The Role of Nighttime Chemistry inThe Role of Nighttime Chemistry inWinter Ammonium Nitrate FormationWinter Ammonium Nitrate Formationin the San Joaquin Valleyin the San Joaquin ValleyMichael McCarthyMichael McCarthySteve BrownSteve BrownFred LurmannFred LurmannPaul RobertsPaul RobertsSonoma Technology, Inc.Sonoma Technology, Inc.Petaluma, CAPetaluma, CAAAAR Specialty ConferenceAAAR Specialty ConferenceFebruary 10, 2005February 10, 2005Atlanta, GAAtlanta, GA902331-fwlObjectivesObjectivesAs part of a larger study examining wintertimeAs part of a larger study examining wintertimePM in the SJV, CRPAQS gas and aerosolPM in the SJV, CRPAQS gas and aerosoldata were used to address two questions:data were used to address two questions:What precursors limit ammonium nitrate formation?What precursors limit ammonium nitrate formation?NH3 or HNO3?NH3 or HNO3?Which nitric acid formation pathways are important?Which nitric acid formation pathways are important?Daytime or Nighttime or Both?Daytime or Nighttime or Both?CRPAQS = California RegionalPM10/PM2.5 Air Quality StudyCRPAQS - 5 Core SitesCRPAQS - 5 Core SitesAverage Distribution ofPM2.5 Chemical ComponentsAverage Distribution ofPM2.5 Chemical Componentsat the Five Core CRPAQS Sites in Winterat the Five Core CRPAQS Sites in Winter(15 IOP days in Dec 2000 – Feb 2001)(15 IOP days in Dec 2000 – Feb 2001)010203040506070BethelIslandFresno Bakersfield Angiola SierraNevada

Concentratoin (ug/m3)ECOCMSO4NH4NO3OtherBased on 3-hr to 8-hr samples fromDRI’s Sequential Filter SamplerOCM = 1.4 x OC15-day Average Phase Distribution of NO15-day Average Phase Distribution of NOx-Related Species-Related SpeciesCRPAQS Winter 2000/2001 IOP DaysCRPAQS Winter 2000/2001 IOP Days01020304050607080Bethel Island Fresno Bakersfield Angiola Sierra NevadaLocation

Concentration (ugm-N/m3)PM25 NO3HNO3NO2 &Other NOyNOHNO3data were not available atBethel Island and BakersfieldRegional Buildup ofRegional Buildup ofPM2.5 NO3 inPM2.5 NO3 inSan Joaquin ValleySan Joaquin ValleyDec 14 - Jan 7 atDec 14 - Jan 7 atCRPAQS sitesCRPAQS sitesComparison of Ammonia and Nitric AcidComparison of Ammonia and Nitric Acid-100102030405060-2 0 2 4 6 8 10 12 14 16 18HNO3 Concentration (ug-N/m3)

NH3 Concentration (ug-N/m3)1:1 Line-4048121620-2 0 2 4 6 8HNO3 Concentration (ug-N/m3)

NH3 Concentration (ug-N/m3)1:1 LineAngiolaFresnoNH3 + HNO3NH3 + HNO3?NH4NO3HNO3 is limiting becauseHNO3 is limiting becauseHNO3 << NH3HNO3 << NH3Comparison of Ammonia and Nitric AcidComparison of Ammonia and Nitric Acidat a Low Ammonia Siteat a Low Ammonia SiteSierra NevadaFoothillsHNO3 is still the limiting speciesHNO3 is still the limiting species-10123456-1 0 1 2 3HNO3 Concentration (ug-N/m3)

NH3 Concentration (ug-N/m3)1:1 LineNitric Acid Formation PathwaysNitric Acid Formation PathwaysDaytime Formation:Daytime Formation:NO2 + OHNO2 + OHÆHNO3Nighttime Formation:Nighttime Formation:NO2 + O3NO2 + O3ÆNO3+ O2NO2 +NO3+ MÆN2O5 + MN2O5 + MN2O5 + H2ON2O5 + H2OÆ2HNO3NO3+ RÆHNO3+ organic products+ organic productsInhibiting Reactions:Inhibiting Reactions:NO3+ hνÆNO + O2NO + O2SunlightSunlightNO3+ hνÆNO2 + ONO2 + ONO3+ NOÆ2 NO2Fresh EmissionsFresh EmissionsNO3+ NO2ÆNO + NO2 + O2NO + NO2 + O2N2O5ÆNO2 +NO3Warm TemperatureWarm TemperatureNO3+ RÆNO2 or RNO3Certain OrganicsNO2 or RNO3Certain Organics15-day Average PM2.5 Nitrate15-day Average PM2.5 NitrateConcentrations by Sampling PeriodConcentrations by Sampling Period0510152025303540 0-5 5-10 10-13 13-16 16-24 0-5 5-10 10-13 13-16 16-24 0-5 5-10 10-13 13-16 16-24 0-5 5-10 10-13 13-16 16-24 0-5 5-10 10-13 13-16 16-24Bethel Island Fresno Bakersfield Angiola Sierra NevadaTime Period (PST) and Location

C oncentration ( u g /m 3 )Daytime HNO3 ProductionDaytime HNO3 Production•Within the 5 diurnal sampling periods, the highestWithin the 5 diurnal sampling periods, the highestPM2.5 nitrate levels occurred atPM2.5 nitrate levels occurred at•1000-1300 PST in Fresno and Bakersfield1000-1300 PST in Fresno and Bakersfield•1300-1600 PST in Angiola, Sierra Nevada Foothills, and1300-1600 PST in Angiola, Sierra Nevada Foothills, andBethel IslandBethel Island•The peaks in ozone concentrations, the key indicatorThe peaks in ozone concentrations, the key indicatorof photochemical activity, occur from 1200-1500 PSTof photochemical activity, occur from 1200-1500 PSTat most SJV sites in winterat most SJV sites in winter•The diurnal pattern of aerosol nitrate concentrationsThe diurnal pattern of aerosol nitrate concentrationsin the SJV suggests the daytime nitric acid formationin the SJV suggests the daytime nitric acid formationis occurring in the regionis occurring in the regionFresnoHourly Concentrations of NO, O3, and PM2.5 NO3Hourly Concentrations of NO, O3, and PM2.5 NO3Dec 28 Dec 29 Dec 30 Dec 3105101520253035400 3 6 9 12 15 18 21 0 3 6 9 12 15 18 21 0 3 6 9 12 15 18 21 0 3 6 9 12 15 18 21

NO3 (ug/m3) and Ozone (ppb)0100200300400500600 NO Concentration (ppb)NO3OzoneNO9 am9 am10 am11 amFresnoHourly Concentrations of NO, O3, and PM2.5 NO3Hourly Concentrations of NO, O3, and PM2.5 NO30510152025303540450 3 6 9 12 15 18 21 0 3 6 9 12 15 18 21 0 3 6 9 12 15 18 21

NO3 (ug/m3) and Ozone (ppb)0100200300400500600 NO Concentration (ppb)NO3OzoneNO9 am9 am9 amFeb 1 Feb 2 Feb 3Angiola Tower - 90 m above groundAngiola Tower - 90 m above groundHourly concentrations of NO, O3, and PM2.5 nitrateHourly concentrations of NO, O3, and PM2.5 nitrate0510152025 12 15 18 21 0 3 6 9 12 15 18 21 0 3 6 9 12 15 18 21 0 3 6 9 12 15 18 21 0 3 6 912/27/2000 12/28/2000 12/29/2000 12/30/2000 12/31/2000Time (PST) and Date

NO3 Concentration (ug/m3)020406080100 NO and Ozone Concentratoin (ppb)NO3OzoneNONightNightNightNightAngiola Tower - 90 m above groundAngiola Tower - 90 m above groundHourly concentrations of NO, O3, and PM2.5 nitrateHourly concentrations of NO, O3, and PM2.5 nitrate0510152025 12 15 18 21 0 3 6 9 12 15 18 21 0 3 6 9 12 15 18 21 0 3 6 9 12 15 18 21 0 3 6 91/31/2001 2/1/2001 2/2/2001 2/3/2001 2/4/2001Time (PST) and Date

NO3 Concentration (ug/m3)020406080100 NO and Ozone Concentratoin (ppb)NO3OzoneNONightNightNightNightAngiola Tower NO and Ozone – Dec & JanAngiola Tower NO and Ozone – Dec & Jan

- 1 0 1 2 3 4 5 6 7 8 9 1 0 1 1 1 2 1 3 1 4 1 5 1 6 1 7 1 8 1 9 2 0 2 1 2 2 2 3 2 4HOUR01020304050607080

7 m N O p p b - 1 0 1 2 3 4 5 6 7 8 9 1 0 1 1 1 2 1 3 1 4 1 5 1 6 1 7 1 8 1 9 2 0 2 1 2 2 2 3 2 4HOUR01020304050607080

7 m N O p p b - 1 0 1 2 3 4 5 6 7 8 9 1 0 1 1 1 2 1 3 1 4 1 5 1 6 1 7 1 8 1 9 2 0 2 1 2 2 2 3 2 4HOUR010203040506070

9 0 m O 3 p p b - 1 0 1 2 3 4 5 6 7 8 9 1 0 1 1 1 2 1 3 1 4 1 5 1 6 1 7 1 8 1 9 2 0 2 1 2 2 2 3 2 4HOUR010203040506070

9 0 m O 3 p p b - 1 0 1 2 3 4 5 6 7 8 9 1 0 1 1 1 2 1 3 1 4 1 5 1 6 1 7 1 8 1 9 2 0 2 1 2 2 2 3 2 4HOUR010203040506070

7 m O 3 p p b - 1 0 1 2 3 4 5 6 7 8 9 1 0 1 1 1 2 1 3 1 4 1 5 1 6 1 7 1 8 1 9 2 0 2 1 2 2 2 3 2 4HOUR010203040506070

7 m O 3 p p b

- 1 0 1 2 3 4 5 6 7 8 9 1 0 1 1 1 2 1 3 1 4 1 5 1 6 1 7 1 8 1 9 2 0 2 1 2 2 2 3 2 4HOUR0510152025303540

9 0 m N O p p b - 1 0 1 2 3 4 5 6 7 8 9 1 0 1 1 1 2 1 3 1 4 1 5 1 6 1 7 1 8 1 9 2 0 2 1 2 2 2 3 2 4HOUR0510152025303540

9 0 m N O p p bOzone Surface (7m)Ozone Aloft (90m)NO Aloft (90m)NO Surface (7m)NO islowaloft atnightO3 isplentifulaloft atnightAngiola TowerAngiola TowerNOyand PM2.5 NO3and PM2.5 NO3-10123456789101112131415161718192021222324HOUR0102030405060708090

9 0 m N O y p p b-10123456789101112131415161718192021222324HOUR0102030405060708090

9 0 m N O y p p b-10123456789101112131415161718192021222324HOUR05101520253035

9 0 m N O 3 u g / m 3-10123456789101112131415161718192021222324HOUR05101520253035

9 0 m N O 3 u g / m 3-10123456789101112131415161718192021222324HOUR0102030405060708090

7 m N O y p p b-10123456789101112131415161718192021222324HOUR0102030405060708090

7 m N O y p p bPM2.5 NO3 Surface (7m)PM2.5 NO3 Aloft (90m)NOy Aloft (90m)NOy Surface (7m)-10123456789101112131415161718192021222324HOUR05101520253035

7 m N O 3 u g / m 3-10123456789101112131415161718192021222324HOUR05101520253035

7 m N O 3 u g / m 3NOy isplentifulaloft atnightRate Limiting FactorsRate Limiting Factors•NOx is abundant in SJV in winterNOx is abundant in SJV in winter•Daytime HNO3 production rates areDaytime HNO3 production rates arelimited by sunlight, VOCs, andlimited by sunlight, VOCs, andbackground ozonebackground ozone•Nighttime HNO3 production is limited byNighttime HNO3 production is limited bybackground ozone which is abundantbackground ozone which is abundantaloft but not at the surfacealoft but not at the surfaceConclusionsConclusions•Particulate NOParticulate NO3concentrations are small relative toconcentrations are small relative togaseous NOgaseous NOyprecursor concentrationsprecursor concentrations•Ammonium nitrate concentrationsare limited by the rate ofAmmonium nitrate concentrationsare limited by the rate ofHNO3formation, rather than bythe availability of NHformation, rather than bythe availability of NH3•HNO3is formed via both daytime photochemistry and aloftis formed via both daytime photochemistry and aloftnighttime chemistrynighttime chemistry•Nighttime chemistry aloft may significantly contribute to theNighttime chemistry aloft may significantly contribute to theregional nature of ammonium nitrate in winter in the SJVregional nature of ammonium nitrate in winter in the SJVAcknowledgementAcknowledgement•Sponsored by San Joaquin Valley AirSponsored by San Joaquin Valley AirPollution Study AgencyPollution Study Agency•Managed by California Air ResourcesManaged by California Air ResourcesBoard staffBoard staffThe EndThe EndPM2.5 nitrate concentrations inFresno and Bakersfield fromPM2.5 nitrate concentrations inFresno and Bakersfield fromJanuary 31 to February 3, 2001January 31 to February 3, 2001010203040500-5 5-10 10-1313-1616-24 0-5 5-10 10-1313-1616-24 0-5 5-10 10-1313-1616-24 0-5 5-10 10-1313-1616-241/31/2001 2/1/2001 2/2/2001 2/3/2001Sampling Period (PST) and Date

Concentration (ug/m3)FresnoBakersfieldPM2.5 nitrate concentrations inSierra Nevada Foothills andPM2.5 nitrate concentrations inSierra Nevada Foothills andAngiola from January 31 to February 3, 2001Angiola from January 31 to February 3, 2001010203040500-5 5-10 10-1313-1616-24 0-5 5-10 10-1313-1616-24 0-5 5-10 10-1313-1616-24 0-5 5-10 10-1313-1616-241/31/2001 2/1/2001 2/2/2001 2/3/2001Sampling Period (PST) and Date

Concentration (ug/m3)Sierra Nevada FoothillsAngiola