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Application of the PTM-MCM to the TORCH-1 campaign

Application of the PTM-MCM to the TORCH-1 campaign. Steve Utembe, Mike Jenkin and David Johnson EPSR Group Department of Environmental Science and Technology. Studies using the PTM.

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Application of the PTM-MCM to the TORCH-1 campaign

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  1. Application of the PTM-MCM to the TORCH-1 campaign Steve Utembe, Mike Jenkin and David Johnson EPSR Group Department of Environmental Science and Technology

  2. Studies using the PTM • Chemical development of air parcels arriving at Writtle site investigated, at six-hourly resolution for the entire campaign • 156 96-hours back trajectories obtained from NOAA • Chemical processing using CRI mechanism • Additional analysis of selected trajectories using MCM v3.1

  3. Brief description of the PTM s u n l i g h t c h e m i s t r y a n d t r a n s p o r t w e l l - m i x e d b o u n d a r y l a y e r b o x c a l c u l a t e o z o n e a l o n g p r e - s e l e c t e d t r a j e c t o r i e s o v e r E u r o p e e m i s s i o n s V O C a n d N O X 4-day back trajectory

  4. Emissions • UK anthropogenic emissions based on NAEI. • Anthropogenic emissions outside UK based on EMEP. • Biogenic VOC emissions based on Simpson (1995). • Idealised seasonal, weekly and diurnal variations applied. • NMVOC emissions speciation based on NAEI for ca. 70% of total. Remaining 30% assigned to surrogates for which chemistry treated.

  5. Emissions speciation: 124 anthropogenic NMVOC butane ethanol alkanes alkenes carbonyls fraction of total toluene alcohols ethers acids esters aromatics chloro-carbons

  6. Ozone: observed vs calculated

  7. Ozone observed vs calculated : sensitivity to trajectory height

  8. Emitted aromatic hydrocarbon: toluene

  9. Emitted aromatic hydrocarbons

  10. Emitted alkyne: acetylene

  11. Emitted alkanes

  12. Emitted cycloalkane: cyclohexane (used as a surrogate for all emitted cycloalkanes)

  13. Emitted alkenes and dienes

  14. Emitted biogenic hydrocarbon: isoprene

  15. Mean hydrocarbon concentrations

  16. Aldehyde with primary and secondary sources: HCHO preliminary HCHO measurements made by UEA

  17. Simulated aldehyde product distributions on 3 example trajectories (N.B. we have simulated concentration data on 1257 carbonyl compounds)

  18. Simulated ketone product distributions on 3 example trajectories

  19. Concentrations of selected carbonyl products from aromatics

  20. Concentrations of selected carbonyl products from biogenics

  21. Organic nitrates and relationship to precursor peroxy radicals • Ozone and organic nitrates are both produced from reaction of peroxy radicals with NO RO2 + NO [ROONO]* RO. + NO2 (R1) + MRONO2 (R2) Correlation between the concentration of the two • [RO2]i [RONO2]i/i where i = k1/k2

  22. Comparison of relative concentrations of RO2 radicals produced from reactions of OH with alkanes and alkenes (O’Brien et al. 1995) -hydroxy Alkyl peroxy RO2’s 24 hours chemical processing

  23. Concentrations at end of day 5 for a series of alkyl and -hydroxyalkyl peroxy radicals calculated with the MCM/PTM show similar distribution of peroxy radicals inferred from the organic nitrate observations of O'Brien et al. Alkyl peroxy RO2’s -hydroxy 5 days chemical processing

  24. Concentration distribution of C1-C5 alkyl nitrates in MCM3.1

  25. Concentration distribution of C2-C4 -hydroxy alkyl nitrates in MCM3.1

  26. Identifying top contributors to total carbonyl distribution in MCM v3.1 • There are 1257 carbonyls in MCM v3.1(!) • What are the dominant carbonyls in air masses of different degrees of photochemical processing?

  27. Top contributors to 90% of total carbonyl concentration CH3COCH3 HCHO Least photochemically processed MEK CH3CHO CH3COCH3 Most photochemically processed HCHO CH3CHO MEK Intermediate

  28. Concluding remarks • Simulation of TORCH-1 campaign using PTM-CRI has allowed emitted VOC speciation to be tested. Simulated and observed hydrocarbon concentrations were generally well correlated. • Simulated concentrations of 6 aromatics, acetylene, 1,3-butadiene and intermediate alkanes were in very good agreement with observations. • Simulated concentrations of alkenes and small alkanes tended to be slightly lower than observations. • Simulated concentrations of larger alkanes were generally greater than those observed: this mainly due to ‘surrogate’ contributions. • MCM allows study of distributions of concentrations of various classes of VOCs

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