006. Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper |

, ∗ 2

data on that day. 3

, HCHO, HONO (from photolysis reaction), NO 3 5876 5875 measured from the Moody Tower by DOAS low light-path 3 budget for the G case (top), GEH case (middle), and GEHP case x Time series comparison of O Diurnal variations of contributions of O

(top graph), middle lightmixing path ratios (middle for 25 graph),2006, August–20 displaying and all September upper the 2006. path three model (bottom The simulations graph) vs. insert the with shows observed simulated a O blow-up for 31 August Fig. 7. (bottom). and alkenes to the HO Fig. 6. Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper |

HONO HONO is ∗ 2 erent in the ﬀ NO erent processes to ﬀ for G case (top), GEH case (mid- 1 − HONO – horizontal transport, DDEP

NO reaction producing HONO, hv 5878 5877 + HONO – is photochemical production of HONO on SF , hv HONO – loss of HONO by gas phase chemical reactions, 2 LOSS

HONO represents OH HONO represents change in HONO mixing ratio due to heterogeneous chem- PROD HONO – vertical transport, HTRAN erences in ozone simulations between GEH-G case (left) and GEHP-G case (right) ﬀ HONO mixing ratio (black line) in ppbv and contribution of di Di HONO – emissions. EMIS – dry deposition, CHEM surfaces, HET istry, VTRAN graphs. GAS HONO formed from excited NO Fig. 9. changes in HONOdle), mixing and ratios GEHP case (columns) (bottom) in in ppbv the h ﬁrst model layer. Note that the scale is di Fig. 8. for 31 August, 2006 at 00:09 a.m. CST (top) and 01:00 p.m. CST (bottom).

5880 5879 Continued. Continued. Fig. 9. Fig. 9.