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Review of Biogenic Volatile Organic Compounds and Their Products

Review of Biogenic Volatile Organic Compounds and Their Products. Brian Lamb (1) , Daniel Grosjean (2) , Betty K. Pun (3) , and Christian Seigneur (3) Biogenic Day 9-10 December 1999. (1) Washington State University, Pullman, WA (2) DGA, Inc., Ventura, CA (3) AER, San Ramon, CA.

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Review of Biogenic Volatile Organic Compounds and Their Products

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  1. Review of Biogenic Volatile Organic Compounds and Their Products Brian Lamb(1), Daniel Grosjean(2), Betty K. Pun(3), and Christian Seigneur(3) Biogenic Day 9-10 December 1999 (1) Washington State University, Pullman, WA (2) DGA, Inc., Ventura, CA (3) AER, San Ramon, CA

  2. Condensable products Emissions Atmospheric reactions Gas/particle partition PM O3 Introduction Biogenic compounds are precursors to ozone (O3) and particulate matter (PM)

  3. Biogenic Volatile Organic Compounds Emission % in North America • Isoprene 31% • Methylbutenol (MBO) 5% • Monoterpenes + sesquiterpenes 22% • Reactive oxygenates 16% • Less reactive oxygenates 26%

  4. Isoprene • Sampling, analytical, eddy covariance flux methods are well-developed Emission Characteristics • Dominant VOC • From deciduous species and spruce • During day-light hours only • Depends on leaf temperature and PAR

  5. Isoprene Data Needs • Vegetation types other than oaks, poplars, aspen, and spruce • Effects of temperature history and season • Landcover data

  6. Monoterpenes • Predominant compounds: a-, b-pinene, limonene, and D3-carene Emission Characteristics • From conifers and some deciduous species • Depends on temperature • Some Mediterranean oaks emit terpenes with isoprene-like light, temperature dependence

  7. Monoterpene Data Needs • Emission capacities of individual monoterpene compounds • Characterization of emission response to • rainfall / humidity • herbivory • Canopy-scale measurements • Comparison of measurements and inventory models

  8. Sesquiterpenes • Semivolatile, low emission capacities • May contribute up to 16% of total BVOC landscape-scale flux Data Needs • Identification of individual sesquiterpenes and their emission capacities • Canopy-scale measurements • Regional emissions estimates

  9. Oxygenated VOC • Methylbutenol, emitted via the light-dependent chloroplast mechanism • Other oxygenates emitted by defense mechanisms or cut and drying vegetation • Regional emissions difficult to quantify due to intermittent emissions • No canopy-scale information • No evaluation at landscape scale

  10. Biogenic Emissions Modeling e = area-average emission capacity D = foliar density g = activity factor for light, temperature, leaf age d = activity factor for other factors r = canopy escape efficiency

  11. Canopy Modeling • Microclimate within a forest canopy as a function of height • temperature (heat flux) • PAR

  12. Measurements and Modeling (Isoprene) • Measurement scale-up studies • 40% difference between leaf and canopy scales • Reconciliation of measurements with models • 30% difference between flux measurement and model for site specific applications • factor of 1.2 to 2 using inverse modeling of ambient concentrations

  13. Chemical Functionality • Saturated aliphatics • Alkanes, alcohols, aldehydes, ketones, acids, esters, ethers • Aromatics • Unsaturated Aliphatics • Alkenes, dienes, terpenes (1 to 3 C=C), sesquiterpenes (1 to 3 C=C) • Unsaturated Oxygenates • alcohols, esters, aldehydes, ketones

  14. Kinetics of Saturated Aliphatics and Aromatics • Saturated aliphatics react only with OH • Aromatics react mainly with OH, NO3 may be a minor pathway • Missing kinetic data for hexanal, camphor, cineole, and p-cymene can be estimated by structure-reactivity relationships • Acetone has the maximum t1/2(1) = 36 days • Hexanal has the minimum t1/2(1) = 6 hours (1) OH = 106 molec/cm3

  15. Kinetics of Unsaturated Compounds Unsaturated VOC react with OH, O3, and NO3 t1/2,OH(1) (hours) t1/2, O3(2) (hours) alkenes 3.0 - 23 1.3 - 160 isoprene 1.9 20 terpenes 0.53 - 3.6 0.01 - 280 sesquiterpenes 0.65 - 4.1 0.02 - >500 oxygenates 1.2 - 6.6 0.60 - 130 (1) OH = 106 molec/cm3; (2) O3 = 30 ppb

  16. Highly Reactive Compounds a-terpinene a-humulene Linalool Reaction with O3 may be the dominant removal process for the more reactive BVOC

  17. First-Generation Products • Example: OH + a-pinene • Pinonaldehyde, acetone, formaldehyde • Organic nitrates, hydroxy nitrates, dihydroxy nitrates, dihydroxycarbonyls • For O3 and OH reactions • Detailed information for alkenes, a-, and b-pinene, and unsaturated alcohols • Limited or no information for >20 BVOC • Less information on NO3 reaction

  18. SOA Formation • 14 BVOC known to form SOA • 10 terpenes (a-pinene most studied) • 2 sesquiterpenes • 2 unsaturated alcohols • Isoprene does not form SOA • SOA composition studied for 5 BVOC (reactions with O3 and OH only): a-, b-pinene, d-limonene, terpinolene, D3-carene

  19. Reactions of First-Generation Products • Kinetic data for first-generation products are limited • Aldehydes removed rapidly by OH reaction • Unsaturated carbonyls react with O3 • Product studies conducted for only 6 first-generation compounds • Very limited information on second-generation products

  20. Detailed BVOC Mechanisms • With the exception of isoprene and a-pinene, detailed mechanisms cannot be constructed for BVOC

  21. CH3CH2 CH2CH2OH + OH C = C H H · CH3CH2CH CHCH2CH2OH OH HO2 NONO2 CH3CH2CH(OH)CCH2CH2OH O + HO2 O3 O · CH3CH2CHOH + HCCH2CH2OH O2 HO2 O CH3CH2CHO HO2 + HOCH2CH2CH(OH)CCH2CH2OH O3 Formation from BVOC · CH3CH2CHCHCH2CH2OH OH NO2 NO2 O2, NO O2, NO CH3CH2CHCH(OH)CH2CH2OH CH3CH2CH(OH)CHCH2CH2OH O O · · Isom. + O2 u.d. · CH2CH2CH(OH)CH(OH)CH2CH2OH NO2 O2, NO · OCH2CH2CH(OH)CH(OH)CH2CH2OH Isom. · HOCH2CH2CH(OH)C(OH)CH2CH2OH O2

  22. Organic Aerosol Partition Theories • Saturation • Fixed yield approach • Absorption into an organic phase • Aqueous dissolution Total concentration (Ctot) Cgas = Psat Cparticle = Ctot - Psat Psat Gas phase only Cgas = Ctot K Cparticle Cgas H Cparticle Cgas

  23. Existing SOA Modules

  24. OC (g) OC (aq) OC (g) OC (l) Modules Under Development • Externally Mixed Aerosols • Surrogate Species Type A (Aqueous) Type B (Organic) e.g., Malic acid, e.g., Octadecanoic acid Glyoxalic acid

  25. Data Needs Chemistry • Products studies • Mechanisms • SOA composition SOA Partition Emissions • Identity of SOA species • Theoretical development • Individual terpene species • Sesquiterpenes and oxygenates • Need instrument development work

  26. Acknowledgement This work is funded by the Coordinating Research Council (CRC), Contract Number A-23

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