大氣環(huán)境化學(xué)-揮發(fā)性有機(jī)物研究

中國城市大氣污染與VOCs研究的需求邵敏北京大學(xué)環(huán)境學(xué)院BackgroundVOCsstudiesRecentworkO3levelsinsummerofBeijing,2000Therelativeincrementalreactivities(RIR)areexpressedasozonereductionin%whenitsprecursorsreducedin%1950sPresent1980sNMVOCs+NOx

+CH4??OzoneabatementstrategiesevolveasourunderstandingoftheO3problemimprovesAbatement

Strategy:O3smogrecognizedasanURBANproblem:

LosAngeles,Haagen-SmitidentifieschemicalmechanismSmogconsideredREGIONALproblem;roleofbiogenicVOCsdiscoveredAGLOBALperspective:roleofintercontinentaltransport,background

Focus:heterogeneousprocess

Oxidants(O3,OH)SO2,NOxFineparticlesVOC、NOxVehicleexhuast,Coalburningetc.hvMajorconcerns:PhotochemicalsmoghasbeenaseriousprobleminmegacitiesFineparticlespresentathighlevelSecondarypollutionextendsregionallyBackgroundVOCsstudiesRecentwork大氣揮發(fā)性有機(jī)物(VOCs)VolatileOrganicCompoundsVeryOftenConfusedproblems（濃度變化，反應(yīng)性和源特征等非常復(fù)雜）Very-wellOrganizedCompetitions（國際上在外場觀測、反應(yīng)機(jī)理、來源研究等方面具有公認(rèn)的優(yōu)勢單位，分別為加州大學(xué)Irvine的Blake,Riverside的Atkinson,以及NCAR的A.Guenther)大氣揮發(fā)性有機(jī)物(VOCs)可能的有毒有害物質(zhì)，室內(nèi)室外的暴露均很重要；大氣臭氧的前體物之一，種類繁多，濃度和化學(xué)活性差異巨大細(xì)粒子的前體物CompetitionsMeasurementtechnique(on-line,continuous,ChemicalionizationMS)Photochemistry(Atkinson)MappingofNaturalEmissions(A.Guenther,NCAR)Secondaryaerosols(RKamens,NCarolina)

VOCs的分析技術(shù)VOCs的來源研究化學(xué)活性分析NMHC鹵代烴CarbonylNMOGHeavyHCVOC揮發(fā)性有機(jī)物（VOCs）半揮發(fā)性有機(jī)物（Semi-volatile）顆粒有機(jī)物

(POM，Particulateorganicmatters)VOCs的測量方法離線在線GC-MS離線分析AnalyticalSystem典型的離線分析系統(tǒng)典型的在線分析系統(tǒng)PTR-MS北京市大氣VOCs分析共測量108種VOCs組分：飽和烷烴： 32 種烯烴： 26 種單環(huán)芳香烴： 20 種鹵代烷烴： 18 種鹵代烯烴： 9 種氯苯： 3 種

GeneralaspectsofambientVOCsinBeijingSeasonalvariationsofVOCgroupsAlkenesandalkanesappearedhigherinNov.,lowerinMarch,muchlowerinJuly;Theconcentrationsofaromaticsinsummerwerehigherthanspring.（張靖等，環(huán)境科學(xué)研究，2003）來源研究源清單

(sourceinventory)簡單直接，誤差較大，難以反映變化受體模式（Receptormodel)依賴源特征，能反應(yīng)變化因素，但不能給出分布ChemicalMassBalance(CMB)ApproachMassbalanceequationsinCMBmodel:TheambientconcentrationCimeasuredatreceptorsite,equalsthesumoftheproductofrelativeabundanceFijofcomponentiinsourcejandcontributionofsourcej.CMBisappliedtoassesstheconcentrationsofeachVOCssources.源成分譜（sourceprofiles)機(jī)動(dòng)車排放的比較——隧道實(shí)驗(yàn)（付琳琳等，環(huán)境科學(xué)學(xué)報(bào)，2005）

VOCsSourceInventoryofBeijingcity,1999VOCsemissions:245Gg/yrCMBmodelperformanceGoodagreementbetweenthemeasuredandcalculatedconcentrationsVOCsSourceapportionmentbyCMB（wt%）

SummaryUncertaintiesofinventory&sourceapportoinmentEmissionfactorbasedonUSandEuropeLackofstationarysourceprofilesSeasonalvariationofsourcecontributionstoambientVOCs

VehicleexhaustisthelargestcontributorineveryseasonThecontributionofpaintsandgasolineevaporationincreasefromwintertosummerDiurnalvariationsofsourcecontributionstoambientVOCs（LiuYingetal.,JESH,2005)VOCs的化學(xué)活性O(shè)HLossRate15％的烯烴貢獻(xiàn)了大約75％的化學(xué)活性；VOCs整體的化學(xué)活性相當(dāng)于乙烯。烯烴組分化學(xué)活性的相對(duì)貢獻(xiàn)(邵敏等，中國科學(xué)，2005，accepted)VOCs控制對(duì)策建議確定優(yōu)先控制物種；加快機(jī)動(dòng)車排放控制（新車，在用車）石油精煉的全加氫工藝通過管理措施減少泄漏Emissions/DepositionsofplantsNO2Deposition

StomotacontroledprocessNOdeposition/emission

CompensationeffectVOCsemissions

Isoprene,terpene,alkanes,alkenes,aromatics,aldehydes,ketones,alkohols,etc..O3

Deposition/precursorofcarbonylsAlgorithmtodescribeVOCsemissionsTingeyetal,1991Guentheretal,1993Schuhetal.,1997BiosynthesisPoolFvocBiosynthesisFvocBiosynthesisPoolFPFBVOCemissionrates:NetphotosynthesisStomataconductivityVOCisemissionratesatleaftemperatureTandlightintensityL(LisidenticaltoPAR);PandBisthefirstandsecondtermoftheequation,isstandardemissionrateindarknessatstandardtemperatureTS(here25oC);isstandardemissionratefromprocessinparallelwithphotosynthesisactivity.TM:enzymeoptimaltemperature.CTP,CT1andCT2areempiricalparametersfortemperaturedependence;aisparametertodescribelightintensitydependence.SeveralDays?However……VOCsNOxOzonePositivefeedbackofbiogenicVOCemissions?InsectseffectBiogenicSourceinventoryofVOCsinBeijingBiogenic:11km2,1htimeresolutionGuentheralgorithm;Digitalland-usefromremotesensing;NDVI,TemperatureandPARfromrealtimemeasurement;Emissionratesmeasuredfor23kindsof39typesofvegetationTVOCIsopreneMonoterpeneOVOCAnnualemission167.93.54.8(unit:109gC)(Source:Wangetal.,Atmos.Environ,2003)Furtherresearchneedsparisontounderstandsources;RoleofVOCsinground-levelozone;