CITES 2005, March 20-23, 2005, Novosibirsk, Russia

Atmospheric Chemistry:Overview and Future Challenges

Allan Gross

Danish Meteorological Institute,Lyngbyvej 100, 2100 Copenhagen , Denmark.& University of Copenhagen, Scientific Computing Chemistry Group,Universitetsparken 5, 2100 Copenhagen , Denmark.CITES 2005, March 20-23, 2005, Novosibirsk, Russia.

Erik Bdtker, Danmarks Meteorologiske Institut

BackgroundThere is a critical need for improving the available mechanistic data in Atmospheric Chemical Transport Models (ACTM), examples: the chemistry of higher molecular weight organic compounds (e.g. aromatic and biogenic compounds), radical reactions (e.g. peroxy peroxy radical reactions),photo-oxidation processes (quantum yields and absorption cross sections), heterogeneous processes.

Furthermore, due to experimental difficulties most rates are measured best near 298 K, i.e. temperature dependence of many reactions is not well characterised (see NIST, IUPAC and NASA).


ContentsWith a description of the new European project GEMS as starting point, the following aspects will be outlined: an overview of atmospheric chemistry (boundary layer and free-troposphere),show important areas where future studies are needed, e.g.:aromatic chemistry,alkene chemistry.a comparison of some of the most frequently used lumped atmospheric chemistry mechanisms will be given (EMEP, RADM2, RACM).Examples of atmospheric environments where these lumped mechanism need to be improved:biogenic environment,marine environment.


Objectives of GEMS (EU-project, 2005-09)

Some components of the system:combines all available remotely sensed and in-situ data to achieve global tropospheric and stratospheric monitoring of the composition and dynamics of the atmosphere from global to regional scale covering the tropospheric and stratosphere:Satellite data, and near-real time measurements.

global data assimilation.

Point 1 will deliver current and operational forecasted 3-dim. global distributions. These distributions will be used for regional air quality modelling.Develop and implement at ECMWF a new validated, comprehensive and operational global data assimilation/forecasting system for atmospheric composition and dynamics.


GEMS Global SystemData input (Assimilation, Satellite, Real-time) Global Greenhouse GassesGlobal Reactive GassesRegional

Air QualityGlobal

AerosolsProducts, User Service GEMS Global SystemCoordinationSystem Integrationoxidants

green house gassesboundaryconditionsoxidants

opticalpropertiesSchematic illustration of the GEMS strategy to build an integrated operational system for monitoring and forecasting the atmospheric chemistry environment: Greenhouse gasses, global reactive gasses, global aerosols and regional air quality.Global Reac-tive Gasses (UV-forecast)Regional Air Quality (RAQ modelling)


Operational deliverablesCurrent and forecasted 3-dim. global distributions of atmospheric key compounds (horizontal resolution 50 km):

greenhouse gases (CO2, CH4, N2O and SF6),reactive gases (O3, NO3, SO2, HCHO and gradually expanded to more species),aerosols (initially a 10-parameter representation, later expanded to app. 30 parameters).

The global assimilation/forecast system will provide initial and boundary conditions for operational regional air-quality and chemical weather forecast systems across Europe:

provide a methodology for assessing the impact of global climate changes on regional air quality. provide improved operational real-time air-quality forecasts.


CLRTAP: UN Convertion on Long-Range Trans-boundary Air Polluton


GEMS Regional Air-Quality Monotoring and Forecastning Partners

Individual20 InstitutesV.-H. Peuch (co.), A. DufourMETEO-FR (Mto-France, Centre National de Recherches Mtorologiques)A. ManningMETO-UK (The Met Office, Exeter, Great-Britain)R. Vautard, J.-P. Cammas, V. Thouret, J.-M. Flaud, G. BergamettiCNRS-LMD (Laboratoire de Mtorologie Dynamique, CNRS-LA (Laboratoire d'Arologie, CNRS-LISA (Laboratoire Inter-Universitaire des Systmes Atmosphriques)D. Jacob, B. LangmannMPI-M (Max-Planck Institut fr Meteorologie)H. EskesKNMI (Koninklijk Nederlands Meteorologisch Instituut)J. Kukkonen, M. SofievFMI (Finnish Meteorological Institute)A. Gross, J.H SrensenDMI (Danmarks Meteorologiske Institut)M. BeekmannSA- UPMC (Universit Pierre et Marie Curie Service dAronomie)C. Zerefos, D. MelasNKUA (Laboratory of Climatology and Atmospheric Environment, University of Athens)M. Deserti, E. MinguzziARPA-SM (ARPA Emilia Romagna, Servizio IdroMeteorologico) F. Tampieri, A. BuzziISAC (Institute of Atmospheric Sciences and Climate Consiglio Nazionale delle Ricerche)L. Tarrason, L.-A. BreivikDNMI (Det Norske Meteorologisk Institutt)H. Elbern, H. JakobsFRIUUK (Rheinisches Institut fr Umweltforschung, Universitt Kln)L. RouilINERIS (Institut National de lEnvironnement Industriel et des Risques)J.Keder, J.SantrochCHMI (Czech Hydrometeorological Institute)F.McGovern B.KellyEPAI (Irish Environmental Protection Agency)W.MillPIEP (Polish Institute of Environmental Protection)D.BriggsICSTM (Imperial College of Science, Technology and Medicine, London)


Models Within RAQ Sub-Project

* E : run at ECMWF ; P : run at partner institute

Contribution Models and Partners Target speciesData assimilationNRT ForecastE / P *Re-analyses simul. E / P *MOCAGEMETEO-FROzone and precursors (RACM); aerosol components (ORISAM); ENVISAT; MOPITT; OMI; IASI; surface dataP and EEBOLCHEMCNR-ISACOzone and precursors (CB-IV or SAPRC90).Surface and profile data.P, then EP, case studiesEURADFRIUUKOzone and precursors (RACM); aerosol components (MADE).SCIAMACHY; MOPITT; surface data.P, then E_____CHIMERECNRS and SA_UPMCOzone and precursors (EMEP or SAPRC90); aerosol components (ORISAM).SCIAMACHY; Surface and profile data.PPSILAMFMIChemically inert aerosols of arbitrary size spectrum_____PP, year 2000MATCHFMIOzone and precursors (EMEP); aerosol components (MONO32)._____PP, year 2000CACDMIOzone and precursors (RACM) and sulphur/DMS; aerosol components._____PP, case studiesMM5-UAMVNKUAOzone and precursors (CB-IV)._____PP, case studiesEMEPmet.noOzone and precursors (EMEP); aerosol components (MM32).MERIS and MODIS for PM informationPP, 2005REMOMPI-MOzone and precursors (RADM2).__________PUMAQ-UKCAUKMOOzone and precs.; aerosol comp._____P_____


Chemical Schemes in USA-modelsWORF-CHEM: RADM2CMAQ: CB-IV, RADM2, RACM, SAPRC99CAMX: CB-IV with improved isoprene chemistry, SAPRC99


RAQ Interfaces and Communication between ECMWF and Partner Institutes


GEMS, SummaryThe GEMS project will develop state-of-the-art variational estimates ofmany trace gases and aerosols,the sources/sinks, andinter-continental transports.

Later on operational analyses will be designed to meet policy makers' key requirements tothe Kyoto protocol,the Montreal protocol, andthe UN Convention on Long-Range Trans-boundary Air Pollution.


Gas-Phase Chemistry Need to be Solved in Regional Air Quality Models

Formation of:ozone,nitrogen oxides,peroxyacetyl nitrate (PAN),hydrogen peroxide,atmospheric acids .....

Need to understand chemical reactions of:nitrogen oxides,VOC .....


Chemistry of the free-troposphere: nitrogen oxides and its connection with,carbon monoxide, andsimplest alkane methane.Polluted environment we have high NOX, and VOC chemistry shall also be included.


Reaction Cycle of HOX and NOx, only VOC methane+H2OO3HOHydrocarbons hHCHOHO2products, RCHORO2NONO2O3hRONO2RO+NO2ROOHRO3NO2RO2NO2H2O2H2O2hHNO3O(3P)Hydrocarbons Hydrocarbons O3H2O2, CORNO3CH4NO3CH3O2COCH3OOHReaction Cycle of HOX and NOx, high VOCsNighttime chem. HCHO


Oxidation Steps of HydrocarbonsRHHOH2ORO2RO2HO2R(ONO2)HOO2HO2NOROOHROHORCHOhHOHONORRO2NO3NO3+O2NO2RO3NO2NO3NO2NO3HNO3h+O2RO2HO2RO2R(-H)O+ROH+O2RO + RO+ O2ROOR+O2ROOH+RO2Green: only alkene pathRed: also other end products but these react further to the given end productRROORCHOOO3C5H12C4H10C6H14CH3C5H11CH3CH3CH4H8C7H16CH3C6H13C3H8C9H20CH3C8H17C10H22CH3C9H19C11H24C12H26C2H4C3H6C4H8C5H10CH3C4H7CH3C4H7C4H6C2H2C6H6CH3C6H5C2H5C6H5(CH3)3C6H3HCHOC2H5CHO(CH3)2CHCHOC3H7CHOCH3CHOCH3C6H4C2H5C3H7C6H5C4H9CHOCH3COCH3CH3COC4H9CH3OHCH3CO2CH3CH7CH3CO2CH3CClC2Cl4CH3ClC2H5CO2CH3C2H5OHCH3COC2H5C6H5CHOCH4C2H6RO3


Gaps in Atmospheric Chemistry, High PrioritiesInorganic chemistry is relatively well known

Problems:alkenesmonocyclic aromatic hydrocarbonspolycyclic aromatics hydrocarbons (PAH)


The Chemistry of Alkenes Reasonable Established. Rate coefficients for HO-alkene reactions of most of the alkenes which have been studies appears to be reasonable accurate.

Gaps, Highest Priorities

the data base for RO2+ RO2, RO2 + HO2, RO2 +NO2 ,RO2 + NO reactions and their products are very limited and complex.E.g. system with only 10 RO2 (no NOX) results in approximately 165 reactions.

ozonolysis of alkenes are important in urban polluted area. Example: O3 + H2C CH2 HCHO + H2COO *

OOOH2COO 37%CO+H2O 38%CO2+H2 13% primary ozonide Criegee biradical

The rate and product yields of the stable Criegee biradical with NO, NO2 and H2O have only been studied for the simplest carbonhydrids. Higher order carbonhyrids should be investigated


Many of the unsaturated dicarbonyl products appear to be very photochemically active. Absorption cross sections only determined from highly uncertain gas-phase measurements.

Examples of compounds it is important to determine the spectra oftrans-butenedial 4-oxo-2-pentanal 3-hexene-2,5-dione 4-hexadienedialsOOOOOOOO(Atmospheric oxidation products from aromatics)


The Chemistry of Aromatics Still Highly Uncertain

Gaps is related both to the rate constant the of aromatic chemistry and the yields of the formed products


Rate coefficients for HO-reactions with monocyclic aromatics

only 23 aromatics have been studied: only studied by one lab.p-cymene tetralin -methyl-styrene -methyl-styrene --dimethyl-styreneiso-propyl-benzene o- m- p-ethyl-toluene tert-butyl-benzene indan indene studied by more than one lab. but with over all uncertainties greater than 30%rate constants for only 20 of the many aromatics products of the oxidation of aromatics have been determined, 14 of these are single studies.


Rate coefficients for HO-reactions with polycyclic aromatics (PAHs) only 16 aromatics have been studied:

only studied by one lab.1-: 2-methyl-naphthalene 2, 3-dimethyl-naphthalene acenaphthalene flouranthene 1-: 2-nitronaphthalene 2-methyl-1-nitron-aphthaleneNO2NO2NO2


HO +PAH studied by more than one lab., rate constant uncertainties for seven PAHsbiphenyl (30%) fluorene (fac. of 1.5) acenaphthene (fac. of 2)phenanthrene (fac. of 2) dibenzo-p-dioxin(fac. of 1.5) dibenzofuran (30%)OO anthracene: one of the most abundant and important PAH in the atmosphereanthracene Rate highly uncertain:

range (18 to 289) 10-12 cm3 molecule-1


3-methyl-phenanthrene pyrene benzo[a]flouoreneRate coefficients for PAHs with vapor pressures greater than app. 10-5 Torr (298 K) should be determined since their reaction with HO may be an improtant removal process, three examples are:HO +PAH


NO3 + aromatics appear unimportant in the atmosphere

Exceptions:a group attached to the atomatic ring have a double bound (ex. indene, styrene),have an OH group attached to the aromatic ring (ex. phenols, cresols).

Only studies: NO3 + & &phenol o-: m-: p-cresol m-nitro-phenolNO2OHOHOH


O3 + aromatics: have gaps but these reactions are not highly important in atmospheric chemistry.

O(3P) + aromatics: unimportant in urban atmosphere.

Atmospheric chemistry of organic compounds sorbed on particles (heterogeneous reactions) and its reactions in aerosols even more uncertain. Important.

PAHs oxidation sorbed on particles. Important.

PAHs + HO more studies are needed.


Non-aromatic products from the oxidation of aromatic compounds additional kinetic and mechanics studies of the rates are needed:Especially the HO initiated reactions,Product studies of HO + aromatics from chamber experiments shows carbon mass losses from 30% to 50%, i.e. quite possible that some yet unidentified reactions pathways. That means the overall atmospheric oxidation mechanism of aromatics is still rather uncertain.

Highest priority, a study the products from the oxidation of most important aromatics:toluene,xylenes, andtrimethyl-substituted benzenes.


Application of Chemistry in Atmospheric Chemical Transport Models

Problems:A Complete Mechanism would require tens of thousands of chemical species and reactions.The reaction mechanisms and rates are not known for most of these.The ordinary differential equation for chemical mechanisms is very stiff, i.e. numerical standard methods are not applicable.

Way of solving it:Using lumped chemical mechanism.Make special ad hoc adjustments to the rate equation to remove stiffness in the lumped mechanism use a fast solver.


Correlation of the rates for NO3 with O(3P)Correlation of the rates for NO3 with HO (line c): addition reactions (lines a & b): abstraction reacs


Correlation of Peroxy Peroxy Radical ReactionsFunction fit depend on number of carbons Function fit depend on the rates from theand the alkyl-alkoxy substitution reactants peroxy-self-reaction rates


Lumped Atmospheric Chemical Mechanisms


Chamber Experiment EC-237PhotolysisNOXEthenePropenetert-2-butenen-butene2, 3-dimethylbutenetoulenem-xyleneRACM and RADM2 are tested against 21 Chamber Experimentsincluded: 9 organic species.Used chamber: Statewide Air Pollution Research Center. Key species tested in the chamber: NO2, NO and O3.


RACM better than RADM2 Ref. Stockwell et al., JGR, 1997


Problems With These Chamber Experiments

50% or more of the total HO comes from the chamber walls (depend on the chamber).Chamber walls can serve as sources or sinks for O3, NOX, aldehydes and ketones.Photolysis maybe uncertain.Chamber experiments are conducted at much higher species concentrations than in the atmosphere (i.e. have a lot of radical reactions which do not occur in the real atmosphere).

If e.g. EUPHORE chamber data were used these problems would be smaller.


O3isoplets

localnoonRef. Gross and Stockwell, JAC, 2004


O3 and HOScatter plots

WithoutEmissions

3 days sim.Local NoonO3O3HOHORef. Gross and Stockwell, JAC, 2004: urban: rural: neither urban nor rural


HO2 and RO2Scatter plots

WithoutEmissions

3 days sim.Local NoonHO2HO2RO2RO2Ref. Gross and Stockwell, JAC, 2004: urban: rural: neither urban nor rural


Mechanism Comparison, Summary

Compared to each other the mechanisms showed clear trends:O3: EMEP > RACM > RADM2 HO and HO2: RACM > EMEP and RACM > RADM2RO2:EMEP > RACM and RADM2 > RACM

The mechanism comparison showed little differences between the three mechanisms, equally good.

However, all these mechanisms are based on the same guessed rates and reactions, i.e. the same amount of uncertainty.

However, few of the simulated scenarios gave very large simulated differences between the mechanisms. This showed that only one typical scenario (which often has been considered to be sufficient) is not enough in order to make a proper mechanism comparison.


Biogenic Chemistry

Several hundreds different BVOC have been identified. Most well known are ethene, isoprene and the monoterpenes.

Isoprene is the major single emitted BVOC.

The BVOC emission depend highly on vegetation type.

BVOC emissions also contain oxygen-containing organics

Estimated global Annual BVOC Emission (Tg/year)


chloroplastsisoprene2-methyl-3-buten-2-olresin ducts or glandsmany tissuescell wallsflowerscell membranesleaves, stems, rootsmonoterpenesformaldehydeformic acidacetaldehydeacetic acidethanolacetoneC6-acetaldehydesC6-alcohols100s of VOCmethanolethylene(Fall, 1999)


Some Biogenic Emitted Hydrocarbonsisoprene -pinene -pinene limonene -terpinene -terpinene campheneterpinolene -phellandrene -phellandrene myrcene ocimene 3-carene p-cymene


Some Oxygen-Containing Organics Biogenic Sources3-methyl-5-hepten-2-one 3-hexenal 2-hexenal thujone methanolethanol n-hexanol 3-hexenol camphor linaloolHOformaldehyde acetaldehyde acetone butanone n-hexanalOOHOHOOOOOOOOHOHOOHOHOOHOO2-methyl-3-buten-2-ol formic acid acetic acid 3-henenyl-acetate 1, 8-cineol


Ref. Ruppert, 1999EUPHORE Chamber Experiment and Simulation without BVOCs (called base mix)


Ref. Ruppert, 1999EUPHORE Chamber Experiment and Simulation: base mix + 90 ppbV -pinene


EUPHORE Chamber Experiment and Simulation: base mix + isoprene

Sim. with RACM Sim. with modified RACMozonetolueneetheneisopreneNO2NO

Ref. Ruppert, 1999


Biogenic Study, Summary

The BVOC emission inventory are calculated from land-use data. The BVOCs emissions from plants are usually only given for isoprene and monoterpenes. However in Kesselmeier and Staudt (Atm. Env., 33, 23, 1999) are BVOCs from other compounds than isoprene and monoterpene presented.

How shall the split of the emissions of monoterpenes into specific species (-pinene, -pinene, limonene etc.) be performed? This is not clear.

BVOC emission inventories have uncertainties of factors 2.5-9.

How good are the land-use data bases to describe the current BVOC?How good are seasonal changes of vegetation described?How good are human changes of vegetation described?

The understanding of biogenic chemistry is very incomplete. Today only one lumped mch. treat other biogenic emitted species than isoprene. RACM also treat API: -pinene and other cyclic terpenes with more than one double bound,LIM: d-limonene and other cyclic diene-terpenes.

Commonly used lumped mechanisms (CBM-IV, RADM2, EMEP and RACM) do not describe the chemistry of isoprene very good.


DMS (DiMethyl Sulphide) Chemistry


DMS (DiMethyl Sulphide) Chemistry Identified Atmospheric Sulphur CompoundsHSCH3SO2OHCS2 CH3S(O)OOHCOSCH3SCH2OOHSO2CH3S(O)2OOHH2SO4 [SULF] CH3OS(O)2OH CH3SCH3 [DMS] CH3OS(O)2OCH2CH3S(O)CH3 [DMSO] CH3S(O)2CH3OOHCH3S(O)2CH3 [DMSO2] HOCH2S(O)2OHCH3SSCH3 [DMDS] HOCH2S(O)2CH2OHCH3SHCH3SO2ONOCH3SOH [MSEA] CH3SO2ONO2CH3S(O)OH [MSIA] CH3S(O)2OH [MSA] It is not an easy task to make a DMS gas-phase mechanism?


A gas-phase DMS mch. was developed during the EU-project period. This DMS mch. included 30 sulphur species and 72 reactions (49 guessed & 23 experimental rates).Based on clean MBL scenarios the DMS ELCID mch. was reduced to 21 sulphur species and 34 reactions (22 guessed & 12 experimental rates).DMS mch. for Atm ModellingThe ELCID gas-phase mch.The ELCID mch. was further reduced by lumping to 15 sulphur species and 20 reactions. This mechanism was used for 3D modelling in the ELCID project.


The Atmospheric Box-modelIn the box the following processes are solved for species i (which can be either a liquid or gas phases species):

dCi/dt = + chemical production chemical loss

+ emission

dry deposition wet deposition

+ entrainment from the free troposphere to the boundary layer

+ aerosol model

+ CCN model + cloud model

Ref. Gross and Baklanov, IJEP, 2004, 22, 52


Clean MBL Scenarios Simulated in the Study

Meteorological Conditions:Ground Albedo 0.10Pressure (mbar) 1013.25Relative Humidity 90 %Cloud Frequency 1 d-1Precipitation Frequency 0.1 d-1Temperature (K) 288.25

Initial Aerosol Distribuitions:Nuclei Mode:Number conc.133 cm-3log() 0.657Geo. Mean Dia . 0.810-6 cmAccumulation mode:Number conc. 66.6 cm-3log() 0.21Geo. Mean Dia. .26610-4 cmInitial Gas-Phase Conc.:H2 2 ppmVCH4 1.7 ppmVCO 0.14 ppmVH2O 3 %N2 78%O2 20 %NO2 400 pptVH2O2 1 pptVHO2 0 pptVCH3O20 pptVHNO3 150 pptVO3 40 ppbVHCHO 10 pptVVOC 5.5 ppbCSO2 2 pptVDMS 100 pptVMSA 1 pptVEmission of SO2 in pptV/min: 0.014Emission of DMS in pptV/min: 0.00, 0.06, 0.12, 0.24, 0.36, 0.48, and 0.60


Emissions of DMS isvaried from 0.0 (blue) to 0.6 (purple) pptV/minEmis. of SO2 = 0.014 pptV/minfor all the simulationsDMSOX in pptVInorganic Sulphur in pptVRef. Gross and Baklanov, IJEP, 2004, 22, 51


Solid line: accumulation mode

Dashed line: nuclei modeParticle number conc. in cm-3Geometic mean diameter in cmRef. Gross and Baklanov, IJEP, 2004, 22, 51


Influence of DMS on acc. mode particles in the clean MBLAIS/W: Amsterdam Island Summer/WinterCGS/W: Cape Grim Summer/WinterEUMELI3: oceanografic cuise south and east of the Canary Islands

DMS % cont. Nnss: DMS contribution in % to accumulation mode nss. aerosols. DMS % cont. Ntot upper (lower) limit: the upper (lower) limit of DMS contribution in % to the sea salt plus the non sea salt accumulation mode aerosols.Ref. Gross and Baklanov, IJEP, 2004, 22, 51

DMS emission in pptV/minAISAIWCGSCGWEUMELI3DMS % cont. Nnss26.813.318.32.9512.9DMS % cont. Ntot upper limit17.89.7212.92.339.44DMS % cont. Ntot lower limit10.05.247.071.215.08


Mechanism ComparisonNumber of SulphurSpeciesReacs.Ref.Koga and Tanaka 33 40JAC, 1992, 17, 201Hertel et al. 36 58Atm. Env. 1994, 38, 2431Capaldo and Pandis 37 71JGR. 1997, 102, 23251JRC ISPRA mch. 32 38Privat comm., 2002ELCID mch. 21 34ELCID proj., 2004Mechanism adjustments: The mechanisms is adjusted such that similar rate constants for the DMS loss, and SO2 and H2SO4 formation are used.Rest of the mechanisms are not changed.


Concentration of DMSOX (pptV)Contour levels from 50 to 850 pptV, increment interval 50 pptVDMS emis. = 0.36 ppt/min: ELCID: JRC ISPRA: , Cap&Pan: Hertel et al.: , Kog&Tan: , 2004, 1992, 1997, 2002, 1995Ref. Gross and Baklanov, ITM, 2004


Concentration of inorganic sulphur (pptV)Contour levels from 10 to 165 pptV, increment interval 15 pptVDMS emis. = 0.36 ppt/min: ELCID: JRC ISPRA: , Cap&Pan: Hertel et al.: , Kog&Tan: max.117.5pptVmax.153.2pptVmax.117.5pptVmax.133.6pptVmax.137.3pptV, 2004, 1997, 2002, 1992, 1995Ref. Gross and Baklanov, ITM, 2004


Particle number concentration (cm-3), Accumulation modeContour levels from 10 to 120 cm-3, increment interval 10 cm-3DMS emis. = 0.36 ppt/min: ELCID: JRC ISPRA: , Cap&Pan: Hertel et al.: , Kog&Tan: max.105.0pptVmax.117.7pptVmax.104.4pptVmax.118.5pptVmax.118.5pptV, 2004, 2002, 1994, 1992, 1997Ref. Gross and Baklanov, ITM, 2004


DMS Study, Summary

DMS important to include in atm. modelling if aerosols and large ocean areas are included in the model domain, since DMS can roughly contribute from 1327% (summer period) and 313% (winter period) of the formation of non sea salt aerosols.from 1018% (summer period) and 110% of the total aerosol formation.

Too simplified DMS chemistry [DMS(g)+HO(g)->SO2(g)->H2SO4(l)] create too many new accumulation mode particles (Gross and Baklanov, ITM, 2004).

The DMS mechanism comparison showed that all five mechanism gave all most the same amount of inorganic DMSOX, sulphur, aerosols, equally good.However, all these DMS mechanisms are based on the same guessed rates and reactions, i.e. the same amount of uncertainty.


DMS Summary, Resent Results

A resent ab initio/DFT study (Gross, Barnes et al., JPC A, 2004, 108, 8659) shows:DMSOH + O2 DMSO + HO2 (the dominant channel)DMSOH + O2 DMS(OH)(OO) (occur, minor channel)DMSOH + O2 CH3SOH + CH3O2(does not occur) However, in DMS mechanisms channels 1 and 2 are often considered to be equal important, and channel 3 is included.

Simulations of DMS chamber experiments (which were performed at different temperatures and NOX concentrations) indicate that we still not fully understand the chemistry of the additional DMS+HO channel. Important chemical mechanisms are missing. (Gross and Barnes, unpublished results).


ConclusionsMore detailed mechanisms of aromatics and peroxide reactions are needed.

The isoprene chemistry should been updated in the lumped mechanisms.

If heterogeneous chemistry also is included in the ACTM many parameters used to described the mass transport of gas-phase species to aerosols and these species aerosol physics are still uncertain/unknown.

The DMS chemistry is still highly uncertain both with respect to rate constant determination and the product mechanism. Furthermore, the emission of DMS is poorly known.

Better description of biogenic emissions is needed before it is meaningful to increase the chemistry of BVOC with more species than isoprene and monoterpene. (personal opinion).

Has described the most important chemistry need for regional scale Atmospheric Chemistry Transport Modelling (ACTM), and has described where atmospheric chemistry still has large uncertainties.


CollaboratorsAtmospheric Science:Senior Scientist Alexander A. Baklanov, Danish Meteorology Institute, Denmark.Senior Scientist Jens H. Srensen, Danish Meteorology Institute, Denmark.Senior Scientist Alix Rasmussen, Danish Meteorology Institute, Denmark.Research Scientist Alexander Mahura, Danish Meteorology Institute, Denmark.

Atmospheric Chemistry:Research Prof. William R. Stockwell, Desert Research Institute, Reno, Nevada, USA.Associate Prof. I. Barnes, University of Wuppertal, Germany.Ph.D. Stud. Marianne Sloth, University of Copenhagen, Denmark and Danish Meteorological Institute, Denmark.

Theoretical and Physical Chemistry:Prof. Kurt V. Mikkelsen, University of Copenhagen, Denmark.Asistant Prof. Balakrishan Naduvalath, State University of Nevada, Las Vegas, USA. Ph.D. Stud. Nuria Gonzales Garcia, Universitat Autonoma de Barcelone, Spain.Research Assistant Hanne Falsig, University of Copenhagen, Denmark.


Erik Bdtker, Danmarks Meteorologiske InstitutErik Bdtker, Danmarks Meteorologiske InstitutErik Bdtker, Danmarks Meteorologiske InstitutErik Bdtker, Danmarks Meteorologiske InstitutErik Bdtker, Danmarks Meteorologiske InstitutErik Bdtker, Danmarks Meteorologiske Institut

Erik Bdtker, Danmarks Meteorologiske InstitutErik Bdtker, Danmarks Meteorologiske InstitutErik Bdtker, Danmarks Meteorologiske InstitutErik Bdtker, Danmarks Meteorologiske InstitutS

Erik Bdtker, Danmarks Meteorologiske InstitutS


Erik Bdtker, Danmarks Meteorologiske InstitutErik Bdtker, Danmarks Meteorologiske Institut

Documents

CITES 2005, March 20-23, 2005, Novosibirsk, Russia