nocturnal processing of no , o3 and voc aloft over houston · 2007-06-12 · nocturnal processing...
TRANSCRIPT
![Page 1: Nocturnal Processing of NO , O3 and VOC aloft over Houston · 2007-06-12 · Nocturnal Processing of NO x, O 3 and VOC aloft over Houston NO 2 NO 3 O 3 N 2 O 5 NO 2 Steven S. Brown,](https://reader033.vdocuments.net/reader033/viewer/2022041814/5e59bd3fee41141ea33eed74/html5/thumbnails/1.jpg)
Nocturnal Processing of NOx, O3and VOC aloft over Houston
NO2
NO3
O3
N2O5
NO2
Steven S. Brown, William P. Dubé, Thomas B. Ryerson, Jeff Peischl, Joost A. de Gouw, Carsten Warneke, Eliot Atlas, Charles A. Brock, Adam G. Wollny, Ann M. Middlebrook, Roya
Bahreini, Michael Trainer, A. R. Ravishankara and Frederick C. Fehsenfeld
![Page 2: Nocturnal Processing of NO , O3 and VOC aloft over Houston · 2007-06-12 · Nocturnal Processing of NO x, O 3 and VOC aloft over Houston NO 2 NO 3 O 3 N 2 O 5 NO 2 Steven S. Brown,](https://reader033.vdocuments.net/reader033/viewer/2022041814/5e59bd3fee41141ea33eed74/html5/thumbnails/2.jpg)
NOx
Emission
O3
HNO3
Deposition
NO2
NO
Peroxy AcetylNitrate
CH3C(O)O2NO2
NOhν
Catalytic O3productionhν
O2
OH
O O3
OH, O2
O3hν, Η2Ο
CH3C(O)O2•
RO2VOC
N2O5
NO2
O3
∆
H2O(l)
NitrateRadical
DinitrogenPentoxide
OrganicNitrates
NO3
Het
VOC
PAN
• 50 - 90% of NOxconverted to NO3 + N2O5overnight
• Large fraction of O3 ifemitted NOx to O3 high
• NO3 strong oxidant for reactive VOC (e.g. alkenes)
![Page 3: Nocturnal Processing of NO , O3 and VOC aloft over Houston · 2007-06-12 · Nocturnal Processing of NO x, O 3 and VOC aloft over Houston NO 2 NO 3 O 3 N 2 O 5 NO 2 Steven S. Brown,](https://reader033.vdocuments.net/reader033/viewer/2022041814/5e59bd3fee41141ea33eed74/html5/thumbnails/3.jpg)
NO3 and N2O5 Instrument“ARNOLD” = Airborne Ringdown Nitrogen Oxide Laser Detector
Bill Dubé
532 nm
662 nm
NO3
NO2
NO3 + N2O5
Laser DetectorOptical Cavity
Pulsed Cavity Ring-down Spectroscopy NO2: 532-nm optical extinctionL.O.D. = 0.1 ppbv @ 1 HzAccuracy = 5%
NO3: 662 nm optical extinctionL.O.D = 0.2 - 2 pptv @ 1 HzAccuracy = 20%
N2O5: Thermal conversion + 662 nm optical extinctionL.O.D. = 0.5 - 2 pptv @ 1 HzAccuracy = 20%
Measure first-order decay rate coefficient of light
intensity from an optical cavityτ0 = 307 µs
Leff = 92 km
![Page 4: Nocturnal Processing of NO , O3 and VOC aloft over Houston · 2007-06-12 · Nocturnal Processing of NO x, O 3 and VOC aloft over Houston NO 2 NO 3 O 3 N 2 O 5 NO 2 Steven S. Brown,](https://reader033.vdocuments.net/reader033/viewer/2022041814/5e59bd3fee41141ea33eed74/html5/thumbnails/4.jpg)
1. Nocturnal NOx Loss vs. TransportKey = Stability / Reactivity of N2O5
2. O3 Loss and transportKey = Nocturnal Odd Oxygen (Ox)
3. Nocturnal VOC OxidationKey = Availability of NO3 & Highly Reactive VOC
4. Vertical StratificationDifference between surface and aloft
Outline
![Page 5: Nocturnal Processing of NO , O3 and VOC aloft over Houston · 2007-06-12 · Nocturnal Processing of NO x, O 3 and VOC aloft over Houston NO 2 NO 3 O 3 N 2 O 5 NO 2 Steven S. Brown,](https://reader033.vdocuments.net/reader033/viewer/2022041814/5e59bd3fee41141ea33eed74/html5/thumbnails/5.jpg)
Night Flights during TexAQS 2006
September 29
October 8
October 10
October 12
• Limited set of nighttime data
• Draw the most general conclusions possible
![Page 6: Nocturnal Processing of NO , O3 and VOC aloft over Houston · 2007-06-12 · Nocturnal Processing of NO x, O 3 and VOC aloft over Houston NO 2 NO 3 O 3 N 2 O 5 NO 2 Steven S. Brown,](https://reader033.vdocuments.net/reader033/viewer/2022041814/5e59bd3fee41141ea33eed74/html5/thumbnails/6.jpg)
Data Analysis I - Steady State Lifetimes
τ(NO3)−1 ≈ kNO3+ kN2O5
Keq[NO2 ]
τ(N2O5 )−1 ≈ kN 2O5+
kNO3
Keq[NO2 ]τ(N2O5 ) ≡ [N2O5 ]kS[NO2 ][O3]
τ(NO3) ≡ [NO3]kS[NO2 ][O3]
τ(SUM ) ≡ [NO3]+[N2O5 ]kS[NO2 ][O3]
τ(SUM ) ≈1+ Keq[NO2 ]
kNO3+ kN 2O5
Keq[NO2 ]
NO2 NO3O3
VOCkS
kNO3
N2O5 HNO3
NO2
Keq
H2O(Het)kN2O5
Oxidation Products
kNO3
kNO3
kNO3
kN2O5
kN2O5
kN2O5
• System must reach steady state • No covariance between kNO3, kN2O5 & NO2Caveats:
![Page 7: Nocturnal Processing of NO , O3 and VOC aloft over Houston · 2007-06-12 · Nocturnal Processing of NO x, O 3 and VOC aloft over Houston NO 2 NO 3 O 3 N 2 O 5 NO 2 Steven S. Brown,](https://reader033.vdocuments.net/reader033/viewer/2022041814/5e59bd3fee41141ea33eed74/html5/thumbnails/7.jpg)
Example 1: North Texas
NO3 N2O5 NO3+N2O5
kNO3-1 = 19 ± 1 min
kN2O5-1 > 10 hours
N2O5 Hydrolysis very slow
kN 2O5≈ 1
4× c ×γ(N2O5 )× SAerosol γ < 10-3
• Neutral (NH4)2SO4 aerosolNH4
+/SO42- > 2
• Measurable aerosol NO3-
• Large Organic / Sulfate Ratio
• γ(N2O5) similar to that seen on this aerosol type in previous campaigns (e.g. New England)
Aerosol:
N2O5 HNO3
H2O (aq)
![Page 8: Nocturnal Processing of NO , O3 and VOC aloft over Houston · 2007-06-12 · Nocturnal Processing of NO x, O 3 and VOC aloft over Houston NO 2 NO 3 O 3 N 2 O 5 NO 2 Steven S. Brown,](https://reader033.vdocuments.net/reader033/viewer/2022041814/5e59bd3fee41141ea33eed74/html5/thumbnails/8.jpg)
Data Analysis II - Nocturnal Odd Oxygen (Ox)
NO + O3 → NO2 + O2 NO2 = 1 Ox
Daytime: Ox ≡ O3 + NO2
NO + O3 → NO2 + O2 NO2 = 1 OxNO2 + O3 → NO3 + O2 NO3 = 2 OxNO3 + NO2 → N2O5 N2O5 = 3 Ox
Nighttime: Ox ≡ O3 + NO2 + 2NO3 + 3N2O5
N2O5 + H2O → 2HNO3 HNO3 = loss of 1.5 Ox
NO3 + VOC reactions Variable, loss of 1-2 Ox
Nocturnal Losses for Ox
![Page 9: Nocturnal Processing of NO , O3 and VOC aloft over Houston · 2007-06-12 · Nocturnal Processing of NO x, O 3 and VOC aloft over Houston NO 2 NO 3 O 3 N 2 O 5 NO 2 Steven S. Brown,](https://reader033.vdocuments.net/reader033/viewer/2022041814/5e59bd3fee41141ea33eed74/html5/thumbnails/9.jpg)
Ox Budget - Oklaunion Power Plant Plume (North Texas)
• NO3 and N2O5 account for most of lost Ox in plumes• Little to no enhancement of HNO3• Corroborates lifetime analysis - slow N2O5 hydrolysis
Slope = -1 for closed Ox budget
![Page 10: Nocturnal Processing of NO , O3 and VOC aloft over Houston · 2007-06-12 · Nocturnal Processing of NO x, O 3 and VOC aloft over Houston NO 2 NO 3 O 3 N 2 O 5 NO 2 Steven S. Brown,](https://reader033.vdocuments.net/reader033/viewer/2022041814/5e59bd3fee41141ea33eed74/html5/thumbnails/10.jpg)
Example 2: Parish Power Plant Intercept - October 12
kNO3-1 > 40 ± 1 min
kN2O5-1 > 6 hours
NO3 N2O5 NO3+N2O5 N2O5 hydrolysis slowγ < 5x10-3
• NO3 and N2O5 (more than) account for lost Ox
• Little to no enhancement in HNO3
• Transport of NOx and Ox
Odd-Oxygen Analysis
Steady State Analysis
![Page 11: Nocturnal Processing of NO , O3 and VOC aloft over Houston · 2007-06-12 · Nocturnal Processing of NO x, O 3 and VOC aloft over Houston NO 2 NO 3 O 3 N 2 O 5 NO 2 Steven S. Brown,](https://reader033.vdocuments.net/reader033/viewer/2022041814/5e59bd3fee41141ea33eed74/html5/thumbnails/11.jpg)
NOx Transport - Parish Plume F(NOx ) = NO3 + 2N2O5
NO2 + NO3 + 2N2O5
NOx conserved within this plume
note: Low VOC case
![Page 12: Nocturnal Processing of NO , O3 and VOC aloft over Houston · 2007-06-12 · Nocturnal Processing of NO x, O 3 and VOC aloft over Houston NO 2 NO 3 O 3 N 2 O 5 NO 2 Steven S. Brown,](https://reader033.vdocuments.net/reader033/viewer/2022041814/5e59bd3fee41141ea33eed74/html5/thumbnails/12.jpg)
Where Does It Go ?N2O5 NO3 NOx
• Overnight transport to region with higher biogenic emissions
• O3 formation potential in rural regions, well removed from urban sources
Isoprene Emission Map
mol km2 hr-1
![Page 13: Nocturnal Processing of NO , O3 and VOC aloft over Houston · 2007-06-12 · Nocturnal Processing of NO x, O 3 and VOC aloft over Houston NO 2 NO 3 O 3 N 2 O 5 NO 2 Steven S. Brown,](https://reader033.vdocuments.net/reader033/viewer/2022041814/5e59bd3fee41141ea33eed74/html5/thumbnails/13.jpg)
Nocturnal Ox Partitioning F(Ox ) = 2NO3 + 3N2O5
O3 + NO2 + 2NO3 + 3N2O5
October 12 Flight
• F(Ox) depends on ratio of emitted NOx to O3 and the stability of N2O5
• 5 - 20% (2 - 11 ppbv) Ox stored as N2O5 within plumes October 12
![Page 14: Nocturnal Processing of NO , O3 and VOC aloft over Houston · 2007-06-12 · Nocturnal Processing of NO x, O 3 and VOC aloft over Houston NO 2 NO 3 O 3 N 2 O 5 NO 2 Steven S. Brown,](https://reader033.vdocuments.net/reader033/viewer/2022041814/5e59bd3fee41141ea33eed74/html5/thumbnails/14.jpg)
Nocturnal VOC Oxidation• Stability of N2O5 regulates availability of NO3
• NO3 on October 12 reached 350 pptv
• Potentially very strong oxidant - depends on VOC mixtureAlkenes (but ethylene very slow)Aldehydes (but formaldehyde very slow)Some aromatics
NO3 averaged to whole air sampler (WAS) time base forOctober 12 flight
![Page 15: Nocturnal Processing of NO , O3 and VOC aloft over Houston · 2007-06-12 · Nocturnal Processing of NO x, O 3 and VOC aloft over Houston NO 2 NO 3 O 3 N 2 O 5 NO 2 Steven S. Brown,](https://reader033.vdocuments.net/reader033/viewer/2022041814/5e59bd3fee41141ea33eed74/html5/thumbnails/15.jpg)
NO3 - VOC Loss Rates & Sink PartitioningkLoss(NO3) = k(NO3 +VOCi )×[VOC]i
i∑
RVOC = k(NO3 +VOCi )×[NO3]×VOCii∑
Houston Ship Channel Emissions
VOC Loss Rates of 0.5 - 4 ppbv hr-1 within plumes emitted from industrial sources
![Page 16: Nocturnal Processing of NO , O3 and VOC aloft over Houston · 2007-06-12 · Nocturnal Processing of NO x, O 3 and VOC aloft over Houston NO 2 NO 3 O 3 N 2 O 5 NO 2 Steven S. Brown,](https://reader033.vdocuments.net/reader033/viewer/2022041814/5e59bd3fee41141ea33eed74/html5/thumbnails/16.jpg)
Emission of very highly reactive VOC ?
(e.g., butadienes, styrene, phenols)
Evidence for oxidation of highly reactive VOCP(NO3) = kNO2 +O3
[O3 ][NO2 ]
τ (NO3)−1 = P(NO3) /[NO3 ]
![Page 17: Nocturnal Processing of NO , O3 and VOC aloft over Houston · 2007-06-12 · Nocturnal Processing of NO x, O 3 and VOC aloft over Houston NO 2 NO 3 O 3 N 2 O 5 NO 2 Steven S. Brown,](https://reader033.vdocuments.net/reader033/viewer/2022041814/5e59bd3fee41141ea33eed74/html5/thumbnails/17.jpg)
Oxidation of highly reactive VOC - Second Chance
• Measured VOC not responsible for increase in NO3 loss rate
• But likely correlated with emission of more reactive VOC
![Page 18: Nocturnal Processing of NO , O3 and VOC aloft over Houston · 2007-06-12 · Nocturnal Processing of NO x, O 3 and VOC aloft over Houston NO 2 NO 3 O 3 N 2 O 5 NO 2 Steven S. Brown,](https://reader033.vdocuments.net/reader033/viewer/2022041814/5e59bd3fee41141ea33eed74/html5/thumbnails/18.jpg)
Vertical Stratification of Nighttime Chemistry
Nocturnal BoundaryLayer (NBL)
IntermediateLayer
ResidualDaytime
BoundaryLayer
Missed approach to BushInternational Airport
• NOx & VOC plumes occur in discrete layers at night• Can be more concentrated, and difficult to find !• Chemistry in Nocturnal Boundary Layer differs significantly
(see Hans Osthoff, Roberto Sommariva Posters for details)
![Page 19: Nocturnal Processing of NO , O3 and VOC aloft over Houston · 2007-06-12 · Nocturnal Processing of NO x, O 3 and VOC aloft over Houston NO 2 NO 3 O 3 N 2 O 5 NO 2 Steven S. Brown,](https://reader033.vdocuments.net/reader033/viewer/2022041814/5e59bd3fee41141ea33eed74/html5/thumbnails/19.jpg)
Conclusions• N2O5 hydrolysis generally inefficient during TexAQS
Consistency between lifetime and Ox analysisAerosol = Neutral (NH4)2SO4 + Organics
• Overnight transport of NOx and Ox in the form of N2O5Most obvious in power plant plumes (low VOC)
• NO3 available as an oxidant in industrial emissionsVOC loss rates 0.5 - 4 ppbv hr-1 in ship channel plumesEvidence for oxidation of extremely reactive VOC
• Vertical StratificationShallow, concentrated NOx plumesLarge difference between surface and aloft
P-3 vs. Ron Brown